A combined observational and modeling approach to study modern dust transport from the Patagonia desert to East Antarctica

Abstract

The understanding of present atmospheric transport processes from Southern Hemisphere (SH) landmasses to Antarctica can improve the interpretation of stratigraphic data in Antarctic ice cores. In addition, long range transport can deliver key nutrients normally not available to marine ecosystems in the Southern Ocean and may trigger or enhance primary productivity. However, there is a dearth of observational based studies of dust transport in the SH. <br><br> This work aims to improve current understanding of dust transport in the SH by showing a characterization of two dust events originating in the Patagonia desert (south end of South America). The approach is based on a combined and complementary use of satellite retrievals (detectors MISR, MODIS, GLAS, POLDER, OMI), transport model simulation (HYSPLIT) and surface observations near the sources and aerosol measurements in Antarctica (Neumayer and Concordia sites). <br><br> Satellite imagery and visibility observations confirm dust emission in a stretch of dry lakes along the coast of the Tierra del Fuego (TdF) island (~54° S) and from the shores of the Colihue Huapi lake in Central Patagonia (~46° S) in February 2005. Model simulations initialized by these observations reproduce the timing of an observed increase in dust concentration at the Concordia Station and some of the observed increases in atmospheric aerosol absorption (here used as a dust proxy) in the Neumayer station. The TdF sources were the largest contributors of dust at both sites. The transit times from TdF to the Neumayer and Concordia sites are 6–7 and 9–10 days respectively. Lidar observations and model outputs coincide in placing most of the dust cloud in the boundary layer and suggest significant deposition over the ocean immediately downwind. Boundary layer dust was detected as far as 1800 km from the source and ~800 km north of the South Georgia Island over the central sub-Antarctic Atlantic Ocean. Although the analysis suggests the presence of dust at ~1500 km SW of South Africa five days after, the limited capabilities of existing satellite platforms to differentiate between aerosol types do not permit a definitive conclusion. In addition, the model simulations show dust lifting to the free troposphere as it travels south but it could not be confirmed by the satellite observations due to cloudiness. <br><br> This work demonstrates that complementary information from existing transport models, satellite and surface data can yield a consistent picture of the dust transport from the Patagonia desert to Antarctica. It also illustrates the limitation of using any of these approaches individually to characterize the transport of dust in a heavily cloudy area

Understanding the transport of Patagonian dust and its influence on marine biological activity in the South Atlantic Ocean

“…The long-range transport shown during this study is consistent with recent works of McConnell et al (2007), Gassó et al (2010), and Li et al (2010) which demonstrate that Patagonian dust can travel thousands of kilometers away from the South American continent reaching the coast of South Africa and West and East Antarctica. As the dust outflow off the coast of South America typically occurs below 2 km, for mineral dust to get transported over such long distances, the dust plumes need to be elevated to heights above the MBL.…”

“…Although, there is no definite agreement, modeling and remote sensing studies have also identified distinct horizontal and vertical transport pathways for South American and Australian dust sources over the SO. South American dust has been shown to largely remain at lower elevations (below 6 km), while Australian dust is likely to be elevated to higher levels of the free troposphere (Krinner and Genthon, 2003;Gassó and Stein, 2007;Li et al, 2008;Krinner et al, 2010;Gassó et al, 2010). Due to extremely limited observational data the labile fraction of Fe in Southern Hemispheric dust (e.g., South America) remains a topic of active debate (Cassar et al, 2007;Boyd and Mackie, 2008).…”

Distribution and recurrence of phytoplankton blooms around South Georgia, Southern Ocean

“…This is not surprising given the various independent factors that can influence surface Chl a concentrations. Among these: mixed layer depth and its effects on bloom dilution (Smetacek and Naqvi, 2008), dust input (e.g., Gassó et al, 2010), composition of the bloom (diatoms versus flagellates) and grazing (Whitehouse et al, 2009). Variations in flow intensity and pathways of the ACC fronts around South Georgia (Thorpe et al, 2002;Park et al, 2010;Boehme et al, 2008) are also among the most important factors likely influencing the interannual variability of the bloom: circulation around and then downstream of shallow topographic features is believed to control the magnitude of sediment-derived iron input to the water column (i.e., due to re-suspension processes) as well as its transport to more distant regions de Jong et al, 2012;Nishioka et al, 2011;Planquette et al, 2007).…”

“…The main sources of iron to the typical bloom area are: dust (Gassó et al, 2010), sediment input from the island or from the deeper enriched layers, through horizontal and vertical advection (Holeton et al, 2005;, island runoff and glacial melt (Korb et al, 2008;Young et al, 2011). Dust events from South America are sporadic, likely increasing in austral summer (Gassó et al, 2010), whereas the input of sediment-derived iron could be considered relatively steady because dependant on circulation; the flow originating from the northwestern shelf of the island and travelling westward along the northern flank of Shag Rocks and then along the MEB-GB margin shows in fact reduced variability (see Fig. 4 and Korb et al, 2008).…”

Potential genesis and implications of calcium nitrate in Antarctic snow

“…Li et al, 2008;Gassó et al, 2010). These dust particles are evidently an important factor, considering that they alter the chemical and optical properties of the atmosphere (Nousiainen and Kandler, 2015).…”