The Arctic Ocean's response to the NAM

The sea ice response of the Arctic Ocean to the Northern Annular Mode (NAM) is studied both in observations and in a numerical ocean general circulation model. The analysis of the observed sea ice concentrations shows the well known seesaw in response between the Labrador Sea and the Greenland and Barents Seas. After band pass filtering the data, it reveals a variation in response in the Greenland Sea between interannual and multidecadal NAM periodicity.

In the numerical model experiments idealized NAM-like wind and windstress forcing anomalies of varying periodicity are applied to the model. This setup allows us to investigate variations in the response to the NAM in a controlled environment. The analysis of the numerical experiments reveals a similar change in response in the Greenland Sea as we found in the observational data. The changes in response appear to be caused by a slow oceanic response component which on interannual timescales does not get strong enough to modify the quicker windstress driven response of the sea ice.