Sea-ice variability in the subarctic North Pacific and adjacent Bering Sea during the past 25 ka: new insights from IP25 and Uk′37 proxy records

• Published in: arktos
• Main Authors: Meheust, Marie, Stein, Rüdiger, Fahl, Kirsten, Gersonde, Rainer
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Springer 2018
• Subjects: Arctic; Bering Sea; Pacific; Phytoplankton; Sea ice; Subarctic
• Online Access: https://epic.awi.de/id/eprint/47473/; https://link.springer.com/content/pdf/10.1007%2Fs41063-018-0043-1.pdf; https://hdl.handle.net/10013/epic.1cbff8e6-cac5-4c74-b982-98a517abfd61

This study focusses on the last glacial–deglacial–Holocene spatial and temporal variability in sea-ice cover based on organic geochemical analyses of marine sediment cores from the subarctic Pacific and the Bering Sea. By means of the sea-ice proxy “IP25” and phytoplankton-derived biomarkers (specific sterols and alkenones), we reconstruct the spring sea-ice conditions, (summer) sea-surface temperature (SST) and primary productivity, respectively. The large variability of sea ice was explained by a combination of local and global factors, such as solar insolation, global climate anomalies and sea-level changes controlling the oceanographic circulation and water mass exchange between the subarctic Pacific and the Bering Sea. During the Last Glacial Maximum, extensive sea-ice cover prevailed over large part of the subarctic Pacific and the Bering Sea. The following deglaciation is characterized by a rapid sea-ice advance and retreat. During cold periods (Heinrich Stadial 1 and Younger Dryas) seasonal sea-ice cover generally coincided with low alkenone SSTs and low primary productivity. Conversely, during warmer intervals (Bølling/Allerød, Early Holocene) reduced sea-ice or ice-free conditions prevailed in the study area. At the northern Bering Sea continental shelf a late-Early/Mid Holocene shift to marginal sea-ice conditions is in line with the simultaneous wide-spread sea-ice recovery observed in the other Arctic marginal seas and is likely initiated by the lower Northern Hemisphere insolation and surface-water cooling.