Paleoceanographic evolution of the Chukchi Sea over the past 7600 years inferred from diatom assemblages

Abstract

The Chukchi Sea plays a critical role in Arctic–Pacific interactions and is currently undergoing a significant retreat of sea ice due to ongoing warming. We present records of diatom assemblages and biogenic silica from a sediment core collected in the central Chukchi Sea, which provides insights into the long-term dynamics of sea ice and Pacific water inflow (PWI) during the middle to late Holocene. Our diatom-based reconstruction of sea ice conditions reveals a long-term declining trend at 7.6–1.3 cal ka BP, coinciding with fluctuating increases in productivity. These changes were likely driven by variations in the warm, nutrient-rich PWI, which is modulated by sea level and atmospheric circulation. Following the establishment of stable sea levels in the middle Holocene, PWI variability appears to have been influenced primarily by the Pacific Decadal Oscillation (PDO) pattern and the strength and position of the Aleutian Low (AL). Notably, the sea-ice records from the central Chukchi Sea align with those from the eastern region, but they contrast with records from northern areas during the late Holocene. This asynchronous pattern of sea-ice development across regions may reflect differences in circulation patterns, such as variations in the strength of PWI branches and significant shifts in Pacific Ocean-atmosphere dynamics. Our findings contribute to a better understanding the links between atmospheric and oceanic processes in the Arctic-Pacific region during the middle to late Holocene.