Enhanced Dust Influx to South Atlantic Sector of Antarctica During the Late-20th Century: Causes and Contribution to Radiative Forcing

Atmospheric dust influences global climate and ocean biogeochemistry. Here we present a high-resolution ice core dust record (1905-2005 CE) from coastal Dronning Maud Land (71 degrees 20 ' S, 11 degrees 35 ' E), East Antarctica, to understand dust flux variability, its causes, and potential contribution to radiative forcing during the 20th century in the South Atlantic sector of East Antarctica (SASA). The dust flux profile (sum of 1-25 mu m size fractions) reveals three stepwise increase during 1905-1929, 1930-1979, and 1980-2005 CE time with an average of 0.83, 4.7, and 12.88 mg center dot m(-2)center dot year(-1), respectively. Our investigation for such dramatic dust flux increase reveals that the increased aridity and favorable wind conditions over Southern South America (SSA), a potential dust source to Antarctica, caused increase in dust production and transport during the late 20th century. The dust flux variability in Southern Hemisphere is concomitant with in-phase relationship between El-Nino Southern Oscillation and Pacific Decadal Oscillations, which influenced the spatial distribution of global wet-dry phase (precipitation pattern). Further, shifting of Southern Annular Mode to positive phase made wind conditions more conducive for long-range dust transport from SSA to coastal Dronning Maud Land region. To the best of our knowledge, this is the first report of past radiative forcing estimates for Antarctica using ice core dust record into a radiative transfer model. Our estimates of radiative forcing corresponding to the enhanced dust flux yield nearly 30% increase in aerosol forcing during the late 20th century. This has resulted 40% decrease in atmospheric cooling rate, which contributed to net atmospheric warming over SASA.