Ice core proxy of Antarctic sea-ice extent

Prior to the satellite era, ice core records have been used as a proxy for past sea-ice extent in Antarctica. This information is important for investigating long-term trends in sea-ice coverage. One of the first studies to correlate ice core data with modern satellite sea-ice extent records was conducted by Curran et al. They used data from the Law Dome ice core and found a significant correlation between the annual concentration of methanesulphonic acid (MSA) in the ice core and the maximum extent of sea ice (for Aug–Sept–Oct) in the region 80°–140°E. Curran et al. concluded there was a 20% decline in the sea-ice extent in this region between the 1950s and 1990s, and observed there was a high degree of decadal variability in the record. Support for this approach was provided by a study in Wilhelm II Land and an array of ice cores in West Antarctica. Recently a comprehensive review of sea-ice proxy information from polar ice cores outlined the importance of studies of this type. Here, we present an updated record for the MSA data from the Law Dome site (to 2013) and investigate the recent changes in Antarctic sea-ice extent. We also include a reanalysis of old Nimbus I satellite information from Sept 1964, which agrees with the sea-ice extent reconstruction.