Abstract
Sea level variability increasingly contributes to coastal flooding and erosion as global sea levels rise, partly due to the thermal expansion of seawater, which accelerates with increasing temperature. Climate model simulations with increasing greenhouse gas emissions suggest that future sea level variability, such as the annual and interannual oscillations that alter local astronomical tidal cycles and contribute to coastal impacts, will also increase in many regions. Here, we present an analysis of the CMIP5 climate model projections of future sea level to show that there is a tendency for a near-global increase in sea level variability with continued warming that is robust across models, regardless of whether ocean temperature variability increases. Specifically, for an upper-ocean warming by 2 °C, which is likely to be reached by the end of this century, sea level variability increases by 4 to 10% globally on seasonal-to-interannual timescales because of the nonlinear thermal expansion of seawater. As the oceans continue to warm, future ocean temperature oscillations will cause increasingly larger buoyancy-related sea level fluctuations that may alter coastal risks.
Highlights
Sea level variability increasingly contributes to coastal flooding and erosion as global sea levels rise, partly due to the thermal expansion of seawater, which accelerates with increasing temperature
In summary, the thermal expansion property of seawater, which is described by the nonlinear characteristic of the equation of state (EOS), contributes to a global-scale tendency for the sea level to become more variable relative to temperature fluctuations with continued greenhouse warming
Such a tendency, which would alter the risks of coastal flooding and erosion beyond changes associated with anticipated accelerating sea level rise[10], exists regardless of whether or not the ocean temperature variability increases in the future
Summary
Sea level variability increasingly contributes to coastal flooding and erosion as global sea levels rise, partly due to the thermal expansion of seawater, which accelerates with increasing temperature. Climate model simulations with increasing greenhouse gas emissions suggest that future sea level variability, such as the annual and interannual oscillations that alter local astronomical tidal cycles and contribute to coastal impacts, will increase in many regions. Coefficient, of thermal expansion increases with greenhouse warming[4,5], seawater density becomes increasingly sensitive to higher temperatures; thereby contributing to observed and future projections of accelerating sea level rise[1,6,7]. Combining the effect of nonlinear thermal expansion with increasing temperature variability, e.g., projected in ENSO-affected areas, the increase in sea level variability must be even larger than that in temperature variability
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