Enhanced Atlantic sea-level rise relative to the Pacific under high carbon emission rates

Abstract

Different ocean basins warm at different rates in response to climate change. A coupled carbon–climate model reveals that high carbon emission rates will lead to greater sea-level rise in the Atlantic than the Pacific on centennial timescales. Thermal expansion of the ocean in response to warming is an important component of historical sea-level rise1. Observational studies show that the Atlantic and Southern oceans are warming faster than the Pacific Ocean2,3,4,5. Here we present simulations using a numerical atmospheric-ocean general circulation model with an interactive carbon cycle to evaluate the impact of carbon emission rates, ranging from 2 to 25 GtC yr−1, on basin-scale ocean heat uptake and sea level. For simulations with emission rates greater than 5 GtC yr−1, sea-level rise is larger in the Atlantic than Pacific Ocean on centennial timescales. This basin-scale asymmetry is related to the shorter flushing timescales and weakening of the overturning circulation in the Atlantic. These factors lead to warmer Atlantic interior waters and greater thermal expansion. In contrast, low emission rates of 2 and 3 GtC yr−1 will cause relatively larger sea-level rise in the Pacific on millennial timescales. For a given level of cumulative emissions, sea-level rise is largest at low emission rates. We conclude that Atlantic coastal areas may be particularly vulnerable to near-future sea-level rise from present-day high greenhouse gas emission rates.