HR: 15:00h
AN: GC43A-04 INVITED     [Abstracts]
TI: The Arctic Amplification Debate
AU: * Serreze, M C
EM: serreze@kryos.colorado.edu
AF: CIRES, University of Colorado, Campus Box 449, Boulder, CO 80309-0449 United States
AU: Francis, J
EM: francis@imcs.rutgers.edu
AF: Rutgers University, Institute of Marine and Coastal Sciences, 71 Dudley Road, New Brunswick, NJ 08901 United States
AB: Largely due to feedbacks involving snow and sea ice, rises in surface air temperature (SAT) in response to greenhouse gas (GHG) loading are expected to be most pronounced in the Arctic, especially for autumn and winter over the Arctic Ocean. Observations document recent warming, but this Arctic Ocean signal is not readily evident. This finding, along with large model-to-model scatter in SAT projections, pronounced variability in SAT over the 20th century, and links between observed SAT changes and atmospheric circulation, questions the concept of Arctic amplification. However, a closer evaluation shows that disparities between observations and models are large only for scenarios well into the future. We offer that the often-perceived mismatch between observations and models projections, and the ensuing debate about Arctic amplification, can be partly rectified by considering the Arctic in the context of an emerging greenhouse signal in which sea ice and snow cover are in a state of preconditioning . At present, SATs over the Arctic Ocean are still fundamentally constrained by the insulating effects of the sea ice cover. In the next several decades, we expect that a threshold will be reached in terms of sea ice loss, allowing Arctic Ocean SATs to increase. While part of this preconditioning is driven by GHG radiative forcing, its is presently more closely tied to low frequency variability on the Northern Annular Mode (NAM). There is in turn growing evidence that GHG forcing may favor the positive mode of the NAM that favors sea ice losses.
DE: 3349 Polar meteorology
DE: 4203 Analytical modeling
DE: 1610 Atmosphere (0315, 0325)
DE: 1635 Oceans (4203)
SC: Global Climate Change [GC]
MN: 2004 AGU Fall Meeting