HR: 09:45h
AN: PP11C-08    [Abstracts]
TI: The Abrupt Climatic Changes During the Last Deglaciation: Direct Land-sea Correlation From a Marine Pollen Record off Southeastern United States
AU: * Desprat, S
EM: sdesprat@whoi.edu
AF: Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Clark, MS#23, Woods Hole, MA 02543, United States
AU: McManus, J F
EM: jmcmanus@whoi.edu
AF: Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Clark, MS#23, Woods Hole, MA 02543, United States
AU: Peteet, D
EM: peteet@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory - NASA/Goddard Institute for Space Studies, 61 Route 9W, Palisades, New York, NY 10964, United States
AB: We present a new direct land-sea correlation covering the last deglaciation in order a) to provide a better documentation of the regional vegetation changes in southeastern North America and b) more particularly to assess the connection of the continental climatic changes to North Atlantic circulation rapid variability. It was achieved using coupled analyses of pollen and marine climatic proxies from core KNR140-GGC39 (Blake Outer Ridge) at very high time-resolution. Mg/Ca ratio, planktonic δ¹⁸O, mean "sortable silt" grain size (mean S̄S̄) were analyzed in order to get records of SST, salinity and bottom current strength at the core site (Evans et al., submitted to Paleoceanography).
The abrupt climatic changes which characterize the last deglaciation, in particular the major cold oscillations Heinrich event 1 (H1) and Younger Dryas (YD), have been widely documented in the North Atlantic and adjacent continents. However, in the tropical and subtropical North Atlantic and southeastern United States, the climatic signature of these events appears quite different and somehow unclear.
Our direct land-sea correlation shows three configurations:
1- H1 period: cold climatic conditions in southeastern US (high percentages of boreal and herbaceous taxa) but only extremely cold at around 17 ka, accumulation of salty water in the subtropics (high δ¹⁸O_{SW- IVC}) and weak bottom current intensity at the site (low mean S̄S̄)
2- Bolling Alleröd interval: abrupt warming in southeastern US (decrease of boreal taxa in favour of Quercus) at the beginning, synchronous to northern export of the salty water previously accumulated and to an increase of the bottom current strength at the site
3- YD period: mild and wet conditions in southeastern US (expansion of Tsuga and Quercus), decrease of the bottom current strength at the site and accumulation of salty water in the subtropical regions but less than during H1.
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4914 Continental climate records
DE: 4952 Palynology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting