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The Indo-Pacific Warm Pool (IPWP) significantly influences the global hydrological cycle through its impact on atmospheric-oceanic circulation. However, gaining a comprehensive understanding of the hydrologic climate dynamics within the IPWP and its broader effects on the global climate have been hindered by spatial and temporal limitations in paleoclimate records on orbital timescales. In this study, we reconstructed precipitation records (approximated from δ18Osw-ivc) over the past 450 kyr, based on planktonic foraminiferal Mg/Ca and δ18O data obtained from International Ocean Discovery Program Site U1486 in the western tropical Pacific. The δ18Osw-ivc record revealed a generally consistent pattern with precession variations over the past 450 kyr, closely corresponding to changes in boreal summer insolation at the equator. The δ18Osw-ivc record displayed an anti-phased relationship with Chinese speleothem δ18O records on the precession band, with lower precipitation in the western tropical Pacific and higher precipitation in the East Asia summer monsoon region during periods of high Northern Hemisphere summer insolation. This anti-phased correlation primarily resulted from the north-south migration of the Intertropical Convergence Zone (ITCZ), influenced by the interhemispheric insolation contrast. By considering additional δ18Osw-ivc records from various locations within the IPWP region, we identified synchronous precipitation changes within the IPWP on the precession band. The synchronization of precipitation on both margins of the ITCZ’s seasonal range and differences between central and marginal regions of the ITCZ within the IPWP revealed the expansion and contraction of the ITCZ on precession band.

Deep atmospheric convection in the Indo‐Pacific Warm Pool (IPWP) represents a major source of heat and moisture, thereby affecting the global climate, but its past changes remain debated. Here, we present sub‐millennial clay mineralogy and elemental records spanning the last 40 Kyr from within the IPWP. From these data, we infer millennial‐scale fluctuations in precipitation, with generally lower precipitation during Heinrich Stadials 1–4, corresponding to El Niño‐like conditions. Higher precipitation coincided with the warm interstadials, accompanied by La Niña‐like conditions. Moreover, our record indicates the lowest precipitation occurred during the late Holocene, supporting the hypothesis of a stronger‐than‐modern Walker circulation during the Last Glacial Maximum. In combination with other proxy records and TraCE‐21 modeling results, we recognize a distinct spatial heterogeneity of precipitation within the IPWP, resulting from the dominant influences of the ENSO‐like system and migration of the Intertropical Convergence Zone in the eastern and western IPWP, respectively. Plain Language Summary Tropical rainfall systems in the Indo‐Pacific Warm Pool (IPWP) play a significant role in transferring energy and moisture. However, their millennial‐scale variabilities in precipitation during the past remain poorly understood. Here, we provide sub‐millennial sediment mineralogy and elemental reconstructions spanning the last 40,000 years from a sediment core in the IPWP. We infer that variability in precipitation induced by atmospheric convection in the IPWP is the main factor controlling the variability in our data through time. Hence, we interpret our records to reflect millennial‐scale fluctuations in precipitation, with lower precipitation during cool stadial periods and higher precipitation during warm interstadials. Such variability corresponds to the changing zonal state of the tropical Pacific atmosphere‐ocean system, in a pattern similar to the modern‐day. Additionally, our record indicates that precipitation was weaker during the late Holocene than during the Last Glacial Maximum (LGM), suggesting that the Pacific atmospheric zonal circulation was stronger during the LGM than today. Furthermore, a model‐data comparison reveals distinct spatial heterogeneity in the precipitation changes, with precipitation in the eastern IPWP (West Pacific) likely controlled mostly by the tropical Pacific atmosphere‐ocean system, whereas precipitation in the western IPWP (Indian Ocean) was driven by latitudinal movement of the Intertropical Convergence Zone. Key Points We present sub‐millennial clay mineral and elemental records from the Indo‐Pacific Warm Pool spanning the last 40 Kyr Our records indicate higher precipitation during La Niña‐like conditions and lower precipitation during El Niño‐like conditions Different patterns and controls on precipitation variability between the eastern and western Indo‐Pacific regions are revealed

The climate response of tropical Southeast Asia to abrupt climate change originating from high northern latitudes remains poorly understood. Here, marine sediments recovered from the Northwest Borneo Trough are analyzed to trace variations in terrigenous material composition associated with sea level and palaeoflood activities over the past 40 ka. We describe for the first time the influence of sea level change on terrigenous deposition from a tropical island with small mountainous rivers surrounded by narrow continental shelves and the coupling between North Atlantic dynamics and climate feedbacks in tropical Southeast Asia during the Dansgaard‐Oeschger stadials. This study demonstrates that climate oscillations occurring at high northern latitudes can be transmitted to tropical Southeast Asia through the functions of sea level, the East Asian winter monsoon and the Intertropical Convergence Zone. Such information is fundamental to correctly assessing future sea level rise and flood risks in tropical Southeast Asia. Plain Language Summary Sea level rise and extreme climate events are two global climate issues currently faced by humanity under the background of global warming. However, the climate feedbacks in tropical Southeast Asia remain unknown, although portions of this region are now densely populated. Here, a gravity core retrieved from the Northwest (NW) Borneo Trough is employed to reveal variations in terrigenous material composition and their controlling factors over the past 40 ka. We found that the terrigenous sediments delivered to the NW Borneo Trough are primarily sourced from NW Borneo, and their deposition is mainly controlled by sea level change and flooding. Further in‐depth analysis reveals that northern high‐latitude cooling could cause floods in NW Borneo both in the modern and during the past by influencing the East Asian winter monsoon (EAWM) and/or the Intertropical Convergence Zone (ITCZ). Furthermore, our new records suggest that a stronger EAWM during cold stadials could have transported high levels of northerly moisture to NW Borneo, resulting in relatively higher speleothem δ18O values in NW Borneo. In short, abrupt climate changes in the high‐latitude Northern Hemisphere can be transmitted to tropical Southeast Asia through the functions of sea level, the EAWM and the ITCZ. Key Points Sea level change and flooding are the main controlling factors for terrigenous deposition from tropical Southeast Asia Northern high‐latitude cooling could lead to the outbreak of floods in Northwest Borneo via atmospheric teleconnection Climate oscillations occurring at high northern latitudes can be transmitted to tropical Southeast Asia

The role of the tropical Pacific Ocean and its linkages to the southern hemisphere during the last deglacial warming remain highly controversial. Here we explore the evolution of Pacific horizontal and vertical thermal gradients over the past 30 kyr by compiling 340 sea surface and 7 subsurface temperature records, as well as one new ocean heat content record. Our records reveal that La Niña-like conditions dominated during the deglaciation as a result of the more intense warming in the western Pacific warm pool. Both the subsurface temperature and ocean heat content in the warm pool rose earlier than the sea surface temperature, and in phase with South Pacific subsurface temperature and orbital precession, implying that heat exchange between the tropical upper water column and the extratropical Southern Ocean facilitated faster warming in the western Pacific. Our study underscores the key role of the thermal coupling between the warm pool and the Southern Ocean and its relevance for future global warming. The mechanism of the last deglacial global warming is key for future climate. Here, the authors shed light on the pivotal role of the thermal coupling between the western Pacific warm pool and the Southern Ocean.

At present, the seasonal melting and expansion of the Antarctic ice sheet affect the location and intensification of the westerlies, as well as the precipitation and continental weathering and erosion in southwest Australia. The Miocene was an important period when the Earth’s climate state transitioned from a warmhouse to an icehouse and the East Antarctic Ice Sheet underwent large-scale melting and expansion. At that time, Australia was closer to the Antarctic region than it is now. This makes Australia an ideal target area for studying the coupling relationship among the atmosphere, hydrosphere, lithosphere, and cryosphere. Based on the comprehensive analysis of the siliciclastic mass accumulation rate, grain size, clay minerals, and elemental composition of the sediments at Site U1516 of the International Ocean Discovery Program Expedition 369, we reconstructed the Miocene climate evolution and the continental weathering and erosion history of southwest Australia on a tectonic time scale. Our indicators show that the climate was dry and that continental weathering and erosion were weak, with a small amount of terrestrial material transported to the ocean during the Early to Middle Miocene (22–12.7 Ma). However, as mentioned in previous studies of nearby sites, precipitation and river runoff increased prominently with enhanced continental weathering at 12.7–8 Ma, which was related to the northward migration or intensification of the westerlies, possibly due to increased sea ice in the Southern Ocean. In addition, we found that the evolution of the South Asian monsoon and the westerly belt were synchronized in the Miocene, which indicates that the South Asian monsoon system at that time may also have been affected by the high-latitude signals of the Southern Hemisphere. We speculate that the significant decrease in deep-sea temperature and the expansion of the surface sea temperature gradient in latitude and longitude until the permanent East Antarctic Ice Sheet formed (∼12.8 Ma) played an important role in the transmission of Antarctic signals to low latitudes.

Evidence on West Antarctic Ice Sheet (WAIS) instability through Pleistocene glacial/interglacial cycles can provide fundamental constraints on interactions between the climate system and cryosphere. To explore such ice sheet‐ocean‐climate processes on orbital timescales over the last ∼770 ka, we provide continuous records of iceberg‐rafted debris (IRD) content and clay mineralogy, supported by detrital Sr‐Nd isotopes from the pronounced IRD peaks, in gravity core ANT34/A2‐10 from the Amundsen abyssal plain. The IRD record reveals interglacial WAIS instability since ∼770 ka, while comparison to the clay mineralogy record and published records of regional oceanic and atmospheric forcing suggests a temporal link with a strengthened Antarctic Circumpolar Current, enhanced deepwater ventilation, and poleward‐shifted southern westerly winds. In addition, the Sr‐Nd isotope signature of the detrital sediments indicates a shift in provenance around Marine Isotope Stage (MIS) 16, potentially linked to regional oceanic circulation changes. We suggest that an expanded Ross Gyre was important for controlling iceberg trajectories and sediment transport to the site before MIS 16, whereas modern‐like iceberg trajectories were established after MIS 16, probably related to a poleward shift of the Amundsen Sea Low after the end of the Mid‐Pleistocene Transition. This reorganization of the ocean and atmospheric circulation was followed by an interval of enhanced WAIS variability during MIS 15 to 13, which was linked to strong orbital and ocean forcing. These insights into the role of ocean‐atmosphere forcing on the past behavior of the WAIS may improve our framework for understanding future changes in this region. Plain Language Summary Understanding the vulnerability of the West Antarctic Ice Sheet (WAIS) to a warming climate is critical for constraining its future contributions to global sea‐level rise. Previous studies on marine sediment cores have provided evidence for WAIS instability in response to warming ocean waters during recent glacial/interglacial cycles. Here, we extend such work over a longer timescale by generating iceberg‐rafted debris (IRD) content and clay mineralogy records from the Amundsen Sea offshore of West Antarctica back to ∼770 ka. Enhanced IRD content during warm interglacial periods provides evidence for the instability of the WAIS and was accompanied by a shift in clay mineralogy. These changes also coincided with a strengthened Antarctic Circumpolar Current, poleward‐shifted southern westerly winds, and improved deepwater ventilation, as indicated by existing studies. This comparison supports ocean forcing as a driver of WAIS instability since ∼770 ka. We also measured strontium and neodymium isotope signatures on selected samples, revealing a switch in sediment supply around Marine Isotope Stage 16 that was probably related to the reorganization of atmospheric and oceanic circulation. The subsequent interval of strong orbital and ocean forcing led to pronounced WAIS variability from ∼480 to 580 ka. These findings improve our framework for understanding future changes in this region. Key Points Interglacial ocean‐forced instability of the West Antarctic Ice Sheet (WAIS) has existed since at least ∼770 ka Differences in sediment provenance before and after Marine Isotope Stage (MIS) 16 may relate to different states of high‐latitude atmospheric and ocean circulation Strong ocean and orbital forcing may have enhanced WAIS instability from MIS 13 to MIS 15

The Indian Coastal Current is the only channel for material exchange between the two largest marginal seas in the northern Indian Ocean: the Bay of Bengal and the Arabian Sea. However, its past history is poorly known, limiting accurate predictions of its future changes. Here, we present a new clay mineral record from south of India supported by interpretations of model simulations to trace its variability over the last 18 000 years. Decreased smectite/(illite + chlorite) ratios during the cold intervals suggest that a stronger northeasterly wind led to a mean southward flow of the Indian Coastal Current in the Bay of Bengal. In contrast, increased smectite/(illite + chlorite) ratios during the warm intervals suggest the opposite scenario. Combining the proxy record with model simulations, we infer that atmospheric circulation changes were the main driver of the changes. Moreover, a possible link is observed between a positive Indian Ocean Dipole (IOD) and weakened southward flow of the Indian Coastal Current in the Bay of Bengal during the Holocene. These findings imply that future warming scenarios, if associated with more intense positive IOD events as proposed, may lead to a reduction in fresh water transport from the Bay of Bengal to the Arabian Sea.

Meridional heat transport of the western Pacific boundary current (the Kuroshio Current) is one of the key factors in global climate change. This current is important because it controls the temperature gradient between low latitudes and the North Pacific and so significantly influences mid-latitude atmosphere-ocean interactions. Here we reconstruct changes in hydrological conditions within the mid-latitude mainstream of the Kuroshio Current based on faunal analysis of planktonic foraminifera in core DSDP 296 from the Northwest Pacific Ocean. This approach enabled us to deduce evolutionary processes within the Kuroshio Current since the Pliocene. A total of 57 species in the coarser section (>150 µim) were identified; results indicate that planktonic foraminiferal faunal evolution has mainly been characterized by three major stages, the first of which comprised mixed-layer warm-water species of Globigerinoides ruber which first appeared between 3.5 and 2.7 Ma and then gradually increased in content. Percentages of another warm-water species of G. conglobatus also gradually increased in number over this interval. Variations in warm-water species indicate a gradual rise in sea surface temperature (SST) and imply initiation of Kuroshio Current impact on the Northwest Pacific Ocean since at least 3.5 Ma. Secondly, over the period between 2.7 and 2.0 Ma, thermocline species of Globigerina calida, Neogloboquadrina humersa, Neogloboquadrina dutertrei , and Pulleniatina obliquiloculata started to appear in the section. This fauna was dominated by G. ruber as well as increasing G. conglobatus contents. These features imply a further rise in SST and its gradually enhanced influence on thermocline water, suggesting strengthening of the Kuroshio Current since 2.7 Ma. Thirdly, between 2.0 Ma and present, increasing contents of thermocline species (i.e., G. calida, N. dutertrei and P. obliquiloculata ) indicate a gradual rise in seawater temperature at this depth and also imply more intensive Kuroshio Current during this period. On the basis of comparative records from cores ODP 806 and DSDP 292 from the low latitude Western Pacific, we propose that initiation of the impact of the Kuroshio Current in the Northwest Pacific and it subsequent stepwise intensifications since 3.5 Ma can be closely related to the closure and restriction of the Indonesian and Central American seaways as well as variations in the Western Pacific Warm Pool (WPWP) and equatorial Pacific region.

Modern observations have presented linkages between subsurface waters of the western Pacific warm pool and both El Niño/Southern Oscillation-related and extratropic-controlled upper-ocean stratification on interannual timescales. Moreover, studies have showed that such controls may operate on orbital cycles, although the details remain unclear. Here we present paired temperature and salinity reconstructions for the surface and thermocline waters in the central western Pacific warm pool over the past 360,000 years, as well as transit modeling results from an Earth system model. Our results show that variations in subsurface temperature and salinity in the western Pacific warm pool have consistently correlated with the shallow meridional overturning cell over the past four glacial-interglacial cycles, and they vary on eccentricity and precession cycles. The shallow meridional overturning cell regulates subsurface waters of the western Pacific warm pool by changing subtropical surface water density and thus equatorial upper-ocean stratification, acting as an El Niño/Southern Oscillation-like process in the precession band. Therefore, the western Pacific warm pool is critical in connecting the austral shallow meridional overturning cell to the Earth’s climate system on orbital timescales.

Two strains, 81s02T and 334s03T, were isolated from the sediment core near the hydrothermal field of southern Okinawa Trough. The cells of both strains were observed to be rod-shaped, non-gliding, Gram-staining negative, yellow-pigmented, facultatively anaerobic, catalase and oxidase positive, and showing optimum growth at 30 °C and pH 7.5. The strains 81s02T and 334s03T were able to tolerate up to 10% and 9% (w/v) NaCl concentration, respectively. Based on phylogenomic analysis, the average nucleotide identity (ANI) and the digital DNA-DNA hybridization (dDDH) values between the two strains and the nearest phylogenetic neighbors of the genus Muricauda were in range of 78.0–86.3% and 21.5–33.9%, respectively. The strains 81s02T and 334s03T shared 98.1% 16S rRNA gene sequence similarity to each other but were identified as two distinct species based on 81.4–81.5% ANIb, 85.5–85.6% ANIm and 25.4% dDDH values calculated using whole genome sequences. The strains 81s02T and 334s03T shared the highest 16S rRNA gene sequence similarity to M. lutimaris SMK-108T (98.7%) and M. aurea BC31-1-A7T (98.8%), respectively. The major fatty acid of strains 81s02T and 334s03T were identified similarly as iso-C15:0, iso-C17:0 3-OH and iso-C15:1 G, and the major polar lipids of the both strains consisted of phosphatidylethanolamine and two unidentified lipids. The strains contained MK-6 as their predominant menaquinone. The genomic G+C contents of strains 81s02T and 334s03T were determined to be 41.6 and 41.9 mol%, respectively. Based on the phylogenetic and phenotypic characteristics, both strains are considered to represent two novel species of the genus Muricauda, and the names Muricauda okinawensis sp. nov. and Muricauda yonaguniensis sp. nov. are proposed for strains 81s02T (=KCTC 92889T = MCCC 1K08502T) and 334s03T (=KCTC 92890T = MCCC 1K08503T).