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Observational evidence for an ocean heat pump induced by tropical cyclones


Ocean mixing affects global climate and the marine biosphere because it is linked to the ocean’s ability to store and transport heat1 and nutrients2. Observations have constrained the magnitude of upper ocean mixing associated with certain processes3,4, but mixing rates measured directly3,5 are significantly lower than those inferred from budget analyses6, suggesting that other processes may play an important role. The winds associated with tropical cyclones are known to lead to localized mixing of the upper ocean7,8,9, but the hypothesis that tropical cyclones are important mixing agents at the global scale10 has not been tested. Here we calculate the effect of tropical cyclones on surface ocean temperatures by comparing surface temperatures before and after storm passage, and use these results to calculate the vertical mixing induced by tropical cyclone activity. Our results indicate that tropical cyclones are responsible for significant cooling and vertical mixing of the surface ocean in tropical regions. Assuming that all the heat that is mixed downwards is balanced by heat transport towards the poles, we calculate that approximately 15 per cent of peak ocean heat transport may be associated with the vertical mixing induced by tropical cyclones. Furthermore, our analyses show that the magnitude of this mixing is strongly related to sea surface temperature, indicating that future changes in tropical sea surface temperatures may have significant effects on ocean circulation and ocean heat transport that are not currently accounted for in climate models.

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Figure 1: Maps of tropical cyclone effects on the upper ocean.
Figure 2: Potential cyclone-induced climate interactions with vertical ocean mixing.


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We thank E. Schneider and K. Emanuel for diffusivity values (used in Fig. 2a) and hurricane track data, respectively. ERA-40 data were provided by the Data Support Section of the Scientific Computing Division at the National Center for Atmospheric Research (NCAR). NCAR is supported by the NSF. NCEP reanalysis data were provided by the NOAA-CIRES Climate Diagnostics Center, Boulder, Colorado, USA, from their website at TMI data are produced by Remote Sensing Systems and sponsored by the NASA Earth Science REASoN DISCOVER Project. Data are available at NODC_WOA98 data were provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, from their website at M.H.’s research is supported by the NSF, the Purdue Research Foundation, the Purdue Cyber Center, and Information Technology at Purdue (ITaP).

Author Contributions R.L.S. and M.H. contributed equally to the writing, data analysis and ideas in this paper.

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Correspondence to Matthew Huber.

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Reprints and permissions information is available at The authors declare no competing financial interests.

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Supplementary Information

This file contains Supplementary Notes, Supplementary Methods, Supplementary Figures S1-S6 with Legends and additional references. The Supplementary Information presents additional material supporting conclusions, interpretations, and implications referenced in the main text. Also, previous results are highlighted, methods section is expanded and error analysis is discussed. (PDF 38196 kb)

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Sriver, R., Huber, M. Observational evidence for an ocean heat pump induced by tropical cyclones. Nature 447, 577–580 (2007).

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