Seasonally Resolved Holocene Sea Ice Variability Inferred From South Pole Ice Core Chemistry

Variability in sea ice is a critical climate feedback, yet the seasonal behavior of Southern Hemisphere sea ice and climate across multiple timescales remains unclear. Here, we develop a seasonally resolved Holocene sea salt record using major ion measurements of the South Pole Ice Core (SPC14). We combine the SPC14 data with the GEOS-Chem chemical transport model to demonstrate that the primary sea salt source switches seasonally from open water (summer) to sea ice (winter), with wintertime variations disproportionately responsible for the centennial to millennial scale structure in the record. We interpret increasing SPC14 and circum-Antarctic Holocene sea salt concentrations, particularly between 8 and 10 ka, as reflecting a period of winter sea ice expansion. Between 5 and 6 ka, an anomalous drop in South Atlantic sector sea salt indicates a temporary sea ice reduction that may be coupled with Northern Hemisphere cooling and associated ocean circulation changes.

Automated summary

This study uses data from the South Pole Ice Core and a chemical transport model to show the seasonal variability in the sources of sea salt in the Southern Hemisphere, with winter variations playing a key role in centennial to millennial scale structures in the record, and explains the potential reasons for the increased Holocene sea salt concentrations.