Mixed-layer salinity budget in the tropical Indian Ocean: seasonal cycle based only on observations
The mixed-layer salinity (MLS) budget in the tropical Indian Ocean is estimated from a combination of satellite products and in situ observations over the 2004–2012 period, to investigate the mechanisms controlling the seasonal MLS variability. In contrast with previous studies in the tropical Indian Ocean, our results reveal that the coverage, resolution, and quality of available observations are now sufficient to approach a closed monthly climatology seasonal salt budget. In the South-central Arabian Sea and South-western Tropical Indian Ocean (SCAS and STIO, respectively), where seasonal variability of the MLS is pronounced, the monthly MLS tendency terms are well captured by the diagnostic. In the SCAS region, in agreement with previous results, the seasonal cycle of the MLS is mainly due to meridional advection driven by the monsoon winds. In the STIO, contrasting previous results indicating the control of the meridional advection over the seasonal MLS budget, our results reveal the leading role of the freshwater flux due to precipitation.
KeywordsTropical Indian Ocean Observations Seasonal cycle Mixed-layer salinity Mixed-layer budget
C.Y. Da-Allada was supported by an Ifremer postdoctoral grant. The ERA-Interim reanalyses products are provided by the European Centre for Medium-Range Weather Forecasts (http://data-portal.ecmwf.int/data/d/interim_mnth/), the NCEP/NCAR reanalysis products are available at http://www.esrl.noaa.gov/psd/data/gridded/data.ncep.reanalysis.derived.surfaceflux.html, the evaporation OAFlux product is provided by the WHOI OAFlux project (http://oaflux.whoi.edu), the Global Precipitation Climatology Project is available at http://wwW.esrl.noaa.gov/psd/data/gridded/data.gpcp.html , the seasonal climatology of mixed-layer depth is available at http://www.ifremer.fr/cerweb/deboyer/mld/Surface_Mixed_Depth.php, and the current data is available at http://www.oscar.noaa.gov for OSCAR currents and for the Global Drifter Program at http://www.aoml.noaa.gov/envids/gld/index.php.
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