Zanna Chase, Ph.D
Oregon State University
The Past 30,000 years on the Southern Chile Margin:
Ventilation, Productivity and Weathering
Wednesday — March 31, 2010
Pacific Forum — 3:00 p.m.
Feedbacks between greenhouse gases and ocean circulation and biogeochemistry represent powerful amplification mechanisms in earth’s climate. This presentation explores two such mechanisms. First I will discuss a reconstruction of oxygen concentrations in bottom water across a depth transect that brackets the present-day water-column extent of Antarctic Intermediate Water (AAIW). Using Re and Mn, we show that the depth range of well-oxygenated AAIW increased off Chile during the Last Glacial Maximum. The data are best explained by a combination of increased oxygenation and increased flux of Antarctic Intermediate Water during the Last Glacial Maximum. Next I will discuss a reconstruction of the origin of terrigenous sediment in the same sediment cores. Such reconstructions have been used to infer the position of westerly winds, which in turn have been implicated in changes in upwelling of CO2-rich waters around Antarctica. We show erosion by ice sheets, and not fluvial erosion, exerts a dominant control on weathering at least in southern Chile.
Next: April 14- Claire Paris