Withdrawn. On the use of acoustic data to characterise the thermohaline stratification in a tropical ocean
Type | Article | ||||||||
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Date | 2021-01 | ||||||||
Language | English | ||||||||
Author(s) | Vieira Assunção Ramilla1, 2, Lebourges-Dhaussy Anne2, Da Silva Alex Costa1, Bourlès Bernard3, Vargas Gary4, Roudaut Gildas2, Bertrand Arnaud1, 4, 5 | ||||||||
Affiliation(s) | 1 : Laboratório de Oceanografia Física Estuarina e Costeira, Depto. Oceanografia, UFPE, Recife, Pernambuco, Brazil 2 : Institut de recherche pour le développement (IRD), UMR 6539 LEMAR Ifremer, Université de Bretagne Occidentale, Technopole Brest Iroise, Plouzané, France 3 : Institut de recherche pour le développement (IRD), IMAGO, Plouzané, France 4 : Universidade Federal Rural de Pernambuco, Recife-PE, Brazil 5 : Institut de recherche pour le développement (IRD), MARBEC, Université Montpellier, Ifremer, IRD, Sète, France |
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Source | Ocean Science (2005-7172) (Copernicus GmbH), 2021-01 | ||||||||
DOI | 10.5194/os-2021-101 | ||||||||
Note | This preprint was under review for the journal OS. A final paper is not foreseen. This preprint has been withdrawn. | ||||||||
Abstract | The use of active acoustic to monitor abiotic structures and processes in the ocean have been gaining ground in oceanography. In some systems, acoustics allow the robust estimation of the depth of the pycnocline or thermocline either directly or indirectly when the physical structures drive the one of organisms. Here, we examined the feasibility of extracting the thermohaline structure (mixed-layer depth, upper and lower thermocline) from echosounder data collected in the oligotrophic Southwestern tropical Atlantic region at two seasons (spring and fall), more precisely in two areas with different thermohaline conditions, at both day and night. For that, we tested three approaches: (i) the vertical extension of the epipelagic community; (ii) the use of acoustic gradients; and (iii) a cross-wavelet approach. Results show that, even if the thermohaline structure impacts the vertical distribution of acoustic scatters, the resultant structuring did not allow for a robust estimation of the thermohaline limits indicating that other oceanographic or biological processes are acting. This result prevents for a fine-scale representation of the upper-layer turbulence from acoustic data. However, studying the proportion of acoustic biomass within each layer provides interesting insights on ecosystem structure in different thermohaline, seasonal and diel scenarios. |
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