| Summary: | Thesis: Ph. D., Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2019 Cataloged from PDF version of thesis. Includes bibliographical references (pages 120-126). Mineral dust is generated in continental interiors and exported by winds to ocean basins, providing a sedimentary archive which is one of the few direct indicators we have of atmospheric circulation in the past. This archive can be utilized in regions of dust transport also affected by monsoons to examine how different climate forcing mechanisms impact the monsoon regions over glacial-interglacial, orbital, and millennial timescales. This thesis generates new eolian dust records from two monsoon regions to reconstruct changes in atmospheric circulation in response to forcing by high-latitude insolation and boundary condition change. In Chapters 2 and 3 I use ²³⁰Thxs-normalization to construct high-resolution eolian dust flux records from sedimentary archives downwind from the West African and East Asian Monsoon regions respectively. The West African margin dust records show variability associated with an interplay between Northern Hemisphere summer insolation forcing and North Atlantic cooling. The longest record at ODP Site 658, stretching back to 67 ka, shows evidence for a "Green Sahara" interval from 60-50 ka and a skipped precessional "beat" from 35-20 ka. This record also shows evidence for abrupt increases in dust flux associated with Greenland stadials. The Shatsky Rise record at ODP Site 1208, downwind of East Asian dust sources, shows variability associated with glacial-interglacial boundary conditions over the last 330 ka, exhibiting high dust during glacial times. The record also exhibits variability associated with a Northern Hemisphere summer insolation control at times overriding the glacial-interglacial signal. In Chapter 4 I demonstrate the feasibility of using ...
|
|---|