HR: 10:20h
AN: PP12A-01    [Abstracts]
TI: North Atlantic freshening and ice-age abrupt climate change--8k and older
AU: * Alley, R B
EM: rba6@psu.edu
AF: Department of Geosciences, Pennsylvania State University, Deike Building, University Park, PA 16802 United States
AB: Strong evidence shows that: 1) a large freshwater flood entered the North Atlantic very rapidly slightly more than 8000 years ago; 2) a widespread, abrupt climate event occurred immediately thereafter; and 3) reconstructed climate anomalies are very similar to those modeled as a response to abrupt North Atlantic freshening. Cause and effect are tightly linked; with high confidence, North Atlantic freshening and associated ocean-circulation changes caused the abrupt climate event. Several older abrupt climate events including the Younger Dryas immediately followed North Atlantic freshening and had anomaly patterns expected for North Atlantic freshening; sufficiently long events show deep-water as well as surface-water and atmospheric signals, as expected. The basic picture from W. Broecker of North Atlantic "conveyor" disruptions causing abrupt climate shifts is thus strongly supported. Differences in forcing and in mean climate state between the past events and future North Atlantic freshening motivate work to assess the possibility of future changes; the past anomalies provide limiting estimates of what might result in the future were a conveyor disruption to occur.
DE: 3344 Paleoclimatology
DE: 4267 Paleoceanography
DE: 1827 Glaciology (1863)
DE: 1600 GLOBAL CHANGE (New category)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting