HR: 0830h
AN: OS21B-1121    [PDF]
TI: High Latitude Climate Variability During the Last Glacial Maximum
AU: * Li, C C
EM: camille@atmos.washington.edu
AF: Department of Atmospheric Sciences, University of Washington, 408 ATG Building, Box 351640, Seattle, WA 98195 United States
AU: Rupper, S
EM: sbr3@u.washington.edu
AF: Department of Earth and Space Sciences, University of Washington, 63 Johnson Hall, Box 351310, Seattle, WA 98195 United States
AU: Wettstein, J J
EM: justinjw@atmos.washington.edu
AF: Department of Atmospheric Sciences, University of Washington, 408 ATG Building, Box 351640, Seattle, WA 98195 United States
AU: Steig, E J
EM: steig@ess.washington.edu
AF: Department of Earth and Space Sciences, University of Washington, 63 Johnson Hall, Box 351310, Seattle, WA 98195 United States
AU: Battisti, D S
EM: david@atmos.washington.edu
AF: Department of Atmospheric Sciences, University of Washington, 408 ATG Building, Box 351640, Seattle, WA 98195 United States
AB: The annular modes are instrinsic patterns of variability in the extratropical atmospheric circulation observed in both the Northern and Southern Hemispheres. Research into the possibility of climate forcings projecting onto these annular modes has generated much excitement in recent years. Many studies to date have focused on the forced response of the annular modes to anthropogenic CO$_2$ and ozone changes over the past few decades as suggestive of potential future climate outcomes. There have also been attempts to describe the variability in proxy records of past climate in terms of preferred phases of the annular modes. However, most of this work has assumed that the spatial signatures of the annular modes have remained stationary over time despite changes in the mean state of the climate system. Due to insufficient paleoclimate records and the complicated relationships between their proxy variables and measured variables (such as temperature and precipitation), observations are typically inadequate to resolve the issue of stationarity. In this study, we address the issue through general circulation model simulations of the last glacial maximum (LGM). The LGM (21 kyr BP) presents an opportunity to explore the sensitivity of climate variability patterns during a relatively well-documented interval of Earth's history in which the climate system was significantly altered by the presence of large, land-based ice sheets in the Northern Hemisphere. We ran a series of experiments using the NCAR CCM3.6 with LGM orbital parameters, CO$_2$ levels, and topography coupled to a data ocean of CLIMAP sea surface temperatures (SSTs) and found Northern Hemisphere high latitude variability to be qualitatively different than that in the modern day. As there is uncertainty over details of the glacial world, we explored the sensitivity of the leading mode of variability to changes in ice sheet topography and tropical SST patterns. Preliminary results indicate that key factors include the influence of the Laurentide ice sheet on stationary waves in the Northern Hemisphere, and the influence of the tropical ocean on teleconnections to the midlatitudes. The range of possible spatial patterns found under different boundary conditions has interesting implications for the interpretation of paleoclimate data. Future work will aim to use these results as an objective platform on which to test the many and varied hypotheses invoked to explain climate variability on a range of time scales.
DE: 1620 Climate dynamics (3309)
DE: 3319 General circulation
DE: 3344 Paleoclimatology
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting