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Probabilistic Machine Learning Estimation of Ocean Mixed Layer Depth from Dense Satellite and Sparse In-Situ Observations
  • Dallas Foster,
  • David John Gagne,
  • Daniel Bridger Whitt
Dallas Foster
Oregon State University
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David John Gagne

Corresponding Author:dgagne@ucar.edu

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Daniel Bridger Whitt
National Center for Atmospheric Research
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The ocean mixed layer plays an important role in subseasonal climate dynamics because it can exchange large amounts of heat with the atmosphere, and it evolves significantly on subseasonal timescales. Estimation of the subseasonal variability of the ocean mixed layer is therefore important for subseasonal to seasonal prediction and analysis. The increasing coverage of in-situ Argo ocean profile data allows for greater analysis of the aseasonal ocean mixed layer depth (MLD) variability on subseasonal and interannual timescales; however, current sampling rates are not yet sufficient to fully resolve subseasonal MLD variability. Other products, including gridded MLD estimates, require optimal interpolation, a process that often ignores information from other oceanic variables. We demonstrate how satellite observations of sea surface temperature, salinity, and height facilitate MLD estimation in a pilot study of two regions: the mid-latitude southern Indian and the eastern equatorial Pacific Oceans. We construct multiple machine learning architectures to produce weekly 1/2 degree gridded MLD anomaly fields (relative to a monthly climatology) with uncertainty estimates. We test multiple traditional and probabilistic machine learning techniques to compare both accuracy and probabilistic calibration. We find that incorporating sea surface data through a machine learning model improves the performance of MLD estimation over traditional optimal interpolation in terms of both mean prediction error and uncertainty calibration. These preliminary results provide a promising first step to greater understanding of aseasonal MLD phenomena and the relationship between the MLD and sea surface variables. Extensions to this work include global and temporal analyses of MLD.
Dec 2021Published in Journal of Advances in Modeling Earth Systems volume 13 issue 12. 10.1029/2021MS002474