A Correction for the Thermal Mass-Induced Errors of CTD Tags Mounted on Marine Mammals

Type Article
Date 2018-06
Language English
Author(s) Mensah Vigan1, Roquet Fabien2, 3, Siegelman-Charbit Lia4, 5, Picard Baptiste6, Pauthenet EtienneORCID2, Guinet Christophe6
Affiliation(s) 1 : Hokkaido Univ, Inst Low Temp Sci, Sapporo, Hokkaido, Japan.
2 : Stockholm Univ, Dept Meteorol MISU, Stockholm, Sweden.
3 : Univ Gothenburg, Dept Marine Sci, Gothenburg, Sweden.
4 : Marine Environm Sci Lab LEMAR, Plouzane, France.
5 : Lab Ocean Phys & Satellite Remote Sensing LOPS, Plouzane, France.
6 : CNRS, Ctr Etud Biol Chize, Villiers En Bois, France.
Source Journal Of Atmospheric And Oceanic Technology (0739-0572) (Amer Meteorological Soc), 2018-06 , Vol. 35 , N. 6 , P. 1237-1252
DOI 10.1175/JTECH-D-17-0141.1
WOS© Times Cited 11
Keyword(s) Data processing, In situ oceanic observations, Instrumentation, sensors, Profilers, oceanic
Abstract

The effect of thermal mass on the salinity estimate from conductivity-temperature-depth (CTD) tags sensor mounted on marine mammals is documented, and a correction scheme is proposed to mitigate its impact. The algorithm developed here allows for a direct correction of the salinity data, rather than a correction of the sample's conductivity and temperature. The amplitude of the thermal mass-induced error on salinity and its correction are evaluated via comparison between data from CTD tags and from Sea-Bird Scientific CTD used as a reference. Thermal mass error on salinity appears to be generally O(10(-2)) g kg(-1), it may reach O(10(-1)) g kg(-1), and it tends to increase together with the magnitude of the cumulated temperature gradient (T-HP) within the water column. The correction we propose yields an error decrease of up to similar to 60% if correction coefficients specific to a certain tag or environment are calculated, and up to 50% if a default value for the coefficients is provided. The correction with the default coefficients was also evaluated using over 22 000 in situ dive data from five tags deployed in the Southern Ocean and is found to yield significant and systematic improvements on the salinity data, including for profiles whose T-HP was weak and the error small. The correction proposed here yields substantial improvements in the density estimates, although a thermal mass-induced error in temperature measurements exists for very large T-HP and has yet to be corrected.

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