Evolution of tides and tidal dissipation over the last glacial cycle

Simulations of the tides from the Last Glacial Maximum (26.5 – 19 kyr BP) to the present show large amplitude and dissipation changes, especially in the semi-diurnal band during the deglacial period. New reconstructions of global ice sheet history and sea levels covering the last glacial cycle allow us to extend the tidal simulations from the last interglacial (~125 kyr BP) to the present. Climate during this period was far from stable with periods of ice sheet advance and lower sea levels interspaced with ice sheet melting and sea level increases. Here, using the sea level and ice history from Gowan et al. (2021; 80 kyr BP to present) and sea level simulations based on the ICE6G_C ice history (Peltier et al., 2015; 122 kyr BP to present), we present simulations of tidal amplitudes and dissipation over the last glacial cycle using the tide model OTIS for the tidal constituents M₂, S₂, K₁ and O₁. Our results show large variations in amplitudes and dissipation over this period for the M₂ tidal constituent with several tidal maxima, whereas for the other constituents, changes are mainly regional. Due to the lower sea levels and altered bathymetry, open ocean dissipation was enhanced with respect to present day levels for most of the glacial cycle for all constituents. This result is important in the context of historical ocean mixing rates. We further highlight the impacts of the differences in bathymetry and ice sheet reconstructions on global tidal dissipation.

Gowan, E.J., Zhang, X., Khosravi, S., Rovere, A., Stocchi, P., Hughes, A.L., Gyllencreutz, R., Mangerud, J., Svendsen, J.I. and Lohmann, G., (2021), A new global ice sheet reconstruction for the past 80 000 years, Nature Communications, 12(1), 1-9.

Peltier, W. R., Argus, D. F., and Drummond, R. (2015), Space geodesy constrains ice age terminal deglaciation: The global ICE-6G_C (VM5a) model, J. Geophys. Res. Solid Earth, 120, 450– 487, doi:10.1002/2014JB011176.