Internal Modes of Multidecadal Variability in the Arctic Ocean

Observations of sea ice extent and atmospheric temperature in the Arctic, although sparse, indicate variability on multidecadal time scales. A recent analysis of one of the global climate models [the Geophysical Fluid Dynamics Laboratory Climate Model, version 2.1 (CM2.1)] in the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change has indicated that Arctic Ocean variability on these time scales is associated with changes in basin-wide salinity patterns. In this paper the internal modes of variability in an idealized Arctic Basin are determined by considering the stability of salinity-driven flows. An internal ocean mode with a multidecadal time scale is found, with a spatial pattern similar to that obtained in the analysis of the CM2.1 results. The modes propagate as a "saline Rossby wave" induced by the background salinity gradient.