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Glacial ocean overturning intensified by tidal mixing in a global circulation model
Author(s) -
Schmittner A.,
Green J. A. M.,
Wilmes S.B.
Publication year - 2015
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2015gl063561
Subject(s) - geology , last glacial maximum , climatology , abyssal zone , ocean current , thermohaline circulation , glacial period , ocean general circulation model , deglaciation , oceanography , shutdown of thermohaline circulation , paleoclimatology , climate model , atmospheric sciences , north atlantic deep water , climate change , general circulation model , geomorphology
Due to lower sea levels during the Last Glacial Maximum (LGM), tidal energy dissipation was shifted from the shallow margins into the deep ocean. Here using a high‐resolution tide model, we estimate that global energy fluxes below 200 m depth were almost quadrupled during the LGM. Applying the energy fluxes to a consistent tidal mixing parameterization of a global climate model results in a large intensification of mixing. Global mean vertical diffusivity increases by more than a factor of 3, and consequently, the simulated meridional overturning circulation accelerates by ~21–46%. In the model, these effects are at least as important as those from changes in surface boundary conditions. Our findings contrast with the prevailing view that the abyssal LGM circulation was more sluggish. We conclude that changes in tidal mixing are an important mechanism that may have strongly increased the glacial deep ocean circulation and should no longer be neglected in paleoclimate simulations.