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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Preprints
https://doi.org/10.5194/bg-2020-119
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2020-119
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  08 Apr 2020

08 Apr 2020

Review status
A revised version of this preprint was accepted for the journal BG and is expected to appear here in due course.

Can ocean community production and respiration be determined by measuring high-frequency oxygen profiles from autonomous floats?

Christopher Gordon1, Katja Fennel1, Clark Richards2, Lynn K. Shay3, and Jodi K. Brewster3 Christopher Gordon et al.
  • 1Department of Oceanography, Dalhousie University, 1355 Oxford Street, Halifax B3H 4R2, Nova Scotia, Canada
  • 2Bedford Institute of Oceanography, Dartmouth, Nova Scotia, Canada
  • 3Department of Ocean Sciences, Rosenstiel School of Marine Sciences, University of Miami, Miami, Florida, USA

Abstract. Oceanic primary production forms the basis of the marine food web and provides a pathway for carbon sequestration. Despite its importance, spatial and temporal variations of primary production are poorly observed, in large part because the traditional measurement techniques are laborious and require the presence of a ship. More efficient methods are emerging that take advantage of miniaturized sensors integrated into autonomous platforms such as gliders and profiling floats. One such method relies on determining the diurnal cycle of dissolved oxygen in the mixed layer and has been applied successfully to measurements from gliders and mixed layer floats. This study is the first documented attempt to estimate primary production from diurnal oxygen changes measured by Argo-type profiling floats, thus accounting for the whole euphotic zone. We first present a novel method for correcting measurement errors that result from the relatively slow response time of the oxygen optode sensor. This correction relies on an in-situ determination of the sensor's effective response time. The method is conceptually straightforward and requires only two minor adjustments in current Argo data transmission protocols: (1) transmission of measurement time stamps, and (2) occasional transmission of downcasts in addition to upcasts. Next, we present oxygen profiles collected by 10 profiling floats in the northern Gulf of Mexico, evaluate whether community production and respiration can be detected, and show evidence of internal oscillations influencing the diurnal oxygen signal. Our results show that profiling floats are capable of measuring diurnal oxygen variations although the confounding influence of physical processes does not permit a reliable estimation of biological rates in our data set. We offer suggestions for recognizing and removing the confounding signals.

Christopher Gordon et al.

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Christopher Gordon et al.

Christopher Gordon et al.

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Latest update: 10 Aug 2020
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Short summary
We describe a method for correcting errors in oxygen optode measurements on autonomous platforms in the ocean. The errors result from the relatively slow response time of the sensor. The correction method includes an in-situ determination of the effective response time and requires the time stamps of the individual measurements. It is highly relevant for the BGC Argo program and also applicable to gliders. We also explore if diurnal changes in oxygen can be obtained from profiling floats.
We describe a method for correcting errors in oxygen optode measurements on autonomous...
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