HR: 08:45h
AN: B31C-04    [Abstracts]
TI: Planet-wide volcanics correlated with Last Glacial abrupt climate changes
AU: * Bay, R C
EM: bay@cletus.physics.berkeley.edu
AF: Physics Department, 366 LeConte Hall University of California, Berkeley, CA 94720 United States
AU: Bramall, N
EM: bramall@socrates.Berkeley.EDU
AF: Physics Department, 366 LeConte Hall University of California, Berkeley, CA 94720 United States
AU: Price, P B
EM: bprice@berkeley.edu
AF: Physics Department, 366 LeConte Hall University of California, Berkeley, CA 94720 United States
AB: We recently reported a correlation in excess of 99.5% between volcanic ash layers recorded in the deep ice core site at Siple Dome, West Antarctica and millennium-timescale abrupt cold periods (Dansgaard-Oeschger events) recorded at Summit, Greenland (GISP2) during the last glacial period. These data, obtained with our deep borehole optical dust logger, are the best evidence yet for a causal connection between volcanism and millennial climate change on the planetary scale, and lead to possibilities of a direct causal relationship. We now present a comparison with other volcanic proxies which demonstrates that the heaviest ash layers we detected at Siple Dome, those sufficiently concentrated for detailed chemical analysis in the core, appear to have come from local sources in West Antarctica, whereas the majority correspond to volcanic events detected throughout the Antarctic continent that correlate strongly with millennial climate changes in the Northern Hemisphere. Excluding the several heaviest ash signals in the Siple Dome data set increases the correlation with climate above the 3-sigma level, more than 800-to-one rejection of the null hypothesis. In June 2004 we deployed a high-resolution logger in the GRIP borehole at Summit, Greenland. We detected of order $\sim$100 volcanic ash layers which correlate weakly if at all with millennial climate change, consistent with studies of other Greenlandic records of volcanism. This contrast may provide an important clue to understanding global volcano-climate interaction as well as the role of the Southern Hemisphere. Of interest is a scenario in which volcanic ash and sulfate abruptly increase the soluble iron in large surface areas of nutrient-limited oceans, particularly the Southern Ocean, and stimulate growth of phytoplankton which enhance cooling by altering ocean albedo and atmospheric chemistry through mechanisms not fully understood. Viewed from another perspective, crustal stresses from ice-sheet loading/unloading and changes in sea-level driven by climate fluctuations are believed to trigger volcanic eruptions, and these data could be evidence supporting a bipolar seesaw model. Large global temperature swings may even be limited by feedback within the volcano-climate system.
DE: 1610 Atmosphere (0315, 0325)
DE: 1615 Biogeochemical processes (4805)
DE: 1620 Climate dynamics (3309)
DE: 0370 Volcanic effects (8409)
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting