Ocean model resolution dependence of Caribbean sea-level projections

René M Van Westen,Riccardo E M Riva,Tjeerd J Bouma,Roland Klees,Carine G Van Der Boog,Caroline A Katsman,Rebecca K James,Julie D Pietrzak,Marcel Zijlema,Henk A Dijkstra,D Cornelis Slobbe,Olga Kleptsova

doi:10.1038/s41598-020-71563-0

Abstract

Sea-level rise poses severe threats to coastal and low-lying regions around the world, by exacerbating coastal erosion and flooding. Adequate sea-level projections over the next decades are important for both decision making and for the development of successful adaptation strategies in these coastal and low-lying regions to climate change. Ocean components of climate models used in the most recent sea-level projections do not explicitly resolve ocean mesoscale processes. Only a few effects of these mesoscale processes are represented in these models, which leads to errors in the simulated properties of the ocean circulation that affect sea-level projections. Using the Caribbean Sea as an example region, we demonstrate a strong dependence of future sea-level change on ocean model resolution in simulations with a global climate model. The results indicate that, at least for the Caribbean Sea, adequate regional projections of sea-level change can only be obtained with ocean models which capture mesoscale processes.

Highlights

Sea-level rise poses severe threats to coastal and low-lying regions around the world, by exacerbating coastal erosion and flooding
By decomposing the components contributing to the satellite-observed global mean sea-level (GMSL) rise between 1993 and 2014, it was shown that the dominant contributor to GMSL is thermal expansion of the o cean[6]
From globally eddy-resolving ocean model simulations[17,18], it is known that explicitly capturing eddies leads to substantially different dynamic sea level (DSL) responses compared to lowerresolution models, for example through the modification of boundary currents

Summary

Conclusions and implications

By analysing model simulations from high- (HR-CESM) and low-resolution (LR-CESM) versions of the Community Earth System Model (CESM) over a 101-year period under a greenhouse gas forcing scenario, we have shown subHsteanattiuaplltyadkieffbeyretnhtere(usppopnesre)soicnetahnecdayunsaems giclosbeaall-emveela(nDtShLe,rηmMo )stienrtihc eseCaa-rleibvbelearniseSe(aη Sga )n,dwihtsicshurirsotuhnedminagisn. contribution of local sterodynamic sea-level rise (at least 75% ). In the Caribbean Sea and surroundings, mesoscale processes (such as the NBC retroflection and eddies) are important for regional sea-level projections. Adequate Caribbean sea-level projections can only be obtained in ocean models which capture mesoscale oceanic processes. We only showed results for the Caribbean, the effects of ocean model horizontal resolution will be important for sea-level projections in other regions and needs to be further investigated. For the Caribbean region, the good news is that changes in dynamic sea-level extremes in the high-resolution model projects a much lower sea-level rise than the low-resolution model, in particular for the many island areas in the eastern part of the region. High-resolution climate models are crucial for a better understanding of future sea-level rise and sea-level extremes, and for planning future investments to adapt to effects of climate change in the Caribbean region and elsewhere over the globe

Methods

Findings

Code availability