Emission, distribution, and transport of mineral dust in the Southern Hemisphere, and the dust deposition in Antarctica during present-day and the Last Glacial Maximum

Mineral dust is an important component of the atmospheric aerosols in the Earth's climate system, but there are relatively few in-depth investigations of the emission, transport, distribution, and deposition of dust aerosols in the Southern Hemisphere (SH). These physical processes are crucial in climate studies, such as in the understanding of the 10--100 times higher dust concentrations in the Antarctic ice cores during the Last Glacial Maximum (LGM) compared with present-day, but are poorly understood. This dissertation conducts an in-depth investigation into the above areas, and addresses the following questions: (1) What are the characteristics of dust emission, distribution, atmospheric burden and deposition in the SH? (2) What are the contributions from the various continental sources? (3) Are there typical meteorological conditions associated with the transport of dust to the high-latitude SH? (4) What are the plausible causes for the observed high dust concentrations in Antarctic ice cores during the LGM?;The methodology consists of three principal steps, using a combination of the Geophysical Fluid Dynamics Laboratory (GFDL) General Circulation Model (GCM) models, a trajectory model (HYSPLIT), and in situ and satellite observations. First, we investigate the dust cycle in the SH and quantify the contributions of the major sources by tagging dust based on its origin, using the GFDL GCM ("AM2.1n"). Second, the transport of the South American Patagonian dust to Antarctica is diagnosed by analyzing the GFDL model results together with results from the trajectory model simulations and using satellite observations. Third, sensitivity experiments are performed using AM2.1n to determine the sensitivity of the source characteristics, circulation, and precipitation on the dust deposition in Antarctic ice cores during the LGM.;The results show that South America, Australia, and Northern Hemisphere are the main sources of the dust atmospheric burden in the SH, with Northern Hemisphere's contributing up to ∼40% over Antarctica. In the case of dust deposition, South America and Australia combine to contribute more than 85% in Antarctica. In the Antarctica, each source dominates half of a hemisphere along 120°E--60°W: the Pacific half is dominated by the Australian dust while the other half is dominated by the South American Patagonian dust. Trajectory analysis indicates that only 13--20% of air masses from Patagonia reach Antarctica, with ¼ of the air masses getting to West Antarctica in 4--5 days and the other ¾ reaching East Antarctica within 7 days. The transport to East Antarctica is driven by the low pressure systems moving eastward in the subpolar low-pressure zone, while southward transport to West Antarctica typically happens when a high pressure system over the Atlantic Ocean blocks depression in the Drake Passage. These two mechanisms are consistent with available satellite observations.;For the LGM climate, the model simulations show that the expansion of source areas and changes in the Antarctic ice accumulation rates together can account for most of the observed increase of dust concentrations in the Vostok, Dome C and Taylor Dome cores, but there is an overestimate of the LGM-to-present ratio in the case of the Byrd core. The source expansion due to the lowering of sea level yields a factor of 2--3 higher contribution than that due to the reduction of continental vegetation. The changes in other climate parameters (e.g., SH precipitation change) are estimated to be relatively less important within the context of this sensitivity study, while the model-simulated LGM surface winds yield a 20--30% reduction rather than an increase in dust deposition in Antarctica. The outcomes of the research provide a fundamental understanding of the emission and distribution of dust in the SH and of the causes for the significant enhancement of the dust deposition in the Antarctic ice cores during the LGM.