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| Titel |
Impact of freshwater release in the North Atlantic under different climate conditions in an OAGCM |
| VerfasserIn |
Didier Swingedouw, Juliette Mignot, Pascale Braconnot, Eloi Mosquet, Masa Kageyama, Ramdane Alkama |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250035777
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| Zusammenfassung |
| The response of climate to freshwater input in the North Atlantic (NA) has raised a
lot of concern about the issue of climate stability since the discovery of abrupt
coolings during the last glacial period. Such coolings have usually been related to a
weakening of the Atlantic meridional overturning circulation (AMOC), probably
associated with massive iceberg surges or meltwater pulses. Additionally, the recent
increase in greenhouse gases in the atmosphere has also raised the possibility of
a melting of the Greenland ice sheet, which may impact the future AMOC, and
thereby the climate. In this study, the extent to which the mean climate influences the
freshwater release linked to ice sheet melting in the NA and the associated climatic
response is explored. For this purpose the simulations of several climatic states (last
interglacial, Last Glacial Maximum, mid-Holocene, preindustrial, and future (2ÃCO2) are
considered, and the climatic response to a freshwater input computed interactively
according to a surface heat flux budget over the ice sheets is analyzed. It is shown that
the AMOC response is not linear with the freshwater input and depends on the
mean climate state. The climatic responses to these different AMOC changes share
qualitative similarities for the general picture, notably a cooling in the Northern
Hemisphere and a southward shift of the intertropical convergence zone (ITCZ) in the
Atlantic and across the Panama Isthmus. The cooling in the Northern Hemisphere is
related to the sea ice cover response, which strongly depends on the responses of the
atmospheric circulation, the local oceanic heat transport, and the density threshold of
the oceanic convection sites. These feedbacks and the magnitude of temperature
and precipitation changes outside the North Atlantic depend on the mean climate. |
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