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| Titel |
Assessing the impact of Laurentide Ice Sheet topography on glacial climate |
| VerfasserIn |
D. J. Ullman, A. N. LeGrande, A. E. Carlson, F. S. Anslow, J. M. Licciardi |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 10, no. 2 ; Nr. 10, no. 2 (2014-03-13), S.487-507 |
| Datensatznummer |
250116934
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| Publikation (Nr.) |
 copernicus.org/cp-10-487-2014.pdf |
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| Zusammenfassung |
| Simulations of past climates require altered boundary conditions to account
for known shifts in the Earth system. For the Last Glacial Maximum (LGM) and
subsequent deglaciation, the existence of large Northern Hemisphere ice
sheets caused profound changes in surface topography and albedo. While
ice-sheet extent is fairly well known, numerous conflicting reconstructions
of ice-sheet topography suggest that precision in this boundary condition is
lacking. Here we use a high-resolution and oxygen-isotope-enabled
fully coupled global circulation model (GCM) (GISS ModelE2-R), along with
two different reconstructions of the Laurentide Ice Sheet (LIS) that provide
maximum and minimum estimates of LIS elevation, to assess the range of
climate variability in response to uncertainty in this boundary condition.
We present this comparison at two equilibrium time slices: the LGM, when
differences in ice-sheet topography are maximized, and 14 ka, when
differences in maximum ice-sheet height are smaller but still exist.
Overall, we find significant differences in the climate response to LIS
topography, with the larger LIS resulting in enhanced Atlantic Meridional
Overturning Circulation and warmer surface air temperatures, particularly
over northeastern Asia and the North Pacific. These up- and downstream effects
are associated with differences in the development of planetary waves in the
upper atmosphere, with the larger LIS resulting in a weaker trough over
northeastern Asia that leads to the warmer temperatures and decreased albedo
from snow and sea-ice cover. Differences between the 14 ka simulations are
similar in spatial extent but smaller in magnitude, suggesting that climate
is responding primarily to the larger difference in maximum LIS elevation in
the LGM simulations. These results suggest that such uncertainty in
ice-sheet boundary conditions alone may significantly impact the results of
paleoclimate simulations and their ability to successfully simulate past
climates, with implications for estimating climate sensitivity to greenhouse
gas forcing utilizing past climate states. |
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