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| Titel |
Ice Core Measurements and GCM Simulation of the Spatial Distribution and Glacial-Interglacial Change of ¹⁷O-excess in Antarctica |
| VerfasserIn |
S. Schoenemann, Q. Ding, E. Steig, A. Schauer |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250059150
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| Zusammenfassung |
| Stable isotope ratios of water in polar precipitation, as measured in ice cores, have been
fundamental to the quantification of past climate variability and change. Recent development
of techniques to measure the 17O/16O ratio precisely has allowed 17Oexcess to be added
to the ice-core isotope toolbox. The combination of δ17O with the conventional
measurements of δ18O and δD – giving the parameter 17Oexcess – provides valuable
new information on the evaporative conditions of the oceanic moisture sources for
Antarctic precipitation. We measured δ17O and δ18O from a number of Antarctic ice
cores (West Antarctic Ice Sheet Divide, Siple Dome, Taylor Dome), and determined
17Oexcesson modern, Holocene, and glacial timescales. These results, combined with
the work of Landais et al. [2008] and Winkler et al. [2011] at Talos Dome, Dome
C, and Vostok, provide the most complete spatial and temporal view of Antarctic
17Oexcess to date. We have added 17Oexcess to the independent isotope modules of two
atmospheric general circulation models (CCSM CAM3 and ECHAM4.6). Both
models are capable of qualitatively reproducing the observed spatial distribution of
modern 17Oexcess in Antarctic precipitation, although our current implementation
of CAM3 currently overestimates the average value of 17Oexcess. Simulation of
glacial-interglacial changes in ECHAM4.6 also realistically captures the differences in
magnitude of the glacial/interglacial changes in 17Oexcess between different ice core
sites, with the details dependent on the magnitude of sea ice changes and to a lesser
degree the chosen supersaturation parameter. Both models show strong gradients in
17Oexcess at the ocean-sea ice boundary, associated with the strong gradient in near
surface water vapor concentration (i.e., the normalized relative humidity). Our results
suggest that the low 17Oexcess values found at Talos Dome and Siple Dome reflect
their proximity to local moisture sources (e.g. from sea ice leads and polynyas)
where evaporation into cold air increases the boundary layer relative humidity,
lowering 17Oexcess. Thus, 17Oexcess in Antarctic precipitation is strongly influenced by
sea ice cover, and may provide an important constraint on past sea ice variations. |
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