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Please join us as we welcome Dr. Ali Mashayek from the department of Earth, Atmospheric and Planetary Sciences at MIT for his seminar titled "Topographic enhancement of turbulent mixing in the Southern Ocean: regional, global and climatic implications". Refreshments will be served.

Abstract

Diapycnal turbulent mixing is believed to play a key role in setting the rate of the ocean Meridional Overturning Circulation (MOC), an important element of the global climate system. Whether mixing is truly important, however, depends on its strength, which remains poorly quantified on global scale. To address this question, a passive tracer was released upstream of the Drake Passage in 2009 as a part of a major US-UK field program. While the mixing rates inferred from large scale dispersion of the tracer are large, those inferred based on localized turbulence measurements made along the path of the tracer are so small that defy the role of mixing as a key driver of the MOC. In this talk I will use an observationally-tuned high resolution numerical model of the Drake Passage region to reconcile the two estimates and will show that mixing is indeed sufficiently strong to play an important role in setting the Southern Ocean branch of the MOC. I will finish by discussing how this recently confirmed enhanced mixing connects with other processes that help drive the deep branch of the ocean MOC, and how together they regulate the climate system through exerting constraints on the global carbon and heat budgets.

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