Arctic Feedbacks and Atmospheric Teleconnection Patterns

Improved descriptions for sea ice growth, sea ice albedo parameterization and snow cover parameterization have been implemented into the coupled regional Arctic atmosphere-ocean-sea ice model HIRHAM-NAOSIM. The summer minimum in Arctic sea ice extent can be considerably improved due to a more realistic representation of the interactions between atmosphere and sea ice.

The impact of arctic feedback processes like snow- and sea ice albedo and interactive stratospheric chemistry in the polar vortex have been investigated and detected that these processes influence global atmospheric teleconnection patterns. The results show a clear sensitivity of the tropospheric circulation dynamics to the stratospheric chemistry. With enabled interactive stratospheric chemistry the model simulations tend to the negative phase of the Arctic Oscillation mode. This also includes an enhanced mid-latitudinal planetary and synoptic scale wave activity. The strengthening of the synoptic scale waves leads to stronger storm tracks.

The decadal-scale climate variability in IPCC AR4 models has been investigated. These models can reproduce the spatial structure of the large-scale atmospheric teleconnection pattern, like the Arctic Oscillation. But they fail to capture the temporal behaviour of the dominant atmospheric teleconnections and the internally generated variability of the climate system. There is the strong need for improved understanding of Arctic regional feedbacks and their impacts on global decadal-scale climate variability. A climate model prediction system from seasons to decades needs to be developed