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CrustalTrudger t1_j2938m6 wrote

> What is the source of energy that raises the level of sea water through thermal expansion?

The increase in the average temperature of the atmosphere. In short, the ocean absorbs heat from the atmosphere, so if the atmosphere warms up, the ocean will warm up as well. Accounting for the behavior of the ocean as effectively a giant heatsink has been shown to be important for understanding temporal changes in atmospheric temperature (e.g., Kosaka & Xie, 2013).

> Is thermal expansion global?

Yes, but it's not necessarily uniform. We can break out two primary components of sea level rise, mass addition (i.e., melting glaciers and continental ice sheets adding mass to the ocean) and so-called steric components that are changes in volume related to changes in density. Within the steric components, both the salinity and temperature influence this, i.e., colder and saltier water is denser and thus for a given mass takes up less volume. Spatial (and temporal) variations in both temperature and salinity mean that the steric component of sea level rise varies spatially, for example, a relatively high rate of sea level rise (compared to global averages) along the central east coast of the US has been partially attributed to warmer, fresher waters in these regions (e.g., Sallenger et al., 2012).

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Baba_Yaga_Stonks t1_j2d4zwe wrote

Correct me if I'm wrong, but the saltiness of the ocean wouldn't affect sea levels surely? Yes salt water if more dense due to it having literal salt added to it, but because its dissolved it doesn't add or take away from the volume?

Or is there something I've misunderstood/am missing?

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CrustalTrudger t1_j2dku87 wrote

You are incorrect, halosteric (i.e., change in sea level due to salinity related changes in density) sea level change is definitely a thing. It's a smaller component than thermosteric changes, e.g. Durack et al., 2014 estimate the magnitude of halosteric changes to be 1/4 of the magnitude of thermosteric changes, but still significant.

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