Sea-Level Rise and Coastal Vulnerability

Global mean sea level rises through two principal mechanisms: the thermal expansion of ocean water as it warms, and the addition of water mass from melting land ice, chiefly the Greenland and Antarctic ice sheets and the world's mountain glaciers. According to the IPCC's Sixth Assessment Report, global mean sea level rose about 20 centimeters between 1901 and 2018, with the rate of rise accelerating markedly in recent decades, from roughly 1.3 mm per year over most of the twentieth century to about 3.7 mm per year between 2006 and 2018 — a rate driven increasingly by ice-sheet mass loss rather than thermal expansion alone, as satellite gravimetry from missions such as GRACE has confirmed.