HR: 10:35h
AN: PP41D-02    [PDF]
TI: Spatial Pattern of Rapid Climatic Oscillations and Vegetation Response During the Last Deglaciation in Northeastern North America
AU: * Yu, Z
EM: ziy2@lehigh.edu
AF: Lehigh University, Department of Earth and Environmental Sciences, 31 Williams Drive, Bethlehem, PA 18015 United States
AB: Large and abrupt climatic oscillations occurred during the last deglaciation evident from ice, lacustrine and marine records in different regions. Stable isotopes retrieved from these records could provide a common proxy in correlating the records and detecting temporal and spatial patterns. The emerging pattern is critical in understanding the nature and forcing mechanisms of climate changes. Here I provide new isotopic and pollen results from the Mid-Atlantic region of USA to expand the existing late-glacial records from the Great Lakes region to the Atlantic Seaboard. White Lake, a marl lake in NW New Jersey, provides high-resolution sedimentary records since ca. 15,000 cal yr BP (15 ka). The chronology of late-glacial and early Holocene period was controlled by 6 AMS$ ^{14}$C dates on terrestrial macrofossils. Oxygen isotopes of marl samples (contain $>$90% carbonates) from this period vary between -8 and -4 permil (VPDB) and show multiple oscillations at millennial and centennial scales, including the Younger Dryas (YD) with ca. 3 permil shifts in $\delta^{18}$O at 12.6-11.3 ka and three cold events of 1-2 permil shifts during the B{\o}lling-Aller{\o}d (B-A) period at 14.3-12.6 ka. Pollen diagram from this site shows strong similarity with previously published pollen records from this region, with the YD event having high boreal taxa ({\it Alnus, Abies, Betula}) after establishment of a mixed deciduous-coniferous forest containing {\it Quercus, Fraxinus} and {\it Ostrya/Carpinus}. A plateau-like B-A period is similar to some (Ammersee, Germany; Cariaco Basin, Caribbean) but not other records (ice cores form Greenland Summit; Crawford Lake, Ontario) around the Atlantic Ocean, suggesting that a strong climate gradient might have existed then. Vegetation shows different sensitivity in responding to the YD at sites along a transect from New Jersey, through western New York, to southern Ontario, which was probably caused by a combination of species migration/availability, location of then ecotones, and amplitudes of climate change. The new results and synthesis indicate that climate gradients have changed dramatically over short time period during the last deglaciation, which must have played a major role in determining the state of climate and climate sensitivity for a given region.
DE: 0400 Biogeosciences
DE: 1045 Low-temperature geochemistry
DE: 1600 GLOBAL CHANGE (New category)
DE: 1620 Climate dynamics (3309)
DE: 3344 Paleoclimatology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting