HR: 16:05h
AN: PP54B-01 INVITED     [Abstracts]
TI: Interactions between Antarctic Sea Ice, Ice Sheets, and Climate Through the Cenozoic
AU: * DeConto, R
EM: deconto@geo.umass.edu
AF: Dept. of Geosciences, University of Massachusetts, Amherst, MA 01003 United States
AU: Pollard, D
EM: pollard@essc.psu.edu
AF: Earth and Environmental Systems Institute, Pennsylvania State University, University Park, PA 16802
AU: Harwood, D
EM: dharwood1@unl.edu
AF: Dept. of Geosciences, University of Nebraska, Lincoln, NE 68588 United States
AB: The seasonal distribution and thickness of Antarctic sea ice has important climatic effects on radiation balance, energy transfer between the atmosphere and ocean, moisture availability, and thermohaline circulation. Here, we explore the role of sea ice and related feedbacks in the Cenozoic evolution of Antarctic climate and ice sheets. We use a numerical climate model with explicit, dynamical representations of sea ice and grounded continental ice sheets to test: 1) the sensitivity of Southern Hemisphere sea ice to early Cenozoic climate forcing (paleogeography, CO2, orbital cycles, and ice sheet configuration); and 2) the importance of sea ice-atmosphere feedbacks on glacial mass balance in the Antarctic interior. In our model, little or no sea ice forms around the Antarctic margin with 3xCO2, regardless of orbital forcing or ice sheet configuration. At 2xCO2 seasonal sea ice distribution is shown to be highly sensitive to ice sheet size and configuration, via the ice sheet's control on Southern Ocean surface temperature and the low-level wind field. As in prior modeling studies, the growth of sea ice produces significant local-regional changes in net radiation and surface heat flux heat, with statistically significant effects on temperature, precipitation, and surface pressure over the sea ice zone and coastal areas. Only limited effects are seen in the continental interior, however, and changes in net annual snow budgets are too small to affect the pace of a growing East Antarctic ice sheet. These results suggest the Cenozoic appearance of Antarctic sea ice was a response to grounded ice volume and was not a critical factor in Paleogene and Neogene episodes of glaciation. The East Antarctic Ice Sheet's control of equatorward sea ice extent has important implications for Southern Ocean deepwater production and implies proxy reconstructions of ancient sea ice may be indicative of conditions in the continental interior. According to our model, the most persistent and thickest sea ice, prior to the development of the West Antarctic Ice Sheet, would have been located along the western margin of the shallow seaway separating east and west Antarctica, a critical area for the formation of ice shelves that could have influenced the early development of the West Antarctic Ice Sheet.
DE: 3334 Middle atmosphere dynamics (0341, 0342)
DE: 4267 Paleoceanography
DE: 4540 Ice mechanics and air/sea/ice exchange processes
DE: 3309 Climatology (1620)
DE: 0315 Biosphere/atmosphere interactions
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting