Mixing Matters, Here's Why - Ocean Mixing Controls Seasonal Sea Surface Cooling in Equatorial Pacific Cold Tongue (Invited)
Abstract
Away from the equator, the seasonal cycle in solar radiation dominates the seasonal cycle in SST. At the equator, the atmosphere heats the ocean throughout the year, yet equatorial oceans also exhibit a seasonal cycle in SST. While atmospheric inputs are well constrained on seasonal timescales, variations in turbulent mixing over such long time scales have never before been measured. Here we show the existence of a distinctive seasonal cycle of subsurface cooling via mixing in the equatorial Pacific cold tongue, using the first multi-year measurements of turbulence in the ocean. In boreal spring, SST rises by 2 K when heating of the upper ocean by the atmosphere exceeds cooling by mixing from below. In boreal summer, SST decreases because cooling from below exceeds heating from above. When the effects of lateral advection are considered, the magnitude of summer cooling via mixing (4 K month-1) is equivalent to that required to counter the heating terms. These results provide the first quantitative assessment of how mixing varies on time scales longer than a few weeks, clearly showing its controlling influence on seasonal cooling of SST in a critical oceanic regime.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFMOS31D..06M
- Keywords:
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- 4490 NONLINEAR GEOPHYSICS Turbulence;
- 4568 OCEANOGRAPHY: PHYSICAL Turbulence;
- diffusion;
- and mixing processes;
- 4294 OCEANOGRAPHY: GENERAL Instruments and techniques;
- 4504 OCEANOGRAPHY: PHYSICAL Air/sea interactions