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

K. Walesby, J. Vialard, P. J. Minnett, A. H. Callaghan, B. Ward

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


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 35 mm/h) resulted in cooler, fresher water (up to 0.15 practical salinity unit (psu) over the upper 7-10 m) 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 × 10-3oC and 22 × 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.

Original languageEnglish (US)
Pages (from-to)3963-3972
Number of pages10
JournalGeophysical Research Letters
Issue number10
StatePublished - May 28 2015


  • Air-Sea Interaction Profiler
  • double diffusion
  • surface ocean boundary layer

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)


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