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| Titel |
Amplification of obliquity forcing through mean annual and seasonal atmospheric feedbacks |
| VerfasserIn |
S.-Y. Lee, C. J. Poulsen |
| 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 ; 4, no. 4 ; Nr. 4, no. 4 (2008-10-15), S.205-213 |
| Datensatznummer |
250001863
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| Publikation (Nr.) |
 copernicus.org/cp-4-205-2008.pdf |
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| Zusammenfassung |
| Pleistocene benthic δ18O records exhibit strong spectral power
at ~41 kyr, indicating that global ice volume has been modulated by
Earth's axial tilt. This feature, and weak spectral power in the
precessional band, has been attributed to the influence of obliquity on mean
annual and seasonal insolation gradients at high latitudes. In this study,
we use a coupled ocean-atmosphere general circulation model to quantify
changes in continental snowfall associated with mean annual and seasonal
insolation forcing due to a change in obliquity. Our model results indicate
that insolation changes associated with a decrease in obliquity amplify
continental snowfall in three ways: (1) Local reductions in air temperature
enhance precipitation as snowfall. (2) An intensification of the winter
meridional insolation gradient strengthens zonal circulation (e.g. the
Aleutian low), promoting greater vapor transport from ocean to land and snow
precipitation. (3) An increase in the summer meridional insolation gradient
enhances summer eddy activity, increasing vapor transport to high-latitude
regions. In our experiments, a decrease in obliquity leads to an annual
snowfall increase of 25.0 cm; just over one-half of this response (14.1 cm)
is attributed to seasonal changes in insolation. Our results indicate that
the role of insolation gradients is important in amplifying the relatively
weak insolation forcing due to a change in obliquity. Nonetheless, the total
snowfall response to obliquity is similar to that due to a shift in Earth's
precession, suggesting that obliquity forcing alone can not account for the
spectral characteristics of the ice-volume record. |
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