What Can Sea Ice Reconstructions Tell Us About Recent Regional Trends in Sea Ice Around Antarctica?

Abstract:

Satellite observations of recent sea ice changes around Antarctica reveal regionally heterogeneous trends, but with an overall increasing trend in Antarctic-wide sea ice extent. Proposed mechanisms to account for increasing sea ice extent around Antarctica include freshening of the ocean surface due to melting of land ice and northward wind drift associated with strengthening of the Southern Ocean westerly winds. In this study we use extended, regional reconstructions of Antarctic sea ice changes from ice core chemistry and reanalysis of the South Orkney fast ice series to examine long-term relationships between Antarctic regional sea ice changes and surface winds.

The formation and breakout of fast ice at the South Orkney islands (Murphy et al., 2014) indicates that westerly wind strength is an important factor in determining spring sea ice retreat in the Weddell Sea region. In contrast, autumn sea ice formation is more strongly influenced by long-lived ocean temperature anomalies and sea ice migration from the previous year, highlighting the multiple influences that act at different times of the year to determine the overall extent of winter sea ice. To assess the hypothesized role of westerly wind changes in driving opposing patterns of recent sea ice change between the Ross Sea and Bellingshausen Sea, we also present a comparison of ice core MSA evidence for sea ice changes derived from the James Ross Island (Mulvaney et al., 2012) and Erebus Saddle (Rhodes et al., 2012) ice cores, and view this in the context of trends in the Southern Annular Mode (Abram et al., 2014) over the last 200 years.

References:

Abram et al., 2014. Evolution of the Southern Annular Mode over the past millennium. Nature Climate Change. doi: 10.1038/nclimate2235

Mulvaney et al., 2012. Recent Antarctic Peninsula warming relative to Holocene temperature and ice-shelf history. Nature. doi: 10.1038/nature11391

Murphy et al., 2014. Variability of sea ice in the northern Weddell Sea during the 20^th century. Journal of Geophysical Research. doi: 10.1002/2013JC009511

Rhodes et al., 2012. Little Ice Age climate and oceanic conditions of the Ross Sea, Antarctica, from a coastal ice core record. Climate of the Past. doi: 10.5194/cp-8-1223-2012