Impact of sea ice friction on ocean tides in the Arctic Ocean, modelling insights at various time and space scales

Abstract

Although ocean tides are one of the major contributors to the energy dissipation in the Arctic Ocean, they remain relatively poorly known, particularly their interactions with the ice cover (sea ice and grounded ice). These interactions are often simply ignored in tidal models, or considered through relatively simple combinations with the bottom friction. In this paper, we investigate the response of a regional pan-Arctic ocean tidal model to the friction under the sea ice cover, in order to better understand the influence of this parameter on tidal estimates. Different periods of time, from seasonal to decadal scales, were considered to analyze the impact of the variations in the sea ice cover on the ocean tides, in the region as well as at global scale. Long-distance effects of Arctic sea ice friction are revealed in the global tidal simulations, resulting in variations of several centimeters in the seasonal tidal amplitudes. Tide gauge and satellite altimetry observations were specifically processed to retrieve the tidal harmonic constituents over different periods and different sea ice conditions, to compare with the model simulations. Improving the knowledge on the interaction between the tides and the sea ice cover, and thus the performance of the tidal models in the polar regions, is of particular interest to generate more realistic simulations with ocean circulation models, to contribute to scientific investigations on the changes in the Arctic Ocean, and also to improve the satellite altimetry observation retrievals at high latitudes, as the tidal signals remain a major contributor to the error budget of the satellite altimetry observations in the Arctic Ocean. This work also highlights the difficulty to assess the temporal evolution of tides in model simulations in the Arctic because of the lack of long (i.e. several decades) hourly tide gauge observation records in the area.