Two maps using color to show sea level and resulting self-attraction and loading field.
The left panel shows a snapshot of the sea level (in meters), whereas the right panel shows the resulting self-attraction and loading (SAL) field (non-dimensional) used as part of the tidal forcing. The right panel demonstrates the smoothed features of the resulting SAL field as compared to the initial field. Credit: Barton et al. [2022], Figure 1
Editors’ Highlights are summaries of recent papers by AGU’s journal editors.
Source: Journal of Advances in Modeling Earth Systems

Coastal impacts from climate change include floods, beach erosion, and storm surges, with each exacerbated by rising sea levels. Ocean tides directly affect each of these impacts, with tides also directly responding to climate change through changes to sea level, coastal geometry, river input, ocean stratification, and the cryosphere. For accurate tide modeling, we need information about the Sun and Moon as well as the self-attraction and loading (SAL) terms. The loading term arises from alterations in the mass felt by the solid earth that leads the crust to expand or compress, and the self-attraction term arises from perturbations to the gravity field due to self-gravity of both the load-deformed solid earth and the ocean tide itself.

Self-consistent and accurate calculations of SAL are generally complex and expensive, thus leading to many approximate methods that have limitations. Barton et al. [2022] present a practical and accurate inline SAL calculation in the ocean component of the Department of Energy Earth system model. Their work shows how improvements to the SAL calculation, along with refinements to ocean grid spacing, enhance both the capability and accuracy available from global tide models.

In addition to enhancing tide models, the authors provide a framework for computing SAL in comprehensive Earth system models used to study climate, as well as storm surge models used for predicting coastal impacts from storms. The methods detailed by Barton et al. are key to the “new wave” of Earth system models that include tides as well as interactive ice sheet models, each of which are relevant to address questions about climate change and its impacts along the world’s coasts.   

Citation: Barton, K. N., Pal, N., Brus, S. R., Petersen, M. R., Arbic, B. K., Engwirda, D., et al. (2022). Global barotropic tide modeling using inline self-attraction and loading in MPAS-Ocean. Journal of Advances in Modeling Earth Systems, 14, e2022MS003207.

—Stephen Griffies, Editor in Chief, JAMES

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