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Ocean Heat Content Changes Induced by Tropical Cyclones
Park, J.J., Kwon, Y.-O. and Price, J.F. 2011. Argo array observation of ocean heat content changes induced by tropical cyclones in the north Pacific. Journal of Geophysical Research 116: 10.1029/2011JC007165.

Park et al. introduce the report of their research by noting that "a cold wake in the sea surface temperature (SST) is perhaps the most outstanding feature of the upper ocean response to a tropical cyclone (TC)," citing Cornillon et al. (1987); and they state that "SST and near-surface cooling under a strong TC is generally accompanied by warming in the subsurface," citing Price (1981) and D'Asaro et al. (2007).

What was done
In the words of the authors, "in situ observations from the autonomous Argo float array [were] used to assess the basin-averaged ocean heat content change driven by tropical cyclones in the North Pacific for 2000-2008," where "a new statistical approach based on pairs of profiles before and after each TC event [was] employed ... to estimate the near-surface and sub-surface heat content changes."

What was learned
Park et al. found that for strong TCs of category 4 or greater, "the sub-surface warming expected from vertical mixing occurs with comparable magnitude to near-surface cooling," but that "when weak TCs (less than or equal to category 3, which are about 86% of the total of TCs) were also considered, the subsurface warming was not detectable in the Argo data set, while near-surface cooling was still significant." In addition, they say that the Argo observations suggest that "the restoring time scale of the near-surface heat content is greater than 30 days, which may be compared with the approximately 10-day timescale for the restoration of sea surface temperature."

What it means
The three researchers write that their data "support the notion that only a thin surface layer is restored quickly to pre-TC conditions, while the rest of the cooled near-surface layer retains the TC-induced response for a good deal longer," which phenomena would tend to decrease the likelihood of another TC occurring in the same general area as soon as it might have occurred in the absence of the studied TC, due to the first TC's cooling of the local waters by the degree and for the amount of time suggested by their findings.

Cornillon, P., Stramma, L. and Price, J.F. 1987. Satellite measurements of sea surface cooling during Hurricane Gloria. Nature 326: 373-375.

D'Asaro, E.A., Sanford, T.B., Niiler, P.O. and Terrill, E.J. 2007. Cold wake of Hurricane Frances. Geophysical Research Letters 34: 10.1029/2007GL030160.

Price, J.F. 1981. Upper ocean response to a hurricane. Journal of Physical Oceanography 11: 153-175.

Reviewed 28 March 2012