What is it about?
The Atlantic Meridional Overturning Circulation (AMOC) is an important part of the climate system because it transports heat, nutrients, carbon and other tracers around the world and between the surface and the deep ocean. Paleoclimate data show that during the last ice age the AMOC was different from today, but we don't currently understand how exactly and why it may have been different. Here, using computer models, we show that lower sea level during that time may have caused increases in tides, which caused more tidal mixing in the deep ocean, which intensified the AMOC.
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Why is it important?
In most previous climate model simulations of the LGM AMOC changes in tidal mixing were neglected. Here we show that this is not warranted. Changes in tidal mixing may have had a strong impact on the LGM AMOC and should be taken into account in future model simulations. More generally better understanding of the AMOC, how it has changed in the past and what processes drive it, is also important for improved projections of future AMOC changes due to human caused climate change.
Perspectives
This paper differs from results of a previous study that has found negligible effects of tidal mixing on the LGM AMOC. We used a higher resolution tide model and I think that our results may therefore be more reliable, but it will be important in the future to examine the model dependency in order to get a more robust understanding of this effect.
Andreas Schmittner
Oregon State University
Read the Original
This page is a summary of: Glacial ocean overturning intensified by tidal mixing in a global circulation model, Geophysical Research Letters, May 2015, American Geophysical Union (AGU),
DOI: 10.1002/2015gl063561.
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