Variability of Circulation and Water Masses in Kvitøya Trough

Abstract

The physical environment of the northern Barents Sea is shaped by the inflow of warm, saline Atlantic Water (AW) and the seasonal cycle of sea ice. Recent years have seen a rapid shift toward more Atlantic conditions, driven by reduced sea ice import and increased influence of AW intrusions. Although seasonal variability is crucial for understanding these changes, observations from the ice-covered season are limited. This study addresses this gap by investigating seasonal variability and circulation in the Kvitøya Trough, a key pathway for AW transport from the Fram Strait Branch along the continental slope north of Svalbard into the northern Barents Sea. Our analysis is based on ADCP and CTD data collected during autumn (2021, 2022) and winter (2022) along transects across the Kvitøya Trough and on the continental slope north of Svalbard. In addition, we incorporate CTD data (2019-2022) from a mooring at the southern end of the trough along with satellite-derived sea ice concentrations and data from atmospheric reanalysis. The observations reveal distinct seasonal differences in the properties and penetration of AW, with warmer and saltier water observed in autumn compared to winter. In winter, colder and denser AW along the continental slope resulted in limited reach to the southern end of the trough. In autumn, warm and saline AW in the boundary current led to a distinct AW core that entered the trough along the western flank and was gradually modified as it progressed southward. A cyclonic circulation pattern was observed in the northern part of the trough, with a northward return flow of modified AW along the eastern slope. In the southern part of the trough, AW influence was confined to the western side, resulting in strong east-west gradients in temperature and salinity. This asymmetry persisted across seasons and is likely shaped by both AW inflow and sea ice conditions. We hypothesise that AW warming of the western surface weakened stratification and promoted mixing, while colder surface conditions in the east enhanced sea ice formation and maintained stronger stratification. We suggest that reduced sea ice concentrations in 2022 limited surface freshening in the subsequent summer. Our findings indicate a lag of approximately three months between seasonal AW warming in the boundary current and its downstream unmodified arrival at the southern end of the trough. This highlights the importance of seasonality in upstream conditions and local preconditioning in modulating AW transport and transformation in the northern Barents Sea.