Dust and associated geochemical fluxes in a firn core from coastal East Antarctica and its linkages with Southern Hemisphere climate variability over the last 50 years

Abstract

High-resolution records of dust and trace element fluxes were studied in a firn core from the coastal Dronning Maud Land, representing the past 50 years, to understand the influence of recent climate variability on the transportation and accumulation of these components in East Antarctica. A doubling of dust flux was observed since 1985, coinciding with a shift in the Southern Annular Mode (SAM) index to more positive values. Strong positive correlation (r = 0.68; p < 10−8) observed between dust flux and the SAM suggests that the positive values of the SAM index are likely to be responsible for the recent increase in dust deposition over East Antarctica, through strengthening of westerly winds. NCEP/NCAR reanalysis data reveals that the polar easterlies consistently strengthened since 1985 at the study region, leading to the sinking of dust materials brought by the stronger westerlies. Significant inverse correlation (r = −0.42, p < 0.00004) between the dust flux and δ18O records (proxy for surface air temperature) further suggests that enhancement of the dust flux is taking place during winter periods, possibly due to the reduced moisture content and increased wind intensity. Interestingly, the timing and amplitude of the insoluble dust flux matched remarkably well with the trace metal fluxes of Ba, Cr, Cu, and Zn, confirming that dust was the main carrier of airborne geochemical tracers to East Antarctica in the recent past. The observed doubling of dust and associated trace metal deposition in East Antarctica have wide-ranging implications for understanding the factors driving the inter-continental transportation of impurities and their environmental impact on Antarctica.