Sea Ice Variability and Trends in the Western Indian Ocean Sector of Antarctica During the Past Two Centuries and Its Response to Climatic Modes

Abstract

Antarctic sea ice is a critical component of the ocean-climate system. Sea ice concentration (SIC) records of various oceanic sectors of Antarctica available since 1979 reveal dramatic changes in recent years; however, there is no consensus yet on drivers of sea ice variability, changes and their future projections. The lack of long-term SIC records has impeded the quantification of sea ice variability, trends and various forcing factors and mechanisms. Here, we present a long-term SIC record (1809−1993 CE) for the Western Indian Ocean Sector (WIOS) of Antarctica derived from a new ice core oxygen isotope (δ18O) record together with three available records from Dronning Maud Land (DML), East Antarctica. This long-term SIC record at annual resolution reveals a significant decline during 1830–1884 CE with a rate of 0.58% ± 0.12% decade−1 followed by moderate increase during 1927–1993 CE with a rate of 0.24% ± 0.11% decade−1. Current satellite-derived SIC records reveal an increase of 2.59 ± 0.86% decade−1 during 1994–2014 CE, which is unprecedented over the last two centuries as determined by the ice core-derived SIC record. The satellite and ice core combined SIC record (1809−2019 CE) also reveals a significant increase in interannual variability at El Niño Southern Oscillation band and decadal variability at 16–32 years band in the last few decades. Our investigation suggests that wind-driven sea-ice dynamics associated with switching phases of Southern Annular Mode and remote teleconnections of Pacific oscillations largely control the interannual to decadal sea ice variability in this region.