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Two sediment cores, KCES1 and ODP797, which were recovered from the Sea of Japan (JS), were measured for alkenone-derived sea surface temperatures ( $$U^{{\text{K}}^{\prime}}_{37} {\text{-SSTs}}$$ ). Our results revealed that the SSTs closely follow the glacial-interglacial cycles during the last 170 ka, except in the last glacial maximum (LGM), during which the SST was higher than in the Holocene. The anomalous high temperature in the LGM is considered as an effect of the intrusion of a low salinity water mass into the JS when the sea level was almost below 130 m. On the glacial-interglacial to orbital timescale, the $$ U^{{\text{K}}^{\prime }}_{37} {\text{-SSTs}} $$ record in the JS correlated well with the benthic foraminiferal δO record and solar insolation, which suggests the dominant control of solar insolation and its related sea ice development on the SST in the JS. On the sub-orbital/millennial timescale, reduced SST corresponds to an enhanced east asian winter monsoon (EAWM) during the last glacial period (MIS3 and MIS4), indicating the dominant control of sea ice expansion due to the enhanced EAWM on the SST in the JS. In contrast, during the last interglacial period (MIS5), the SST in the JS was controlled by variations in the east Asian summer monsoon. These results highlight the key role of solar insolation and associated glacial-interglacial conditions in the variations of the SST in the JS since the last 170 ka. [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]

Paleontological records of six sediment cores in the Okhotsk Sea (OS) marked the regional environmental changes over the last 140 kyr on orbital time scales. The diatom assemblages and content of diatom frustules in the sediments during Marine Isotope Stage (MIS) 6–1 indicate the dramatic climatic and environmental changes in the OS. A small abundance and low diatom species diversity as well as the high percentage of near-ice species indicate the cold surface environmental condition during glacial time (MIS 6, 4, 2) with low temperatures, cold climate conditions and extended sea ice cover. The presence of extinct redeposited species in the glacial assemblages indicates a low sea level during this time. The proportion of ice species enlarged and diatom abundance reduced due to increase of the influence of the sea ice, reflecting the sharp climatic cooling of adjacent land and regional environmental deterioration. The subsequent increase in diatoms productivity at 129.8–117.0 kyr BP and 8.3–5.5 kyr BP indicates the strong climate warming accompanied by decrease of sea ice coverage and surface water stratification (mixing of surface and intermediate water) during the warmest MIS in the Okhotsk Sea. The diatom abundance and high content of the oceanic and warm-water species reflect the warm surface environmental condition during MIS 5e and 1 since 8.3 kyr due to decrease of the sea ice influence. [ABSTRACT FROM AUTHOR]

We present a reconstruction of Holocene sea-ice variability from sediment core GA306-GC3, from the Holsteinsborg Dyb off West Greenland, which provides an index of palaeoceanographic and palaeoenvironmental conditions within this climatically sensitive region during the last 6700 yr. The reconstructed sea-ice record, combined with previously published proxy data, suggests that relatively warm conditions with reduced sea-ice extent prior to 5000 cal. yr BP were associated with the Holocene Thermal Maximum. Subsequent cooling and extensive sea-ice cover between ca. 5000 and 4000 cal. yr BP was followed by even colder conditions and persistent sea-ice cover during the Neoglacial cooling phase, particularly after ca. 1500 cal. yr BP. There is a positive correlation between West Greenland sea-ice cover and solar activity over the past 5000 yr, but the correlation is much weaker prior to 5000 cal. yr BP. In addition, there is a strong link between West Greenland sea ice and changes in the abundance of arctic benthic foraminifera species, related to different water masses of the West Greenland Current during the entire interval, even prior to 5000 cal. yr BP. Our findings indicate that sea-ice variability off West Greenland was driven not only by solar activity, but also by ocean circulation (the strength of cold Polar water from the East Greenland Current and warm Atlantic water from the Irminger Current). [ABSTRACT FROM AUTHOR]

Deciphering the origin of sedimentary material in the Arctic can contribute to a deeper understanding of modern transport and sedimentation processes. Here, the application of rare earth elements (REEs) is particularly promising, as they can serve as indicators of sources as well as chemical and physical conditions and processes. This study aimed to determine the distribution of REE sources in the bottom sediments and the forms of their occurrence on the East Siberian Arctic Shelf. The concentrations and distributions of the REEs and major and trace metals, grain size, and mineral composition of 72 surficial sediment samples and two sediment cores that were collected from the Laptev and East Siberian seas were studied. Increasing REE content, the predominance of light REE, and close correlation with Zr, Nb, Y, Sc, and Ti were revealed in the Laptev and western East Siberian sea sediments in the zone of influence of the Lena River runoff. The source of the REEs was the eroded Yedoma complex along the coast. The REE content in the sub-colloidal fraction of the sediments was comparable to the REE concentration of the bulk bottom sediments and varied in the East Siberian Sea from 104 to 220 mg kg−1, with the maximum content around the submarine valley of the Indigirka River, in the Laptev Sea, ranging from 124 to 197 mg kg−1. The findings could be used to study ice dynamics and to conduct lithostratigraphic and paleoceanographical reconstructions of the Central Arctic. • Sediment from the two Arctic seas were analyzed for major and trace elements. • Rare earth element content is increasing in Laptev and East Siberian Sea sediments. • Source of the rare earth elements was the eroded Yedoma complex along the coast. • Findings can inform lithostratigraphic and paleoceanographical reconstructions. [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]

Abstract: A diatom-based sea-ice concentration (SIC) transfer function was developed by using 72 surface samples from west of Greenland and around Iceland, and validated against associated modern SIC. Canonical correspondence analysis on surface sediment diatoms and monthly average of SIC indicated that April SIC is the most important environmental factor controlling the distribution of diatoms in the area, justifying the development of a diatom-based SIC transfer function. The agreement between reconstructed SIC based on diatoms from West Greenland and the satellite and modelled sea-ice data during the last ~75yr suggests that the diatom-based SIC reconstruction is reliable for studying the palaeoceanography off West Greenland. Relatively warm conditions with a strong influence of the Irminger Current (IC) were indicated for the early part of the record (~5000–3860cal. yr BP), corresponding in time to the latest part of the Holocene Thermal Maximum. Between 3860 and 1510cal. yr BP, April SIC oscillated around the mean value (55%) and during the time interval 1510–1120cal. yr BP and after 650cal. yr BP was above the mean, indicating more extensive sea-ice cover in Disko Bugt. Agreement between reconstructed April SIC and changes in the diatom species suggests that the sea-ice condition in Disko Bugt was strongly influenced by variations in the relative strength of two components of the West Greenland Current, i.e. the cold East Greenland Current and the relatively warm IC. Further analysis of the reconstructed SIC record suggests that solar radiation may be an important forcing mechanism behind the historic sea-ice changes. [Copyright &y& Elsevier]