Increased Sea Ice Duration in Moubray Bay, Northwest Ross Sea Linked to Early Holocene Wind Strength

Abstract

Sea ice in the Ross Sea plays a critical role in the formation of dense water masses, ice sheet stability, and air-sea gas exchange, and also supports unique ecosystems. However, its seasonal and spatial variability makes it challenging to include in model simulations. To address this, new sea ice records that extend beyond the satellite era and include periods of climate change are essential. This new sediment record from Moubray Bay, northwest Ross Sea, reconstructs environmental conditions between similar to 11,300 and similar to 10,900 cal yr BP-a time of rapid retreat of marine-based ice sheets and coastal glaciers in the region. The diatom assemblage is dominated by three taxa: Fragilariopsis curta, Corethron pennatum, and Chaetoceros resting spores. Variations in their relative abundances reveal changes in wind strength, water column structure, and sea ice concentration and duration. Between similar to 11,300 and similar to 11,200 cal yr BP, environmental conditions are characterized by a stabilized water column due to fresh meltwater influx, and weaker winds, which resulted in shorter sea ice duration and reduced winter sea ice concentration. This continued after similar to 11,200 cal yr BP but stronger winds linked to deepening of Amundsen Sea Low-like circulation triggered short-term water column stratification. Sea ice concentration and duration increased after similar to 11,100 cal yr BP driven by cooling of the sea surface by stronger southerly winds. Concurrent changes in early Holocene marine and terrestrial climate records from the Ross Sea indicate a shift in atmospheric circulation during the early Holocene.