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![A map showing the present current system in the East China Sea after Ichikawa and Beardsley [2002] and location of cores KY07-04-01 and A7. Gray solid and dotted arrows indicate the Kuroshio Current, the Tsushima Warm current (TSWC), and the Taiwan Warm Current (TWWC), respectively. Dark gray solid arrows represent flows of the Chinese Coastal Water and Changjiang River Diluted Water (CDW). Contours are the isobaths. Numbers indicate the locations of the following: (1) Tsushima Strait, (2) the Okinawa Trough, (3) East Taiwan Strait, (4) Taiwan Strait, and (5) Changjiang River mouth.](profile/Yoshimi-Kubota/publication/251426570/figure/fig2/AS:669978483249170@1536746726750/A-map-showing-the-present-current-system-in-the-East-China-Sea-after-Ichikawa-and.png)
A map showing the present current system in the East China Sea after Ichikawa and Beardsley [2002] and location of cores KY07-04-01 and A7. Gray solid and dotted arrows indicate the Kuroshio Current, the Tsushima Warm current (TSWC), and the Taiwan Warm Current (TWWC), respectively. Dark gray solid arrows represent flows of the Chinese Coastal Water and Changjiang River Diluted Water (CDW). Contours are the isobaths. Numbers indicate the locations of the following: (1) Tsushima Strait, (2) the Okinawa Trough, (3) East Taiwan Strait, (4) Taiwan Strait, and (5) Changjiang River mouth.
Source publication
Variations in Mg/Ca-based sea surface temperature and oxygen isotope ratio (δ18O) of the surface water in the northern East China Sea (ECS) were reconstructed with high resolution during the last 18 kyr using planktic foraminifera. Millennial-scale variations between warmer, more saline surface water and cooler, less saline surface water were recog...
Contexts in source publication
Context 1
... The ECS is a marginal sea bounded by the Asian continent on its west, Taiwan Island on its southwest, the Ryukyu Islands on its southeast, and Kyushu and the Korean Peninsula on its northeast and north, respectively (Figure 2). The continental shelf shallower than 200 m occupies more than 70% of the entire ECS. ...
Context 2
... Okinawa Trough, of which maximum water depth is greater than 2000 m, lies in the southeastern part of the ECS along the Ryukyu Arc. Today, the warmer and more saline Kuroshio Water (KSW), Taiwan Warm Water (TWW), and the cooler and less saline Changjiang Diluted Water (CDW) influence the surface conditions of the ECS [Ichikawa and Beardsley, 2002;Zhang et al., 2007] (Figure 2). The surface hydrog- raphy of the ECS changes drastically through a year due to the significant influence of the EASM. ...
Context 3
... Monsoon-related process drives seasonal and annual SSS variability in the ECS. Namely, the fresher surface water in the northwestern ECS especially during summer reflects the high fresh water discharge from the Changjiang (Yangtze) River (Figure 2). The Changjiang River, whose average annual discharge is 900 km 3 /yr (2.8 × 10 4 m 3 /s) [Changjiang Water Resources Commission, 2001], supplies approximately 80% of the total discharge of fresh water to the ECS [Ichikawa and Beardsley, 2002]. ...
Context 4
... 14.1 m in the length, was recovered from the northern edge of the Okinawa Trough at a water depth of 758 m during KY07-04 cruise conducted by R. V. Kaiyo affiliated with Japan Agency for Marine-Earth Science and Technology (JAMSTEC) (Figure 2). Core KY07-04-1 was composed of homogeneous olive-gray silty clay with intercalations of two ash layers. ...
Context 5
... order to examine the Kuroshio influence at the core site, d 18 O sw record from the studied site in the northern ECS is compared to that from site A7 in the southern ECS studied by Sun et al. [2005], which is located at the central Okinawa Trough and under the influence of the mainstream of the Kuroshio Current. Today, site A7 is dominantly influenced by the KSW as is demonstrated in Figure 2, which shows that modern SSS at the site A7 is approximately 1.0 higher than at site KY07-04-01 during summer (Figure 3d). In order to remove the influence of the Kuroshio Water on SSTs and SSSs at the studied site, d 18 O sw of core A7 is subtracted from d 18 O sw of core KY07- 04-01. ...
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Citations
... The East China Sea, a marginal sea in the northwestern Pacific, is characterised by one of the largest continental shelves on Earth, where the EASM strongly influences surface waters (Chang et al., 2009;Kubota et al., 2010;Sun et al., 2005aSun et al., , 2005b. Sea surface salinity (SSS) is affected by atmospheric forcing (e.g., evaporation, precipitation, and wind), and fluvial runoff . ...
... Forming a passage between continental China and the northwestern Pacific Ocean, OT sediments are expected to provide a paleoenvironmental record of both continental and oceanic influences during the last deglaciation . Almost all the previous SSS reconstructions from the OT were based on estimates of the oxygen isotope composition of seawater (δ 18 O sw ) (Chang et al., 2009;Jian et al., 2000;Kubota et al., 2010;Lin et al., 2006;Sun et al., 2005aSun et al., , 2005bWang et al., 2016;Xiang et al., 2007;Yu et al., 2009). However, additional reliable proxies of past SSS variability are required to improve our understanding of its long-term evolution. ...
... The trend of increasing SSS in the southern OT as reconstructed based on our diatom record (Fig. 4A) and based on the δ 18 O w record from core OKT-3 ( Fig. 4B; Wang et al., 2016), is consistent with the weakening of EASM deduced from the stalagmite δ 18 O records in both South and North China, in phase with weakening summer insolation in the Northern Hemisphere during the Holocene Wang et al., 2005;Yang et al., 2019). However, the δ 18 O w -based SSS at sites A7 and MD012404 in the middle OT show no significant trend during the mid- (Sun et al., 2005a(Sun et al., , 2005b and core KY07-04-01 (E; Kubota et al., 2010) from south to north. The dashed line shows the relative abundance of coastal water diatoms (%) in core MD05-2908. ...
... Insights into Quaternary EAM history are furthermore obtained from, e.g., the oxygen isotope composition (δ 18 O) of cave speleothems from southeast China (7,8), pollen assemblages (9,10) or Si/Al ratios of lake sediment records (11), and the δ 18 O, Mg/Ca ratio and assemblages of foraminifera in marine sediments (12,13). However, most of these proxies are influenced by both temperature and precipitation, resulting in the long-lasting confusion and debate in the understanding of orbital-scale EAM climate variability and dynamics. ...
Numerous proxy reconstructions have provided general insight into late Quaternary East Asian Monsoon variability. However, challenges persist in precisely assessing absolute temperature impacts on proxy variations. Here, we use two independent paleothermometers, based on bacterial membrane lipids and clumped isotopes of snail shells, in the same section of the western Chinese Loess Plateau to establish a robust land surface temperature record spanning the past approximately 21,000 years. Our independent temperature records consistently reveal (i) similar land surface temperatures between the Last Glacial Maximum and late Holocene and (ii) a gradual cooling Holocene, which contrasts with the climate model predictions. We propose that changes in soil moisture availability over the deglaciation modulates the land surface temperature recorded by the proxies. A land surface energy partitioning model confirms this mechanism, suggesting that effects of soil moisture availability should be properly considered when comparing proxy records with climate model outputs.
... East Asian Monsoon is generated by the thermal contrast between the Asian continent and the northwestern Pacific. Summer monsoon precipitation over the Changjiang drainage basin results in a large volume of freshwater discharge (Fig. 1a) that reduces the sea surface salinity in the East China Sea (ECS) (Sun et al., 2005;Chang et al., 2009, Kubota et al., 2010. The Changjiang freshwater discharge accounts for ~ 90 % of the total fluvial discharge to the ECS (Isobe et al., 2002), and its influence exceeds that of the local rainfall over the ECS (Chen et al., 1994). ...
... The Changjiang freshwater enters the estuary to form Changjiang Diluted Water (CDW) via mixing with the ambient seawater (Ichikawa and Beardsley, 2002). The structure and pathway of the CDW in the Chinese coastal area change seasonally (Kubota et al., 2010). In summer, CDW has a bimodal structure consisting of a southward coastal jet and northeastward spread. ...
... In summer, CDW has a bimodal structure consisting of a southward coastal jet and northeastward spread. In winter, it flows southward along the Chinese coast (Kubota et al., 2010). ...
... b. Sharply decreased GPI during the BA SST generally increases over the WNP during the BA compared with the HS1, though with two peaks and a valley in terms of temporal evolution (Fig. S6). The modeled overall SST warming is in accordance with proxies (Bolliet et Chen et al. 2010;Kubota et al. 2010;Rosenthal et al. 2003;Stott et al. 2002;Xu et al. 2021; (Fig. 5a). In contrast to the SST change, the evolution of GPI over the WNP shows a sharp decrease around 14.5 and 13.5 ka, and a sudden increase around 14 ka (Fig. 1b). ...
To deepen our understanding of the behavior of tropical cyclones (TCs) over the western North Pacific (WNP) and its response to various external forcings, we investigate the variation of TC genesis potential over the WNP during the past 20 ka that experienced several large forcings. Using a set of transient simulations and a genesis potential index, our results indicate that TC genesis potential in the storm season shows an overall increase averaged over the WNP during the Heinrich Stadial 1 (HS1; ~17−16 ka) relative to the last glacial maximum. Subsequently, there is a sharp decrease in genesis potential during the Bølling-Allerød (BA; ~13.5 ka) relative to the HS1, which is followed by an increase during the Younger Dryas (YD; ~12.9−11.7 ka). During the Holocene, TC genesis potential shows a slight decrease during the earlymiddle Holocene (~11.7−6 ka), while a significant increasing trend afterwards. Further analysis shows that the contribution of each genesis factor to the genesis potential change varies greatly with time, which is in turn tied to changes in external forcings. The increased meltwater fluxes dominate the increased genesis potential during the HS1 and YD, whereas all external forcings (i.e., changes in meltwater, ice sheets, CO 2 , and insolation) contribute to genesis potential change during the BA. The long-term increasing trend from the mid-Holocene to the present is controlled by orbital insolation. These results may help improve our understanding on past TC activity and shed lights on TC response to various external forcings in a long-term future.
... Previous temperature reconstructions of the OKT have focused on SST, using fossil planktonic foraminiferal assemblages and their shell Mg/Ca, alkenones U 37 K ′ and transfer functions based on radiolarian and planktonic foraminifera (e.g., Li et al., 2001;Sun et al., 2005;Zhao et al., 2005;Chen et al., 2010;Zhao et al., 2015;Chang et al., 2008;Kubota et al., 2010). SST reconstructions using various proxies have highlighted the overall changes in SST in the OKT over the past tens of thousands of years. ...
... Chang et al., 2015;Doose-Rolinski et al., 2001;Elmore et al., 2015;Emeis & Dawson, 2003;Eynaud et al., 2009;Fan et al., 2018;Farmer et al., 2008;Flower et et al., 1994;Huguet et al., 2006;Ijiri et al., 2005;Isono et al., 2009;Keigwin & Jones, 1995;Keigwin et al., 2005;Kennett et al., 2007;M. Kienast et al., 2001;Kim et al., 2004Kim et al., , 2007Kim et al., , 2012Kristjánsdóttir et al., 2017;Kubota et al., 2010;Lea et al., 2003;Marchitto et al., 2010;Martrat et al., 2003Martrat et al., , 2007Martrat et al., , 2014McClymont et al., 2012;Minoshima et al., 2007;Mohtadi et al., 2014;Moossen et al., 2015;Overpeck et al., 1996;Pelejero et al., 1999;Praetorius et al., 2015;Rühlemann et al., 1999;Riethdorf et al., 2013;Rigual-Hernández et al., 2017;Rodrigo-Gámiz et al., 2014;Rodrigues et al., 2010;Rosenthal et al., 2003;Sachs, 2007;Saraswat et al., 2013;Schmidt, Chang, et al., 2012;Schmidt, Weinlein, et al. 2012b;Schmidt & Lynch-Stieglitz, 2011;Schmidt et al., 2004;Schwab et al., 2012;Sejrup et al., 2011;Shintani et al., 2011;Staubwasser et al., 2003;Steinke et al., 2008;Stott et al., 2007;Sun et al., 2005;Thornalley et al., 2010;Tierney et al., 2016;Tiwari et al., 2015;Weldeab et al., 2005Weldeab et al., , 2007Werner et al., 2013;Yamamoto et al., 2013;Zhao et al., 1995;Ziegler et al., 2008). We followed the approach in Routson et al. (2019) and calculated the bootstrapped zonal average SST over four latitudinal bands: 60°N − 80°N, 40°N − 60°N, 20°N − 40°N, and 0°N − 20°N. ...
Variations of the sea surface temperature (SST) and primary productivity in the northeast Pacific have far‐reaching implications. In addition to influencing the regional and global temperature and hydroclimate, these conditions also control marine ecosystems and their services, which subsequently impact regional economies. Yet, our understanding of the variability and controls of northeast Pacific SST and productivity on timescales exceeding observational records remains limited. Here, we use marine sediment records from seven locations, spanning 25.2°N–59.6°N, in the northeast Pacific to characterize the millennial‐scale variability of SST and productivity from 9,000 to 1,000 years BP. We explore the dynamics of their spatiotemporal evolution and compare these data with transient climate model outputs to identify potential drivers. Through a heat budget analysis and optimal fingerprinting analysis, we characterize the spatial pattern of forcings. We find that SST varied spatially in the northeast Pacific, with higher latitudes exhibiting greater magnitude changes than lower latitudes, which differs from previous work suggesting regional synchronicity and coherence during the Holocene. Our analysis did not find evidence for coherent variability of primary producer community nor carbon export, highlighting the difficulty of identifying the complex interactions between environmental conditions, producers, and carbon export. Model‐proxy disagreement demonstrates the need for higher resolution model frameworks, but shows nonetheless that observed variability in the proxy records can be explained by a combination of greenhouse gas and orbital forcing. We suggest that the complex SST variations and marine ecosystem responses to forced changes are important factors that can drive disagreements in model projections.
... The distribution of planktic foraminifera was basically consistent with the direction of ocean currents. Since planktic foraminifera mostly live in tropical open oceans, there have been no reports of planktic foraminifera in the North Yellow Sea and Bohai Sea, but there have been many studies in the East China Sea and South China Sea (Kubota et al.,2010;Schiebel and Hemleben, 2005). Samples of this experiment were collected in June in summer. ...
Foraminiferal environmental DNA (eDNA) is an efficient and reliable indicator of environmental changes. Here, we investigated the foraminiferal diversity of 25 stations (33–36°N) in the Yellow Sea based on eDNA and presented the first assessment on the correlations between foraminifera diversity and environmental conditions in the region. A total of 71 sediment samples were collected and local environmental parameters were measured. The foraminiferal eDNA was extracted from the samples and part of the small subunit (SSU) rRNA gene was amplified from the samples. After high–throughput sequencing, 1,701,899 amplified reads were detected and clustered into 426 operational taxonomic units (OTUs). The benthic foraminiferal eDNA community diversity and group diversity showed significant positive correlations with water depth and total inorganic carbon (TIC) in sediments, and significant negative correlations with temperature and total organic carbon (TOC) in sediments. However, in terms of the correlation between relative abundance and environmental factors, there were wide variations from species to species. In this work, planktic foraminiferal eDNA was detected in the sediments, and its OTUs number could reflect the changes in ocean currents and upper layer water masses to a certain extent. This is the first study on relationship of foraminiferal eDNA and environmental factors in the Yellow Sea shelf region of the western Pacific Ocean, and it demonstrates that community parameters in foraminiferal eDNA could be a valuable proxy for environmental changes in the shelf sea.
... By the same token, the TSC might account for northward mixing of group A and group B in sites 5-12 and restrict southward expansion of group B into sites 1-4 ( Figure 1), thereby, shaping asymmetrical distributions of the two haplotype groups. Additionally, coastal China was characterized by a stronger northward monsoon during the last deglaciation, i.e., the East Asian Summer Monsoon, which might drive stronger northward surface currents (Kubota et al., 2010). The stronger northern surface currents during the deglaciation process might be another factor constraining the dispersal directions of the two haplotype groups. ...
The modern coast of China is characterized by complicated hydrology, which might be a potential factor shaping genetic structure of marine organisms. Tridentiger barbatus is a widespread benthic goby in coastal China whose range expansion might depend on larval dispersal in its spawning season. We explored the genetic structure of T. barbatus and its interrelationships with coastal currents, planktonic larval duration, and Pleistocene climate fluctuations. Genealogies of Cytb, Rh, and RAG1 reveal two lineages in T. barbatus, namely the southern and northern lineages. The southern lineage is distributed through the South China Sea to the South Yellow Sea but is absent from the North Yellow Sea and Bohai Sea. The HYCOM average flow field indicates an eddy between the North and South Yellow Seas, which might cause larval retention and limit dispersal of the southern lineage into the North Yellow Sea and the Bohai Sea. The northern lineage is distributed through the South Yellow Sea to the Bohai Sea but is absent from the South China Sea and East China Sea. The distribution of the northern lineage fits the eastward deflection of the Yellow Sea Coastal Current at the boundary of the East China Sea and South Yellow Sea, which might limit southward larval dispersal of the northern lineage into the East China Sea. We also uncovered two Cytb haplotype groups within the southern lineage, namely groups A and B, whose distributions might be shaped by the northward Taiwan Strait Current. The coincidence between the genetic structure of T. barbatus and the coastal currents and eddies strongly implies significant roles of larval dispersal and current transportation in shaping the genetic structure of T. barbatus. In addition, significant isolation by distance is found in the southern lineage, which coincides with its short planktonic larval duration (20–30 days). The inference on divergence time suggests that the observed lineages and haplotype groups in T. barbatus originated in the Pleistocene glaciations. Therefore, the coastal currents, planktonic larval duration, and historical glacial isolation are proposed as important factors shaping the genetic structure of T. barbatus.
... However, such records in marine sediments are sparse (Xu et al., 2018 and references therein). The Okinawa Trough (OT) has been regarded as an ideal location for paleoclimatic, paleohydrogeological, and paleoceanographic studies because it is within the influence of the climate of both the high-latitude North Atlantic and the low-latitude western Pacific Ocean (Sun et al., 2005;Kubota et al., 2010;Ruan et al., 2015;Xu et al., 2018). The seasonal variations in EAM are driven by Northern Hemisphere summer and winter solar insolation, reflecting teleconnection with the high-latitude North Atlantic Wang et al., 2005;Ruan et al., 2015;Huang and Sarnthein, 2021). ...
... The Kuroshio Current (KC) originates from the western Pacific warm pool and transports massive amounts of warm and salty water into the OT Zheng et al., 2016). Paleoclimate indicators have demonstrated the influences of both the EAM and KC on the OT paleoclimate, such as oxygen isotopes (Kubota et al., 2010), Mg/Ca ratios of planktonic foraminifera (Sun et al., 2005), alkenone unsaturation index (U K' 37 ; Ruan et al., 2015), and the tetraether index of 86 carbon atoms (TEX 86 ; Xu et al., 2018). Sea surface temperatures (SSTs) from different locations of the OT tend to reveal different controlling factors on the paleoclimate (Ruan et al., 2015;Zhao et al., 2015;Xu et al., 2018). ...
... TEX H 86 has been used to reconstruct the paleotemperature records of the southern and northern OT, and a gradual warming trend has been identified since the Holocene (Yamamoto et al., 2013;Zhao et al., 2015;Xu et al., 2018). Generally, shifts in the main axis and changes in the KC strength, variations in EAM, sea-level changes, and freshwater inputs are potential factors for paleoclimate changes in the OT (Jian et al., 2000;Kubota et al., 2010;Zhao et al., 2015). The influence of the EAM on SST variations was identified in the middle and northern OT (Yu et al., 2009;Kubota et al., 2010). ...
The ubiquity of glycerol dibiphytanyl glycerol tetraethers (GDGTs) and their temperature sensitivity make them one of the most effective tools for paleoclimate reconstruction. High- and low-latitude climates influence the Okinawa Trough (OT). It receives diverse inputs from the East China Sea, the western Pacific, and the Kuroshio Current, providing good conditions for paleoclimate studies. Here, isoprenoid GDGTs (isoGDGTs), branched GDGTs, and hydroxylated GDGTs (OH-GDGTs) were studied to reconstruct the sea surface temperature (SST) of the central OT for the past 8.2 kyr using the tetraether index of 86 carbon atoms at low latitudes (TEXH 86) and the ring index of OH-GDGTs (RI-OH). The GDGT-0/crenarchaeol ratios ranged from 0.39 to 0.98. The branched and isoprenoid tetraether index and the methane index values were lower than 0.1 and 0.5, respectively, indicating that the isoGDGTs were mainly derived from marine Thaumarchaeota and that TEXH 86 could be used to reconstruct the paleotemperatures. The TEXH 86 SSTs ranged from 21.6 to 27.2°C during 8.2 kyr. The overall range of TEXH 86 SSTs is close to the UK’ 37 SST of the middle OT and reflects the mean annual SST. In contrast, RI-OH temperatures varied from 17.4 to 26.0°C, showing a lower trend than TEXH 86 SSTs. The core top RI-OH temperature is 24.1°C, in line with the mean annual seawater temperature at 40 m (24.2°C) in the study area, which likely reflects the subsurface temperature in this case. The small overall warming trend of TEXH 86 SSTs agrees with the increasing intensity of the Kuroshio Current during the last 8.2 kyr, indicating that the SST evolution is governed by the Kuroshio Current that transports heat from the western tropical Pacific. The decreasing temperature differences between TEXH 86 and RI-OH and between UK’ 37 and RI-OH showed increased mixing of the upper water column, which was in good accordance with the increasing low-latitude winter insolation decoupling from the East Asian summer monsoon. The cold event that occurred at 7.4–6.6 kyr was magnified (∼5°C) at the TEXH 86 and RI-OH temperatures and possibly caused by tephra’s significant input (∼7.3 kyr).
... and feedback mechanisms associated with changes in the carbon cycle, including atmospheric CO 2 drawdown and ocean carbon storage (e.g., Chalk et al., 2017;DeMenocal, 1995;Farmer, Goldstein, et al., 2019;Hönisch et al., 2009;Higgins et al., 2015;Hasenfratz et al., 2019;Kender et al., 2018;Lear et al., 2016;Martínez-Garcia et al., 2011;Pena & Goldstein, 2014;Ruddiman, 2003Ruddiman, , 2004Sosdian et al., 2018;Shackleton, 2000). Large-scale atmospheric circulation patterns, such as the East Asian monsoon, have also been suggested as possible important influences, acting as fast conveyers of climate signals and triggers between ocean basins and across continents (Clark et al., 1999;Kubota et al., 2010;Porter & An, 1995;Tada, 2004;Tada et al., 2015a). ...
Large‐scale atmospheric circulation patterns, such as the East Asian monsoon, have been proposed as possible feedbacks of the mid‐Pleistocene transition (MPT). Marine sediments of the Japan Sea (JS) record variations in the East Asian monsoon over long timescales and may be crucial for understanding of the MPT. To interpret these sediments correctly an understanding of the JS palaeoceanography is necessary. So far, the JS palaeoceanography has been extrapolated across the MPT from studies of the most recent glacial‐interglacial cycles. These suggest a good connection and unrestricted water‐mass exchange with the open ocean during interglacial sea‐level highstands, while during glacial sea‐level lowstands the JS is nearly isolated. Glacial isolation often results in poor carbonate preservation and unusually low oxygen isotope (δ¹⁸O) ratios from low‐saline/low‐δ¹⁸O waters accumulating in the basin. Using the sediments of Integrated Ocean Drilling Program (IODP) Site U1427, a shallow‐water site in the southern JS, we present a continuous foraminiferal δ¹⁸O record encompassing the MPT. This record shows the JS‐typical low glacial δ¹⁸O values in the late phase of the MPT, across Marine Isotope Stages (MIS) 24‐17, while earlier MPT glacials, across MIS 39‐25, are characterized by high δ¹⁸O values. We propose that high glacial δ¹⁸O values are the result of an improved connection between the shallow, southern JS and adjacent ocean during early MPT glacials. The impact of this palaeoceanographic mode, if continued to deep‐water sites, would make the interpretation of dark/light sediment layers as glacial/interglacial deposits uncertain.
