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

摘要

The understanding of present atmospheric transport processes from SouthernHemisphere (SH) landmasses to Antarctica can improve the interpretation ofstratigraphic data in Antarctic ice cores. In addition, long range transportcan deliver key nutrients normally not available to marine ecosystems in theSouthern Ocean and may trigger or enhance primary productivity. However,there is a dearth of observational based studies of dust transport in theSH.This work aims to improve current understanding of dust transport in the SHby showing a characterization of two dust events originating in thePatagonia desert (south end of South America). The approach is based on acombined and complementary use of satellite retrievals (detectors MISR,MODIS, GLAS, POLDER, OMI), transport model simulation (HYSPLIT) and surfaceobservations near the sources and aerosol measurements in Antarctica(Neumayer and Concordia sites).Satellite imagery and visibility observations confirm dust emission in astretch 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 CentralPatagonia (~46° S) in February 2005. Model simulations initializedby these observations reproduce the timing of an observed increase in dustconcentration at the Concordia Station and some of the observed increases inatmospheric aerosol absorption (here used as a dust proxy) in the Neumayerstation. The TdF sources were the largest contributors of dust at bothsites. The transit times from TdF to the Neumayer and Concordia sites are 6–7and 9–10 days respectively. Lidar observations and model outputs coincidein placing most of the dust cloud in the boundary layer and suggestsignificant deposition over the ocean immediately downwind. Boundary layerdust was detected as far as 1800 km from the source and ~800 km northof the South Georgia Island over the central sub-Antarctic Atlantic Ocean.Although the analysis suggests the presence of dust at ~1500 km SW ofSouth Africa five days after, the limited capabilities of existing satelliteplatforms to differentiate between aerosol types do not permit a definitiveconclusion. In addition, the model simulations show dust lifting to the freetroposphere as it travels south but it could not be confirmed by thesatellite observations due to cloudiness.This work demonstrates that complementary information from existingtransport models, satellite and surface data can yield a consistent pictureof the dust transport from the Patagonia desert to Antarctica. It alsoillustrates the limitation of using any of these approaches individually tocharacterize the transport of dust in a heavily cloudy area.