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We integrate benthic foraminiferal stable isotopes, X‐ray fluorescence elemental ratios, and carbonate accumulation estimates in a continuous sedimentary archive recovered at International Ocean Discovery Program Site U1443 (Ninetyeast Ridge, Indian Ocean) to reconstruct changes in carbonate deposition and climate evolution over the interval 13.5 to 8.2 million years ago. Declining carbonate percentages together with a marked decrease in carbonate accumulation rates after ~13.2 Ma signal the onset of a prolonged episode of reduced carbonate deposition. This extended phase, which lasted until ~8.7 Ma, coincides with the middle to late Miocene carbonate crash, originally identified in the eastern equatorial Pacific Ocean and the Caribbean Sea. Interocean comparison reveals that intense carbonate impoverishment at Site U1443 (~11.5 to ~10 Ma) coincides with prolonged episodes of reduced carbonate deposition in all major tropical ocean basins. This implies that global changes in the intensity of chemical weathering and riverine input of calcium and carbonate ions into the ocean reservoir were instrumental in driving the carbonate crash. An increase in U1443 Log (Ba/Ti) together with a change in sediment color from red to green indicate a rise in organic export flux to the sea floor after ~11.2 Ma, which predates the global onset of the biogenic bloom. This early rise in export flux from biological production may have been linked to increased advection of nutrients and intensification of upper ocean mixing, associated with changes in the seasonality and intensity of the Indian Monsoon. Extended episode of low carbonate accumulation (carbonate crash) between ~13.2 and ~8.7 Ma in the equatorial Indian OceanMost intense phase of carbonate crash in Indian Ocean coincides with reduced carbonate deposition in Atlantic and Pacific OceansEarly onset of biogenic bloom at ~11.2 Ma in Indian Ocean related to intensification of Indian Monsoon

We present centennial‐scale records of sea surface temperature and oxygen isotopes from the Celebes Sea, Makassar Strait, Flores Sea, and northwestern Banda Sea, which provide new insights into the variability of Indonesian hydroclimate over the past 25 kyr. Deglacial warming was generally gradual with an amplitude of 3–4 °C. Statistical evaluation of the temperature data suggests that the onset of deglacial sea surface temperatures warming in the tropical Indonesian Sea occurred earlier than the global atmospheric CO2rise. In contrast to previous terrestrial precipitation records, our ice volume‐corrected δ18O of seawater (δ18Osw) does not support widespread aridity in central Indonesia during the last glacial period. While δ18Oswwas substantially enriched during Heinrich Stadial 1 and the Younger Dryas, δ18Oswvalues were only ~0.2‰ heavier during the Last Glacial Maximum than during the Holocene. Heavier δ18Oswduring Heinrich Stadial 1 and the Younger Dryas either reflects a decline in precipitation amount and/or increased δ18O of rainfall in central Indonesia, both likely caused by a southward displacement of the tropical rain belt. Comparison of the Celebes Sea, Makassar Strait, Flores Sea, and Banda Sea records suggests that rainfall isotope and/or amount changes were comparable over Borneo and Sulawesi during the last termination. Deglacial warming in the central Indonesian Archipelago started before 18 kaδ18Oswrecords do not support widespread aridity in central Indonesia during the last glacial periodHeavier δ18Oswduring stadials either reflect a decline in precipitation amount and/or increased δ18O of rainfall in central Indonesia

We present a high‐resolution (~20 to 100 years temporal resolution) reconstruction of hydrological changes in the Makassar Strait over the last 14 kyr from Core SO217‐18517 retrieved off the Mahakam Delta (1°32.198′S, 117°33.756′E; 698 m water depth) during the SO217 Makassar‐Java Cruise. Sea surface temperatures, based on Mg/Ca of Globigerinoides ruberand alkenone UK′37, and seawater δ18O reconstructions, based on G. ruberδ18O and Mg/Ca, in combination with sortable silt grain size measurements and X‐ray fluorescence (XRF) core scanner derived elemental data provide evidence for increased precipitation during the Bølling‐Allerød (BA) and early Holocene and for warmer and more saline surface waters and a decrease in the intensity of the Indonesian Throughflow (ITF) during the Younger Dryas (YD). XRF derived Log (Zr/Rb) records, sortable silt data and increased sedimentation rates indicate decreased winnowing, interpreted as a slowdown of the ITF thermocline flow during the YD. We attribute this decline in ITF intensity to slowdown of the Atlantic meridional overturning circulation during the YD. We suggest that changes in Makassar Strait surface hydrology during this interval of Northern Hemisphere cooling and Southern Hemisphere warming were related to a southward displacement of the Intertropical Convergence Zone. Multiproxy records of Makassar Strait hydrology over the past 14 kaSlowdown of Indonesian Throughflow and drying of Borneo during Younger DryasLatitudinal displacement of ITCZ controlled Makassar Strait surface hydrology

We investigated the onset and development of Cretaceous Oceanic Anoxic Event 2 (OAE2) in a newly drilled core (SN°4) from the Tarfaya Basin (southern Morocco), where this interval is unusually expanded. High‐resolution (centimeter‐scale equivalent to centennial) analysis of bulk organic and carbonate stable isotopes and of carbonate and organic carbon content in combination with XRF scanner derived elemental distribution reveal that the ocean‐climate system behaved in a highly dynamic manner prior to and during the onset of OAE2. Correlation with the latest orbital solution indicates that the main carbon isotope shift occurred during an extended minimum in orbital eccentricity (~400 kyr cycle). Shorter‐term fluctuations in carbonate and organic carbon accumulation and in sea level related terrigenous discharge were predominantly driven by variations in orbital obliquity. Negative excursions in organic and carbonate δ13C preceded the global positive δ13C shift marking the onset of OAE2, suggesting injection of isotopically depleted carbon into the atmosphere. The main δ13C increase during the early phase of OAE2 in the late Cenomanian was punctuated by a transient plateau. Maximum organic carbon accumulation occurred during the later part of the main δ13C increase and was associated with climate cooling events, expressed as three consecutive maxima in bulk carbonate δ18O. The extinctions of the thermocline dwelling keeled planktonic foraminifers Rotalipora greenhornensisand Rotalipora cushmanioccurred during the first and last of these cooling events and were likely associated with obliquity paced, ocean‐wide expansions, and intensifications of the oxygen minimum zone, affecting their habitat space on a global scale. The onset of OAE2, which corresponds to a two‐stepped increase in δ13C spanning ~100 kyr, is preceded by negative carbon isotope excursionsA three‐stepped transient climate cooling with intermittent brief anoxic episodes occurred in the latest stage of the main δ13C increaseTwo major extinction events of thermocline dwelling planktonic foraminifers were closely linked to intensifications of the OMZ

Obliquity influences the latitudinal position of the Intertropical Convergence Zone (ITCZ). However, the specific forcing mechanism remains unclear due to scarcity of long‐term and high‐resolution precipitation records from the Indo‐Pacific region. Here, we present a new, extended, high‐resolution (∼2 kyr) precipitation record covering the past ∼410 kyr from a marine sedimentary sequence collected at the southern margin of the ITCZ's latitudinal displacement within the Indo‐Pacific region. By integrating this new precipitation record with the published precipitation records at the northern margin of the ITCZ's latitudinal displacement, we found that precipitation in the Northern and Southern Hemispheres varied in anti‐phase on the obliquity band, indicating that the latitudinal migration of the ITCZ was dominated by obliquity. The obliquity forcing on the latitudinal migrations of the ITCZ could be imparted by variations in the North Atlantic sea ice cover, resulting from Agulhas leakage induced changes in the ventilation strength of the Atlantic meridional overturning circulation. We used a combined marine temperature and oxygen isotope record offshore northwestern Australia to reconstruct precipitation change at the southern margin of the Intertropical Convergence Zone (ITCZ)'s latitudinal displacement during the past ∼410 kyr. By integrating the new precipitation record with the published Northern Hemisphere subtropical precipitation records, we found that the latitudinal migration of the ITCZ during the past ∼410 kyr was strongly influenced by orbital obliquity, the tilt of the Earth's rotational axis. We propose that obliquity forcing was transmitted from the Southern Hemisphere middle latitudes to the Northern Hemisphere high latitudes via changes in the ventilation strength of the Atlantic meridional overturning circulation modulated by the Agulhas leakage that transfers water mass from the Indian Ocean to the Atlantic Ocean. The resulting changes in North Atlantic sea ice cover further drove the latitudinal migration of the ITCZ. Core U1483 surface seawater δ18O reflects precipitation at the southern margin of the Intertropical Convergence Zone (ITCZ)'s latitudinal displacement on the obliquity bandObliquity dominated latitudinal migration of the ITCZ by modulating the North Atlantic sea ice cover Core U1483 surface seawater δ18O reflects precipitation at the southern margin of the Intertropical Convergence Zone (ITCZ)'s latitudinal displacement on the obliquity band Obliquity dominated latitudinal migration of the ITCZ by modulating the North Atlantic sea ice cover

The transfer of surface and intermediate water from the Pacific to Indian Ocean through the Indonesian passages (Indonesian Throughflow: ITF) strongly influences the heat and freshwater budgets of tropical water masses, in turn affecting global climate. Here, we use combined δ18O and Mg/Ca analyses of surface and thermocline planktonic foraminifers to estimate variations in sea surface temperature, salinity and mixed layer thickness over the last 140 ka. Comparison of water mass properties reveals a steeper thermocline temperature gradient in the Timor Strait than in the eastern Indian Ocean during glacials, implying a decrease in ITF cool thermocline outflow. A major freshening and cooling of thermocline waters occurred at c. 9.5 ka, when sea level rose above a critical threshold, allowing establishment of a shallow marine connection from the South China Sea to the Java Sea. Comparison of benthic δ13C profiles (c. 1800 to 3000 m water depth) suggests vigorous mixing of Indian Ocean and ITF outflow intermediate waters during interglacials. In contrast, deep and intermediate water masses became more stratified during glacials. Lower δ13C values at c. 3000 m water depth reflect a decrease in deepwater ventilation, probably related to slowdown of the global thermohaline circulation during glacials.

The East China Sea (ECS) seasonally receives a high organic input due to the terrestrial organic matter influx, which is controlled by the East Asian Summer Monsoon (EASM), and the increased productivity driven by upwelling of the subsurface Kuroshio Current (KC). Changes in benthic foraminiferal assemblage composition in combination with paleoceanographic proxy data (CaCO3(%), TOC (%), δ13Cpf, and δ18Obf) are used to reconstruct bottom water oxygenation and organic export flux variability over the last 400 kyr in the ECS. Multivariate analyses of benthic foraminiferal census data identified six biofacies characteristic of varying environmental conditions. These results suggest that enhanced EASM precipitation and KC upwelling directly influenced organic export flux and bottom water oxygen content in the ECS. The ECS bottom water was suboxic during Marine Isotope Stage (MIS) 11 to 8; suboxic to dysoxic between MIS 7 and 6, strongly dysoxic between mid‐MIS 5 and 4, and exhibited high variability between MIS 3 and 1. Spectral analysis of relative abundances of representative genera Quinqueloculina(oxic), Bulimina(suboxic), and Globobulimina(dysoxic) reveals a robust 23 kyr signal, which we attribute to precessionally‐paced changes in surface productivity and bottom water oxygenation related to KC variability over the past 400 kyr. Four distinct phases of bottom water oxygenation were identified during the last 400 kyr in the East China SeaEast Asian Summer Monsoon and Kuroshio Current influenced East China Sea productivity, organic export flux, and bottom water oxygenationPrecessional variability modulates bottom water oxygenation in ECS Four distinct phases of bottom water oxygenation were identified during the last 400 kyr in the East China Sea East Asian Summer Monsoon and Kuroshio Current influenced East China Sea productivity, organic export flux, and bottom water oxygenation Precessional variability modulates bottom water oxygenation in ECS

We collected a suite of core top samples during R/V Sonne Cruise SO257 in May 2017 along the southwestern front of the Indo‐Pacific Warm Pool (IPWP) to monitor the variability of Southern Hemisphere tropical and subtropical sea surface hydrology and to assess temperature and salinity reconstructions with data sets reflecting conditions in the post‐monsoonal season. In our core top samples, a steep increase in planktic δ18O, associated with a decrease in sea surface temperature (SST), indicates that the southwestern front of the IPWP is located between 23° and 24°S during austral fall. We additionally reconstructed SST, sea surface salinity ,and δ18O seawater (δ18Osw) over the last 450 kyr in two sediment successions located within and beyond the monsoonal rain belt. Our records show that SST was highly coherent and phase‐locked with atmospheric pCO2during the last 450 kyr. The regional differences in the δ18Oswrecords reveal that the Western Australian Margin north of 15°S remained seasonally under the influence of IPWP water masses, even during glacials. The temporal variability in upper ocean hydrology along the Western Australian Margin is not directly coupled to local monsoonal precipitation, but is strongly affected by advective mixing of Indonesian Throughflow derived water masses. Southwest front of modern Indo‐Pacific Warm Pool (IPWP) during austral fall is located between 23° and 24°SWestern Australian Margin north of 15°S remained seasonally influenced by IPWP throughout past 450 kyrUpper ocean hydrology off Western Australia represents an integrated signal of monsoonal precipitation and advective mixing Southwest front of modern Indo‐Pacific Warm Pool (IPWP) during austral fall is located between 23° and 24°S Western Australian Margin north of 15°S remained seasonally influenced by IPWP throughout past 450 kyr Upper ocean hydrology off Western Australia represents an integrated signal of monsoonal precipitation and advective mixing

The late Miocene was a period of declining CO2levels and extensive environmental changes, which likely had a large impact on monsoon strength as well as on the weathering and erosion intensity in the South Asian Monsoon domain. To improve our understanding of these feedback systems, detrital clays from the southern Bay of Bengal (International Ocean Discovery Program Site U1443) were analyzed for the radiogenic isotope compositions of Sr, Nd, and Pb to reconstruct changes in sediment provenance and weathering regime related to South Asian Monsoon rainfall from 9 to 5 Ma. The 100 kyr resolution late Miocene to earliest Pliocene record suggests overall low variability in the provenance of clays deposited on the Ninetyeast Ridge. However, at 7.3 Ma, Nd and Pb isotope compositions indicate a switch to an increased relative contribution from the Irrawaddy River (by ∼10%). This shift occurred during the global benthic δ13C decline, and we suggest that global cooling and increasing aridity resulted in an eastward shift of precipitation patterns leading to a more focused erosion of the Indo‐Burman Ranges. Sr isotope compositions were decoupled from Nd and Pb isotope signatures and became more radiogenic between 6 and 5 Ma. Grassland expansion generating thick, easily weatherable soils may have led to an environment supporting intense chemical weathering, which is likely responsible for the elevated detrital clay 87Sr/86Sr ratios during this time. This change in Sr isotope signatures may also have contributed to the late Miocene increase of the global seawater Sr isotope composition. The South Asian or Indian monsoon affects the lives of billions. Through the erosion and weathering of rocks, the monsoon also has the potential to remove carbon dioxide from the atmosphere through increased weathering in the region including the Himalaya Mountains. The late Miocene, between 9 and 5 million years ago, was a period of global cooling and proliferation of grasslands in different regions including South Asia. Here, we examine the composition of clays formed by rock weathering during the late Miocene to determine their source region around the Bay of Bengal. The results suggest a generally stable mixture of sources with the strongest sources being regions with the highest monsoon rainfall today. We identify slight changes in the mixture of sources, which accompany a global change in carbon cycling, highlighting the role monsoon climate likely played in these changes. Toward the end of the Miocene, we identify a change in the Sr isotopes, which was not caused by source changes but by the strength of the rock weathering. This change has been observed in global records and it seems likely that it was driven by rock weathering in the South Asian Monsoon region. Radiogenic isotope compositions of detrital clays from the Bay of Bengal indicate a generally stable provenance from 9 to 5 MaA step change in Nd and Pb isotope compositions at ∼7.3 Ma reflects a climatically driven eastward shift in precipitation patterns resulting in enhanced erosion of the Indo‐Burman RangesElevated 87Sr/86Sr between 6 and 5 Ma was likely related to increased chemical weathering caused by thicker soils and by C4 plant expansion Radiogenic isotope compositions of detrital clays from the Bay of Bengal indicate a generally stable provenance from 9 to 5 Ma A step change in Nd and Pb isotope compositions at ∼7.3 Ma reflects a climatically driven eastward shift in precipitation patterns resulting in enhanced erosion of the Indo‐Burman Ranges Elevated 87Sr/86Sr between 6 and 5 Ma was likely related to increased chemical weathering caused by thicker soils and by C4 plant expansion

The Indonesian Throughflow (ITF), as the sole low‐latitude conduit connecting the Pacific and Indian Oceans, regulates the thermohaline balance between these oceans. Thus, investigating the variability in the ITF and its relationship with the precessional forcing is crucial for understanding the drivers of tropical climate change. Here, we reconstruct the history of the ITF over the past ∼120 kyr based on high‐resolution (∼400 years) δ18O and Mg/Ca records of Globigerinoides ruberand Pulleniatina obliquiloculatafrom core SO217‐18540 retrieved from the Flores Sea upwelling region within the main pathway of the ITF. A comparison of these new records with published paleo‐oceanographic and climatological data from the western tropical Pacific Ocean suggests that annual mean conditions in the Flores Sea were controlled by ITF variability rather than by monsoonal upwelling. Our results further indicate that precessional insolation was a major forcing for the hydrological evolution of the ITF during the past 120 kyr. We suggest that the precessional insolation forcing paced ITF variability by modulating the mean state of El Niño‐Southern Oscillation‐like conditions and latitudinal shifts and/or expansion/contraction of the Intertropical Convergence Zone. The Indonesian Throughflow (ITF) is the only low‐latitude current transporting warmer, fresher water masses from the Pacific to the Indian Ocean, regulating the interocean heat and fresh water budgets. The ITF is strongly influenced by shifts in winds and temperatures across the tropical Pacific Ocean (El Niño‐Southern Oscillation; ENSO) and by variations in the latitudinal position and intensity of the hottest part of the tropical climate belt (Intertropical Convergence Zone; ITCZ). Hence, understanding past ITF variability is highly relevant to constrain projections of future tropical climate change. Here, we present new upper ocean temperature and salinity records spanning the last 120 kyr from core SO217‐18540 retrieved within the main ITF pathway. These records are based on δ18O and Mg/Ca analyses of surface and deeper dwelling microscopic zooplankton shells (foraminifera). We found that variations in the ITF intensity and vertical structure were controlled by the ∼20 kyr wobble of the Earth's axis, which affects the distribution of incoming solar radiation. We ascribe this pattern of variability to shifts in the intensity and/or position of the ITCZ and to changes in winds and temperatures over the tropical Pacific Ocean, similar to the modern ENSO but acting on longer timescales in Earth's history. The first δ18O and Mg/Ca records of G. ruberand P. obliquiloculatathat span the last 120 kyr from the main Indonesian Throughflow (ITF) pathway are presentedPrecessional insolation influenced the thermal evolution of the ITF by modulating the mean state of ENSO‐like conditionsPrecessional variability in ENSO‐like states coupled to the intensity and latitudinal extent of the Intertropical Convergence Zone forced changes in δ18Osw‐cof the ITF The first δ18O and Mg/Ca records of G. ruberand P. obliquiloculatathat span the last 120 kyr from the main Indonesian Throughflow (ITF) pathway are presented Precessional insolation influenced the thermal evolution of the ITF by modulating the mean state of ENSO‐like conditions Precessional variability in ENSO‐like states coupled to the intensity and latitudinal extent of the Intertropical Convergence Zone forced changes in δ18Osw‐cof the ITF

The long‐term evolution of the East Asian Monsoon and the processes controlling its variability under changing climate boundary conditions remain enigmatic. Here, we integrate new and published high‐resolution planktic and benthic foraminiferal isotope data with proxy records for chemical weathering derived from diffuse reflectance spectroscopy at Ocean Drilling Program Site 1146 (South China Sea) to reconstruct the evolution of the summer monsoon between ∼17 and 5 Ma. Our records show that an overall warm and humid tropical climate prevailed over southeastern Asia during the Miocene Climatic Optimum, suggesting northward expansion of the tropical rain belt in response to greenhouse gas forcing. By contrast, monsoon seasonality increased during the middle Miocene Climatic Transition in tandem with Antarctic glacial expansion and global cooling. Substantial weakening of the summer monsoon between ∼12.7 and 10.9 Ma supports that decreased weathering and riverine input of nutrients and alkalinity contributed to carbonate depletion in the deep ocean during the Carbonate Crash. Intensification of monsoonal circulation and strengthening of the biological pump through the late Miocene promoted carbon burial, drawdown of atmospheric CO2,and climate cooling during the Biogenic Bloom. These results underscore the dynamic evolution of the East Asian Monsoon throughout the middle to late Miocene. Variations in local insolation forcing and in Southern Hemisphere ice volume, influencing the latitudinal thermal gradient, evaporation‐moisture budgets, and the strength of the tropical convection, exerted major controls on the development of the monsoon. Equable, warm, and humid climate over Southeast Asia during Miocene Climatic Optimum due to latitudinal expansion of tropical convectionIntensification of seasonal monsoonal regime linked to stepwise climate cooling during middle Miocene Climatic TransitionDecreased riverine input of alkalinity to ocean due to summer monsoon decline contributed to middle to late Miocene Carbonate Crash Equable, warm, and humid climate over Southeast Asia during Miocene Climatic Optimum due to latitudinal expansion of tropical convection Intensification of seasonal monsoonal regime linked to stepwise climate cooling during middle Miocene Climatic Transition Decreased riverine input of alkalinity to ocean due to summer monsoon decline contributed to middle to late Miocene Carbonate Crash

Sea surface temperatures (SSTs) of the tropical Pacific Ocean exert powerful controls on regional and global climates. Previous studies have suggested that during warm climate phases, the east‐west temperature gradient collapsed. To date, there has been no high‐resolution reconstruction of sea surface conditions in both the east and west Pacific Ocean during the Miocene Climate Optimum (MCO) and across the middle Miocene climate transition (MMCT); therefore, our understanding of the mean oceanographic state during this major global climatic shift is limited. Here, we present new SST reconstructions for the eastern Pacific Ocean (15.5–13.3 Ma) which show a clear east‐west temperature gradient of ∼4°C during the warmest interval of the Neogene, implying that the oceanographic processes that produce the modern gradient were present and active. There is no shift in the east‐west gradient across the MMCT indicating that the gradient was not impacted by global cooling and ice growth. We find a 2°C sea surface cooling in the eastern equatorial Pacific, that lags the benthic foraminiferal δ18O positive shift by 150 kyr, indicating that tropical temperature did not decrease synchronously with the expansion of the Antarctic ice sheet. Reconstructed variations in the δ18O composition of seawater, determined by combining our Mg/Ca and δ18O records, reveal a freshening in the eastern Pacific Ocean after 13.8 Ma, suggesting changes in the hydrological cycle and in tropical fronts in response to the new icehouse regime. In the modern ocean, there is a large temperature gradient between the western and eastern tropical Pacific Ocean due to the contrast between the West Pacific Warm Pool waters and cold upwelling waters in the east. We used the geochemistry of fossil microorganisms sampled from a sediment core to reconstruct sea surface temperatures during an interval of the Earth's history (15.5–13.3 million years ago) that was warmer than today. Our results indicate that during the warmest climate phase of the last 23 million years, there was still a temperature gradient between the western and eastern Pacific and this gradient continued throughout a subsequent interval of climate cooling. High resolution foraminiferal δ18O coupled with Mg/Ca, provide detail on temperature and δ18O composition of seawater between 15.5 and 13.3 MaMiocene SST records reveal an E‐W gradient of ∼4°C across the Pacific, which remained constant through an interval of ice sheet expansionSurface water freshening post 13.8 Ma suggests changes to the hydrological cycle/tropical fronts due to enhanced meridional thermal gradients High resolution foraminiferal δ18O coupled with Mg/Ca, provide detail on temperature and δ18O composition of seawater between 15.5 and 13.3 Ma Miocene SST records reveal an E‐W gradient of ∼4°C across the Pacific, which remained constant through an interval of ice sheet expansion Surface water freshening post 13.8 Ma suggests changes to the hydrological cycle/tropical fronts due to enhanced meridional thermal gradients

Tectonics and regional monsoon strength control weathering and erosion regimes of the watersheds feeding into the Bay of Bengal, which are important contributors to global climate evolution via carbon cycle feedbacks. The detailed mechanisms controlling the input of terrigenous clay to the Bay of Bengal on tectonic to orbital timescales are, however, not yet well understood. We produced orbital‐scale resolution geochemical records for International Ocean Discovery Program Site U1443 (southern Bay of Bengal) across five key climatic intervals of the middle to late Miocene (15.8–9.5 Ma). Our new radiogenic Sr, Nd, and Pb isotope time series of clays transported to the Ninetyeast Ridge suggest that the individual contributions from different erosional sources overall remained remarkably consistent during the Miocene despite major tectonic reorganizations in the Himalayas. On orbital timescales, however, high‐resolution data from the five investigated intervals show marked fluctuations of all three isotope systems. Interestingly, the variability was much higher within the Miocene Climatic Optimum (around 16–15 Ma) and across the major global cooling (~13.9–13.8 Ma) until ~13.5 Ma, than during younger time intervals. This change is attributed to a major restriction on the supply of High Himalayan erosion products due to migration of the peak precipitation area toward the frontal domains of the Himalayas and the Indo‐Burman Ranges. The transient excursions of the radiogenic isotope signals on orbital timescales most likely reflect climatically driven shifts in monsoon strength. A consistent mix of clay sources contributed to the Bay of Bengal throughout the middle to late MioceneA marked change in detrital Sr, Nd, and Pb isotope variability at 13.5 Ma was related to Miocene global coolingTransient orbital‐scale fluctuations in clay source most likely reflect changes in monsoon intensity

We reconstructed the variability of the Earth's strongest hydrological system, the Indian monsoon, over the interval 6.24 to 4.91 Ma at International Ocean Discovery Program (IODP) Expedition 353 Site U1448 in the Andaman Sea. We integrated high‐resolution benthic and planktic foraminiferal carbon and oxygen isotopes with Mg/Ca measurements of the mixed layer foraminifer Trilobatus sacculiferto reconstruct the isotopic composition of seawater (δ18Osw) and the gradient between planktic and benthic foraminiferal δ13C. A prominent increase in mixed layer temperatures of ~4°C occurred between 5.55 and 5.28 Ma, accompanied by a change from precession‐ to obliquity‐driven variability in planktic δ18O and δ18Osw. We suggest that an intensified cross‐equatorial transport of heat and moisture, paced by obliquity, led to increased summer monsoon precipitation during warm stages after 5.55 Ma. Transient cold stages were characterized by reduced mixed layer temperatures and summer monsoon failure, thus resembling late Pleistocene stadials. In contrast, an overall cooler background climate state with a strengthened biological pump prevailed prior to 5.55 Ma. These findings highlight the importance of internal feedback processes for the long‐term evolution of the Indian monsoon. Increase of ~4°C in Indian Ocean mixed layer temperatures from 5.55 to 5.28 MaChange from precession‐ to obliquity‐driven variability of Indian monsoon rainfall coincident with warming at 5.55 MaFailure of Indian summer monsoon during transient cold stages

The Intertropical Convergence Zone (ITCZ), which is the heaviest rain belt on Earth, significantly influences global hydroclimate change and livelihood of nearly 40% of the global population. However, long‐term precipitation records are sparse from the Indo‐Pacific region, especially from the southern margin of the Indo‐Pacific ITCZ, restricting our understanding of the overall natural variability of the ITCZ in the past. In this study, we present a new summer monsoonal precipitation record that spans the last 410 kyr from the southern margin of the Indo‐Pacific ITCZ, based on the logarithmic ratio between terrigenous fraction K and pelagic fraction Ca (ln(K/Ca)). Contents of both elements were derived from X‐ray fluorescence scanning on sediment cores from Site U1483 (13°05.24′S, 121°48.25′E, water depth 1,733 m) that was drilled offshore northwestern Australia during International Ocean Discovery Program Expedition 363. Comparison of the new precipitation record with published precipitation records from the northern margin and meteorological center of the Indo‐Pacific ITCZ shows that precipitation changed nearly in‐phase between the hemispheres on the precession band, possibly linked to expansion and contraction in the latitudinal extent of the Indo‐Pacific ITCZ. In contrast, interhemispheric precipitation was nearly in anti‐phase on the obliquity band, likely due to latitudinal migration of the Indo‐Pacific ITCZ. Our findings imply that tropical hydroclimate cycles were regulated by the orbital forcing but with significantly different response to changes of the ITCZ on precession and obliquity bands. A new summer monsoonal precipitation record that spans the last 410 kyr from the southern margin of the Indo‐Pacific ITCZ was presentedInterhemispheric precipitation in‐phasing on precession band could be linked to expansion and contraction of the Indo‐Pacific ITCZInterhemispheric precipitation anti‐phasing on obliquity band could be due to latitudinal migration of the Indo‐Pacific ITCZ