Modeling of Polar Ocean Tides at the Last Glacial Maximum: Amplification, Sensitivity, and Climatological Implications

Abstract

Diurnal and semidiurnal ocean tides are calculated for both the present day and the Last Glacial Maximum. A numerical model with complete global coverage and enhanced resolution at high latitudes is used including the physics of self-attraction and loading and internal tide drag. Modeled present-day tidal amplitudes are overestimated at the standard resolution, but the error decreases as the resolution increases. It is argued that such results, which can be improved in the future using higher-resolution simulations, are preferable to those obtained by artificial enhancement of dissipative processes. For simulations at the Last Glacial Maximum a new version of the ICE-5G topographic reconstruction is used along with density stratification determined from coupled atmosphere?ocean climate simulations. The model predicts a significant amplification of tides around the Arctic and Antarctic coastlines, and these changes are interpreted in terms of Kelvin wave dynamics with the aid of an exact analytical solution for propagation around a polar continent or basin. These polar tides are shown to be highly sensitive to the assumed location of the grounding lines of coastal ice sheets, and the way in which this may contribute to an interaction between tides and climate change is discussed. Globally, the picture is one of energized semidiurnal tides at the Last Glacial Maximum, with an increase in tidal dissipation from present-day values, the dominant energy sink being the conversion to internal waves.