Heat and salinity transport between the permanent pycnocline and the mixed layer due to the obduction process evaluated from a gridded Argo dataset

Yoshimi Kawai, Shigeki Hosoda, Kazuyuki Uehara, Toshio Suga

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

It is necessary for air–sea interaction and climate research to evaluate heat and salinity transport between the mixed layer (ML) and the permanent pycnocline and its contribution to the ML properties. The authors have calculated the obduction and subduction rates with the Eulerian definition using a 1°-grid Argo dataset and incorporated the obduction rate into the ML budget analysis in order to assess the impact of the entrained permanent pycnocline water on the ML temperature and salinity. They have successfully separated the effect of obduction on the ML from the entrainment of the seasonal pycnocline, and specified the regions where the obduction impact is noticeable. The ML heating rate due to obduction was smaller than ± 0.1 K/yr on average over most of the domain, but it was larger than − 0.5 K/yr in places around the Circumpolar Current, in the northeastern tropical Pacific, the southwestern tropical Indian Ocean, and the northeastern North Atlantic. The salinizing rate due to obduction exceeded ± 0.02 psu/yr in these areas, and in the subarctic North Pacific and the eastern South Pacific. The waters entrained from the permanent pycnocline warm and salinize the ML in the high latitudes due to the dichothermal structure. The method applied in this study also enabled us to assess the residence time and route of obducted and subducted water parcels below the ML. Furthermore, the authors examined the changes of obduction and subduction related with the marine heatwave that occurred in the northeastern North Pacific around 2014.

Original languageEnglish
Pages (from-to)75-92
Number of pages18
JournalJournal of Oceanography
Volume77
Issue number1
DOIs
Publication statusPublished - 2021 Feb

Keywords

  • Argo float
  • Budget
  • Marine heatwave
  • Mixed layer
  • Obduction

ASJC Scopus subject areas

  • Oceanography

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