Ocean submesoscales as a key component of the global heat budget

Zhan Su,Patrice Klein,Dimitris Menemenlis,Jinbo Wang,Andrew F Thompson

doi:10.1038/s41467-018-02983-w

Zhan Su, Patrice Klein + Show 3 more

Open Access

https://doi.org/10.1038/s41467-018-02983-w

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Abstract

Recent studies highlight that oceanic motions associated with horizontal scales smaller than 50 km, defined here as submesoscales, lead to anomalous vertical heat fluxes from colder to warmer waters. This unique transport property is not captured in climate models that have insufficient resolution to simulate these submesoscale dynamics. Here, we use an ocean model with an unprecedented resolution that, for the first time, globally resolves submesoscale heat transport. Upper-ocean submesoscale turbulence produces a systematically-upward heat transport that is five times larger than mesoscale heat transport, with winter-time averages up to 100 W/m2 for mid-latitudes. Compared to a lower-resolution model, submesoscale heat transport warms the sea surface up to 0.3 °C and produces an upward annual-mean air–sea heat flux anomaly of 4–10 W/m2 at mid-latitudes. These results indicate that submesoscale dynamics are critical to the transport of heat between the ocean interior and the atmosphere, and are thus a key component of the Earth’s climate.

Highlights

Recent studies highlight that oceanic motions associated with horizontal scales smaller than 50 km, defined here as submesoscales, lead to anomalous vertical heat fluxes from colder to warmer waters
Comparison with a lower resolution simulation shows that submesoscale vertical heat transport warms the sea surface by 0.06–0.3 °C and produces an upward annual mean air–sea heat flux anomaly of 4–10 W/m2 in most mid-latitude areas
Our numerical simulation of the global ocean has permitted an estimate of the vertical heat fluxes caused by submesoscale motions at ~10–50 km range

Summary

Introduction

Recent studies highlight that oceanic motions associated with horizontal scales smaller than 50 km, defined here as submesoscales, lead to anomalous vertical heat fluxes from colder to warmer waters. Compared to a lower-resolution model, submesoscale heat transport warms the sea surface up to 0.3 °C and produces an upward annual-mean air–sea heat flux anomaly of 4–10 W/m2 at mid-latitudes These results indicate that submesoscale dynamics are critical to the transport of heat between the ocean interior and the atmosphere, and are a key component of the Earth’s climate. We find that submesoscale turbulence produces a large and systematically upward heat transport globally throughout the upper ocean: the winter-time averages are 20–100 W/m2 across most of the mid-latitudes, peaking at 500–1000 W/m2 over shorter intervals of days to weeks These amplitudes, consistent with recent in situ observations[11], are comparable to air–sea heat fluxes, and are more than five times larger than the mesoscale vertical heat transport in most regions of the ocean. The same global maps but with a higher pixel resolution can be found at web.gps.caltech.edu/~zhan/nailed/Figure1a.png over days to months, and are a key component of the global heat budget

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