Abstract
The world ocean plays a key role in redistributing heat in the climate system and hence in regulating Earth’s climate. Yet statistical analysis of ocean heat transport suffers from partially incomplete large-scale data intertwined with complex spatiotemporal dynamics as well as from potential model misspecification. We present a comprehensive spatiotemporal statistical framework tailored to interpolating the global ocean heat transport using in situ Argo profiling float measurements. We formalize the statistical challenges using latent local Gaussian process regression accompanied by a two-stage fitting procedure. We introduce an approximate expectation-maximization algorithm to jointly estimate both the mean field and the covariance parameters, and refine the potentially underspecified mean field model with a debiasing procedure. This approach provides data-driven global ocean heat transport fields that vary in both space and time and can provide insights into crucial dynamical phenomena, such as El Niño & La Niña, as well as the global climatological mean heat transport field which by itself is of scientific interest. The proposed framework and the Argo-based estimates are thoroughly validated with state-of-the-art multimission satellite products and shown to yield realistic subsurface ocean heat transport estimates.
Funding Statement
We would like to acknowledge high-performance computing support from Cheyenne (doi:10.5065/D6RX99HX) provided by NCAR’s Computational and Information Systems Laboratory, sponsored by the National Science Foundation. Donata Giglio and Mikael Kuusela acknowledge support from NOAA (Awards NA21OAR4310261 and NA21OAR4310258). Donata Giglio also acknowledges support from NASA (Award NNH20 ZDA001N-PO). Alison Gray acknowledges support from NASA (Award NNX80NSSC19K 1252), the U.S. Argo Program through NOAA (Award NA15OAR4320063), and the Microsoft Faculty Fellowship program.
Acknowledgments
We are grateful to the Statistical Oceanography and STAMPS groups and especially to Fred Bingham, Sarah Gille, and Matt Mazloff for constructive discussions and suggestions related to Argo, Spray data, and physical oceanography. We appreciate the constructive feedback by the Editor, the Associate Editor, and the two anonymous reviewers which substantially improved the utility and readability of the paper.
Citation
Beomjo Park. Mikael Kuusela. Donata Giglio. Alison Gray. "Spatiotemporal local interpolation of global ocean heat transport using Argo floats: A debiased latent Gaussian process approach." Ann. Appl. Stat. 17 (2) 1491 - 1520, June 2023. https://doi.org/10.1214/22-AOAS1679
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