02 Dec 2022
02 Dec 2022
Status: this preprint is open for discussion.

Interactions between ocean heat budget terms in HighResMIP climate models measured by the rate of information transfer

David Docquier1, Stéphane Vannitsem1, Alessio Bellucci2, and Claude Frankignoul3,4 David Docquier et al.
  • 1Royal Meteorological Institute of Belgium, Brussels, Belgium
  • 2Italian National Research Council, Institute of Atmospheric Sciences and Climate (CNR-ISAC), Bologna, Italy
  • 3Sorbonne University, Paris, France
  • 4Woods Hole Oceanographic Institution, Woods Hole, United States

Abstract. The Liang-Kleeman rate of information transfer is used to quantify interactions between the different terms of the ocean heat budget at monthly time scale over the period 1988–2017 in three coupled global climate models participating in the High Resolution Model Intercomparison Project (HighResMIP), as well as in the Ocean Reanalysis System 5 (ORAS5). In particular, we focus on the influences of ocean heat transport convergence (dynamical influence) and net surface heat flux (thermodynamical influence) on ocean heat content tendency. At least two different configurations are used for each model, allowing to investigate the impact of ocean resolution on these causal relationships. A very small number of regions with a dynamical influence is found at high ocean resolution (≤ 0.25°) and ORAS5 reanalysis when considering the upper 50 m, while a thermodynamical influence is present in a large number of regions. The number of regions with a dynamical influence increases when taking into account the upper 300 m and becomes comparable to the thermodynamical influence. Interestingly, low-resolution model configurations (1° in the ocean) show a much larger number of regions with a significant dynamical influence for both depth integrations (upper 50 m and 300 m) compared to high-resolution model configurations. The reason for the large difference in dynamical influence between low and high resolutions partly comes from the spatial distribution of ocean velocity field, which is highly variable at high resolution, leading to a smaller dynamical influence. High resolution is therefore key in representing realistically the causal interactions between the ocean and atmosphere.

David Docquier et al.

Status: open (until 25 Feb 2023)

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David Docquier et al.

Model code and software

Liang Index to quantify interactions between ocean heat budget terms David Docquier

David Docquier et al.


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Short summary
Understanding whether variations in ocean heat content are driven by air-sea heat fluxes or by ocean dynamics is of crucial importance to enhance climate projections. We use a relatively novel causal method to quantify interactions between ocean heat budget terms based on climate models. We find that low-resolution models overestimate the influence of ocean dynamics in the upper ocean, and that changes in ocean heat content are dominated by air-sea fluxes at high resolution.