Deglacial changes in dust flux in the eastern equatorial Pacific

Publication Type  Journal Article
Year of Publication  2007
Authors  McGee, D.; Marcantonio, F.; Lynch-Stieglitz, J.
Journal Title  Earth and Planetary Science Letters
Volume  257
Issue  1-2
Pages  215-230
Journal Date  May 15
ISBN Number  0012-821X
Accession Number  ISI:000246858100018
Key Words  dust flux; eastern equatorial pacific; deglacial; th-230-profiling; itcz; odp leg 138; last glacial maximum; intertropical convergence zone; north pacific; eolian dust; paleoclimatic interpretations; extraterrestrial he-3; global distribution; continental

Atmospheric dust levels may play important roles in feedbacks linking continental source areas, tropical convection, marine productivity, and global climate. These feedbacks appear to be particularly significant in the tropical Pacific, where variations in local convection and productivity have been demonstrated to have impacts on climate at higher latitudes. Modeling of past dust levels and related feedbacks has been limited, however, by a paucity of observational data. In this study we present a temporal and spatial survey of dust fluxes to the eastern equatorial Pacific over the past 30 kyr. Glacial and Holocene fluxes of Th-232, a proxy for continental material, were calculated by normalization to Th-230 from a north-south transect of cores along 110 degrees W between 3 degrees S and 7 degrees N (ODP sites 848-853). Fluxes were 30-100% higher during the last glacial, suggesting increased dustiness in both hemispheres during the glacial period. In both time periods, dust fluxes decrease towards the south, reflecting scavenging of Northern Hemisphere dust by precipitation at the ITCZ. The Holocene meridional dust flux gradient between 7 degrees N and 3 degrees S is characterized by a steep drop in dust levels at the southern edge of the modem range of the ITCZ, while the gradient is shallower and more nearly linear during the last glacial. This change may indicate that the glacial ITCZ in this region was a less effective barrier to interhemispheric dust transport, most likely due to a decrease in convective intensity and precipitation during the last glacial; alternatively, the change in gradient may be explained by increased variability in the location of the glacial ITCZ. Our data do not appear to require a mean southerly displacement of the glacial ITCZ, as suggested by the results of other studies. (c) 2007 Elsevier B.V. All rights reserved.


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URL  <Go to ISI>://000246858100018
DOI  DOI 10.1016/j.epsl.2007.02.033