An Assessment of the Precision and Confidence of Aquatic Eddy Correlation Measurements

Type Article
Date 2015
Language English
Author(s) Donis Daphne1, Holtappels Moritz2, Noss Christian3, Cathalot CecileORCID4, Hancke Kasper5, Polsenaere PierreORCID6, Wenzhoefer Frank1, Lorke Andreas3, Meysman Filip J. R.7, Glud Ronnie N.8, McGinnis Daniel F.9
Affiliation(s) 1 : HGF MPG Research Group for Deep-Sea Ecology and Technology, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, and Max Planck Institute for Marine Microbiology, Bremen, Germany
2 : Department of Biogeochemistry, Max Planck Institute for Marine Microbiology, Bremen, Germany
3 : Institute for Environmental Sciences, University of Koblenz-Landau, Landau, Germany
4 : Royal Netherland Institute for Sea Research (NIOZ), Yerseke, Netherlands
5 : Nordic Center for Earth Evolution, Department of Biology, University of Southern Denmark, Odense, Denmark, and Greenland Climate Research Centre, Greenland Institute of Natural Resources, Nuuk, Greenland
6 : Department of Analytical, Environmental and Geo-Chemistry, Vrije Universiteit Brussel, Brussels, Belgium
7 : Royal Netherland Institute for Sea Research (NIOZ), Yerseke, Netherlands, and Department of Analytical, Environmental and Geo-Chemistry, Vrije Universiteit Brussel, Brussels, Belgium
8 : Nordic Center for Earth Evolution, Department of Biology, University of Southern Denmark, Odense, Denmark, and Greenland Climate Research Centre, Greenland Institute of Natural Resources, Nuuk, Greenland, and Arctic Research Centre, University of Aarhus, Aarhus, Denmark, and Scottish Marine Institute, Scottish Association for Marine Science, Oban, United Kingdom
9 : Nordic Center for Earth Evolution, Department of Biology, University of Southern Denmark, Odense, Denmark, and Department of Experimental Limnology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany
Source Journal Of Atmospheric And Oceanic Technology (0739-0572) (American Meteorological Society), 2015 , Vol. 32 , N. 3 , P. 642-655
DOI 10.1175/JTECH-D-14-00089.1
WOS© Times Cited 26
Mot-Clé(s) Turbulence, Boundary layer, Fluxes, Instrumentation/sensors, Optimization, Experimental design
Abstract The quantification of benthic fluxes with the aquatic eddy correlation (EC) technique is based on simultaneous measurement of the current velocity and a targeted bottom water parameter (e.g., O2, temperature). High-frequency measurements (64 Hz) are performed at a single point above the seafloor using an acoustic Doppler velocimeter (ADV) and a fast-responding sensor. The advantages of aquatic EC technique are that 1) it is noninvasive, 2) it integrates fluxes over a large area, and 3) it accounts for in situ hydrodynamics. The aquatic EC has gained acceptance as a powerful technique; however, an accurate assessment of the errors introduced by the spatial alignment of velocity and water constituent measurements and by their different response times is still needed.

Here, this paper discusses uncertainties and biases in the data treatment based on oxygen EC flux measurements in a large-scale flume facility with well-constrained hydrodynamics. These observations are used to review data processing procedures and to recommend improved deployment methods, thus improving the precision, reliability, and confidence of EC measurements. Specifically, this study demonstrates that 1) the alignment of the time series based on maximum cross correlation improved the precision of EC flux estimations; 2) an oxygen sensor with a response time of <0.4 s facilitates accurate EC fluxes estimates in turbulence regimes corresponding to horizontal velocities < 11 cm s−1; and 3) the smallest possible distance (<1 cm) between the oxygen sensor and the ADV’s sampling volume is important for accurate EC flux estimates, especially when the flow direction is perpendicular to the sensor’s orientation.
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Donis Daphne, Holtappels Moritz, Noss Christian, Cathalot Cecile, Hancke Kasper, Polsenaere Pierre, Wenzhoefer Frank, Lorke Andreas, Meysman Filip J. R., Glud Ronnie N., McGinnis Daniel F. (2015). An Assessment of the Precision and Confidence of Aquatic Eddy Correlation Measurements. Journal Of Atmospheric And Oceanic Technology, 32(3), 642-655. Publisher's official version : https://doi.org/10.1175/JTECH-D-14-00089.1 , Open Access version : https://archimer.ifremer.fr/doc/00275/38577/