1. Influence of Deep‐Ocean Warming on Coastal Sea‐Level Decadal Trends in the Gulf of Mexico.
- Author
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Steinberg, Jacob M., Piecuch, Christopher G., Hamlington, Benjamin D., Thompson, Phillip R., and Coats, Sloan
- Subjects
SEA level ,SEAWATER salinity ,ABSOLUTE sea level change ,OCEAN bottom ,OCEAN ,OCEAN circulation ,OCEAN temperature - Abstract
Based on latest estimates (e.g., https://sealevel.nasa.gov), global mean sea level has risen nearly 100 mm since 1993. However, the rate of rise has not been constant in space or time and recent observations (since ∼ 2008) reveal pronounced regional acceleration in the Gulf of Mexico (GoM). Here we use model solutions and observational data to identify the physical mechanisms responsible for enhanced rates of coastal sea‐level rise in this region. We quantify the effect of offshore subsurface ocean warming on coastal sea‐level rise and its relationship to regional hypsometry, the distribution of ocean area with depth. Using an Estimating the Circulation and Climate of the Ocean (ECCO) state estimate, we establish that coastal sea‐level changes at the 10‐year timescale are largely the result of changes in regional ocean mass, reflected in ocean bottom pressure. These coastal bottom pressure changes reflect both net mass flux into the Gulf, as well as internal mass redistribution within the Gulf, which can be understood as an isostatic ocean response to subsurface warming. We test the relationships among coastal sea‐level, bottom pressure, and subsurface warming identified in ECCO using observations from satellite gravimetry, altimetry, tide gauges, and Argo floats. Estimates of mass redistribution explain a significant fraction of coastal sea‐level trends observed by tide gauges. For instance, at St. Petersburg, Florida, this mass redistribution mechanism accounts for >50% of the coastal sea‐level trend observed between 2008 and 2017. This study thus elucidates a physical mechanism whereby coastal sea‐level responds to open‐ocean subsurface density change. Plain Language Summary: We investigate drivers of coastal sea‐level rise in the GoM. Using both model output and observational data we consider the relationship between warming of the ocean at depths below the surface and away from the coast and sea‐level rise at the coast. Changes in ocean bottom pressure throughout the GoM over recent decadal periods reveal a redistribution of water from deeper to shallower regions that coincides with warming throughout the water column. This analysis incorporates observations of coastal sea‐level from tide gauges along the US GoM coast, ocean temperature and salinity from profiling floats, ocean bottom pressures from satellite gravimetry, and sea surface height from satellite altimetry. Results reveal that offshore warming below the surface contributes importantly to coastal sea‐level rise. Its relative contribution is greater in the eastern Gulf, where rates of vertical land motion are smaller than in the western Gulf. Key Points: Recently observed sea‐level trends along the US Gulf coast are consistent with higher future sea‐level rise scenariosSubsurface ocean warming has caused mass redistribution within the Gulf of Mexico (GoM) contributing to positive coastal sea‐level trendsMass redistribution within and mass import into the GoM explain a dominant fraction of eastern Gulf trends in sea‐level [ABSTRACT FROM AUTHOR]
- Published
- 2024
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