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The ocean is the largest active carbon reservoir on Earth. Organic carbon (OC), as the primary species of carbon sequestration in the ocean, plays an important role in the global carbon cycle through its deposition and burial. In this study, sedimentary OC data from 5796 stations, together with relevant geochemical and sedimentological parameters in the Bohai Sea, Yellow Sea, and East China Sea (BYES) were used to summarize and elucidate the distribution and burial patterns of sedimentary OC, and assess carbon sink effect of sedimentary OC burial. The results show that the OC content in the sediments of the BYES ranges from 0.00% to 2.12%, with an average content of 0.47%±0.26%. OC content is significantly correlated with finegrained sediments, with an average OC content in mud areas being 39% higher than that in non-mud areas. Modern OC buried in the BYES are mainly deposited in 7 major mud areas, with a total sedimentary OC burial flux of approximately 8.20 Mt C yr−1. Among them, the burial flux of biospheric OC is 6.92 Mt C yr−1, equivalent to the OC consumption amount of silicate weathering of the 9 major river basins in the eastern China. In its natural state, the annually sequestered OC in the sediments of the eastern China seas is equivalent to 25.37 Mt of atmospheric CO2, indicating a significant carbon sink effect. The distribution and burial of terrigenous OC in the BYES are mainly influenced by the large river inputs and complex marine hydrodynamic environment, while human activities such as dam construction have significantly altered the OC burial in these coastal mud areas. [ABSTRACT FROM AUTHOR]

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]

We report quantitative carbon isotope evidence showing that porewater dissolved organic carbon (DOC) is produced from different sources in Arctic Ocean sediments, resulting in dramatic changes in both δ13C and Δ14C values of DOC. The very low δ13C (−42.7‰) and Δ14C (−947‰) values measured for porewater DOC indicate that bacteria consume methane hydrate‐derived OC and convert a significant fraction of this δ13C depleted and old OC (44–97%) into DOC in the sediments of the Arctic Ocean. We suggest that the production of extremely old, methane‐derived porewater DOC (5,430–23,600 years) in Arctic Ocean sediment is an important pathway for carbon cycling that provides not only a necessary energy source for microbial communities in this extreme environment but also an ancient DOC source that could flux and contribute to the old and biologically recalcitrant DOC found in the deep ocean. Plain Language Summary: Dissolved organic carbon (DOC) produced in sediment porewater is a crucial intermediary during the early diagenesis of organic matter in marine sediments, and DOC production is also an important pathway of carbon cycling in the ocean. In this study, we present radiocarbon and stable carbon isotope results measured for porewater DOC and sedimentary solid phase total organic carbon in sediment cores collected from the Arctic Ocean. We find that the carbon isotopic signatures of porewater DOC differed dramatically between samples produced from mostly marine‐derived organic matter (δ13C = −22.9‰, Δ14C = −80‰) in the Chukchi Sea shelf and samples produced from methane hydrate‐derived organic matter (δ13C = −42.7‰, Δ14C = −947‰) on the Arctic slope. We estimate that in the slope region, 44–97% of the extremely old DOC preserved in the sediment was produced from methane hydrate. The production of this ancient, methane‐bearing porewater DOC could be an important but insufficiently studied pathway for carbon cycling that provides not only a necessary energy source for microbial communities in the Arctic sediment but also an ancient DOC source that could contribute to the old and biologically recalcitrant DOC found in the deep ocean. Key Points: Large shifts in both δ13C and Δ14C values of porewater DOC were found in Arctic Ocean sedimentPorewater DOC has a very low δ13C value (−42.7‰) and old 14C age (23,000 years), consistent with being produced from methane hydrate OCThe extremely old DOC produced in Arctic Ocean sediment could be an important source of old DOC in the deep ocean [ABSTRACT FROM AUTHOR]

Do non-dipole geomagnetic field behaviors persistently exist in the subarctic Pacific Ocean over the past 140 ka? Paleomagnetic records from globally distributed locations are essential for fully understanding geomagnetic field variations, particularly non-dipole field fluctuations [1]. The weak field intensities during ~64-70 and ~15-17 ka indicate decay of the dipole field and probably growing dominance of non-dipole fields [13]. Dipole field dominance, extremely high- and low- latitude flux patches, and weak Pacific hemisphere variations are robust field characteristics that have occurred over the past few hundred years [15]. [Extracted from the article]

We studied 19 targets currently using organochlorine pesticides (CUOCPs) from 98 samples in the Western Pacific Ocean and the East China Sea collected in 2019, 2020, and 2021. The samples were analyzed using a novel High-throat/High-volume Solid-Phase Extraction method. Eighteen individual CUOCPs were above the method detection limits. The levels of ∑ 19 CUOCPs ranged from 0.13 to 17.80 ng/L, with an average of 3.13 ± 14.67 ng/L. Dicofol was the main pollutant in the Western Pacific Ocean, while Pyridaben dominated the East China Sea. In the summer, land-source input was the primary source in the Western Pacific Ocean and the East China Sea. Historical residues were the main source in the East China Sea in spring. In the summer, the ecological risk assessment results indicated a relatively low risk to the Western Pacific Ocean and the East China Sea. [Display omitted] • Hi-throat/Hi-volume SPE method was first applied to detect marine CUOCPs. • Land-source input in summer and historical residues in spring were the dominant sources in the East China Sea. • The medium ecological risk was in the Western Pacific Ocean, while the low risk was in the East China 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 source, amount, and trajectory of icebergs discharged into the western Arctic Ocean provide essential clues to Arctic ice sheet development and its feedback on Atlantic meridional overturning circulation (AMOC). Nd and Sr isotopes, ice-rafted debris, and mineral components were used to trace the icebergs that were first discharged into the western Arctic Ocean and then exported to the North Atlantic Ocean. The records indicated that the iceberg outburst (large-scale iceberg export via the Fram Strait) since the Late Pleistocene does not entirely depend on the iceberg discharge from the Laurentide ice sheet (LIS), which is mainly the result of multi-source ice interactions over the western Arctic Ocean. In marine isotope stage 5 (MIS5) and the MIS3a (39–29 ka), the LIS did not reach its maximum extent, discharging its most massive icebergs into the western Arctic Ocean. However, most icebergs were trapped in the western Arctic Ocean, instead of being exported to the North Atlantic Ocean. Different scenarios occurred in the MIS4 and MIS2, when the East Siberian ice sheet (ESIS) emerged and icebergs in the western Arctic Ocean began to accumulate robustly. Ice streams from the LIS or Eurasian ice sheet (EAIS) were finally deflected and pushed to the Fram Strait by the ice streams from the ESIS. The ESIS expansion may thus play a more positive role than the LIS-iceberg discharge in triggering Laurentide-source iceberg outbursts in the western Arctic Ocean. Our findings shed new light on the origin of icebergs in the North Atlantic Ocean and mechanisms of AMOC instability. • Complete sequence of Laurentide iceberg discharge was studied. • Nd & Sr isotope distributions provide new evidence for East Siberian ice sheet. • East Siberian ice streams triggered iceberg outbursts in Arctic Ocean. • Iceberg outbursts weakened the Atlantic meridional overturning circulation. [ABSTRACT FROM AUTHOR]

Sediment cores from the Northwind Ridge north of the Arctic Chukchi-Alaskan margin were analyzed for a suite of stratigraphic and provenance proxies. Based on the correlation to previously studied regional records, cores under study present sedimentary environments of Marine Isotope Stages (MIS) 1–11 (∼0.4 Ma) on millennial time scales. Contrasting glacial-interglacial conditions and provenance were characterized by means of clay-mineral and geochemical (elemental and isotopic) proxies along with grain size. Interglacial environments are interpreted as sea-ice dominated, with pre-Holocene sediment transported mostly from the East Siberian to Chukchi-Alaskan margin. In comparison with the recent conditions, this pattern suggests a stronger Transpolar Drift expanding into the Canada Basin at the expense of the Beaufort Gyre, or stronger along-shelf currents. Glacial intervals prior to MIS4 have a predominantly North American signature with carbonaceous or terrigenous source rocks. Carbonaceous inputs marked by Ca peaks are tracked to the western Canadian Arctic Archipelago eroded by the Laurentide Ice Sheet (LIS). Terrigenous sources (Zr peaks) are likely related to areas impacted by the Innuitian Ice Sheet and/or the LIS Mackenzie ice stream. MIS 4 and 2 intervals have a different composition with the Siberian/Chukchi rather than North American provenance. A stronger winnowing indicated by grain size in the glacial intervals suggests a stronger mid-depth circulation. Study results provide new boundary conditions for modeling paleocirculation and glaciations in the western Arctic Ocean. • Contrasting glacial-interglacial conditions and provenance were characterized. • Pre-Holocene interglacials have sea-ice dominated depositional environment, margin provenance and a stronger TPD. • Glacial intervals prior to MIS4 have a predominantly North American signature with carbonaceous or terrigenous rocks. • MIS4 and 2 intervals have more interglacial compositions with the Siberian/Chukchi rather than North American source. [ABSTRACT FROM AUTHOR]