HR: 17:04h
AN: OS34A-05    [Abstracts]
TI: Fram Strait Ice Export: Variability and its Impact on Climate
AU: * Koenigk, T
EM: kahl@dkrz.de
AF: Max Planck Institut fuer Meteorologie, Bundesstrasse 53 , Hamburg, 20146 Germany
AU: Jungclaus, J
EM: jungclaus@dkrz.de
AF: Max Planck Institut fuer Meteorologie, Bundesstrasse 53 , Hamburg, 20146 Germany
AU: Mikolajewicz, U
EM: mikolajewicz@dkrz.de
AF: Max Planck Institut fuer Meteorologie, Bundesstrasse 53 , Hamburg, 20146 Germany
AB: The global coupled atmosphere-ocean-sea ice model ECHAM5/MPI-OM is used to investigate the interannual to decadal variability of the ice export through the Fram Strait. The interannual variability of the ice export in the model is mainly caused by variations in the pressure gradient across the Fram Strait. We show in this study that large scale atmospheric modes like the stratospheric polar vortex and the wave number one of the Arctic sea level pressure are responsible for a considerable part of the variability in the pressure gradient across Fram Strait. Decadal variability in the ice export is mainly caused by a coupled atmosphere-ocean-sea ice mode that is characterised by a clockwise propagation of ice thickness anomalies in the Arctic Basin and associated SLP anomalies. This is shown by using lag-EOFs of the SLP and the sea ice thickness of the 500-year control integration of the coupled model and by sensitivity experiments. Furthermore the impact of large anomalies in the ice export through the Fram Strait on the atmospheric and oceanic climate is analysed. Anomalous exported ice is propagating southward in the East Greenland Current, melting and flowing as freshwater signal into the Labrador Sea after one to two years. This freshwater anomaly leads to a negative salinity anomaly and to a decrease in the oceanic convection in the Labrador Sea and vice versa after low ice exports. As a consequence more ice is formed in the Labrador Sea and the heat flux to the atmosphere and thus the air temperature and the precipitation is changed in this region. Besides this local effect, the changes in the heat fluxes have an impact on the large scale atmospheric circulation. After large ice exports and corresponding low heat fluxes to the atmosphere in the Labrador Sea, a positive sea level pressure anomaly extends from the Labrador Sea over the North Atlantic to Europe while the pressure is reduced over the Nordic Seas. The related anomalous wind field is modifying the sea ice transport in the Arctic.
DE: 4207 Arctic and Antarctic oceanography
DE: 4215 Climate and interannual variability (3309)
DE: 4283 Water masses
DE: 4540 Ice mechanics and air/sea/ice exchange processes
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting