Twentieth-century sea ice variability in the Weddell Sea and its effect on moisture transport: Evidence from a coastal East Antarctic ice core record

Abstract

High-resolution study of deuterium excess (d-excess), sea salt sodium (ss-Na+), and methane sulfonic acid (MSA) in an ice core from coastal Dronning Maud Land (cDML), East Antarctica, revealed the history of moisture transport and sea ice extent (SIE) during the last century. Backward wind trajectories show that air parcels were mainly derived from the Weddell Sea region. The d-excess profile shows a dramatic shift from an average value of 8‰ during 1905–1920 to −1‰ during ~1940 and thereafter positive excursion during 1940–1980. The dramatic shift during 1920–1940 has been attributed to the reduced moisture supply from low/mid-latitude to Antarctica associated with shifting of Southern Annular Mode (SAM) from positive to negative mode. The ss-Na+ flux profile shows systematic positive excursion during 1940–1980 which coincide with that of the d-excess profile. The MSA flux shows a negative excursion during 1950–1965, overlapping with the period of positive excursions in ss-Na+ and d-excess profiles. The concomitant increase of ss-Na+ and d-excess values and positive excursions during 1940–1980 indicate higher SIE. Based on significant correlation between the Na+ flux and satellite-derived winter SIE record of the Weddell Sea, ~10% increase in SIE is estimated compared to its average value of the last century. The power spectrum analysis of d-excess and ss-Na+ flux shows a significant periodicity at ~3.5 years, exactly matching with that of the winter SIE in the Weddell Sea. Wavelet analysis of SAM index and Southern Oscillation Index (SOI) shows the highest common power in 4 to 8 year band, overlapping with the periods of higher SIE and opposite phase in 10 to 16 year band, overlapping with the periods of higher d-excess. This study highlights the role of SAM and its teleconnection to El Niño Southern Oscillations (ENSO) in controlling sea ice and moisture source variability in annual to decadal scale in the coastal regions of Antarctica.