The density and vertical distribution of living calcareous foraminifera have been studied in six box cores from the shelf depressions in the Western Barents Sea in relation to total organic carbon content and flux to the seafloor, primary production, sedimentation rates, bottom-water masses and stable isotopes. It appears that at least several infaunal species—like Melonis barleeanus, Islandiella norcrossi and perhaps Nonionellina labradorica, Cribroelphidium excavatum clavatum and Cassidulina reniforme—might penetrate down to 8–10 cm below the sediment surface searching for a favorable microhabitat. A deep penetration of some living specimens, notably epifaunal Cibicides lobatulus, into the sediment might result from bioturbation and survival inside polychaete tubes. The highest foraminiferal abundances (up to 130–240 sp/50 cm³) of the six cores were found in the most productive areas on the West Spitsbergen shelf and in the mouth of the Isfjorden (Svalbard) and likely resulted from fast sedimentation and mass accumulation rates of marine organic matter. These factors seemed to be responsible for deeper penetration and habitat depth of the above-mentioned species on the shelf as compared to the northern Barents Sea continental slope. However, the abundance of living calcareous foraminifera on the slope was much higher than in our study, probably due to a greater flux of particulate organic matter produced during the seasonal phytoplankton bloom along the ice-edge margin. In general, more depleted δ¹⁸O values (of unstained foraminifera) are found in the box cores obtained beneath pure Atlantic water compared to those beneath cooler bottom water. Estimated δ¹⁸O disequilibrium effects for Nonionellina labradorica (0.28‰), Cibicides lobatulus (−0.76‰) and Melonis barleeanus (−0.41‰) support previous findings for these species.

Environmental changes in the surface and bottom water layers of the Ingøydjupet Basin and the history of the Atlantic Water inflow to the southwestern Barents Sea during the last 16 ka are reconstructed based on planktic and benthic foraminiferal assemblages. The multiproxy study of sediment cores PSh-5159R and PSh-5159N, including AMS ¹⁴C dating, provides a time resolution of about 200 years for the deglaciation, 100 years for the Holocene, and 25–50 years for the last 400 years. Stable polar conditions with the sea ice at the surface were typical for the Early Deglaciation period. Unstable bottom settings and the onset of ice rafting marked the Oldest Dryas. The cold Atlantic Water inflow increased notably during the Bölling-Alleröd interstadial nearby the site location and then decreased during the Younger Dryas. The initial Holocene was characterized by abrupt warming in bottom and surface water layers, especially ∼9.7–7.6 ka BP. Stable conditions prevailed during the Middle Holocene. Remarkable changes in the sea-surface temperature and bottom environments occurred during the last 2.5 cal. ka BP.

Deglacial dissolved oxygen concentrations were semiquantitatively estimated for intermediate and deep waters in the western Bering Sea using the benthic foraminiferal-based transfer function developed by Tetard et al. (2017), Tetard et al. (2021a). Benthic foraminiferal assemblages were analyzed from two sediment cores, SO201-2-85KL (963 m below sea level (mbsl), the intermediate-water core) and SO201-2-77KL (2,163 mbsl, the deep-water core), collected from the Shirshov Ridge in the western Bering Sea. Intermediate waters were characterized by an oxygen content of ∼2.0 ml L⁻¹ or more during the Last Glacial Maximum (LGM)–Heinrich 1 (H1), around 0.15 ml L⁻¹ during the middle Bølling/Allerød (B/A)–Early Holocene (EH), and a slight increase in [O₂] (∼0.20 ml L⁻¹) at the beginning of the Younger Dryas (YD) mbsl. Deep-water oxygen concentrations ranged from 0.9 to 2.5 ml L⁻¹ during the LGM–H1, hovered around 0.08 ml L⁻¹ at the onset of B/A, and were within the 0.30–0.85 ml L⁻¹ range from the middle B/A to the first half of YD and the 1.0–1.7 ml L⁻¹ range from the middle to late Holocene. The [O₂] variations remind the δ¹⁸O NGRIP record thereby providing evidence for a link between the Bering Sea oxygenation at intermediate depths and the deglacial North Atlantic climate. Changes in the deep-water oxygen concentrations mostly resemble the deglacial dynamics of the Southern Ocean upwelling intensity which is supposed to be closely coupled with the Antarctic climate variability. This coherence suggests that deglacial deep-water [O₂] variations were primarily controlled by changes in the circulation of southern-sourced waters. Nevertheless, the signal from the south at the deeper site might be amplified by the Northern Hemisphere climate warming via an increase in sea-surface bioproductivity during the B/A and EH. A semi-enclosed position of the Bering Sea and sea-level oscillations might significantly contribute to the magnitude of oxygenation changes in the study area during the last deglaciation. Interregional correlation of different proxy data from a wide range of water depths indicates that deglacial oxygenation changes were more pronounced in the Bering and Okhotsk marginal seas than along the open-ocean continental margin and abyssal settings of the North Pacific.

Five assemblages of benthic foraminifers reflecting the changes in the properties of the intermediate water masses and the biological productivity during different periods of the last glacial-interglacial cycle are defined based on the abundances and relative contents of indicative species in the upper 9 m of giant Core MD02-2529 from the Cocos Ridge. High bioproductivity and low oxygen content in the bottom water layer and sediments are established for the interstadial period based on the high abundance of the species Uvigerina peregrina, U. hispida, and C. pachyderma (Assemblage I) and especially for the Last Glacial Maximum (Assemblage II) with the dominant role of the same species and E. smithi. The transition from the glaciation to the current interglacial (Termination I, Assemblage III) is characterized by a high share of the epifaunal species C. wuellerstorfi and H. subhaidingeri, which indicates enhanced hydrodynamic activity and ventilation of the intermediate water washing the bottom. The end of Termination I was marked by strengthened selective dissolution of carbonate microfossils due to the increased influx of fresh organic matter to the bottom and/or advection of more aggressive intermediate waters. The diverse Early Holocene assemblage (Assemblage IV) points to variable ecological niches, while the abundance of the infaunal U. hispida in Assemblage V indicates low productivity of the surface waters and a low oxygen concentration in the bottom sediments of the Late Holocene.

The benthic and planktonic foraminiferal assemblages and the distribution of coarse grain-size factions were studied in the upper 4.5 m of the Core SO201-2-85KL (57°30.30′ N, 170°24.79′ E, water depth 968 m) retrieved from the Shirshov Ridge. This part of the core covers 7.5 to 50 kyr BP. The glacial period is established to be characterized by low surface water productivity, the wide distribution of sea ice and/or icebergs in this area, and a high oxygen concentration in the bottom layer. Enhanced productivity is inferred from the maximum abundance of planktonic foraminifers at the very beginning of the deglaciation. The late Bølling-Allerød interstadial and the early Holocene were marked by the further two-phase increase in the surface productivity and the weakened ventilation of the bottom water.