Climate change and sedimentary methane in the Bering Sea
Mea S. Cook
Postdoctoral Investigator, Geology & Geophysics
Woods Hole Oceanographic Institution
Tuesday, 12:00 Noon
September 5, 2006
The calcium carbonate shells of foraminifera from Bering Sea sediments. Carbon isotope ratios in the yellowish foraminifera (right) suggest there were episodes of abundant methane in surface sediments, which may be associated with warm climate events of the last glacial period.
In Bering Sea sediments deposited during the last glacial period, 60 to 30 thousand years ago, there are episodes of very low delta carbon-13 measured in planktonic and benthic foraminifera. The anomalous carbon isotope ratios (as low as -14 permil PDB) during the excursions are probably due to a coating of carbonate minerals that formed in association with vigorous microbial consumption of methane. This suggests that there were periodic fluxes of methane to surface sediments. The duration and timing of the carbon isotope events are similar to interstadials, abrupt, warm climate events that pervaded the last glacial period. Our data are part of a growing body of geochemical evidence that sedimentary methane may interact with the climate system on short time scales and could have contributed to rapid climate change in the past.