 |
| Titel |
Decadal trends in the Antarctic sea ice extent ultimately controlled by ice–ocean feedback |
| VerfasserIn |
H. Goosse, V. Zunz |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1994-0416
|
| Digitales Dokument |
URL |
| Erschienen |
In: The Cryosphere ; 8, no. 2 ; Nr. 8, no. 2 (2014-03-18), S.453-470 |
| Datensatznummer |
250116079
|
| Publikation (Nr.) |
 copernicus.org/tc-8-453-2014.pdf |
|
|
|
|
|
| Zusammenfassung |
| The large natural variability of the Antarctic sea ice is a key
characteristic of the system that might be responsible for the small
positive trend in sea ice extent observed since 1979. In order to gain
insight of the processes responsible for this variability, we have analysed
in a control simulation performed with a coupled climate model a positive
ice–ocean feedback that amplifies sea ice variations. When sea ice
concentration increases in a region, in particular close to the ice edge,
the mixed layer depth tends to decrease. This can be caused by a net inflow
of ice, and thus of freshwater, that stabilizes the water column. A second
stabilizing mechanism at interannual timescales is associated with the
downward salt transport due to the seasonal cycle of ice formation: brine is
released in winter and mixed over a deep layer while the freshwater flux
caused by ice melting is included in a shallow layer, resulting in a net
vertical transport of salt. Because of this stronger stratification due to
the presence of sea ice, more heat is stored at depth in the ocean and the
vertical oceanic heat flux is reduced, which contributes to maintaining a
higher ice extent. This positive feedback is not associated with a
particular spatial pattern. Consequently, the spatial distribution of the
trend in ice concentration is largely imposed by the wind changes that can
provide the initial perturbation. A positive freshwater flux could
alternatively be the initial trigger but the amplitude of the final response
of the sea ice extent is finally set up by the amplification related to
the ice–ocean feedback. Initial conditions also have an influence as the chance
to have a large increase in ice extent is higher if starting from a state
characterized by a low value. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|