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MISU Research seminar | Etienne Pauthenet

The thermohaline structure of the ocean in a reduced-dimension space

by Etienne Pauthenet
PhD student at the Department of Meteorology (MISU)

Time: 8 November 2018, 14h15–14h45
Venue: Rossbysalen C609, Arrhenius Laboratory, 6th floor

Abstract
The global ocean thermohaline structure is projected in a reduced-dimension space. The variance and covariance of temperature (T) and salinity (S) profiles from the Monthly Isopycnal & Mixed-layer Ocean Climatology (MIMOC) is analyzed with a multivariate functional principal component analysis (multivariate FPCA). It allows to decompose the main variations of T and S into vertical modes that concentrate the variance. The first three modes contain more than 92% of the variance, providing a surprisingly simple three dimensional visualization of the main TS structure of the ocean.

This representation illustrates vividly the central place of the Southern Ocean within the global ocean. The first mode is thermally driven and represents well the surface circulation of the gyres. The second mode is driven by salinity and is mainly displaying the salinity asymmetry between the Pacific and Atlantic covarying with the salinity domination of the stratification in the Southern Ocean. The third mode is identifying the low and high salinity intermediate waters, covarying with the freshwater inputs of the upper ocean.

This method has a large potential for data calibration, as the use of functions (B-splines) to represent a profile allows us to project any profile on the basis of vertical modes. A new profile can then be located relatively to a given climatology and its quality assessed straightforwardly. This method could also be used to understand climate variability in heat content, salt content and the link to dynamic height anomaly.
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