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The Western Subarctic Gyre (WSG) in the North Pacific represents the termination of the Atlantic Meridional Overturning Circulation (AMOC). It has been strongly influenced by periodic glaciations of adjacent landmasses, orbital- and millennial-scale variability of its environment, and ventilation, which, to date, have been poorly studied. In this study, we investigated sediment core LV76-21 recovered from the Detroit Seamount using several productivity and lithological proxies, δ18O records of planktic and benthic foraminifera (δ18Opf and δ18Obf), AMS 14C data. We also used the published results from three well-dated cores from the Detroit and Tenji Seamounts. Comparison of the δ18Opf and δ18Obf records allowed us to establish iceberg discharge events 1 and 1' at 39–36.8 and 42–40 ka, respectively, in the WSG over the last 43 kyr. This was accompanied by considerable lightning of δ18Opf relative to the coeval δ18Obf values. The lithological results have also shown variable sea-ice influence on the regional environment during Marine Isotope Stage 3 and particularly 2, with sea ice extensions at 28.5–25.5 ka and 17.6–16.6 ka, and its significant loss since the Bølling–Allerød warming. We used high resolution δ18Obf records from studied cores as a subtle proxy of contribution of North Atlantic Deep Water (NADW) to Lower Circumpolar Deep Water (LCDW), which originating from around Antarctica and have slightly different δ18Obf values, in order to reconstruction of its spatial variability in the context of regional deep-water ventilation. The contribution of NADW to LCDW in the ventilation of the western flank of Detroit Seamount significantly increased during the interglacial and long-lasting Dansgaard–Oeschger interstadials, which was synchronous with the AMOC intensification. Over the last 43 kyr, the deep water of its eastern flank has been constantly ventilated by the LCDW with low contribution of NADW. • ●Sediment core LV76-21 recovered from the Detroit Seamount is analyzed. • ●Productivity and lithological proxies, δ18O records, and 14C data are derived. • ●Iceberg discharge and sea-ice influences are identified over the last 43 kya. • ●NADW inputs into deep-water ventilation are synchronous with AMOC intensification. • ●The eastern flank of the Detroit Seamount has been constantly ventilated by ABW. [ABSTRACT FROM AUTHOR]

Coarse fraction (CF) content, grain-size distribution, roundness of CF, gravels and pebbles, and examination of surface of pebbles were studied in core LV28-44-4, recovered from the eastern Okhotsk Sea (OS). The age model of the studied core was based on the AMS 14 C data, tephrochronology, δ 18 O benthic foraminifera record, and correlation of peaks of productivity proxies with long-lasted Dansgaard-Oeschger (DO) interstadials. The results show that sea ice was the main transport agent for CF (ice-rafted debris, IRD) in the eastern OS. Published mineralogical studies of clastic material of the OS indicated that the coast of western Kamchatka was the main source of IRD in the eastern OS. We found 19 peaks of IRD, which mostly coincided with DO stadials. The distribution of CF indicates a different pattern of IRD supply during MIS 4, 3, and 2. Comparison of IRD records in the eastern and central parts of the OS allow us to reconstruct millennial changes in ice and wind modes for MIS 4–MIS 2. Significant strengthening of northeastern and eastern winds during DOSs of MIS 3 and of northern and north-western winds during MIS 2 were observed. [ABSTRACT FROM AUTHOR]

As the main heat and water mass sources, the warm and saline Pacific waters have significant influence on sea ice and intermediate water circulation in the Sea of Okhotsk (SO). However, the long-term history of Pacific warm water intrusion into the SO remains unknown, impeding accurate predictions of its future changes. In this study, provenance proxies (clay mineral assemblages and trace element ratios (<2 μm)) from surface sediments and Site LV87-55-1 were used to investigate the history of Pacific water intrusion into the SO over the past 20 kyr. Provenance analysis indicates that sediments in the central SO primarily originated from the Amur River before 11.7 ka, with a significant rise in sediment input from the Kamchatka Peninsula since that time. By integrating published data on sediment grain size, sea surface temperature (SST), and sea-ice diatoms, we observed that the enhanced inflow of Pacific warm water into the SO led to intensified counterclockwise surface currents and the retreat of sea ice since the early Holocene, which subsequently resulted in a noticeable shift in sediment sources in the central SO. Furthermore, based on modern observation and TraCE-21 model simulations, we deduce that the intensified Aleutian Low (AL) since the early Holocene stimulated the East Kamchatka Current (EKC) through increased Sverdrup transport caused by cyclonic wind patterns. This, in turn, facilitated greater intrusion of Pacific warm water into the SO. Overall, our findings suggest an increase in Pacific warm water intrusion into the SO under future global warming scenarios, potentially posing a significant threat to the marine environment of both the SO and the subarctic Pacific. • Provenance records indicate enhanced intrusion of Pacific water into the SO since 11.7 ka. • Increased warm water intrusion results from enhanced Aleutian Low since 11.7 ka. • Future warming climate would stimulate more Pacific water intrusion into the SO. [ABSTRACT FROM AUTHOR]

The subarctic Pacific Ocean, which is linked to both polar and tropical climates, is an area of high marine productivity and is sensitive to ocean-atmosphere CO 2 flux. However, the mechanisms underlying the drivers of its productivity dynamics or patterns remain elusive. Using biogenic barium, opal, and terrigenous input in a sediment core for the past 230 kyr, we present a continuous high-resolution nutrient availability dynamic for the subarctic Pacific Ocean and assess possible changes to sea ice and glacial North Pacific Intermediate Water on nutrient upwelling in the region. We suggest that export production in this region is controlled by the freshwater discharge associated with moisture and heat from low-latitude and the iceberg discharge from Kamchatka glaciations under a weak Aleutian Low. These findings indicate that both high- and low-latitude climate systems forced the evolution of the marine environment and primary productivity in the high-latitude North Pacific. • The reduced nutrient availability was governed by expanding sea ice and North Pacific Intermediate Water formation. • The melting water variations in freshwater discharge associated with the low latitude moisture. • High- and low-latitude climate systems force the evolution of the high-latitude marine primary productivity. [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 response of benthic foraminifera (BF) and radiolarian production in the central Okhotsk Sea (OS) to orbital and millennial changes of climate and environment over the last 136 kyr have been studied on the basis of the sediment core PC-7R, with available productivity, geochemical and lithological records and a modified age model. We used the calculated accumulation rate of microfossils (AR, fluxes) of the main ecological groups and species indicative of radiolarians and of BF as quantity responses in their production, which is related to environmental and hydrological changes of the water column and surface sediment in the central OS and to global and regional climate changes. The responses of the opportunistic BF Alabaminella weddellensis and the suboxic group during the last 136 kyr were mostly related to changes in organic fluxes from the surface, sea ice cover and surface sediment oxygenation at both orbital and millennial time scales. The AR of radiolarians from the surface, dichothermal and mesopelagic groups significantly differed from the AR of BF. The AR has a maximum during the middle and late Marine Isotope Stage 5e and lower values during the earlier Holocene, while the minimum happened during cold Marine Isotope Stages 6, 4 and 2 with maximal ventilation of OS intermediate water. Production of the mesopelagic radiolarian Cycladophora davisiana in the OS was mostly related to the lateral delivery of terrigenous material and OM into the water column from the northwestern shelf and/or from the western subarctic Pacific. Due to the sensitivity of marine organisms to environmental conditions, the production of radiolarians and BF sharply changed with the extinction of Amphimelissa setosa, since Heinrich Stadial 8 is related to the termination of global environment cooling and the hydrology changes of the early last glacial. • Benthic foraminifera and radiolarian responses in Okhotsk Sea to orbital and millennial climate changes over last 136 kyr. • Production of benthic foraminifera mainly changes in response to autochthonous organic fluxes to floor and sea ice cover. • Production of surface, dichothermal radiolarian and Amphimelissa setosa varied broadly synchronously with productivity. • Production of C. davisiana was responded to organic transport from subarctic western Pacific and northwestern Okhotsk Sea. • HS 8 in the Okhotsk Sea denotes the termination of the Northern Hemisphere climate cooling with extinction of A. setosa. [ABSTRACT FROM AUTHOR]