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Locations of Hulu, Sanbao, and Dongge Caves (a), monthly precipitation and average air temperature at Nanjing City from 1981 to 2010 (http://data.cma.cn) (b), and schematic map of Hulu Cave (c). The positions of drip sites (black dots) and stalagmite HL162 (black star) are shown in (c).
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A precisely ²³⁰ Th-dated stalagmite δ ¹³ C profile from Hulu Cave, China, is presented to characterize the frequency and pattern of millennial-scale Asian monsoon (AM) variability from 160.6 to 132.5 ka. Evidence for an antiphased relationship of the δ ¹³ C and δ ¹⁸ O on the millennial scale suggests that the δ ¹³ C is indicative of the local hydro...
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... In some cases, stalagmite δ 13 C may respond to millennial climate changes more sensitively than stalagmite δ 18 O. The oxygen and carbon isotope records of stalagmites in China show millennial-time-scale oscillations, for instance, some records from Hulu Cave [20,22]. Other records from stalagmites in southern China show that the amplitude of millennial-time-scale events recorded by δ 13 C is twice as large as that of the δ 18 O record during the last two glacial cycles [22,23]. ...
... The oxygen and carbon isotope records of stalagmites in China show millennial-time-scale oscillations, for instance, some records from Hulu Cave [20,22]. Other records from stalagmites in southern China show that the amplitude of millennial-time-scale events recorded by δ 13 C is twice as large as that of the δ 18 O record during the last two glacial cycles [22,23]. The structural characteristics of D-O (Dansgaard-Oeschger) events documented in stalagmite δ 13 C are more similar to the record of the NGRIP (North GRIP) ice core than the δ 18 O stalagmite record [18,24]. ...
Speleothem δ13C in monsoonal China differs from speleothem δ18O, which is widely used as a climatic proxy for several complex control reasons. Nevertheless, δ13C records have the potential to reveal the implications of hydroclimatic changes. This study reports a speleothem δ13C record from Didonghe (DDH) Cave in central China spanning 34 to 13 kyr BP. After we investigated the factors that influence speleothem δ13C, we found that the δ13C record showed that DDH Cave can prompt directional shifts via local hydroclimatic changes, such as in vegetation types, biomass, and rock–water interaction processes, suggesting that δ13C is mainly controlled by the local hydroclimate. Ensemble empirical mode decomposition (EEMD) results revealed a coupling relationship between δ18O and δ13C on multiple timescales, which suggested that changes in precipitation caused by large-scale monsoonal circulation are controlled by regional hydrological conditions to a great extent. However, the hydrological conditions of the cave were relatively mild and humid during the last glacial maximum (LGM), which revealed the impact of evaporation on changes in the region’s hydrological conditions. We also found that the δ18O and δ13C profiles decoupled when δ13C changed with a shift in the location of the westerly during HS1. The δ13C record correlates well with other paleoclimate records, suggesting that regional hydrological conditions are also modulated by the Earth’s internal and external driving factors.
... The 134-ka event is a strong ASM interval centered at 134.5 ka in the penultimate deglaciation, characterized by a significantly negative oxygen isotope (δ 18 O) excursion in the speleothem records from the ASM domain (e.g., Cheng et al., 2006;Kelly et al., 2006;Wang et al., 2018;Duan et al., 2019). Atmospheric methane (CH 4 ) and nitrous oxide (N 2 O) also show significant peaks at approximately 134 ka, as recorded in the European Project for Ice Coring in Antarctica (EPICA) Dome C (EDC) ice core records (Schmidely et al., 2021). ...
... Changes in the amplitude of temperature/precipitation at various timescales are main factors of the above phenomenon (Genty et al., 2003). In this study, we suggest that millennial-scale positive excursions in our δ 13 C record are linked to increasing summer monsoon rainfall (Wang et al., 2018). ...
... Our Zhangjia δ 18 O record spans the weak monsoon interval-II (WMI-II) (Cheng et al., , 2009Kelly et al., 2006;Wang et al., 2018), which is characterized by higher δ 18 O values with an average of approximately −5.8‰. The Zhangjia record revealed two stages of the WMI-II: WMI-IIa (132.8-134.1 ka) and WMI-IIb (134.4-136.4 ...
The penultimate deglaciation was characterized by a sub-millennial-scale warm event in the Heinrich Stadial 11(HS11), termed the 134-ka event. However, its precise timing and structure remain poorly constrained due to the lack of high-resolution and precisely dated records. We present an oxygen isotope record of a speleothem with well-developed annual lamina from Zhangjia Cave, located on the north margin of the Sichuan Basin, characterizing Asian summer monsoon (ASM) changes in the 134-ka event, which included an increase excursion of ca. 149 years and decrease excursion of ca. 200 years, inferred from 3.3‰ δ ¹⁸ O variations. This event also divided the weak ASM interval-II (WMI-II), corresponding to HS11, into two stages, the WMI-IIa 132.8–134.1 ka and WMI-IIb 134.4–136.4 ka. With a comparable climatic pattern globally, the 134-ka event is essentially similar to the millennial-scale events in last glacial–deglacial period. Particularly, the observed weak-strong-weak ASM sequence (138.8–132.8 ka) is largely controlled by changes in the Atlantic Meridional Overturning Circulation (AMOC) forced by the meltwater of northern high-latitude ice sheets. Moreover, our results underpin that AMOC, rather than the global ice volume, is more critical to ASM variations during the last two deglaciations.
... The alternating relationship between the two hemispheres on the millennial scale has been of great concern for several glacial periods that occurred after the MBE Wang et al., 2018;Yang et al., 2020). This relationship was first identified during the last glacial period. ...
... For example, high-resolution data and the improved synchronization of bipolar ice records have demonstrated that each millennialscale event had an Antarctic counterpart during the last glacial period (EPICA Community Members, 2006;Jouzel et al., 2007;Capron et al., 2012). Because of the regular occurrence of glacial-interglacial cycles, a similar millennial-scale variability pattern has been identified over the past four glacial ages (for example, Wang et al., 2008;Jouzel et al., 2007) and the seesaw relationship on the millennial scale between the two hemispheres Wang et al., 2018;Yang et al., 2020). However, not all millennial-scale variability patterns have analogs in the southern hemisphere, considering the relatively low resolution of the ice core record (for example, Yang et al., 2020). ...
... As previously mentioned, with strong similarities in fluctuation and frequency, millennial-scale variations have been identified in an extensive region over several glacial periods, suggesting that the frequent occurrence of millennial-scale events is the most important feature of the glacial climate Wang et al., 2008;Cheng et al., 2009;. These millennial-scale variations indicate an anti-phase relationship between the two hemispheres (WAIS Divide Project Members, 2015;Wang et al., 2018;Yang et al., 2020) through the bipolar seesaw model (Stocker and Johnsen, 2003). For example, the stalagmite record from Yongxing Cave was strongly affected by Antarctic temperature variability on sub-orbital timescales during MIS 3 . ...
... Hulu Cave (32°30′N, 119°10′E), near Nanjing City, is lo-cated in the lower reach of the Yangtze River. Its position is shown in Figure 1, and a detailed description is given in previous studies (e.g., Wang et al., 2001;Duan et al., 2015;Wang et al., 2018). The current meteorological conditions are dominated by distinct seasonal changes in rainfall under a subtropical monsoon climate. ...
The rainfall changes in East Asian summer monsoon (EASM) regions on the orbital timescale remain controversial due to the lack of reliable rainfall records. Here, we present new multiproxy records (δ18O, δ13C, Sr/Ca and Mg/Ca) of a 230Th-dated stalagmite from Hulu Cave in central eastern China. Multiproxy records reconstruct a regional hydroclimate history from 340 to 261 kyr BP (thousand years before present), approximately covering the antepenultimate glacial period. The δ18O record is dominated by the precessional cycles, suggesting that EASM responds to changes in Northern Hemisphere summer insolation (NHSI) on the orbital timescale. Significant correlations amongst the δ13C, Sr/Ca and Mg/Ca suggest that a common factor, i.e., the local hydrological cycle, controlled their variability, and their leading principal component can be used as a proxy linked to regional rainfall. This composite record bears a good similarity to those from the Chinese Loess Plateau, showing a gradually decreasing rainfall during the antepenultimate glacial period, consistent with changes in global ice volume. Superimposed on the long-term trend, three relative wetter intervals were responding to the higher NHSI periods, suggesting that EASM rainfall variability was induced by integrated effects of global ice volume and NHSI. The increased ice sheets and lower NHSI resulted in an increased meridional temperature gradient and southward shift of the westerlies, which shortened the duration of Meiyu and midsummer rainfall. The differences between the rainfall record and the stalagmite δ18O record indicate that the latter represents the overall EASM intensity linked to monsoon circulation, but does not directly reflect the rainfall changes at the cave sites.
... As speleothems are often protected within a cave, they are not subject to the same degree of physical and chemical weathering which affects preservation of other surface records. In this regard, speleothems are often long, encompassing tens of thousands of years, which allows researchers to study climate changes on orbital and millennial time scales (e.g., Cheng et al., 2009;Wang et al., 2018). ...
Speleothems are increasingly valued as important paleoclimate archives and yet the removal of samples from caves can come at a cost to natural heritage, impacting delicate environments with limited mechanisms for repair. Conservation of cave environments is a key responsibility for scientists and, with this in mind, we are working to develop and implement techniques that allow us to extract valuable scientific data, with minimal impact. In this study, we demonstrate the utility of low-impact reconnaissance dating surveys on caves in southern Tasmania and southwest Western Australia as a precursor to the removal of stalagmites for paleoclimate reconstruction. Small flakes of calcite were discretely extracted from the base and tip of fallen stalagmites and dated using U-Th techniques. We specifically targeted stalagmites that have naturally fallen or been previously broken by human interference, to further reduce our impact on the caves. This approach provides maximum and minimum age constraints for each stalagmite and valuable information of growth frequencies without the need to remove whole samples from the cave. Selecting the most appropriate samples to analyze based on reconnaissance ages greatly reduces the quantity of speleothem material to be removed from a cave to locate a desired interval of past time, mitigating the impacts of the research. Moreover, the reconnaissance age data enable us to build an archive of speleothem ages from the cave for future scientific research and to provide information on the age and nature of cave development, useful for cave management purposes and other studies. To assess the accuracy of this method we compared the reconnaissance age with the results of a detailed age evaluation on a small number of stalagmites removed from the caves. We have found this method to be effective and has allowed us to successfully identify several stalagmites suitable for our scientific objectives.
... In Asia, Chinese speleothem δ 18 O analysis reveals that millennial-scale strong Asian Monsoon events (Chinese Interstadials) took place throughout MIS 6 (Cheng et al., 2006). Infrequent but longer-duration strong Asian Monsoon events characterised the early part of MIS 6 prior to 160 ka, whilst up to 15 shorter-duration and smaller amplitude strong Asian Monsoon events are evident during the mid-late part of MIS 6 (Cheng et al., 2006;Wang et al., 2008Wang et al., , 2018. Stronger Asian Monsoons are thought to arise as a result of reduced North Atlantic sea-ice cover associated with a stronger AMOC, leading to a northward shift in the ITCZ over the Atlantic and the Pacific (Zhang and Delworth, 2005;Wang et al., 2018). ...
... Infrequent but longer-duration strong Asian Monsoon events characterised the early part of MIS 6 prior to 160 ka, whilst up to 15 shorter-duration and smaller amplitude strong Asian Monsoon events are evident during the mid-late part of MIS 6 (Cheng et al., 2006;Wang et al., 2008Wang et al., , 2018. Stronger Asian Monsoons are thought to arise as a result of reduced North Atlantic sea-ice cover associated with a stronger AMOC, leading to a northward shift in the ITCZ over the Atlantic and the Pacific (Zhang and Delworth, 2005;Wang et al., 2018). ...
... Whether mainland Europe experienced multiple equivalent interstadial events during mid-late MIS 6 remains unclear. The synthetic δ 18 O record of Barker et al. (2011) does predict D-O-type warming events over Greenland continuing into the mid-late MIS 6, typically corresponding with strong Asian Monsoons (Wang et al., 2018) and weak South American Monsoons (Burns et al., 2019). Some mid-late MIS 6 climate variability is observed in European speleothem records (e.g. ...
Exploring the mode and tempo of millennial-scale climate variability under evolving boundary conditions can provide insights into tipping points in different parts of the Earth system, and can facilitate a more detailed understanding of climate teleconnections and phase relationships between different Earth system components. Here we use fossil diatom and stable carbon and oxygen isotope analysis of lake sediment deposits (core I-284) from the Ioannina basin, NW Greece, to explore in further detail millennial-scale climate instability in southern Europe during Marine Isotope Stage 6 (MIS 6; ca. 185–130 ka). This interval correlates with the Vlasian Stage in Greece and the Late Saalian Substage in northern Europe, which were both characterised by extensive glaciations. The new dataset resolves at least 18 discrete warmer/wetter intervals, many of which were associated with strong Asian Monsoon events and North Atlantic interstadials. A number of cooler/drier intervals are also identified in the I-284 record, which are typically associated with weaker Asian Monsoon events and North Atlantic stadials, consistent with a variable Atlantic Meridional Overturning Circulation. Unlike the subdued changes in tree populations that are observed at Ioannina during mid-to-late MIS 6, the diatom record contains frequent high amplitude oscillations in species assemblages, pointing to its sensitivity at a time when the lake system must have been close to environmental thresholds. Millennial-scale variability in diatom species assemblages continues into late MIS 6 at Ioannina, contributing important evidence for an emerging picture of frequent and persistent climate instability even at times of high global ice volume.
... In the Southern Alps, only a small part of MIS 9 was covered by stalagmite records (Columbu et al., 2018). In China, studies on stalagmite records have provided insights into the evolution of the Asian summer monsoon (ASM), particularly for millennial-scale climate oscillations for the past several glacialinterglacial cycles (Wang et al., 2008(Wang et al., , 2018Cheng et al., 2016). A long-term Chinese cave record extending back to the past 640 kyr provides a chronologic benchmark for correlating global millennial-scale events (Clemens et al., 2018). ...
... During rainy season, the precipitation could flow rapidly through the soils, presenting a 'dampening model' (an isotopic equilibrium between the water and the biogenic CO 2 in soils) and forcing the d 13 C to increase (Kong et al., 2005). However, the d 18 O and d 13 C records in LS26 presented slightly positive correlation, which is in line with the Western Europe cave records (Genty et al., 2003) rather than the records from Hulu cave in China (Kong et al., 2005;Wang et al., 2018). However, due to lack of the reproducibility and the complexity of the impact factors as mentioned above, the specific meaning of the d 13 C record on the sub-millennial scales in LS26 remains elusive, even though prominent climatic meaning of stalagmite d 13 C was confirmed in Western Europe (e.g. ...
... In addition, a series of ASM intensified processes were identified during the MIS 9, especially in the period of MIS9.3, MIS9.2 and MIS9.1, similar to the Chinese interstadial (CIS) in the last and penultimate glaciation (Wang et al., 2001(Wang et al., , 2018Cheng et al., 2006). It is suggested that Greenland warmings during the last glaciation were caused by changes in the intensity of the AMOC (Lynch Stieglitz, 2017), which transports heat from the tropics to the high latitudes. ...
A 67-yr-resolution δ¹⁸O profile of a²³⁰Th-dated stalagmite from Luoshui Cave, central China, is presented to refine the Asian summer monsoon (ASM) history from 336 to 290 kyr BP. The sub-stages of Marine Isotope Stage 9 (MIS 9) are clearly reflected in the Luoshui δ¹⁸O record, in line with changes in the Northern Hemisphere summer insolation (NHSI). The concurrency of eight weak monsoon intervals (WMIs) between 320 and 290 kyr BP and shifts in the Atlantic oceanic circulation suggest that monsoon weakening was forced by northern high-latitude climate oscillations with north-south shifts in the Intertropical Convergence Zone (ITCZ). Spectrum analyses show a cyclic change of 1–4 kyr between 320 and 290 kyr BP, similar to the Dansgaard-Oeschger cycles during the last glacial period. This suggests a relatively unstable monsoon state when the northern ice volume reached intermediate levels. The detrended δ¹⁸O agrees well with the δ¹³C record on the millennial to sub-millennial scales, suggesting a coupling of monsoon climate and cave environment. After removal of the summer insolation signal at 65°N, the residual Luoshui δ¹⁸O record is highly similar to orbital- and millennial-scale temperature changes in Antarctica in an anti-phased fashion, revealing the significant influence of Southern Hemispheric climates on ASM intensity. The absence of counterparts of the two WMIs between 315 and 310 kyr BP in Antarctica, however, indicates a complicated teleconnection.
... In the past decade, Chinese scientists have conducted a wide range of researches on the nature and mechanism of the millennial events in the past two glacial-interglacial cycles and published a number of important papers in the field. For example, Wang et al. (2001Wang et al. ( , 2008, Cheng et al. (2006Cheng et al. ( , 2016a, Cai et al. (2006Cai et al. ( , 2015, Li et al. (2007, Liu D et al. (2008Liu D et al. ( , 2013Liu D et al. ( , 2018, Zhou et al. (2008Zhou et al. ( , 2011, Wu et al. (2009), Yang et al. (2010), Zhao et al. (2010), Ma et al. (2012), Duan et al. (2014), Duan et al. (2016a), Jiang et al. (2016), Kathayat et al. (2016), , Han et al. (2016), Zhang et al. (2017), Wang Q et al. (2018), Cui et al. (2018), Du et al. (2019), and Zhang et al. (2019a) revealed the monsoon climate patterns and dynamics on the millennial-scale, which have produced important influences. Recently, Du et al. (2019) have proposed a climate dynamic based scheme to correlate the Asian monsoon intensity with Greenland temperature to replace the simple 'middle-point' correlation scheme commonly used in the past. ...
Stalagmite is one kind of secondary carbonates formed in limestone caves (speleothem). After cave water droplets containing Ca²⁺ and HCO 3⁻ drip onto floor, carbonate in the water might become supersaturated due to CO2 degassing under certain conditions, resulting in the formation of stalagmite in a process year after year. Stalagmite is one of important geological archives for paleoclimate research. The advantages include wide spatial distribution, suitable for U-Th and U-Pb dating, enriched in climate proxies, continuity, long time span, comparability and lower sampling cost etc. These factors have propelled stalagmite paleoclimate research to the forefront of global paleoclimatology with an irreplaceable role. The stalagmite paleoclimate study started in the western countries, mainly in Europe and America in 1960s–1970s, while the relevant research in China was progressively developed in the 1980s–1990s after the Reform and Opening up. Although there was a huge gap between the overall research level in China and western countries, a solid research foundation, as well as a number of talent teams were established during the period. In the 21st century, starting from the publication of stalagmite records from Hulu Cave in Nanjing in 2001, the stalagmite paleoclimate research in China has ushered in a flourishing development and a real leap on the basis of international cooperation, resulting in significant international impacts. The landmark achievements, including establishment of the world’s longest (640000 years) East Asian monsoon stalagmite record, as well as the longest Indian monsoon (280000 years), South American monsoon (250000 years), North American westerly climate (330000 years), Central Asian westerly climate (135000 years), and northwestern China westerly climate (500000 years), have laid a milestone in the paleoclimate study in these climate domains. Importantly, these stalagmite records have revealed the relationship of Asian monsoon variations with solar insolation climate change in polar regions, and the South American monsoon changes on orbital-suborbital timescales, which have provided new geological observations for the development of orbital-suborbital climate theory; elaborated coupling and differentiation relationships between the Asian monsoon and the westerly climate; reconstructed the history of Asian monsoon changes in the Holocene in detail, and thus the hydrological and climate variances behind Chinese and Indian civilization-cultural evolutions. Furthermore, a large number of high-resolution stalagmite records over the past 2000 years have been reconstructed, which are important for understanding short-term climate variability and magnitude, events, cycles, and thus the future climate projection. The achievements have also involved the improvements of a number of important techniques, such as U-Th dating method, the establishments of various hydroclimatic proxies, as well as the contributions to the reconstruction of the atmosphere ¹⁴C variation history over the past ∼54000 years. On the perspective of the future, the Chinese stalagmite community should continue to develop key techniques, further clarify the hydroclimatic significance of stalagmite proxies, impel the integration of related disciplines, and concentrate on key scientific issues in global climate change and major social demands.
... However, compared to δ 18 O records, they have been underutilized in paleoenvironmental studies of speleothems in China. Nevertheless, in a specific cave environment, δ 13 C and trace elements can be applied as hydrological tracers at a local scale (Genty et al., 2003;Sinclair et al., 2012;Huang et al., 2016;Zhao et al., 2016;Wang et al., 2018). Moreover, a relationship between δ 13 C and trace element ratios in speleothems has been observed; for example, owing to the impact of prior calcite precipitation (PCP) and CO 2 degassing under low-flow conditions, metal/Ca ratios and δ 13 C are elevated in dripwater and hence in stalagmites (Treble et al., 2003;Johnson et al., 2006;Fairchild and Treble, 2009;Stoll et al., 2012;Chen and Li, 2018). ...
... Modern observations of dripwater and rainwater at the cave site support this interpretation . Following the reasoning of previous studies (Wang et al., 2001(Wang et al., , 2008Liu et al., 2014;Duan et al., 2015;Cheng et al., 2016;Wang et al., 2018), we conclude that the stalagmite δ 18 O record is a proxy of the East Asian summer monsoon (EASM), with intervals of δ 18 O depletion representing stronger monsoon. However, stalagmite δ 18 O records are likely to integrate the effects of complex hydroclimatic processes, including moisture sources, degree of Rayleigh fractionation, and seasonal duration and intensity of monsoon rainfall. ...
A ²³⁰ Th/U-dated stalagmite from Hulu Cave was analyzed for δ ¹⁸ O, δ ¹³ C, and trace elements. A ~10-yr-resolution δ ¹⁸ O record, spanning 51.7–42.6 ka, revealed Dansgaard-Oeschger (DO) events 14 to 11. A similar rapid transition and synchronous timing of the onset of DO 12 is evident between the Greenland and Hulu Cave records, which suggests a common forcing mechanism of DO cycles in the North Atlantic and monsoonal region of Asia. Centennial-scale monsoonal oscillations in the cave δ ¹⁸ O record are indicative of hydroclimatic instability during interstadials. After removing the signals of remote moisture sources, the proportion of moisture from nearby sources is found to be higher during stadials than during interstadials. To explain this, we propose that the movement of the westerly jet is an important control on the balance of nearby and distant moisture sources in East Asia. In addition, the records of δ ¹³ C and trace element ratios, which are proxies of local environmental changes, resemble the δ ¹⁸ O record on the scale of DO cycles, as well as on even shorter timescales. This suggests that hydrological processes and biological activity at the cave site respond sensitively to the monsoonal changes.
... A large number of Chinese speleothem δ 18 O records can be utilized to characterize millennialscale climate variability corresponding to Dansgaard-Oeschger events [214] and Heinrich stadials/interstadials [215] in the Northern Hemisphere. This list include records from the Hulu [5,9,71], Sanbao [9], Dongge [12], Dragon [52], Songjia [139], Suozi [216], Xinya [163], Xinglong [161], Kulishu [77,161], Wulu [43,146], Kesang [21], Xiaobailong [13,160], Dashibao [43], Yangkou [167][168][169], Sanxing [119], Yongxing [173], Qingtian [69], Xianyun [158,159] caves, etc. Among the above records, the Hulu [5,9,71], Sanbao [9], Kesang [21], Dongge [12], Xinya [163], Yangkou [167][168][169], Kulishu [77], Xinglong [161], Xiaobailong [160] and Suozi [216] records are incorporated in the SISAL_v1 database. ...
Asian summer monsoon (ASM) variability significantly affects hydro-climate, and thus socio-economics, in the East Asian region, where nearly one-third of the global population resides. Over the last two decades, speleothem δ18O records from China have been utilized to reconstruct ASM variability and its underlying forcing mechanisms on orbital to seasonal timescales. Here, we use the Speleothem Isotopes Synthesis and Analysis database (SISAL_v1) to present an overview of hydro-climate variability related to the ASM during three periods: the late Pleistocene, the Holocene, and the last two millennia. We highlight the possible global teleconnections and forcing mechanisms of the ASM on different timescales. The longest composite stalagmite δ18O record over the past 640 kyr BP from the region demonstrates that ASM variability on orbital timescales is dominated by the 23 kyr precessional cycles, which are in phase with Northern Hemisphere summer insolation (NHSI). During the last glacial, millennial changes in the intensity of the ASM appear to be controlled by North Atlantic climate and oceanic feedbacks. During the Holocene, changes in ASM intensity were primarily controlled by NHSI. However, the spatio-temporal distribution of monsoon rain belts may vary with changes in ASM intensity on decadal to millennial timescales.
