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Observations indicative of rain-induced double diffusion in the ocean surface boundary layer

TitleObservations indicative of rain-induced double diffusion in the ocean surface boundary layer
Publication TypeJournal Article
Year of Publication2015
AuthorsWalesby K., Vialard J., Minnett P.J, Callaghan AH, Ward B.
JournalGeophysical Research Letters
Date Published2015/05
Type of ArticleArticle
ISBN Number0094-8276
Accession NumberWOS:000356631300042
Keywordsair-sea interaction; double diffusion; fluxes; impact; microstructure; north-atlantic; Profiler; salt fingers; stratification; surface ocean boundary layer; thermohaline staircase; turbulence

Double diffusion can result in the formation of thermohaline staircases, typically observed in the ocean interior. The observations presented here were acquired in the ocean surface boundary layer with the autonomous microstructure Air-Sea Interaction Profiler. An intense rain event (rainfall rates of up to 35mm/h) resulted in cooler, fresher water (up to 0.15practical salinity unit (psu) over the upper 7-10m) overlaying warmer, saltier water, a situation potentially conducive to double-diffusive mixing. Although not as crisp as interfaces in the interior ocean because of elevated background mixing, a total of 303 thermohaline interfaces were detected within and at the base of the fresh layer, with mean changes in temperature (T) and salinity (S) across interfaces of 20 x 10(-3 degrees)C and 22 x 10(-3)psu, respectively. These results call for new studies to disambiguate whether such interfaces are formed through double-diffusive mixing or shear instabilities and understand any long-term impacts on near-surface stratification.

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