HR: 08:45h
AN: PP21E-04    [Abstracts]
TI: North Atlantic Responses for Heinrich and the 8.2 ka Events: Comparison of the Atmosphere-Ocean-Sea Ice Responses to Freshwater Perturbations in a Climate Model
AU: * Otto-Bliesner, B L
EM: ottobli@ucar.edu
AF: National Center for Atmospheric Research, Climate and Global Dynamics Division 1850 Table Mesa Drive, Boulder, CO 80305 United States
AU: Brady, E C
EM: brady@ucar.edu
AF: National Center for Atmospheric Research, Climate and Global Dynamics Division 1850 Table Mesa Drive, Boulder, CO 80305 United States
AU: Briegleb, B P
EM: bruceb@ucar.edu
AF: National Center for Atmospheric Research, Climate and Global Dynamics Division 1850 Table Mesa Drive, Boulder, CO 80305 United States
AU: Morrill, C
EM: morrill@ucar.edu
AF: National Center for Atmospheric Research, Climate and Global Dynamics Division 1850 Table Mesa Drive, Boulder, CO 80305 United States
AB: Geologic records for the Heinrich 1 (H1) event and the 8.2 ka event indicate anomalous freshwater impulses into the North Atlantic. The H1 event, when the Earth was still in a glacial state, has been associated with significant iceberg discharge into the North Atlantic and a shutdown of the North Atlantic thermohaline circulation (THC). The 8.2 event, during our current interglacial, has been associated with a large outburst flood into Hudson Bay as the last remnants of the North American ice sheet melted rapidly. Using the NCAR Community Climate System Model (CCSM), regional responses to a large freshwater forcing, 1 Sv for 100 years into the North Atlantic from 50-70°N (proposed by CMIP for present-day) are investigated for both the glacial background climate of the H1 event and the interglacial background climate of the 8.2 event. In both scenarios, the North Atlantic climate simulated by CCSM responds dramatically, with an almost complete shutdown of the THC, regional cooling in excess of 12°C, and equatorward expansion of sea ice during the freshwater impulse. The rates of change and recovery differ for the glacial cold versus interglacial warm background climate states on which the freshwater perturbations are applied. During the freshwater perturbation, the THC decreases more rapidly and the North Atlantic sea ice increases less rapidly for the 8.2 event as compared to the H1 event. The recovery of the North Atlantic climate after the end of the freshwater perturbation takes ~250 years for the interglacial background state but in excess of ~400-500 years for the glacial background state. We will show results illustrating important atmosphere-ocean-sea ice feedbacks that define the North Atlantic responses for these events.
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 1626 Global climate models (3337, 4928)
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4962 Thermohaline
DE: 9604 Cenozoic
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005