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A model for atmospheric CO2 over Phanerozoic time
Abstract
A new model has been constructed for calculating the level of atmospheric CO2 over Phanerozoic time which is much simpler mathematically than the BLAG model, but more complex geologically and biologically. Mathematical simplification comes about by following the cycle of carbon only, lumping all carbonate minerals together, combining the ocean and atmosphere into one reservoir, and calculating atmospheric CO2 level as a series of successive ocean-atmosphere steady states. Results suggest that there has been a notable pattern of varying atmospheric CO2 level over the past 570 my with high levels during the Mesozoic and early Paleozoic and low levels during the Permo-Carboniferous and late Cenozoic. -from Author
... Interactions between the long-term carbon cycle and global climate govern the habitability of our planet. These interactions are mediated by complex relationships with factors such as geography, lithology, climate feedbacks, and more (Bluth and Kump, its own advantages and drawbacks (Arndt et al., 2011;Bergman, 2004;Berner, 1991Berner, , 2004Colbourn et al., 2013;Donnadieu et al., 2004Donnadieu et al., , 2006Francois and Walker, 1992;Goddéris and Joachimski, 2004;Lenton et al., 2018;Mills et al., 2017;Ozaki and Tajika, 2013;Ridgwell et al., 2007;Zeebe, 2012). 25 One major challenge in building these models is balancing the complexity of the global climate system with the computational efficiency needed to simulate thousands to millions or billions of years of time. ...
... Based on the model's intended applications, different frameworks address this trade-off in different ways. Lower-dimensional box models, for example, tend to distill global climate down to a few simple parameters (and in many cases, a single forcing variable, pCO 2 ), usually opting to ignore many factors such as geography, orbital forcing, and ice sheet dynamics (Berner, 1991;Bergman, 2004;Caves et al., 30 2016; Kump and Arthur, 1997;Lenton et al., 2018;Zeebe, 2012). The simpler representation of climate makes these models highly efficient while leaving room for more complex representations of other factors, such as sedimentary reservoirs and ocean biogeochemical cycling (Zeebe, 2012;Ozaki and Tajika, 2013). ...
... The carbon cycle model follows other one-box models that are commonly employed for tracking long-term (i.e., on timescales of > 10 5 years) changes to the carbon cycle and δ 13 C (e.g. Berner, 1991;. The input fluxes of C into the ocean-atmosphere system include volcanism and solid Earth degassing (F volc ), organic carbon weathering (F w,org ), and 260 carbonate weathering (F w,carb ), and the output fluxes are the burial of organic carbon and carbonate carbon in marine sediments (F b,org and F b,carb , respectively). ...
Models of the carbon cycle and climate on geologic (>10^4 year) timescales have improved tremendously in the last 50 years due to parallel advances in our understanding of the Earth system and the increase in computing power to simulate its key processes. Despite these advances, balancing the Earth System's vast complexity with a model's computational expense is a primary challenge in model development. Running longer simulations spanning hundreds of thousands of years or more generally requires reducing the complexity of the modeled climate system. However, simpler model frameworks often leave out certain features of the climate system, such as radiative feedbacks, shifts in atmospheric circulation, and the expansion and decay of ice sheets, which can have profound effects on the long-term carbon cycle. Here, we present a model for climate and the long-term carbon cycle that captures many fundamental features of global climate while retaining the computational efficiency needed to simulate millions of years of time. The Carbon-H2O Coupled HydrOlOgical model with Terrestrial Runoff And INsolation, or CH2O-CHOO TRAIN, couples a one-dimensional (latitudinal) moist static energy balance model of climate with a model for rock weathering and the long-term carbon cycle. The key advantages of this framework are (1) it simulates fundamental climate forcings and feedbacks; (2) it accounts for geographic configuration; and (3) it is highly customizable, equipped to easily add features, change the strength of feedbacks, and prescribe conditions that are often hard-coded or emergent properties of more complex models, such as climate sensitivity and the strength of meridional heat transport. The CH2O-CHOO TRAIN is capable of running million-year-long simulations in about thirty minutes on a laptop PC. This paper outlines the model equations, presents a sensitivity analysis of the climate responses to varied climatic and carbon cycle perturbations, and discusses potential applications and next stops for the CH2O-CHOO TRAIN.
... T he chemical dissolution of rocks at Earth's surface modulates the concentration of CO 2 in the atmosphere and, thereby, Earth's climate (1)(2)(3). Understanding how weathering rates are affected by tectonic and climatic boundary conditions is critical to modeling Earth's evolution over geologic time and to assessing Earth's systemic response to natural and anthropogenic perturbations. Rates of chemical weathering are controlled, to first order, by the supply of fresh minerals to the weathering zone, the availability of reactive fluids, and the kinetics of mineral dissolution (3,4). ...
... Understanding how weathering rates are affected by tectonic and climatic boundary conditions is critical to modeling Earth's evolution over geologic time and to assessing Earth's systemic response to natural and anthropogenic perturbations. Rates of chemical weathering are controlled, to first order, by the supply of fresh minerals to the weathering zone, the availability of reactive fluids, and the kinetics of mineral dissolution (3,4). In turn, the supply of fresh minerals is directly linked to the exhumation of rocks at Earth's surface (5)(6)(7). ...
Uplift and erosion modulate the carbon cycle over geologic timescales by exposing minerals to chemical weathering. However, the erosion sensitivity of mineral weathering remains difficult to quantify. Solute-chemistry datasets from mountain streams in different orogens isolate the impact of erosion on silicate weathering—a carbon dioxide (CO 2 ) sink—and coupled sulfide and carbonate weathering—a CO 2 source. Contrasting erosion sensitivities of these reactions produce a CO 2 -drawdown maximum at erosion rates of ~0.07 millimeters per year. Thus, landscapes with moderate uplift rates bolster Earth’s inorganic CO 2 sink, whereas more rapid uplift decreases or even reverses CO 2 sequestration. This concept of an “erosion optimum” for CO 2 drawdown reconciles conflicting views on the impact of mountain building on the carbon cycle and permits estimates of geologic CO 2 fluxes dependent upon tectonic changes.
... These vegetationclimate interactions vary in concert with local climatic conditions (e.g., temperature, water and light availability), and a change in plant community structure and function can influence climate by controlling the rate of carbon exchange 7 . Well known 'box' models for Phanerozoicscale biogeochemistry, such as GEOCARB 1,2,8,9 and COPSE 10,11 , attempt to represent feedbacks between the plant biosphere and climate. The inclusion of land plants in these types of model has a long history 9 , and the initial colonisation of the land is commonly thought to have drawn down CO 2 and cooled the climate in the middle to late Paleozoic Era 2,11 , although this remains uncertain 12,13 . ...
... Well known 'box' models for Phanerozoicscale biogeochemistry, such as GEOCARB 1,2,8,9 and COPSE 10,11 , attempt to represent feedbacks between the plant biosphere and climate. The inclusion of land plants in these types of model has a long history 9 , and the initial colonisation of the land is commonly thought to have drawn down CO 2 and cooled the climate in the middle to late Paleozoic Era 2,11 , although this remains uncertain 12,13 . ...
Long computation times in vegetation and climate models hamper our ability to evaluate the potentially powerful role of plants on weathering and carbon sequestration over the Phanerozoic Eon. Simulated vegetation over deep time is often homogenous, and disregards the spatial distribution of plants and the impact of local climatic variables on plant function. Here we couple a fast vegetation model (FLORA) to a spatially-resolved long-term climate-biogeochemical model (SCION), to assess links between plant geographical range, the long-term carbon cycle and climate. Model results show lower rates of carbon fixation and up to double the previously predicted atmospheric CO2 concentration due to a limited plant geographical range over the arid Pangea supercontinent. The Mesozoic dispersion of the continents increases modelled plant geographical range from 65% to > 90%, amplifying global CO2 removal, consistent with geological data. We demonstrate that plant geographical range likely exerted a major, under-explored control on long-term climate change.
... Based on the model's intended applications, different frameworks address this tradeoff in different ways. Lower-dimensional box models, for example, tend to distill global climate down to a few simple parameters (and, in many cases, a single forcing variable, pCO 2 ), usually opting to ignore many factors such as geography, orbital forcing, and ice sheet dynamics (Berner, 1991;Bergman, 2004;Kump and Arthur, 1997;Lenton et al., 2018;Zeebe, 2012). The simpler representation of climate makes such models highly efficient while leaving room for more complex representations of other factors, such as sedimentary reservoirs and ocean biogeochemical cycling (Zeebe, 2012;Ozaki and Tajika, 2013). ...
... The carbon cycle model follows other one-box models that are commonly employed for tracking long-term (i.e., on timescales of > 10 5 years) changes to the carbon cycle and δ 13 C (e.g., Berner, 1991;Kump and Arthur, 1999). The input fluxes of C into the ocean-atmosphere system include volcanism and solid-Earth degassing (F volc ), organic carbon weathering (F w,org ), and carbonate weathering (F w,carb ), and the output fluxes are the burial of organic carbon and carbonate carbon in marine sediments (F b,org and F b,carb , respectively, all in moles per year). ...
Models of the carbon cycle and climate on geologic (>104-year) timescales have improved tremendously in the last 50 years due to parallel advances in our understanding of the Earth system and the increase in computing power to simulate its key processes. Still, balancing the Earth system's complexity with a model's computational expense is a primary challenge in model development. Simulations spanning hundreds of thousands of years or more generally require a reduction in the complexity of the climate system, omitting features such as radiative feedbacks, shifts in atmospheric circulation, and the expansion and decay of ice sheets, which can have profound effects on the long-term carbon cycle. Here, we present a model for climate and the long-term carbon cycle that captures many fundamental features of global climate while retaining the computational efficiency needed to simulate millions of years of time. The Carbon–H2O Coupled HydrOlOgical model with Terrestrial Runoff And INsolation, or CH2O-CHOO TRAIN, couples a one-dimensional (latitudinal) moist static energy balance model of climate with a model for rock weathering and the long-term carbon cycle. The CH2O-CHOO TRAIN is capable of running million-year-long simulations in about 30 min on a laptop PC. The key advantages of this framework are (1) it simulates fundamental climate forcings and feedbacks; (2) it accounts for geographic configuration; and (3) it is flexible, equipped to easily add features, change the strength of feedbacks, and prescribe conditions that are often hard-coded or emergent properties of more complex models, such as climate sensitivity and the strength of meridional heat transport. We show how climate variables governing temperature and the water cycle can impact long-term carbon cycling and climate, and we discuss how the magnitude and direction of this impact can depend on boundary conditions like continental geography. This paper outlines the model equations, presents a sensitivity analysis of the climate responses to varied climatic and carbon cycle perturbations, and discusses potential applications and next stops for the CH2O-CHOO TRAIN.
... Rock weathering affects the atmospheric CO2 balance by consuming CO2 in the atmosphere or soil and plays an important role in the global carbon cycle and climate change [1][2][3]. However, the carbon sink from rock weathering was considered a long-term (10 4 -10 6 years) geological process in previous global carbon cycle models, and it was believed that the carbon cycle driven by lithosphere-related carbonate weathering did not actively participate in the modern carbon cycle, making no or negligible contri-butions to current atmospheric CO2 sources and sinks [4,5]. With the deepening of research, the karst carbon sink effect has gradually been recognized. ...
... The normalized inorganic charge balance (NICB) value of samples was calculated using the following formula: NICB = (TZ + − TZ − )/(TZ + + TZ − ) × 100% (4) where TZ + = Na + + K + + 2Mg 2+ + 2Ca 2+ and TZ − = Cl − + 2SO4 2− + HNO3 − + NO3 − in meq/L. Evapotranspiration factor (Ef) was calculated using the following formula: ...
Accurate estimate of carbonate weathering and the related carbon sink flux induced by anthropogenic H2SO4 is of great significance for improving understanding of the hydrogeochemical evolution and the global carbon cycle. Here, to quantitatively evaluate the influence of anthropogenic H2SO4 on different lithological carbonate weathering and the related carbon sink budget, karst spring water in the typical limestone and mixed limestone–dolomite catchments in Yaji and Beidiping affected by acid precipitation in southwest China were sampled monthly for the analysis of hydrochemical and δ13CDIC characteristics. Results show for the period of sampling (August 2013 to December 2014) that the average contribution rates of atmospheric inputs and carbonate weathering to total dissolved cations are 2.24% and 97.8%, and 3.09% and 96.9% in Yaji and Beidiping, respectively. The δ13CDIC values (−17.0% to −14.7‰) and the [Ca2+ + Mg2+]/[HCO3−] (0.98 to 1.25) and [Ca2+ + Mg2+]/[HCO3− + SO42−] (approximately 1) equivalent ratios of samples prove that H2CO3 and H2SO4 simultaneously participate in carbonate weathering. The contribution rates of H2SO4 to [Ca2+ + Mg2+] and [HCO3−] produced by carbonate weathering in Yaji and Beidiping are 0–30% and 0–18%, and 0–37% and 0–23%, with average values of 14% and 7%, and 19% and 11%, respectively, suggesting that the influence of H2SO4 on different lithological carbonate weathering is different. H2SO4 precipitation participating in carbonate weathering increases the weathering rate by 14–19%, whereas it decreases the flux of karst carbon sink by 7–11% in Southwest China. Therefore, anthropogenic acids have influenced the global carbon cycle and climate change by carbonate weathering due to the large karst areas in the world, and their influences on different lithological carbonate weathering should not be ignored in the regional and global carbon cycles in future studies.
... Chief among these was limited access to essential mineral nutrients, particularly given the skeletal mineral soils 26 , the dense biological soil crusts 27 , and lack of roots and vasculature of the earliest land plants 28,29 . Thanks to the remarkable ability of symbiotic fungi to extract nutrients from minerals 30 and transfer these nutrients to their plant partners, symbioses with mycorrhiza-like fungi were likely critical to the success and diversification of early land plants 5,31 . ...
... Physiological 32,33 and genetic evidence [34][35][36] supports the hypothesis that early plant-fungal associations were mutualistic, and that mycorrhiza played a key role in land colonization by early plants. In supplying land flora with otherwise poorly available nutrients, alongside other non-nutritional benefits, early mycorrhiza-like fungi helped drive proliferation and diversification of ever more complex land plants, increasing the net global photosynthetic drawdown of atmospheric CO 2 and burial of organic carbon 30,37 . Climate models suggest that these processes, together with other biological and tectonic factors 38 , helped to drive a 10-fold reduction in atmospheric CO 2 levels during the Paleozoic Era, with concentrations falling from $3000 to 300 ppm ( Figure 1). ...
For more than 400 million years, mycorrhizal fungi and plants have formed partnerships that are crucial to the emergence and functioning of global ecosystems. The importance of these symbiotic fungi for plant nutrition is well established. However, the role of mycorrhizal fungi in transporting carbon into soil systems on a global scale remains under-explored. This is surprising given that ∼75% of terrestrial carbon is stored belowground and mycorrhizal fungi are stationed at a key entry point of carbon into soil food webs. Here, we analyze nearly 200 datasets to provide the first global quantitative estimates of carbon allocation from plants to the mycelium of mycorrhizal fungi. We estimate that global plant communities allocate 3.93 Gt CO2e per year to arbuscular mycorrhizal fungi, 9.07 Gt CO2e per year to ectomycorrhizal fungi, and 0.12 Gt CO2e per year to ericoid mycorrhizal fungi. Based on this estimate, 13.12 Gt of CO2e fixed by terrestrial plants is, at least temporarily, allocated to the underground mycelium of mycorrhizal fungi per year, equating to ∼36% of current annual CO2 emissions from fossil fuels. We explore the mechanisms by which mycorrhizal fungi affect soil carbon pools and identify approaches to increase our understanding of global carbon fluxes via plant-fungal pathways. Our estimates, although based on the best available evidence, are imperfect and should be interpreted with caution. Nonetheless, our estimations are conservative, and we argue that this work confirms the significant contribution made by mycorrhizal associations to global carbon dynamics. Our findings should motivate their inclusion both within global climate and carbon cycling models, and within conservation policy and practice.
... This geological process leads to the progressive decay of rock substrates, turning bedrock into regolith and releasing elements that fuel global biogeochemical cycles 1 . In particular, the chemical weathering of Mg-and Ca-silicates coupled to the deposition of Mg-and Ca-carbonates results in a net flux of CO 2 from the atmosphere to the lithosphere that controls atmospheric CO 2 concentrations, and hence, climate over geological timescales (>10 5 years) 2 . In addition, rock-forming minerals constitute an essential source of elements required to form secondary aluminosilicate minerals constitutive of the soil matrix and necessary to the development of ecosystems 3 . ...
... 179 , Paenibacillus polymyxa 180 , and Bacillus subtilis 75 , or the fungi Paxillus involutus 181 and Talaromyces flavus 92,182 . Even though this approach has shown the catalyzing role of microorganisms on mineral dissolution, it presents several limitations: (1) A discrepancy may exist between metabolism and phenotype expressed in in vitro experiments and in natural conditions, (2) the use of axenic cultures may oversimplify more complex microbial communities found in the field and (3) may not be fully representative of the effective distribution of these microorganisms in the field 183 , and (4) the focus on solution-based biotic dissolution may mostly evaluate the weathering capabilities of microorganisms mediated through the fluid (i.e., their ability to influence fluid-mineral systems via e.g., pH changes in the bulk fluid, as opposed to weathering occurring at the direct mineral-microorganism interface). The latter contrasts with in situ conditions, especially along unsaturated rock factures, or forest soil which are freely draining and seasonally dry for extended periods of time 184 . ...
Rock weathering is a key process in global elemental cycling. Life participates in this process with tangible consequences observed from the mineral interface to the planetary scale. Multiple lines of evidence show that microorganisms may play a pivotal—yet overlooked—role in weathering. This topic is reviewed here with an emphasis on the following questions that remain unanswered: What is the quantitative contribution of bacteria and fungi to weathering? What are the associated mechanisms and do they leave characteristic imprints on mineral surfaces or in the geological record? Does biogenic weathering fulfill an ecological function, or does it occur as a side effect of unrelated metabolic functions and biological processes? An overview of efforts to integrate the contribution of living organisms into reactive transport models is provided. We also highlight prospective opportunities to harness microbial weathering in order to support sustainable agroforestry practices and mining activities, soil remediation, and carbon sequestration.
... Based on the model's intended applications, different frameworks address this trade-off in different ways. Lower-dimensional box models, for example, tend to distill global climate down to a few simple parameters (and in many cases, a single forcing variable, pCO 2 ), usually opting to ignore many factors such as geography, orbital forcing, and ice sheet dynamics (Berner, 1991;Bergman, 2004; Caves et al., 30 2016;Kump and Arthur, 1997;Lenton et al., 2018;Zeebe, 2012). The simpler representation of climate makes these models highly efficient while leaving room for more complex representations of other factors, such as sedimentary reservoirs and ocean biogeochemical cycling (Zeebe, 2012;Ozaki and Tajika, 2013). ...
... The carbon cycle model follows other one-box models that are commonly employed for tracking long-term (i.e., on timescales of > 10 5 years) changes to the carbon cycle and δ 13 C (e.g. Berner, 1991;Kump and Arthur, 1999). The input fluxes of C 260 into the ocean-atmosphere system include volcanism and solid Earth degassing (F volc ), organic carbon weathering (F w,org ), and carbonate weathering (F w,carb ), and the output fluxes are the burial of organic carbon and carbonate carbon in marine sediments (F b,org and F b,carb , respectively). ...
Models of the carbon cycle and climate on geologic (>104 year) timescales have improved tremendously in the last 50 years due to parallel advances in our understanding of the Earth system and the increase in computing power to simulate its key processes. Despite these advances, balancing the Earth System's vast complexity with a model's computational expense is a primary challenge in model development. Running longer simulations spanning hundreds of thousands of years or more generally requires reducing the complexity of the modeled climate system. However, simpler model frameworks often leave out certain features of the climate system, such as radiative feedbacks, shifts in atmospheric circulation, and the expansion and decay of ice sheets, which can have profound effects on the long-term carbon cycle. Here, we present a model for climate and the long-term carbon cycle that captures many fundamental features of global climate while retaining the computational efficiency needed to simulate millions of years of time. The Carbon-H2O Coupled HydrOlOgical model with Terrestrial Runoff And INsolation, or CH2O-CHOO TRAIN, couples a one-dimensional (latitudinal) moist static energy balance model of climate with a model for rock weathering and the long-term carbon cycle. The key advantages of this framework are (1) it simulates fundamental climate forcings and feedbacks; (2) it accounts for geographic configuration; and (3) it is highly customizable, equipped to easily add features, change the strength of feedbacks, and prescribe conditions that are often hard-coded or emergent properties of more complex models, such as climate sensitivity and the strength of meridional heat transport. The CH2O-CHOO TRAIN is capable of running million-year-long simulations in about thirty minutes on a laptop PC. This paper outlines the model equations, presents a sensitivity analysis of the climate responses to varied climatic and carbon cycle perturbations, and discusses potential applications and next stops for the CH2O-CHOO TRAIN.
... Long-term climate variability reflects the interplay between temporal changes in solid Earth carbon outgassing and the efficiency of silicate weathering feedbacks, which draw down CO 2 by precipitating carbonate minerals-but the relative contributions of these two mechanisms through time are debated 68 . Commonly, sea-level fluctuations have been used as a proxy for seafloor production and mid-ocean-ridge carbon degassing estimates 69 in global carbon cycle models [69][70][71] . Alternatively, solid Earth outgassing has been constrained via crustal production and seafloor spreading rates 72 and from subduction flux derived from a full-plate model 73 . ...
... Long-term climate variability reflects the interplay between temporal changes in solid Earth carbon outgassing and the efficiency of silicate weathering feedbacks, which draw down CO 2 by precipitating carbonate minerals-but the relative contributions of these two mechanisms through time are debated 68 . Commonly, sea-level fluctuations have been used as a proxy for seafloor production and mid-ocean-ridge carbon degassing estimates 69 in global carbon cycle models [69][70][71] . Alternatively, solid Earth outgassing has been constrained via crustal production and seafloor spreading rates 72 and from subduction flux derived from a full-plate model 73 . ...
Concealed deep beneath the oceans is a carbon conveyor belt, propelled by plate tectonics. Our understanding of its modern functioning is underpinned by direct observations, but its variability through time has been poorly quantified. Here we reconstruct oceanic plate carbon reservoirs and track the fate of subducted carbon using thermodynamic modelling. In the Mesozoic era, 250 to 66 million years ago, plate tectonic processes had a pivotal role in driving climate change. Triassic–Jurassic period cooling correlates with a reduction in solid Earth outgassing, whereas Cretaceous period greenhouse conditions can be linked to a doubling in outgassing, driven by high-speed plate tectonics. The associated ‘carbon subduction superflux’ into the subcontinental mantle may have sparked North American diamond formation. In the Cenozoic era, continental collisions slowed seafloor spreading, reducing tectonically driven outgassing, while deep-sea carbonate sediments emerged as the Earth’s largest carbon sink. Subduction and devolatilization of this reservoir beneath volcanic arcs led to a Cenozoic increase in carbon outgassing, surpassing mid-ocean ridges as the dominant source of carbon emissions 20 million years ago. An increase in solid Earth carbon emissions during Cenozoic cooling requires an increase in continental silicate weathering flux to draw down atmospheric carbon dioxide, challenging previous views and providing boundary conditions for future carbon cycle models. Oceanic plate carbon reservoirs are reconstructed and the fate of subducted carbon is tracked using thermodynamic modelling, challenging previous views and providing boundary conditions for future carbon cycle models.
... The Earth's carbon cycle is profoundly influenced by natural rock and mineral weathering, playing a crucial role in the long-term removal of CO 2 from the atmosphere (Berner 1991, Schlesinger 1991. Terrestrial and marine weathering processes significantly contribute to carbon sequestration over geological timescales (Lenton and Britton 2006), and rock weathering consumes approximately 0.3 gigatons of carbon (GtC) annually (Gaillardet et al 1999, IPCC 2021. ...
The spreading of crushed olivine-rich rocks in coastal seas to accelerate weathering reactions sequesters atmospheric CO2 and reduces atmospheric CO2 concentrations. Their weathering rates depend on different factors, including temperature and the reaction surface area. Therefore, this study investigates the variations in olivine-based enhanced weathering rates across 13 regional coasts worldwide. In addition, it assesses the CO2 sequestration within 100 years and evaluates the maximum net-sequestration potential based on varying environmental conditions. Simulations were conducted using the geochemical thermodynamic equilibrium modeling software PHREEQC. A sensitivity analysis was performed, exploring various combinations of influencing parameters, including grain size, seawater temperature, and chemistry. The findings reveal significant variation in CO2 sequestration, ranging from 0.13 to 0.94 metric tons (t) of CO2 per ton of distributed olivine-rich rocks over 100 years. Warmer coastal regions exhibit higher CO2 sequestration capacities than temperate regions, with a difference of 0.4 t CO2/ t olivine distributed. Sensitivity analysis shows that smaller grain sizes (10 µm) exhibit higher net CO2 sequestration rates (0.87 t/t) in olivine-based enhanced weathering across all conditions, attributed to their larger reactive surface area. However, in warmer seawater temperatures, olivine with slightly larger grain sizes (50 and 100 µm) displays still larger net CO2 removal rates (0.97 and 0.92 t/t), optimizing the efficiency of CO2 sequestration while reducing grinding energy requirements. While relying on a simplified sensitivity analysis that does not capture the full complexity of real-world environmental dynamics, this study contributes to understanding the variability and optimization of enhanced weathering for CO2 sequestration, supporting its potential as a sustainable CO2 removal strategy.
... Most biogeochemical models have ignored evaporite-driven perturbations to seawater chemistry 148,149 , assuming that over timescales >100 kyr, evaporite precipitation and weathering are balanced. Formation of kilometre-thick MSC evaporites, and their preservation over the subsequent ~5 million years of Earth history, reflects approximately 7-10% net evaporite-ion extraction from ocean water over this period 4,38 . ...
... Geochemical weathering plays an important role in regulating CO 2 in the atmosphere over geological time scales (Raymond, 2017;Yu et al., 2019). To understand how CO 2 in the atmosphere has evolved, we need to first quantify the weathering rates or CO 2 consumption rates (Berner, 1991;Berner and Kothavala, 2001). Liu et al. (2019b) found that the rock weathering of the Yarlung Tsangpo River Basin on the TP, which comprises only 0.16% of the global surface area, can consume 0.54% of the global CO 2 consumptions. ...
... Earlier, it was reported that the atmospheric CO 2 of the earth was higher compared to the present. According to the geochemical carbon balance model, the atmospheric CO 2 level during Triassic, Jurassic, and Cretaceous might contain CO 2 content five to eight times greater than today [156][157][158]. According to the model, the atmospheric CO 2 dropped from a range of 2800-1400 to below 1000 lL L -1 in the Eocene, Miocene, and Pliocene. ...
Background:
Despite the exposure to arid environmental conditions across the globe ultimately hampering the sustainability of the living organism, few plant species are equipped with several unique genotypic, biochemical, and physiological features to counter such harsh conditions. Physiologically, they have evolved with reduced leaf size, spines, waxy cuticles, thick leaves, succulent hydrenchyma, sclerophyll, chloroembryo, and photosynthesis in nonfoliar and other parts. At the biochemical level, they are evolved to perform efficient photosynthesis through Crassulacean acid metabolism (CAM) and C4 pathways with the formation of oxaloacetic acid (Hatch-Slack pathway) instead of the C3 pathway. Additionally, comparative genomics with existing data provides ample evidence of the xerophytic plants' positive selection to adapt to the arid environment. However, adding more high-throughput sequencing of xerophyte plant species is further required for a comparative genomic study toward trait discovery related to survival. Learning from the mechanism to survive in harsh conditions could pave the way to engineer crops for future sustainable agriculture.
Aim of the review:
The distinct physiology of desert plants allows them to survive in harsh environments. However, the genomic composition also contributes significantly to this and requires great attention. This review emphasizes the physiological and genomic adaptation of desert plants. Other important parameters, such as desert biodiversity and photosynthetic strategy, are also discussed with recent progress in the field. Overall, this review discusses the different features of desert plants, which prepares them for harsh conditions intending to translate knowledge to engineer plant species for sustainable agriculture.
Key scientific concepts of review:
This review comprehensively presents the physiology, molecular mechanism, and genomics of desert plants aimed towards engineering a sustainable crop.
... Recent studies show that the global pCO 2 of the Middle Jurassic was higher than today and gradually increased during the Middle Jurassic interval (Berner, 1991(Berner, , 1994(Berner, , 1999Berner and Kothavala, 2001;Royer et al., 2001Royer et al., , 2004Hesselbo et al., 2003). Our investigation based on fossil Ginkgoites species suggests the palaeo-CO 2 levels about 1123 ppmv for the Middle Jurassic, comparable to the results obtained by McElwain and Chaloner (1996;Brachyphyllum crucis, 1248ppmv), McElwain (1998 Pagiophyllum ordinatum, 1098 ppmv), Chen et al. (2001;Ginkgoites huttonii, 1020 ppmv), Sun et al. (2007;G. ...
Fossils of Ginkgophyta are widely recognized as one better proxy to estimate Mesozoic and Cenozoic atmospheric CO2 levels. In this study, the fossil Ginkgoites species, Ginkgoites huttonii (Sternberg) Heer is described based on a collection from the Middle Jurassic (Bajocian) deposits in Northeast Iran. The palaeoatmospheric CO2 level during Middle Jurassic in Iran is estimated for the first time based on the stomatal ratio (SR) method using this plant fossil. We show that the palaeoatmospheric CO2 concentration was about 1123 ppmv as calculated from stomatal parameters measured in this study. A comparison of our results with previously reported geochemical models indicates close accordance with the GEOCARB II model for Middle Jurassic.
... Variations in pCO 2 of modern oceans during the last 50 years have caused temporal and spatial variations in calcite and aragonite saturation (Sulpis et al., 2018). Changes in ancient atmospheric CO 2 , oceanic pCO 2 and ocean saturations are well-documented (Berner, 1991(Berner, , 1997Berner & Kothavala, 2001) and can be caused by a variety of scenarios like variations in pelagic carbonate precipitation, global temperatures, continental glaciers, and oceanic circulation (Berner, 1974). Obviously, these factors can be closely related. ...
Abstract Cenozoic limestones from Hawaii and Enewetak were studied to characterise diagenesis in deep sea water. Hawaii samples were from subsea outcrops of drowned Pleistocene reefs 150–1,505 m deep (maximum age 550–600 ka). Most samples had early fibrous aragonite and high‐magnesium calcite cements precipitated in shallow sea water. Partial dissolution of aragonite (including coral) and high‐magnesium calcite were significant at 412 m and increased to 1,505 m. Crusts of ‘stubby’ sparry calcite cement (2–8 mol.% MgCO3; ‘lower Mg calcite’) precipitated on early aragonite and high‐magnesium calcite cements at 473–1,358 m. Dissolution of aragonite and high‐magnesium calcite was incomplete. Aragonite and high‐magnesium calcite were not neomorphosed to low‐magnesium calcite ( 1,000 m. Coralline algae showed little petrographic alteration, but Mg decreased downward from 15 to 1.5 mol.% MgCO3. In both areas, aragonite dissolution, alteration of high‐magnesium calcite, and precipitation of lower‐Mg calcite cements occurred in deep sea water (>300 m) undersaturated for aragonite, but supersaturated for low‐magnesium calcite. Original high‐magnesium calcite was partially dissolved in Hawaii samples, but converted to low‐magnesium calcite in deep Enewetak cores, possibly due to gradual deepening at Enewetak. Dolomitisation and low‐magnesium calcite dissolution occurred below the calcite saturation depth (approximately 1,000 m) in Enewetak, but not deep Hawaii samples, possibly because dolomitisation is slower. Temporal variations in carbonate saturation, especially related to pCO2, are interpreted as the main control on mineralogy during marine diagenesis now and in many ancient oceans.
... The fractions of total OC within intermediate reactivity bins, i ∈ [2,99], are calculated with the CDF: ...
Quantifying the organic carbon (OC) sink in marine sediments is crucial for assessing how the marine carbon cycle regulates Earth’s climate. However, burial efficiency (BE) – the commonly-used metric reporting the percentage of OC deposited on the seafloor that becomes buried (beyond an arbitrary and often unspecified reference depth) – is loosely defined, misleading, and inconsistent. Here, we use a global diagenetic model to highlight orders-of-magnitude differences in sediment ages at fixed sub-seafloor depths (and vice-versa), and vastly different BE’s depending on sediment depth or age horizons used to calculate BE. We propose using transfer efficiencies (Teff’s) for quantifying sediment OC burial: Teff is numerically equivalent to BE but requires precise specification of spatial or temporal references, and emphasizes that OC degradation continues beyond these horizons. Ultimately, quantifying OC burial with precise sediment-depth and sediment-age-resolved metrics will enable a more consistent and transferable assessment of OC fluxes through the Earth system.
... contribute to changes in the carbon cycle and hence contribute to changes in atmospheric CO 2 and global climate (Berner, 1991(Berner, , 2003(Berner, , 2004Sleep et al., 2012;Sleep & Zahnle, 2001;Walker et al., 1981). ...
Decades of research have resulted in characterization of the ocean floor manifestations of mid‐ocean ridge (MOR) hydrothermal systems, yet numerical models accounting for the connections between heat transfer, hydrology and geochemistry have been slow to develop. The Thermo‐hydro‐chemical code ToughReact can be used to describe the coupled effects of fluid flow, heat transfer, and fluid‐rock chemical interactions that occur in MOR systems. We describe the results of 2‐dimensional simulations of steady state flow in fractured diabase with mineral‐fluid chemical reactions. Basal heating and specified permeability yield maximum temperature of 400°C. Total fluid flux and high fracture flow velocities are in accord with observations. Fluid chemistry, mineralogical changes and ⁸⁷Sr/⁸⁶Sr ratios can be compared to observations to assess and calibrate models. Simulated high temperature fracture fluids have Mg and SO4 near zero, elevated Ca and ⁸⁷Sr/⁸⁶Sr of about 0.7040. Total alteration is 10%–50% for simple models of spreading. Anhydrite forms mainly near the base of the upwelling zone and results in substantial local fracture porosity reduction. A calibrated model is used to predict how Sr isotopes and other features of altered oceanic crust would be different in the Cretaceous (95 Ma) early Proterozoic (1,800 Ma) and Archean (3,800 Ma), when seawater may have had high Ca and Sr concentrations, lower pH, higher temperature, and lower Na, Mg, and SO4. The simulations are offered as a start on what ultimately may require a longer‐term community effort to better understand the role of MOR thermo‐hydro‐chemical systems in Earth evolution.
... The data were normalized to the erosion rates for the Miocene, rather than the Pliocene or Quaternary, in order to avoid the effect of extensive continental glaciation over the past ∼5 Myrs on the observed rate (Berner & Kothavala 2001). Erosion was assumed to affect silicate, organic carbon, and sulfide weathering, but not carbonate or sulfate weathering, as it seemed that elevation had little effect on carbonates and sulfates, which can readily dissolve in the subsurface (Berner & Berner 1987;Berner 1991Berner , 2006. ...
An oxygen-rich atmosphere is essential for complex animals. The early Earth had an anoxic atmosphere, and understanding the rise and maintenance of high O 2 levels is critical for investigating what drove our own evolution and for assessing the likely habitability of exoplanets. A growing number of techniques aim to reproduce changes in O 2 levels over the Phanerozoic Eon (the past 539 million years). We assess these methods and attempt to draw the reliable techniques together to form a consensus Phanerozoic O 2 curve. We conclude that O 2 probably made up around 5–10% of the atmosphere during the Cambrian and rose in pulses to ∼15–20% in the Devonian, reaching a further peak of greater than 25% in the Permo-Carboniferous before declining toward the present day. Evolutionary radiations in the Cambrian and Ordovician appear consistent with an oxygen driver, and the Devonian “Age of the Fishes” coincides with oxygen rising above 15% atm. ▪ An oxygen-rich atmosphere is essential for complex animals such as humans. ▪ We review the methods for reconstructing past variation in oxygen levels over the past 539 million years (the Phanerozoic Eon). ▪ We produce a consensus plot of the most likely evolution of atmospheric oxygen levels. ▪ Evolutionary radiations in the Cambrian, Ordovician, and Devonian periods may be linked to rises in oxygen concentration.
Expected final online publication date for the Annual Review of Earth and Planetary Sciences, Volume 51 is May 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
... The data were normalized to the erosion rates for the Miocene, rather than the Pliocene or Quaternary, in order to avoid the effect of extensive continental glaciation over the past ∼5 Myrs on the observed rate (Berner & Kothavala 2001). Erosion was assumed to affect silicate, organic carbon, and sulfide weathering, but not carbonate or sulfate weathering, as it seemed that elevation had little effect on carbonates and sulfates, which can readily dissolve in the subsurface (Berner & Berner 1987;Berner 1991Berner , 2006. ...
... Functionally, this returns tending towards 0.25 when biomass is very low, and a linear scaling with NPP when biomass rises. The choice of 0.25 relates to the four-fold enhancement between simple ground covers and higher plants used in rst-generation long-term carbon cycle models such as GEOCARB 62,63 , and based on eld and laboratory studies 37 . We vary this 'preplant' factor between 0.15 -1 in the SI and modify the linear scaling to account for this. ...
The Permian–Triassic Mass Extinction (PTME), life’s most severe crisis1, has been attributed to intense global warming triggered by CO2 emissions from Large Igneous Province volcanism2–8. It remains unclear, however, why super-greenhouse conditions persisted for around five million years after the volcanic episode, when Earth system feedbacks should have returned temperatures to pre-extinction levels within a few hundred thousand years8. Here we use fossil occurrences and lithological indicators of climate to reconstruct spatio-temporal maps of plant productivity and biomass changes through the Permian–Triassic and undertake climate-biogeochemical modelling to investigate the unusual longevity and intensity of warming. Our reconstructions show that terrestrial vegetation collapse during the PTME, especially in tropical regions, resulted in an Earth system with low levels of organic carbon sequestration and chemical weathering, leading to limited drawdown of greenhouse gases. This led to a protracted period of extremely high surface temperatures, during which biotic recovery was delayed for millions of years. Our results support the idea that thresholds exist in the climate-carbon system beyond which warming may be amplified substantially.
... A variety of evolutionary innovations in the ecophysiology of land plants and other components of the terrestrial biota are proposed to have been transformative for the carbon cycle as the relevant clade became widespread and ecologically dominant, but how the carbon cycle can be transformed is highly constrained. The reaction of silicate minerals and CO 2 -both introduced to Earth's surface via volcanismforms clays and releases ions to solution to be later precipitated as marine carbonates (Berner 1991). This net chemical weathering reaction modulates atmospheric CO 2 concentration and regulates Earth's climate over geological time (Urey 1952). ...
Evolutionary events may impact the geological carbon cycle via transient imbalances in silicate weathering, and such events have been implicated as causes of glaciations, mass extinctions, and oceanic anoxia. However, suggested evolutionary causes often substantially predate the environmental effects to which they are linked—problematic when carbon cycle perturbations must be resolved in less than a million years to maintain Earth's habitability. What is more, the geochemical signatures of such perturbations are recorded as they occur in widely distributed marine sedimentary rocks that have been densely sampled for important intervals in Earth history, whereas the fossil record—particularly on land—is governed by the availability of sedimentary basins that are patchy in both space and time, necessitating lags between the origination of an evolutionary lineage and its earliest occurrence in the fossil record. Here, we present a simple model of the impact of preservational filtering on sampling to show that an evolutionary event that causes an environmental perturbation via weathering imbalance should not appear earlier in the rock record than the perturbation itself and, if anything, should appear later rather than simultaneously. The Devonian Hangenberg glaciation provides an example of how evolutionary events might be more fruitfully considered as potential causes of environmental perturbations. Just as the last samplings of species lost in mass extinction are expected to come before the true environmental event, first appearance should be expected to postdate the geological expression of a lineage's environmental impact with important implications for our reading of Earth history.
... This results in a skewing of the Monte Carlo simulation, generating a modeled Earth system with higher CO 2 and thus temperature (see fig. S2), earlier in the Cretaceous, than would otherwise be predicted if NEOCARBSULF used the sea-level inversion degassing rates from previous GEOCARB(SULF) modeling (38,48,60). ...
Mapping the history of atmospheric O2 during the late Precambrian is vital for evaluating potential links to animal evolution. Ancient O2 levels are often inferred from geochemical analyses of marine sediments, leading to the assumption that the Earth experienced a stepwise increase in atmospheric O2 during the Neoproterozoic. However, the nature of this hypothesized oxygenation event remains unknown, with suggestions of a more dynamic O2 history in the oceans and major uncertainty over any direct connection between the marine realm and atmospheric O2. Here, we present a continuous quantitative reconstruction of atmospheric O2 over the past 1.5 billion years using an isotope mass balance approach that combines bulk geochemistry and tectonic recycling rate calculations. We predict that atmospheric O2 levels during the Neoproterozoic oscillated between ~1 and ~50% of the present atmospheric level. We conclude that there was no simple unidirectional rise in atmospheric O2 during the Neoproterozoic, and the first animals evolved against a backdrop of extreme O2 variability.
... The uncertainty in global runoff ( Fig. 2A) is derived from an ensemble of model runs where the degassing rates are varied between different recent estimates (Brune et al., 2017;Mills et al., 2019) and the contribution of land plants to amplifying weathering rates is varied between no change and a 7-fold increase (e.g. Berner, 1991;Lenton, 2001). Other sources of uncertainty, not quantified here, are other global processes that have uncertainty and will impact the CO 2 level, such as continental lithology or organic carbon cycle imbalance. ...
Global mean sea level is a key component within the fields of climate and oceanographic modelling in the Anthropocene. Hence, an improved understanding of eustatic sea level in deep time aids in our understanding of Earth’s paleoclimate and may help predict future climatological and sea level changes. However, long-term eustatic sea level reconstructions are hampered because of ambiguity in stratigraphic interpretations of the rock record and limitations in plate tectonic modelling. Hence the amplitude and timescales of Phanerozoic eustasy remains poorly constrained. A novel, independent method from stratigraphic or plate modelling methods, based on estimating the effect of plate tectonics (i.e., mid-ocean ridge spreading) from the ⁸⁷Sr/⁸⁶Sr record led to a long-term eustatic sea level curve, but did not include glacio-eustatic drivers. Here, we incorporate changes in sea level resulting from variations in seawater volume from continental glaciations at time steps of 1 Myr. Based on a recent compilation of global average paleotemperature derived from δ¹⁸O data, paleo-Köppen zones and paleogeographic reconstructions, we estimate ice distribution on land and continental shelf margins. Ice thickness is calibrated with a recent paleoclimate model for the late Cenozoic icehouse, yielding an average ∼1.4km thickness for land ice, ultimately providing global ice volume estimates. Eustatic sea level variations associated with long-term glaciations (> 1 Myr) reach up to ∼90m, similar to, and is at times dominant in amplitude over plate tectonic-derived eustasy. We superimpose the long-term sea level effects of land ice on the plate tectonically driven sea level record. This results in a Tectono-Glacio-Eustatic (TGE) curvefor which we describe the main long-term (>50 Myr) and residual trends in detail.
... Furthermore, the annual atmospheric CO 2 consumed by chemical weathering of silicate rocks is 0.133-0.169 Pg C yr −1 (Berner, 1991(Berner, , 1994(Berner, , 2004(Berner, , 2006Berner et al., 1983;Berner & Kothavala, 2001;Gaillardet et al., 1999;Hartmann et al., 2009;Moon et al., 2014;Suchet et al., 2003;Suchet & Probst, 1995;Zhang et al., 2021a). ...
The Carbonate rock weathering Carbon Sink (CCS) and Silicate rock weathering Carbon Sink (SCS) play a significant role in the carbon cycle and global climate change. However, the spatial‐temporal patterns and trends of the CCS and SCS from 1950 to 2099 have not been systematically quantified. Thus, Supported by long‐term hydrometeorological data under the RCP8.5, we use the accepted Suchet and Hartmann models to determine the following. First, we found except for the difference in their weathering rates, the SCS covers 37.2 million km² more area than the CCS. The CCS Flux (CCSF) and SCS Flux (SCSF) are 5.36 and 1.22 t/km²/yr, respectively. Similarly, the Full CCS (FCCS, 0.3 Pg/yr) is more than the Full SCS (FSCS, 0.08 Pg/yr). Furthermore, the CCS (7.01 kg/km²) and SCS (3.95 kg/km²) are in a state of overall increase. In addition, the mid‐to‐high latitudes of the northern hemisphere are aggravated by warming (0.03°C) and humidity (0.65 mm), while the decrease in runoff in the mid‐latitudes of the southern hemisphere reduces karstification. Specifically, by 2099, the CCSF in the mid‐latitudes of the southern hemisphere will decrease by 5.72%. Instead, the CCSF in the northern hemisphere and lower latitudes of the southern hemisphere will exhibit a gentle upward slope. Particularly, the peak regions of the global FCCS (65.63 Tg/yr) and FSCS (33.01 Tg/yr) are the tropical zone. In conclusion, this study contributes a high‐resolution and long‐time series CS datasets for the CCS and SCS. We provide data and a theory for solving terrestrial carbon sink loss.
... rock weathering and the deposition of organic material). Modeling has clearly indicated large variations in CO 2 concentrations throughout Phanerozoic time, with high concentrations through most of the Paleozoic, with a drop during the Devonian and Carboniferous, relatively high values during the early Mesozoic, and then low values again in the Cenozoic (Berner, 1991(Berner, , 1994(Berner, , 2001. The CO 2 curve calculated for the past 500 Ma matches the climate record at several key pointsit is low during the ice ages of the Carboniferous and Permian and rises to a maximum during the much warmer climate of the Cretaceous, perhaps warmer on a global basis than at any other time during the Phanerozoic when the temperature difference between the poles and the Equator was about half that at present. ...
This review summarizes the stable isotope composition of the gases and aerosols comprising the Earth's atmosphere. Recent technical progress in analytical methodologies has enabled analysis the H- and O-isotopic composition of water vapor by remote sensing, precise measurement of the rare isotopes ¹⁷O, ³³S and ³⁶S, the recognition of mass-independent isotope fractionations, and determination of the stable isotope composition of volatile metals in aerosols. Together these approaches have resulted in new insights into atmospheric processes and permitted the delineation of atmospheric constituents derived from natural versus anthropogenic sources. Ice core analysis has demonstrated that the isotope composition of the atmosphere has changed continuously as a consequence of both past climate cycles and more recently because of fossil fuel and other anthropogenic emissions. Isotope proxies and geochemical modeling have recognized that the nature of the atmosphere has varied throughout geologic history and will continue to do so in the near future.
... L'altération des roches à la surface du globe possède une place importante dans le cycle long du carbone (³ 10 6 ans). Au cours des temps géologiques, l'altération chimique des continents a joué un rôle important dans la régulation des teneurs en CO2 de l'atmosphère (Walker et al., 1981 ;Berner, 1991, atmosphérique). L'abondance relative des phases minérales altérées, leur altérabilité, va conditionner les effets de l'altération sur les teneurs en CO2 atmosphérique. ...
Les risques gravitaires sont à l’origine de catastrophes importantes pouvant engendrer des dégâts matériels et humains, ils sont aussi l’un des mécanismes principaux de dénudation des chaines de montagne. Il est maintenant clairement établi qu’il existe un lien entre l’instabilité gravitaire et l’eau qu’elle reçoit. La compréhension du fonctionnement des aquifères de milieux instables est d’une importance fondamentale dans l’étude de ces structures complexes dont la déstabilisation implique des enjeux considérables. C’est dans cet esprit que cette thèse s’intéresse à la relation entre le milieu instable et les écoulements souterrains du versant de Séchilienne (Isère, France). Ce travail vise à caractériser dans un premier temps le fonctionnement hydrogéologique de l’aquifère du milieu instable au travers de l’analyse de deux exutoires au sein de l’instabilité. L’utilisation de données hydrogéologiques recueillies sur le long terme permet une analyse temporelle fournissant de bonnes informations sur le fonctionnement, le dynamisme et la recharge de l’aquifère à plusieurs échelles allant du cycle hydrologique à l’année. Les analyses corrélatoires se révèlent être un bon outil quant à la compréhension du fonctionnement hydrodynamique de l’aquifère. L’apport de la chimie des eaux, est essentielle à l’identification des signatures hydrochimiques caractérisant le versant. Elle permet par ailleurs d’obtenir des informations sur l’état d’altération du versant, la composition chimique des eaux dépendant des interactions eau-roche. L’analyse comparative des deux exutoires au sein de l’instabilité couplée à l’analyse d’un exutoire de la zone stable reflète l’hétérogénéité des milieux instables et fracturés. Ce travail s’axe dans une deuxième partie, sur le couplage entre traceurs isotopiques et chimie des éléments majeurs, afin de préciser l’amplitude des réactions d’altération chimique des phases minérales induites par les interactions eau-roches à l’intérieur du versant. L’utilisation d’un modèle de mélange permet d'attribuer les différents éléments majeurs à différentes sources et de quantifier l'implication des acides sulfurique et carbonique comme source de protons. Les résultats montrent que l'instabilité crée des conditions favorables et durables au sein de la rupture, par l'ouverture de nouvelles fractures apportant des surfaces fraîches et réactives permettant la production d'acide sulfurique par oxydation de la pyrite. Les résultats obtenus permettent d’autre part d’affiner le modèle hydrogéologique préexistant par la mise en évidence de la contribution de la dissolution du gypse au budget sulfate des eaux. L’originalité de ce travail réside également dans nos résultats qui montrent le comportement du glissement de terrain de Séchilienne qui, malgré son rôle dans l'accélération de l'altération chimique et physique des roches, agit à l’échelle des temps géologiques (c'est-à-dire à des échelles de temps plus longues que les précipitations de carbonate dans l'océan) comme une source de CO2 dans l'atmosphère.
The rotation of the Earth and the related length of the day (LOD) are predominantly affected by tidal dissipation through the Moon and the growth of the Earth's core. Due to the increased concentration of mass around the rotation axis of the spinning Earth during the growth of the core the rotation should have been accelerated. Controversially the tidal dissipation by the Moon, which is mainly dependent on the availability of open shallow seas and the kind of Moon escape from a nearby position, acts towards a deceleration of the rotating Earth. Measurements of LOD for Phanerozoic and Precam-brian times open ways to solve questions concerning the geodynamical history of the Earth. These measurements encompass investigations of growth patterns in fossils and depositional patterns in sediments (Cyclostratigraphy, Tidalites, Stromatolites, Rhythmites). These patterns contain information on the LOD and on the changing distance between Earth and Moon and can be used as well for a discussion about the growth of the Earth's core. By updating an older paper with its simple approach as well as incorporating newly published results provided by the geoscientific community, a moderate to fast growth of the core in a hot early Earth will be favored controversially to the assumption of a delayed development of the core in an originally cold Earth. Core development with acceleration of Earth's rotation and the contempora-neous slowing down due to tidal dissipation during the filling of the ocean may significantly interrelate.
Silicate weathering, which is of great importance in regulating the global carbon cycle, has been found to be affected by complicated factors, including climate, tectonics and vegetation. However, the exact transfer function between these factors and the silicate weathering rate is still unclear, leading to large model–data discrepancies in the CO2 consumption associated with silicate weathering. Here we propose a simple parameterization for the influence of vegetation cover on erosion rate to improve the model–data comparison based on a state-of-the-art silicate weathering model. We found out that the current weathering model tends to overestimate the silicate weathering fluxes in the tropical region, which can hardly be explained by either the uncertainties in climate and geomorphological conditions or the optimization of model parameters. We show that such an overestimation of the tropical weathering rate can be rectified significantly by parameterizing the shielding effect of vegetation cover on soil erosion using the leaf area index (LAI), the high values of which are coincident with the distribution of leached soils. We propose that the heavy vegetation in the tropical region likely slows down the erosion rate, much more so than thought before, by reducing extreme streamflow in response to precipitation. The silicate weathering model thus revised gives a smaller global weathering flux which is arguably more consistent with the observed value and the recently reconstructed global outgassing, both of which are subject to uncertainties. The model is also easily applicable to the deep-time Earth to investigate the influence of land plants on the global biogeochemical cycle.
We present Earth's Oxygenation and Natural Systematics (EONS): a new, fully coupled biogeochemical model of the atmosphere, ocean, and their interactions with the geosphere, which can reproduce major features of Earth's evolution following the origin of life to the present day. The model, consisting of 257 unique fluxes between 96 unique chemical reservoirs, includes an interactive biosphere, cycles of carbon, nitrogen, phosphorus, and oxygen, and climate. A nominal model run initialized in the Eoarchean resolves emergent surface oxygenation, nutrient limitations, and climate feedbacks. The modeled atmosphere oxygenates in stepwise fashion over the course of the Proterozoic; a nearly billion year lag after the evolution of photosynthesis at 3.5 Ga is followed by a great oxidation event at 2.4 Ga, which appears to be caused by the gradual buildup of organic matter on the continents imposing nutrient limitation on the biosphere by removing key nutrients from the ocean system. The simple climate system shows significant temperature shifts punctuate the oxygenation process, implying that major biological transitions possibly destabilized Earth's climate. This work demonstrates that forward modeling the entirety of Earth's history with relatively few imposed boundary forcings is feasible, that the Earth system is not at steady state, and that our understanding of coupled C‐N‐P‐O cycling as it functions today can explain much of the Earth's evolution.
Earth’s long-term climate is driven by the cycling of carbon between geologic reservoirs and the atmosphere-ocean system. Our understanding of carbon-climate regulation remains incomplete, with large discrepancies remaining between biogeochemical model predictions and the geologic record. Here, we evaluate the importance of the continuous biological climate adaptation of vegetation as a regulation mechanism in the geologic carbon cycle since the establishment of forest ecosystems. Using a model, we show that the vegetation’s speed of adaptation to temperature changes through eco-evolutionary processes can strongly influence global rates of organic carbon burial and silicate weathering. Considering a limited thermal adaptation capacity of the vegetation results in a closer balance of reconstructed carbon fluxes into and out of the atmosphere-ocean system, which is a prerequisite to maintain habitable conditions on Earth’s surface on a multimillion-year timescale. We conclude that the long-term carbon-climate system is more sensitive to biological dynamics than previously expected, which may help to explain large shifts in Phanerozoic climate.
Keteleeria Carrière (Pinaceae) is a small genus of evergreen conifer trees, with three to five extant species and six variants distributed across China, Laos, and Vietnam. A new species of conifer fossil wood, Keteleeria huolinhensis sp. nov., is described in the Lower Cretaceous Huolinhe Formation in Inner Mongolia, China. This species is characterized by a heterogeneous pith, endarch primary xylem, the presence of axial resin canals, abietinean radial tracheid pitting, mostly taxodioid and occasionally cupressoid cross-field pitting, nodular horizontal and end walls of ray parenchyma cells, and uniseriate rays of 1–15 (mainly 1–8) cell height. This newly discovered fossil wood represents the earliest record of Keteleeria wood, and sheds light on its evolutionary history and palaeogeographical distribution range of the genus Keteleeria. Cladistic analysis based on 12 morphological characteristics supports the assignment of Protopiceoxylon as the ancestral group of Keteleerioxylon and Keteleeria, reflecting the evolution of radial tracheid pitting from the mixed to abietinean type. Quantitative analysis of the growth rings indicated that K. huolinhensis sp. nov. is an evergreen tree with a Leaf Retention Time (LRT) of 1–3 years. The growth ring patterns in the present fossil wood specimen suggest that the Huolinhe Basin experienced a temperate climate with regular seasonal fluctuations, and relatively sufficient water supply during the Early Cretaceous. Traumatic resin canals, wound scars, presumed fungal remains, and insect tracks in the stem contribute to a further understanding of the complex ecological relationships in the Early Cretaceous Huolinhe flora.
Mammals have dominated Earth for approximately 55 Myr thanks to their adaptations and resilience to warming and cooling during the Cenozoic. All life will eventually perish in a runaway greenhouse once absorbed solar radiation exceeds the emission of thermal radiation in several billions of years. However, conditions rendering the Earth naturally inhospitable to mammals may develop sooner because of long-term processes linked to plate tectonics (short-term perturbations are not considered here). In ~250 Myr, all continents will converge to form Earth’s next supercontinent, Pangea Ultima. A natural consequence of the creation and decay of Pangea Ultima will be extremes in $$p_{\mathrm{CO}_2}$$ p CO 2 due to changes in volcanic rifting and outgassing. Here we show that increased $$p_{\mathrm{CO}_2}$$ p CO 2 , solar energy ( F ⨀ ; approximately +2.5% W m ⁻ ² greater than today) and continentality (larger range in temperatures away from the ocean) lead to increasing warming hostile to mammalian life. We assess their impact on mammalian physiological limits (dry bulb, wet bulb and Humidex heat stress indicators) as well as a planetary habitability index. Given mammals’ continued survival, predicted background $$p_{\mathrm{CO}_2}$$ p CO 2 levels of 410–816 ppm combined with increased F ⨀ will probably lead to a climate tipping point and their mass extinction. The results also highlight how global landmass configuration, $$p_{\mathrm{CO}_2}$$ p CO 2 and F ⨀ play a critical role in planetary habitability.
A rigorous examination of empirical data confirms the fact that there is no threat from CO2 to People. Fossil Fuels (i.e., Oil, Natural Gas, and Coal) are the underpinning of modern living in the 21stcentury and that CO2 is essential for the thriving of both People and Plants. The geologic record shows that the Earth’s climate has always been changing naturally during the past 600 million years in terms CO2 and temperature, without CO2 emissions from Fossil Fuels by humans. Aplot of CO2vs. Temperature for the last 600 million years shows basically no correlation for most of this time (Berner, 2004; Scotese et al., 2021). If the Net-Zero CO2 policy were to be implemented in 2050, large numbers of people would die and the modern human civilization would come to a sudden halt, and humans left alive would have to revert back to the lifestyles of the Neanderthals. A climate-change model for 200 years (1900─2100) is proposed based on four basic parameters, namely, CO2, Temperature, Population, and GDP (gross domestic product) per capita. In this model, calculations based on the Max Planck’s Curve by Van Wijngaarden and Happer (2020), an increase in Temperature by 2100 would be trivial even if CO2 is nearly doubled in value to 800 ppm. The CO2 in the atmosphere helps not only to modulate the Earth’s Temperature suitable for human survival, but also to enhance Global Greening.
Iron (Fe) is an essential element for life, and its geochemical cycle is intimately linked to the coupled history of life and Earth's environment. The accumulated geologic records indicate that ferruginous waters existed in the Precambrian oceans not only before the first major rise of atmospheric O2 levels (Great Oxidation Event; GOE) during the Paleoproterozoic, but also during the rest of the Proterozoic. However, the interactive evolution of the biogeochemical cycles of O2 and Fe during the Archean-Proterozoic remains ambiguous. Here, we develop a biogeochemical model to investigate the coupled biogeochemical evolution of Fe-O2 -P-C cycles across the GOE. Our model demonstrates that the marine Fe cycle was less sensitive to changes in the production rate of O2 before the GOE (atmospheric pO2 < 10-6 PAL; present atmospheric level). When the P supply rate to the ocean exceeds a certain threshold, the GOE occurs and atmospheric pO2 rises to ~10-3 -10-1 PAL. After the GOE, the marine Fe(II) concentration is highly sensitive to atmospheric pO2 , suggesting that the marine redox landscape during the Proterozoic may have fluctuated between ferruginous conditions and anoxic non-ferruginous conditions with sulfidic water masses around continental margins. At a certain threshold value of atmospheric pO2 of ~0.3% PAL, the primary oxidation pathway of Fe(II) shifts from the activity of Fe(II)-utilizing anoxygenic photoautotrophs in sunlit surface waters to abiotic process in the deep ocean. This is accompanied by a shift in the primary deposition site of Fe(III) hydroxides from the surface ocean to the deep sea, providing a plausible mechanistic explanation for the observed cessation of iron formations during the Proterozoic.
Data were obtained from the literature to identify past changes in and the present status of the coastal carbon cycle. They indicate that marine coastal ecosystems driving the coastal carbon cycle cover, on average, 5.8% of the Earth’s surface and contributed 55.2% to carbon transport from the climate-active carbon cycle to the geological carbon cycle. The data suggest that humans not only increase the CO 2 concentration in the atmosphere but also mitigate (and before 1860 even balanced) their CO 2 emissions by increasing CO 2 storage within marine coastal ecosystems. Soil degradation in response to the expansion and intensification of agriculture is assumed to be a key process driving the enhanced CO 2 storage in marine coastal ecosystems because it increases the supply of lithogenic matter that is known to favour the burial of organic matter in sediments. After 1860, rising CO 2 concentrations in the atmosphere indicate that enhanced CO 2 emissions caused by land-use changes and the burning of fossil fuel disturbed what was a quasi-steady state before. Ecosystem restoration and the potential expansion of forest cover could mitigate the increase of atmospheric CO 2 concentrations, but this carbon sink to the atmosphere is much too weak to represent an alternative to the reduction of CO 2 emission in order to keep global warming below 1.5–2.°C. Although the contribution of benthic marine coastal ecosystems to the global CO 2 uptake potential of ecosystem restoration is only around 6%, this could be significant given national carbon budgets. However, the impact on climate is still difficult to quantify because the associated effects on CH 4 and N 2 O emissions have not been established. Addressing these uncertainties is one of the challenges faced by future research, as are related issues concerning estimates of carbon fluxes between the climate-active and the geological carbon cycle and the development of suitable methods to quantify changes in the CO 2 uptake of pelagic ecosystems in the ocean.
The geologic record shows that the Earth’s climate has always been changing naturally during the past 600 million years in terms of CO2 and temperature, without CO2 emissions from Fossil Fuels by humans. There were both warming and cooling periods prior to the appearance of human beings on the Planet Earth. The Anthropogenic Global Warming (AGW) is attributed to the Industrial Age that commenced in 1760 in the Great Britain and later in the USA. The principal driver behind the Industrial Revolution has been Fossil Fuels (i.e., Oil, Natural Gas, and Coal). Since 1900, Fossil Fuels have been the single most important driver of the modern human civilization. If the Net–Zero CO2 policy were to be implemented, large numbers of people would die and the modern human civilization would come to a sudden halt, and humans left alive would have to revert back to the lifestyles of the Neanderthals who lived 40,000 years ago without the benefits of Fossil Fuels. The failure of the Net–Zero policy is already evident by (1) the Germany’s shift back to coal from unreliable wind to face the energy crisis caused by the Russia-Ukraine War on 24th February 2022, (2) the bankruptcy of Sri Lanka in 2022 caused by the ESG (Environmental, Social, and Governance) policy that banned chemical fertilizers, and (3) the major victory by the Dutch pro-farmers party (BBB) in the 2023 provincial elections in opposition to the Dutch government’s climate policy to eliminate nitrogen emissions by reducing 30% of livestocks in the Netherlands. A climate-change model for 200 Years (1900–2100) is proposed based on four basic parameters, namely, CO2, Temperature, Population, and GDP per capita. The model shows a steady increase in all four parameters from 1900 to 2100. In this model, calculations based on the Max Planck’s Curve by Van Wijngaarden and Happer (2020), an increase in CO2 and Temperature by 2100 would be trivial and that would not hinder either the population growth or the GDP growth. Therefore, Climate Change is not an existential threat. The proposed road-map for the future is to continue to use the Fossil Fuels as usual. The ultimate driver of the Earth’s climate is the omnipotent Sun, not humans. The CO2 in the atmosphere helps not only to modulate the Earth’s Temperature suitable for human survival, but also to enhance Global Greening. Therefore, we should shift our resources and attention away from Global Warming and aim towards eliminating Global Poverty.
Secular variations in the major ion chemistry and isotopic composition of seawater on multimillion-year time scales are well documented, but the causes of these changes are debated. Fluid inclusions in marine halite indicate that the Li concentration in seawater [Li+]SW declined sevenfold over the past 150 million years (Ma) from ~184 μmol/kg H2O at 150 Ma ago to 27 μmol/kg H2O today. Modeling of the lithium geochemical cycle shows that the decrease in [Li+]SW was controlled chiefly by long-term decreases in ocean crust production rates and mid-ocean ridge and ridge flank hydrothermal fluxes without requiring changes in continental weathering fluxes. The decrease in [Li+]SW parallels the 150 Ma increase in seawater Mg2+/Ca2+ and 87Sr/86Sr, and the change from calcite to aragonite seas, KCl to MgSO4 evaporites, and greenhouse to icehouse climates, all of which point to the importance of plate tectonic activity in regulating the composition of Earth's hydrosphere and atmosphere.
Background
Continental weathering plays an important role in regulating atmospheric CO 2 levels. Chemical weathering in glacial areas has become an intensely focused topic in the background of global change compared with other terrestrial weathering systems. However, research on the weathering of the glacial areas in the Yarlung Tsangpo River Basin (YTRB) is still limited.
Methods
In this article, the major ions of the Chaiqu and Niangqu catchments in the YTRB have been investigated to illustrate the chemical weathering rates and mechanisms of the glacier areas in the YTRB.
Results
Ca ²⁺ and HCO${}_{3}^{-}$ dominate the major ions of the Chaiqu and Niangqu rivers, accounting for about 71.3% and 69.2% of the TZ ⁺ of the Chaiqu (the total cations, TZ ⁺ = Na ⁺ + K ⁺ + Ca 2 + + Mg ²⁺ , in µeq/L), and about 64.2% and 62.6% of the TZ ⁺ of the Niangqu. A Monte Carlo model with six end-members is applied to quantitatively partition the dissolved load sources of the catchments. The results show that the dissolved loads of the Chaiqu and Niangqu rivers are mainly derived from carbonate weathering (accounting for about 62.9% and 79.7% of the TZ ⁺ , respectively), followed by silicate weathering (about 25.8% and 7.9% of the TZ ⁺ , respectively). The contributions of precipitation and evaporite to the Chaiqu rivers are about 5.0% and 6.2%, and those to the Niangqu rivers are about 6.3% and 6.2%. The model also calculated the proportion of sulfuric acid weathering in the Chaiqu and Niangqu catchments, which account for about 21.1% and 32.3% of the TZ ⁺ , respectively. Based on the results calculated by the model, the carbonate and silicate weathering rates in the Chaiqu catchment are about 7.9 and 1.8 ton km ⁻² a ⁻¹ , and in the Niangqu catchment, the rates are about 13.7 and 1.5 ton km ⁻² a ⁻¹ . The associated CO 2 consumption in the Chaiqu catchment is about 4.3 and 4.4 × 10 ⁴ mol km ⁻² a ⁻¹ , and about 4.3 and 1.3 × 10 ⁴ mol km ⁻² a ⁻¹ in the Niangqu catchment. The chemical weathering rates of the glacier areas in the YTRB show an increasing trend from upstream to downstream. Studying the weathering rates of glacier catchments in the Tibetan Plateau (TP) reveals that the chemical weathering rates of the temperate glacier catchments are higher than those of the cold glacier catchments and that lithology and runoff are important factors in controlling the chemical weathering of glacier catchments in the TP. The chemical weathering mechanisms of glacier areas in the YTRB were explored through statistical methods, and we found that elevation-dependent climate is the primary control. Lithology and glacial landforms rank second and third, respectively. Our results suggest that, above a certain altitude, climate change caused by tectonic uplift may inhibit chemical weathering. There is a more complex interaction between tectonic uplift, climate, and chemical weathering.
The advent of oxygenic photosynthesis represents the most prominent biological innovation in the evolutionary history of the Earth. The exact timing of the evolution of oxygenic photoautotrophic bacteria remains elusive, yet these bacteria profoundly altered the redox state of the ocean-atmosphere-biosphere system, ultimately causing the first major rise in atmospheric oxygen (O2 )-the so-called Great Oxidation Event (GOE)-during the Paleoproterozoic (~2.5-2.2 Ga). However, it remains unclear how the coupled atmosphere-marine biosphere system behaved after the emergence of oxygenic photoautotrophs (OP), affected global biogeochemical cycles, and led to the GOE. Here, we employ a coupled atmospheric photochemistry and marine microbial ecosystem model to comprehensively explore the intimate links between the atmosphere and marine biosphere driven by the expansion of OP, and the biogeochemical conditions of the GOE. When the primary productivity of OP sufficiently increases in the ocean, OP suppresses the activity of the anaerobic microbial ecosystem by reducing the availability of electron donors (H2 and CO) in the biosphere and causes climate cooling by reducing the level of atmospheric methane (CH4 ). This can be attributed to the supply of OH radicals from biogenic O2 , which is a primary sink of biogenic CH4 and electron donors in the atmosphere. Our typical result also demonstrates that the GOE is triggered when the net primary production of OP exceeds >~5% of the present oceanic value. A globally frozen snowball Earth event could be triggered if the atmospheric CO2 level was sufficiently small (<~40 present atmospheric level; PAL) because the concentration of CH4 in the atmosphere would decrease faster than the climate mitigation by the carbonate-silicate geochemical cycle. These results support a prolonged anoxic atmosphere after the emergence of OP during the Archean and the occurrence of the GOE and snowball Earth event during the Paleoproterozoic.
Riverine dissolved matter reflects geochemical genesis information, which is vital to understand and manage the water environment in a basin. The Ganjing River located in the hinterland of the Three Gorges Reservoir was systematically investigated to analyze the composition and spatial variation of riverine ions, probe the source and influencing factors, and assess the chemical weathering rates and CO2 consumption. The results showed that the total dissolved solid value (473.31 ± 154.87 mg/L) with the type of “HCO3−–Ca2+” was higher than that of the global rivers’ average. The hydrochemical parameters were relatively stable in the lower reservoir area of the Ganjing River, which was largely influenced by the backwater of Three Gorges Reservoir. The carbonate weathering source contributed 69.63% of TDS (Total dissolved solids), which generally dominated the hydrochemical characteristics. The contribution rates of atmospheric rainfall were relatively low and stable in the basin, with an average of 4.01 ± 1.28%. The average contribution rate of anthropogenic activities was 12.05% in the basin and even up to 27.80% in the lower reservoir area of the Ganjing River, which illustrated that the impoundment of Three Gorges Reservoir had brought great challenges to the water environment in the reservoir bay. The empirical power functions were tentatively proposed to eliminate the dilution effect caused by runoff discharge on the basis of previous studies. Accordingly, the rock weathering rate was calculated as 23.54 t/km2 in the Ganjing River Basin, which consumed atmospheric CO2 with a flux of 6.88 × 105 mol/y/km2. These results highlight the geochemical information of tributaries in the hinterland of the Three Gorges Reservoir, have significant implications for understanding the impact of impoundment, and provide data support for the integrated management of water resources in the Ganjing River Basin.
The third edition of Gordon Bonan's comprehensive textbook introduces an interdisciplinary framework to understand the interaction between terrestrial ecosystems and climate change. Ideal for advanced undergraduate and graduate students studying ecology, environmental science, atmospheric science, and geography, it reviews basic meteorological, hydrological, and ecological concepts to examine the physical, chemical, and biological processes by which terrestrial ecosystems affect and are affected by climate. This new edition has been thoroughly updated with new science and references. The scope has been expanded beyond its initial focus on energy, water, and carbon to include reactive gases and aerosols in the atmosphere. The new edition emphasizes the Earth as a system, recognizing interconnections among the planet's physical, chemical, biological, and socioeconomic components, and emphasizing global environmental sustainability. Each chapter contains chapter summaries and review questions, and with over 400 illustrations, including many in color, this textbook will once again be an essential student guide.
Over geological timescales, Earth’s atmospheric CO2 concentration is determined by the long-term carbon cycle. Here the principal CO2 sources are tectonic degassing and the weathering of carbonate or organic-rich rocks, and the sinks are the deposition of carbonate minerals and organic carbon in sediments. The global carbon cycle has a self-regulation mechanism because the weathering of silicate rocks, which provides key elements for marine carbonate formation, is temperature dependent and can remove more carbon when Earth’s CO2 levels and temperature rise. Nevertheless, changes in carbon inputs and outputs can drive substantial variation in CO2 levels over geological time, and this has been the most important factor controlling the long-term variations in global average surface temperature over the Phanerozoic. Therefore, reconstructing the long-term carbon cycle and Phanerozoic changes in atmospheric CO2 levels is an important area of geochemical research.
Earth system box models have traditionally been used to study the long-term carbon cycle and to understand what controls changes in CO2 concentration. Early box models, such as the GEOCARB and COPSE models, mathematically expressed the physical and chemical properties of the Earth’s surface in a dimensionless way, using a single box for the ocean or land surface and a single value for global temperature or rate of precipitation. These models succeeded in reconstructing some aspects of atmospheric CO2 variations during the Phanerozoic but were limited because they cannot represent Earth’s surface in 3D, so could not properly represent continental weathering processes. The GEOCLIM model improved on this method by using a large dataset of physical climate model simulations to approximate a 3D climate and land surface for a set of specific times in Earth’s history, which allowed it to evaluate weathering processes and simulate uplift-driven glaciation in the late Palaeozoic.
A further step was made in the SCION model to approximate between different continental maps and therefore run the 3D weathering functions continuously over geological time by a method of interpolation. The variations of Phanerozoic atmospheric CO2 levels predicted by the SCION model show the following major features: (1) High atmospheric CO2 content (>1000 ppm) from the Cambrian to Silurian period; (2) A significant decrease of atmospheric CO2 concentration in the carboniferous and a following recovery in the Permian; (3) Low atmospheric CO2 content in Jurassic; (4) A peak in CO2 concentration during the Cretaceous and a decline through the Cenozoic. However, the modelling results still show some inconsistencies with the proxy records of atmospheric CO2, such as a higher atmospheric CO2 prediction during the Palaeozoic and a lower atmospheric CO2 prediction during the Jurassic. Future work is needed to more accurately simulate the Earth’s carbon cycle in these models. This includes revising the plate tectonic and paleogeographic boundary conditions to modern standards, replacing the one-box ocean with a multi-box or 3D ocean component, distinguishing the more reactive silicate lithologies on the continental maps to better represent their influences on silicate weathering, and improving the expression of land plant evolution and biogeography.
The formation and dissolution of salt giants impacts ocean chemistry on thousand-million year timescales. Gypsum precipitation and weathering changes the oceanic calcium concentration with implications for the carbon cycle and global temperatures. However, the connectivity of salt giants with the global ocean is necessarily restricted, making the timing of Ca 2+ extraction and return more uncertain. Here we reconstruct the final phase of gypsum precipitation of the Late Miocene Mediterranean Salt Giant using micropaleontology, sedimentology and 87 Sr/ 86 Sr analyses on the most complete record preserved at Eraclea Minoa on Sicily and explore its implications for global climate. Precessional gypsum-marl couplets (Upper Gypsum) characterize the last 200 kyrs (Stage 3) of the Messinian Salinity Crisis (MSC; 5.97-5.332 Ma) in both intermediate (500-1000 m) and deep (>1000 m) Mediterranean basins. The interbedded selenitic gypsum layers contain well-preserved calcareous nannofossil assemblages dominated by Reticulofenestra minuta, a marine species which tolerates stressful conditions. Marine water is also required to explain the gypsum 87 Sr/ 86 Sr data, which describe a small range of ratios (0.708704-0.708813) lower than coeval ocean water. Mass-balance calculations indicate that during gypsum precipitation, the Atlantic made up ≤20% of a Mediterranean ("Lago-Mare") water mass dominated by low salinity discharge from large river systems and Eastern Paratethys. This suggests episodic extraction of calcium and sulfate ions from the ocean throughout MSC Stage 3. The marls commonly contain shallow (30-100 m) brackish-water ostracods of Paratethyan (Black Sea) origin. Marls with Paratethyan ostracods are also found in both marginal (<500 m) and deep Mediterranean settings. This indicates that marl-deposition was not synchronous across the basin, but that it occurred in intermediate and deep basins during base-level lowstands at insolation minima and on the shallow Mediterranean margins during insolation maxima-driven highstands. These high-amplitude base-level fluctuations exposed the evaporites to weathering, but ponded the products in the Mediterranean basin until reconnection occurred at the beginning of the Pliocene.
Earth’s climate history is important for understanding the dynamics and feedbacks of the climate system. However, atmospheric sciences generally focus on shorter timescales, while geological sciences focus on longer timescales, but a unified picture is desired. This paper reviews the observations of Earth’s climate history from 4.5 billion years to one minute with emphasis on temperature, sea level, and atmospheric carbon dioxide. Earth’s climate history shows dominant climate modes such as the supercontinent cycles, interglacial cycles, millennial cycles, multi-decadal oscillation, interannual oscillation, seasonal cycle and diurnal cycle. The amplitudes of the dominant climate variability generally decrease from the billion-year timescales to interannual timescales, then significantly increase at subannual to diurnal timescales.
Paleoclimate reconstruction of continental environments has been hampered by the limited evidence. A thick sequence of Jurassic continental deposits in the Sichuan Basin, Southwest China yields abundant paleosols that may offer valuable insights regarding Jurassic climate scenarios. A succession of 169 paleosols belonging to Protosols, Calcisols, and Argillisols from 23 detailed stratigraphic sections was recognized and characterized macro‐ and micromorphologically and assessed for mineral and geochemical compositions. Quantitative paleoclimate reconstructions using bulk geochemical proxies, the depth to and the stable oxygen isotopic composition of paleosol carbonates indicated a predominant alternation of semiarid and arid cool/warm–temperate climatic conditions punctuated by several episodes of subhumid and humid climates that generally prevailed in the Sichuan Basin during the Jurassic. The estimated paleoatmospheric CO2 concentrations (pCO2) from calcic paleosols yielded a low range of ~104±58 – ~610±152 ppmv during the Middle Jurassic. The terrestrial paleotemperature changes in the Sichuan Basin coincided with the pCO2 variations, which probably resulted from global geological events (e.g., volcanic activities, magmatic and oceanic events, and the ephemeral caps development) in the Middle Jurassic. Jurassic climatic fluctuations in the basin were likely attributed to true polar wander due to global plate motion, megamonsoon effect linked to global and regional paleogeography, and regional paleotopography.
Location, specific topography, and hydrographic setting together with climate change and strong anthropogenic pressure are the main factors shaping the biogeochemical functioning and thus also the ecological status of the Baltic Sea. The recent decades have brought significant changes in the Baltic Sea. First, the rising nutrient loads from land in the second half of the 20th century led to eutrophication and spreading of hypoxic and anoxic areas, for which permanent stratification of the water column and limited ventilation of deep-water layers made favourable conditions. Since the 1980s the nutrient loads to the Baltic Sea have been continuously decreasing. This, however, has so far not resulted in significant improvements in oxygen availability in the deep regions, which has revealed a slow response time of the system to the reduction of the land-derived nutrient loads. Responsible for that is the low burial efficiency of phosphorus at anoxic conditions and its remobilization from sediments when conditions change from oxic to anoxic. This results in a stoichiometric excess of phosphorus available for organic-matter production, which promotes the growth of N2-fixing cyanobacteria and in turn supports eutrophication.
This assessment reviews the available and published knowledge on the
biogeochemical functioning of the Baltic Sea. In its content, the paper
covers the aspects related to changes in carbon, nitrogen, and phosphorus (C, N, and P) external loads, their transformations in the coastal zone, changes in organic-matter production (eutrophication) and remineralization (oxygen availability), and the role of sediments in burial and turnover of C, N, and P. In addition to that, this paper focuses also on changes in the marine CO2 system, the structure and functioning of the microbial community, and the role of contaminants for biogeochemical processes. This comprehensive assessment allowed also for identifying knowledge gaps and future research needs in the field of marine biogeochemistry in the Baltic Sea.
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