| Summary: | The Arctic Ocean has a characteristic stable stratification with fresh and cold water occupying the upper few hundred meters and the warm and more saline Atlantic waters underneath. These water masses are separated by the cold halocline. The stability of the cold halocline regulates the upward directed turbulent heat flux from the Atlantic water to the Arctic water. This heat flux is a part of the arctic energy budget and is important for large scale sea ice formation and melting. Due to the strong vertical stratification combined with its almost circular boundary, the Arctic Ocean supports internal centennial scale Rossby modes. In this study we investigate these modes in a theoretical framework. We apply the free surface two layer model with a linear damping on the sphere and solve this in idealised geometries. We solve this system numerically by a finite difference scheme based on the Arakawa C-grid. We find that solutions to the system have a damping time scale comparable to the propagation time scale. Furthermore, this damping time scale is nearly independent of the local damping coefficient. For a circular [] geometry the amplitude is zero at the boundary. Interestingly, for a more realistic sector-geometry we find finite amplitudes at the borders. We interpret this within the present model as anomalies in the halocline height being exported as fresh water anomalies via the Fram Strait where, further south, they may modulate deep water formation and the overall strength of the thermohaline circulation.
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