ABSTRACT (0526559/0525880) Ravizza/ Peucker-Ehrenbrink Intellectual Merit It is widely believed that global chemical weathering rates respond to global climate change, acting as natural thermostat for the Earth. The goal of this research is to use the marine osmium (Os) isotope record in sediments to monitor chemical weathering during unusual episodes of abrupt climatic warming and cooling to see if evidence can be found for self-regulating of climate change. To accomplish this goal, the marine Os isotope record in sediments will be examined to see if warming events in the Eocene are associated with rising seawater 187Os/188Os ratios (indicative of increased weathering rates), and if cooling events in the Oligocene and Miocene are associated with falling seawater 187Os/188Os ratios (indicative of decreased weathering rates). Archived sedimentary material from Ocean Drilling Program and Deep Sea Drilling Project cores will be analyzed. For each climate event at least two Os isotope records from different core locations will be measured. This will allow a test of the global coherence of the marine Os isotope record. By comparing the Os isotope data to existing paleo-climate/ paleoceanographic records the relative timing of changes in important proxy records will be able to be determined. For example, a close temporal association between decreasing global ice volume and rising 187Os/188Os will support the notion that physical weathering associated with glaciation is driving the changes in the marine Os record. Alternatively, if Os isotope shifts lead ice volume changes this will imply that the marine Os isotope record is more strongly influenced by the broad climate regime than by glacial weathering in the strict sense.
Broader Impacts The broader impacts of this research include public outreach, student education and training, and archiving of data into readily accessible public databases. The work will support a graduate student and undergraduate at the University of Hawaii for two years, providing them with practical work experience that will help them make informed decisions about pursuing additional education or employment. The research also supports international collaboration with European scientists working on paleoclimate proxies and provides salary support for female technicians at Hawaii and Woods Hole. In addition, a Woods Hole Oceanographic Institution undergraduate summer intern will be trained. Research results will be incorporated into required courses at the University of Hawaii.
