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

Abstract

Atmospheric dust influences global climate and ocean biogeochemistry. Here we present a high-resolution ice core dust record (1905 from coastal Dronning Maud Land (71°20′S, 11°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 μm size fractions) reveals three stepwise increase during 1905 -1929 , 1930-1979 , and 1980 with an average of 0.83, 4.7, and 12.88 mg·m −2 ·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-Niño 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.Plain Language Summary Atmospheric dust plays an important role in global climate variability through the changes in radiative forcing. Like other parts of Antarctica, the coastal Dronning Maud Land (cDML) in East Antarctic is vulnerable to such changes in radiative balance. However, causative factors for the dust deposition and impact of dust originated radiative forcing on this region remain unknown due to lack of long-term records of dust-derived radiative forcing estimates. Toward this, we have undertaken a systematic ice core-based study from cDML region to reconstruct past records of dust influx, its potential sources, causative factors for the dust production in the Southern Hemispheric continents, and understanding its role on the radiative forcing during the 20th century . Our radiative forcing estimates corresponding to approximately four fold increase in dust influx in the late 20th century indicate an increase in atmospheric warming. The present study would help to better understand the long-term Antarctic climate variability by providing radiative forcing input to the climate models and to improve our current knowledge about the role of dust in contributing to Southern Hemisphere warming during the 20th century.

Improved representation of the global dust cycle using observational constraints on dust properties and abundance

“…We furthermore do not use recently analyzed dust cycle results from CMIP5 models (Pu and Ginoux, 2018;Wu et al, 2020) because less than half of CMIP5 models with prognostic dust cycles reported total deposition fluxes, which are needed for the analyses against measurements (see previous section). In addition, many CMIP5 models did not include a prognostic dust cycle and instead read in pre-calculated dust emissions (Lamarque et al, 2010). But note that CMIP5 model errors against measurements are similar to those for AeroCom models and those for our model ensemble (e.g., compare Figs.…”

Application of visual stratigraphy from line-scan images to constrain chronology and melt features of a firn core from coastal Antarctica

“…The DML coast is characterised by distinct topographic features like ice rises having their specific local flow, climate regime and surface mass-balance variability (Lenaerts and others, 2014; Drews and others, 2015; Matsuoka and others, 2015; Goel and others, 2017; Rignot and others, 2019; Pratap and others, 2021). The coastal DML also offers opportunities for reconstructing annually resolved decadal to multi-decadal variability in temperature, westerly winds, sea ice and their interactions with various regional climatic modes (Naik and others, 2010; Philippe and others, 2016; Goel and others, 2020; Laluraj and others, 2020; Thamban and others, 2020; Ejaz and others, 2021; Pratap and others, 2021).

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Improved representation of the global dust cycle using observational constraints on dust properties and abundance

“…The inverse model results characterize the dust cycle for the years 2004-2008, whereas the concentration data were taken for different dates in the period 1981-2000 (Prospero et al, 1989;Arimoto et al, 1995) and the deposition flux measurements were taken one to several decades earlier (Edwards et al, 2006;McConnell et al, 2007). This mismatch in time periods could cause modeled deposition fluxes to exceed measured fluxes as several studies have 780 reported increases in dust emissions from South America and in dust deposition at Antarctica over the past century or so (McConnell et al, 2007;Gasso and Torres, 2019;Laluraj et al, 2020). Furthermore, there is substantial interannual variability in dust concentration that could affect the mismatch in time between models and measurements, especially for less dusty regions such as in the SH (Smith et al, 2017).…”