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Processes controlling environmental change in the subarctic Pacific Ocean on millennial to orbital timescales are not well understood. Here we use a 230‐kyr sedimentary record from the northwest Pacific Ocean to assess the response of late Pleistocene sediment dynamics to orbital forcing. Combining a source‐to‐sink perspective based on sedimentological records with climate model reanalysis, we reveal that fluctuations in sediment provenance were closely linked to obliquity‐forced changes in atmospheric circulation modes. Specifically, the position of the Aleutian Low controlled sediment transport from the Bering Sea and Aleutian Arc sources. Furthermore, a distinct shift in North Pacific ocean circulation during the Last Glacial Maximum may have been related to a strengthened Siberian High. The coincidence of atmospheric mode switches with changes in sea‐ice extent and North Pacific Intermediate Water formation in the marginal seas suggests that this coupled ocean‐atmosphere system may have acted as a regional amplifier of global climate variability. Plain Language Summary: We use a sedimentary record from the northwest Pacific Ocean to assess the sensitivity of regional sediment transport dynamics to orbital forcing over the last 230 thousand years. By combining the sedimentological records with climate model simulations, we suggest that changes in sediment transport could have resulted from obliquity‐scale changes in atmospheric climatic modes, and specifically the position of the Aleutian Low. Moreover, we found a shift in the location of intermediate water formation during the Last Glacial Maximum, which may have been related to a strengthened Siberian High. This coupled ocean‐atmosphere system represents a potential amplifier of climate variability, such that improved constraints on its past behavior could provide insight into how climatic signals are transferred between regional and global scales. Key Points: Source‐to‐sink studies in the subarctic Pacific Ocean based on geochemical, clay mineralogic and environmental magnetic proxiesThe glacial/interglacial transition can be interpreted to be resulted from atmospheric climatic modes induced by Aleutian low‐forcingThis ocean‐atmosphere response is an amplifying feedback mechanism within the climate system [ABSTRACT FROM AUTHOR]

Paleoceanographic evidence commonly indicates that Last Glacial Maximum surface temperatures in the Japan Sea were comparable to modern conditions, in striking difference to colder neighboring regions. Here, based on a core from the central Japan Sea, our results show similar UK′37‐ and TEXL86‐derived temperatures between 24.7 and 16.3 ka BP, followed by an abrupt divergence at ~16.3 ka BP and a weakening of divergence after ~8.7 ka BP. We attribute this process to a highly stratified glacial upper ocean controlled by the East Asian Summer Monsoon, increasing thermal gradient between surface and subsurface layers during the deglaciation and the intrusion of Tsushima Warm Current since the mid‐Holocene, respectively. Therefore, we suggest that threshold‐like changes in upper‐ocean temperatures linked to sea level rise and monsoon dynamics, rather than just sea surface temperatures, play a critical role in shaping the thermal and ventilation history of this NW Pacific marginal sea. Plain Language Summary: Abnormally warm surface ocean conditions in the Japan Sea during last glacial are a mystery in Pacific paleoenvironmental history. We analyzed records of UK′37‐ and TEXL86‐derived temperatures from the central Japan Sea, which suggests an oceanographic evolution from a highly stratified glacial upper ocean, to a deglacial surface‐subsurface thermal gradient control, and subsequently to modern well‐ventilated conditions since the intrusion of the Tsushima Warm Current started after the mid‐Holocene. Our results suggest a combination of critical factors of oceanographic change, rather than a stand‐alone thermal feature, in changing the history in the Japan Sea. Key Points: Alkenone and TEX86 temperatures represent summer SST during the last glacial with low sea level (<−90 m)Isoprenoidal GDGT community structure index indicates a stratified upper ocean during glacial timeIncreasing tetraether lipid‐based temperature indicates strengthening of the Tsushima Warm Current in the central Japan Sea in the Holocene [ABSTRACT FROM AUTHOR]

Abstract: Kveithola Trough, an E–W trending glacial trough in the NW Barents Sea, was surveyed for the first time during the EGLACOM cruise of R/V OGS-Explora in summer 2008. Swath bathymetry shows that the seafloor is characterized by E–W trending mega-scale glacial lineations (MSGL) that record a fast flowing ice stream draining the Svalbard/Barents Sea Ice Sheet (SBIS) during the Last Glacial Maximum (LGM). MSGL are overprinted by transverse sediment ridges about 15km apart which give rise to a staircase axial profile of the trough. Such transverse ridges are interpreted to be grounding-zone wedges (GZWs) formed by deposition of subglacial till during episodic ice stream retreat. Sub-bottom (CHIRP) and multi-channel reflection seismic data show that the present-day morphology is largely inherited from the palaeo-seafloor topography at the time of deposition of the transverse ridges, overlain by a draping glaciomarine unit which in places is over 15m thick. Our data allow the reconstruction of depositional processes which accompanied deglaciation of the Spitsbergen Bank area. The sedimentary drape deposited on top of the GZWs is suggested to have accumulated at a very high rate, (on average in the order of 1–1.5m ka−1) and therefore may potentially preserve a high-resolution palaeoclimatic record of deglaciation and post-glacial conditions in this sector of the Barents Sea. [ABSTRACT FROM AUTHOR]

Some studies have used excesses of 230Th (230Th xs) in marine cores from low sedimentation rate sites for the setting of a late Pleistocene stratigraphy, but the temporal and spatial variability of 230Th xs fluxes in the Arctic Ocean remains poorly understood. In this paper, we review all available 230Th data from the Arctic Ocean to document the regional 230Th xs behavior within the geological time frame of the latest glacial/interglacial cycles. We evaluate the potential roles of bathymetry, sedimentological regimes, and geochemical properties of the sediment in relation to 230Th xs fluxes. The 230Th xs inventories in the sediment accumulated since the Last Glacial Maximum suggest that 230Th xs fluxes are linked to the sea-ice regime, brine production rate and sinking, organic carbon fluxes, ice-rafting pathways, seawater exchange between the Arctic, Atlantic, and Pacific oceans, nepheloid transportation, and possibly other unidentified factors. During "warm" intervals, the development of "ice factories" over shelves and enhanced detrital and organic matter fluxes related to high sea levels and high summer insolation conditions constitute major parameters governing 230Th xs -records. During glacials, under a perennial ice cover or ice shelf, 230Th xs was partly exported through Fram Strait into the Nordic Seas, and possibly partly built up in the water column, depending on the ventilation rate of the deep-water masses. At the sea floor over slopes and ridges, the winnowing of fine fractions and brines-related compounds by deep currents leads to post-sedimentary redistributions of 230Th xs. These features do not invalidate chronostratigraphic inferences made using 230Th xs -records in sediments but shed light on their use and limitations. Sedimentary profiles of 230Th xs allow the identification of interglacial-interstadial and glacial stages in low sedimentation rate settings. This remains valid for sediments encompassing from recent to Marine Isotope Stage 11 (MIS 11), with some reservations depending on the sedimentary characteristics of the site considered. The 230Th xs records have been initially proposed for the setting of an "extinction age" assigned to the final decay of the excess within the one-sigma uncertainty of its estimate. We show here that this extinction ages may vary between ∼200 to ∼420 kyr, mostly depending on the site-specific relationship between 230Th deposition and sedimentary regime, and on any potential post-depositional effects, which may include redox-driven U mobility and 230Th xs losses linked to fine sediment fractions winnowing. • Validation of 230Th xs as an age-determination tool in the Arctic Ocean. • Invalid age interpolation revealed by the discontinuous 230Th burial in the Arctic. • The importance of insolation and sea level in governing Arctic 230Th scavenging. • Postdeposition of 230Th-enriched components driven by the active deep-water exchange. [ABSTRACT FROM AUTHOR]

The Quaternary history of the Arctic Ocean reflects pronounced periodic changes in marine and glacial environments. This variability is an important component of the Arctic paleoclimatic system. For more insight, we use isotopic measurements on the detrital (Nd-Sr-Pb) and authigenic (Nd) phases of the Quaternary sediments from the central Arctic Ocean. We analyze core ICE4 from ∼3 km water depth off the Lomonosov Ridge. This core was previously studied for other sedimentary proxies (Dong et al., 2022). The analyzed record is estimated to cover major Late Pleistocene Weichselian/Wisconsinian glaciations occurring over the last ∼100–200 ka. Our results provide new evidence that glacially-derived waters from the glaciated margins reached the bottom of the deep Arctic basins. We infer that these waters were delivered to the deep basins by hyperpycnal flows originating from subglacial outbursts accompanying overflow meltwater and iceberg discharge during glacial/deglacial events. Voluminous outbursts during the older, presumed Early/Middle Weichselian glaciation, ca. 115-35 ka, are traced to the West Siberian margin impacted by the Eurasian Ice Sheet. Similar sedimentary layers are found in longer records from the central Arctic Ocean at older stratigraphic intervals. Sediments constrained to the Last Glacial Maximum have less pronounced glacigenic inputs with a stronger Laurentide Ice Sheet signature. The circulation patterns were likely dependent on the interplay of the timing and extent of the Laurentide and Eurasian ice sheets. • Late Pleistocene sediment record from Eurasia Basin, Arctic Ocean. • Isotope proxies in the detrital (Nd, Sr, Pb) and authigenic (Nd) phases. • Eurasian Ice Sheet waters transported to deep basins via hyperpycnal flows. • Less glacigenic inputs with a stronger Laurentide signature during LGM. [ABSTRACT FROM AUTHOR]

The role of the Southern Ocean in releasing CO 2 (sequestered in the global ocean during the Last Glacial Maximum) into the atmosphere during deglaciation is an important topic for investigation of Earth's climate. Changes in global deep water circulation associated with upwelling of Circumpolar Deep Water (CDW) around Antarctica may have played a part in the CO 2 release, but remain poorly studied. The potential response of the Pacific Ocean, including the North Pacific, to upwelling of CDW with its vast reservoir of CO 2 remains unresolved. Here we combine productivity proxies, oxygen and carbon isotope values in benthic and planktic foraminifera, data on the occurrence and abundance of ice-rafted debris, and benthic foraminiferal species composition in three sediment cores with published data for three cores from the Northern Emperor Rise for the Last Glacial Maximum, deglaciation and Holocene in order to elucidate the North Pacific role in CO 2 redistribution in the past. Age models of the cores are based on radiocarbon data calibrated by 14C atmospheric plateau tuning. The calcium carbonate content in all cores increased abruptly around 14.5 ka, indicating an influx of relatively young water enriched in carbonate ion, oxygen and nutrients, and sourced in the Southern Oceans. A decrease in the extent of sea ice at the NER area during early deglaciation is reflected in sharp increases in the productivity of siliceous phytoplankton near the onset of Bølling/Allerød warming, possibly facilitated by the influx of Southern Ocean-sourced nutrient-rich waters. • Stable isotope, lithological and micropaleontological proxies of 6 cores from the Western Subarctic Gyre (WSG) were studied. • Age models of cores over the last 25kyr were modified by radiocarbon data calibrated by 14C atmospheric plateau tuning. • Multiple lines of evidences support abrupt flushing of Southern Ocean origin water into the deep WSG since 14.5 ± 0.2 ka. [ABSTRACT FROM AUTHOR]

The recently revised chronostratigraphy of the central Arctic Ocean sedimentary sequences (https://doi.org/10.1002/2017GC007050) provides the means to insert the Arctic paleoceanography into the Earth's global climate history. Based on magnetostratigraphy, 14C ages and 230Th-231Pa excess extinction ages in a series of sedimentary cores raised from the Mendeleev and Lomonosov ridges by the R/V Polarstern, Healy and MV Xue Long ice-breakers, with chronological complementary information from pre-2000 studies, we have been able to estimate sedimentation rates ranging from less than a few mm/ka to a few cm/ka along these ridges, with the highest accumulation rates eastward, near the ice-factories of the Russian shelf. On the central Arctic ridges, sediment supplies are essentially linked to sea ice rafting when the shelf areas are seasonally open, and iceberg rafting, during stadial intervals with streaming along the Fennocandian-Russian ice margin. It has been possible to outline specific features of these Arctic Ocean records combining sedimentological, mineralogical, geochemical (stable, radiogenic isotopes) and micropaleontological data. Sedimentation rates are highly variable, with hiatuses (for example during the last glacial maximum) and sporadic recordings of intervals with active ice-sheets or active sea ice production and transport through the Trans Polar Drift (TPD) and the Beaufort Gyre (BG). Layers with finer sediment are linked to the deposition of sediments uploaded on shelves, especially in the Laptev Sea area. They record relatively high sea-level intervals, when shelves were submerged. Such recent intervals, marked by high excesses in 230Th and 231Pa, match, at least partly, interglacials (Marine Isotopic Stages -MIS- 1, 5, 7, 9, 11) and some interstadials. One of these relatively high interstadial sea-level dated at ca. 40-50 ka (MIS 3), suggests that the sea-ice factories over shelves have operated when the global sea-level rose above ~ 40 m below its present position. Maximum sea-ice rafting, productivity and biogenic carbonate fluxes are tightly linked, with delays of a few millennia, to maximum insolation peaks in the Northern Hemisphere. They seem thus linked to the orbital forcing of high sea levels and warm North Atlantic Water penetration into the Arctic Ocean. The corresponding sedimentary intervals do not record full interglacial intervals. The most illustrative example is that of the Holocene, recorded by a 1 to 2 cm-thick mixed-layer at core tops of the central Arctic ridges, with biogenic carbonates mean ages of ca. 8 ka. One immediate inference from these observations is that the Quaternary records from the central Arctic Ocean are highly discontinuous, and although orbitally-controlled, partly out of phase with paleoceanographic and paleoclimate records from other oceans and continental areas. The Arctic Ocean may have thus played an intermittent and complex role, nearly that of a jocker, in the high latitude climate-ocean system, either through atmospheric or thermohaline connections through the Bering and Fram strait gateways. [ABSTRACT FROM AUTHOR]

Pronounced Quaternary circulation and depositional changes in the Arctic Ocean basins remain poorly understood. We investigate sediment core ARC5-ICE4 (ICE4) in the Eurasian (Amundsen) Basin off the Lomonosov Ridge to reconstruct glacial-interglacial variability in sediment sources and circulation. The ICE4 record features variable lithologies including distinct glacigenic deposits with Ice Rafted Debris (IRD). The sediment age is constrained by a combination of the organic carbon 14C with paleomagnetic data and correlation to earlier developed stratigraphies. The derived sedimentation rates constitute several cm/kyr (6.5 cm/kyr average) consistent with estimates from regional geophysical data. The developed age model covers the time interval from ca. 10 to 75 ka including Late and Middle Weichselian/Wisconsinian glaciations. Respective glacigenic sediments were primarily deposited by pulsed iceberg discharge. The Last Glacial Maximum and deglaciation is expressed in sharp IRD peaks including mineral proxies of the Laurentide Ice Sheet with an apparent millennial-scale variability. The older glacigenic sedimentary unit with abundant IRD of predominantly Siberian provenance was deposited during deglaciation of the Middle Weichselian (MIS 4/3) Eurasian Ice Sheet. These sedimentary differences indicate diverging impacts of the two glaciations on the Arctic Ocean, including ice-sheet sizes/geometries and oceanic circulation. • Continuous 75-ka Arctic Ocean sediment record from Eurasia Basin off Lomonosov Ridge. • New stratigraphic constraints including 14C OC and paleomagnetic inclination data. • Different circum-Arctic ice sheet extent and circulation inferred for MIS 2 and 4. [ABSTRACT FROM AUTHOR]

The Sea of Japan, located in the humid zone, was subjected to significant freshening of surface waters and a decrease in ventilation of deep waters during the glacial eustatic drop in relative sea level (RSL) and a decrease in water exchange with Pacific due to the shallowness of its straits. As a result, the δ18O values of planktic foraminifera (δ18O pf) decreased by several ppm, in contrast to the increase of ones in the Red Sea, depending on the degree of RSL drop. The good preservation of planktic foraminifera in the sediments of the Sea of Japan during the Last Glacial Maximum (LGM) and deglaciation allows us to significantly refine and supplement the available evidences of the global sea level changes over the 33–15 ka. Based on the obtained and published records of δ18O pf of five cores from different parts of the sea and the general chronology of the accumulation of dark layers in the sediments of the Sea of Japan, we calculated the δ18O pf stacks with high and low resolution (0.13 kyr for two cores and 0.5 kyr for other three cores) for the time 33–15 ka. Both stacks showed significant RSL falls at the onset of LGM (32–29 ka), during 21.8–20.3 ka, and an abrupt rise at 17 ka consistently with previously published data. The higher resolution stack additionally showed two phases of RSL falls at the onset of the LGM followed by a slow decrease until 22 ka, with a short and abrupt descent at around 25 ka. According to both stacks the lowest sea level around 18.5–17.5 ka was preceded by a short rise just before 19 ka. A significant RSL rise at 17 ka was followed by an abrupt and short fall at nearly 16.5 ka and then prolonged rise since around 16.2 ka. • Two stacks of planktic foraminifera δ18O records were calculated over the 33-15 ka with a higher and lower resolution. • Chronology was based on synchronicity of dark layers formation ruled by surface water salinity and ventilation changes. • Both stacks showed significant relative sea level (RSL) falls at 32–29 ka, during 21.8-20.3 ka, and abrupt rise at 17 ka. • A higher resolution stack additionally showed millennial-centennial RSL changes over Last Glacial Maximum and since 17 ka. [ABSTRACT FROM AUTHOR]

Sediment core ARC5-ICE6 from the Makarov Basin was used to reconstruct circum-Arctic glaciation and surface-ocean circulation history for the Middle to Late Pleistocene, ∼0.5–0.7 Ma. Sedimentary proxies include elemental composition, coarse grain content, clay mineralogy, and radiogenic isotopes (Sr-Nd-Pb). Earlier studied records from the central Arctic Ocean were compared with ICE6 for a broader paleoceanographic context. Results indicate predominant sediment delivery from the Eurasian shelves and glaciated mainland with intermittent glacial inputs from North America. Low proxy variability prior to Marine Isotope Stage (MIS) 6 (∼0.2 Ma) suggests persistent sediment transport by sea ice via the Transpolar Drift and limited glaciation at the Eurasian margin. Since MIS 6, sediment inputs and provenance exhibit large shifts between glacial- and interglacial-type environments. The overall northern Eurasian Ice Sheet (EAIS) expansion was possibly related to climatic cooling and growth of a perennial sea ice in the Arctic Ocean. Provenance indicators from MIS 6, 5b and 4/3 reflect EAIS expansions followed by deglacial meltwater discharge from west Siberia. This provenance indicates a strong cyclonic circulation in the Arctic Ocean characterized by a significantly eastward-extended Transpolar Drift. Different glaciogenic sourcing and attendant circulation are proposed for several events within MIS 5 and 3, where proxies indicate increased sediment inputs from North America rather than Eurasian ice sheets. Overall limited glacial influence inferred for MIS 3 is consistent with relatively high sea level reconstructed for this interstadial. The Last Glacial Maximum is barely identifiable in the ICE6 record due to low glacial inputs and/or depositional hiatus. • Predominant sediment delivery from the Eurasian shelves to the southern Makarov Basin during the mid-late Pleistocene. • Intensified glaciation on Eurasian continent since MIS 6 and heterogeneous development of the ice sheets. • Strong cyclonic circulation during intensive glacial/stadials MIS 6, 5b and 4/3. [ABSTRACT FROM AUTHOR]

The Japan Sea is ideal for investigating deep water formation due to its unique topography and hydrography. However, because of the scarcity of reliable indicator and high-resolution ventilation records, the driving mechanisms behind ventilation changes in the entire Japan Sea since the Last Glacial Maximum (LGM) remain elusive. In this study, we analyze the radiolarian assemblage in three sediment cores from the southwestern, central, and northwestern Japan Sea to reveal ventilation variations over the last 25 ka. Our results suggest that weak ventilation was a widespread phenomenon in the Japan Sea during the LGM. This is inferred by the low relative abundances of species belonging into the Japan Sea Proper Water (JSPW) Assemblage, which are indicative of deep water ventilation in the Japan Sea. The JSPW Assemblage have gradually become the predominant species in studied cores from the last deglaciation to the early Holocene, suggesting an abrupt transition from oxygen poorer to oxygen richer conditions. All investigated regions show re-ventilation during the deglaciation, albeit at different times. The JSPW ventilation in the central Japan Sea started during the 19 ka Melt-water Pulse (MWP) and remained in an interglacial mode after MWP-1A (~14.7 ka), presumably due to the opening of the Tsushima Strait and intrusion of the Tsushima Warm Current (TWC). An abrupt increase in productive shallow water export during the Bølling-Allerød (B/A) was likely the key factor causing poorly oxygenated deep-water conditions in the southwestern Japan Sea. In contrast, the weakening ventilation in the northwestern Japan Sea during the B/A and Younger Dryas was probably caused by the blocking effect of the sea ice. • New 25 ka-long radiolarian assemblage records along a meridional transect offer a comprehensive history of deep-water ventilation in the Japan Sea. • The JSPW ventilation underwent drastic changes from suboxic to oxic conditions during the last deglaciation. • The drastic changes in the deep ventilation in the Japan Sea were sensitive to eustatic sea-level. [ABSTRACT FROM AUTHOR]

Assessing modern radiolarian distribution in the marginal seas is essential for understanding its relationship to hydrographic and environmental variables, upon which subsequent interpretation of past radiolarian records can be made reliably. Here, we combine published radiolarian assemblages in 69 surface sediments from the Japan Sea with those obtained from 15 new surface sediments in this study to determine the modern distribution of radiolarians. The Tsushima Warm Current (TWC) taxa are only found in the south of the Subpolar Front. The results of redundancy analysis confirm that the temperature at 10 m depth (temperature 10m) is the main factor controlling the spatial variability of TWC taxa. The water depth plays a key role in affecting the abundances of Japan Sea Proper Water (JSPW) Assemblage including Larcopyle buetschlii Dreyer (adult), Cycladophora davisiana Ehrenberg, and Actinomma group. The JSPW Assemblage can be used as a reliable indicator of ventilation changes in the Japan Sea. Based on the newly developed TWC taxa and JSPW Assemblage, we further reconstructed the water column structure in the central Japan Sea over the past 25 ka. There was weak ventilation in the central Japan Sea even during the Last Glacial Maximum (LGM), although a distinct decrease in the TWC inflow resulted in surface-water freshening and water column stratification. After the LGM, the TWC taxa together with JSPW Assemblage resumed in the central Japan Sea at the 19 ka meltwater pulse (MWP). The MWP-1A was clearly marked by an enhanced intrusion of the TWC. Synchronously, JSPW was ventilated deeply down after ~14.6 ka attaining to the similar level of the Holocene as a result of changing sea surface conditions. Along with the continuing sea-level rise, the matured TWC entered the Japan Sea at 7 ka and since then the modern hydrographic condition has been established. We suggest that the changes in the sea level and TWC strength predominantly determined the surface hydrography and deep ventilation in the central Japan Sea since 25 ka, and the TWC might have notably affected the Japan Sea since the Bølling-Allerød. • Radiolarian distribution patterns in the surface sediments are correlated well with water column environmental variables. • The water structure of the Japan Sea since the last deglaciation is reconstructed based on radiolarian assemblages. • Inflow of the TWC into the central Japan Sea resumed at around 19 ka, earlier than previously thought. • The modern-like deep water ventilation in the central Japan Sea has been established during the B/A. [ABSTRACT FROM AUTHOR]