The development of ocean currents and the response of the cryosphere on the Southwest Svalbard shelf over the Holocene

Abstract

While general trends in the inflow of Atlantic Water (AW) to the European Arctic over the present interglacial (the Holocene) are well known, regional changes in climate and the AW current and subsequent environmental responses are less well established. In particular, there is only limited knowledge on the development of ocean currents after the last deglaciation. Here, to better understand past water mass dynamics and their effects on sea ice cover and the environment throughout the Holocene, we present a multiproxy record from core OCE2019-HR7-GC retrieved from the southwestern Svalbard inner shelf, a highly dynamic frontal area influenced by different ocean currents and local water masses. For sea ice reconstructions, we focus on the specific sea ice biomarker IP25 in combination with the phytoplankton biomarkers dinosterol and brassicasterol. We further reconstruct surface and bottom water temperatures using alkenones and Mg/Ca and prevailing water masses using foraminifera assemblages. Finally, we compare our sea ice and temperature records with published marine sediment and ice core data from the area. We observe extensive sea ice cover between 11 and 10.2 kyr BP, which was likely linked to the Preboreal Oscillation. Based on our reconstructions, the period between 10 and 7 kyr BP was characterized by the warmest Holocene conditions on the SW Svalbard shelf. This interval is also associated with high surface water productivity and an enhanced AW influx that drove strong erosive activity at the bottom. After 6.5 kyr BP, the SW Svalbard shelf was characterized by a dynamic environment with cold and unstable conditions that lasted until 3.5 kyr BP. After 3.5 kyr BP, we observed an increase in sea ice cover and iceberg rafting over our site once more, which likely indicated seasonally fluctuating ice margins, with low AW influx, which lasted until 2.2 kyr BP. A brief warm period accompanied by strong bottom currents occurred between 2.2 and 1.8 kyr BP. The environment returned to a colder state with the presence of sea ice until 1.5 kyr BP, which was followed by warmer conditions between 1.5 and 1 kyr BP.