SCRIPPS INSTITUTION OF OCEANOGRAPHY, UC SAN DIEGO. Surfrider Foundation. Sea Level Rise. Well over seventy percent of our planet is covered by water.
This was not always the case. During the last ice age, massive ice sheets covered portions of the northern and southern hemispheres (Figure 1). When the massive ice sheets melted, they released the water locked inside them – enough to make the seas rise by about 120m (390 ft) (Waelbroeck et al., 2002; Schneider von Deimling, et al., 2006; Rahmstorf, 2007). Global mean sea level (MSL) has been rising since the end of the last ice age almost 18,000 years ago. Measures of sea level refer to the level of the ocean's surface halfway between high and low tide (to find out more about how sea level is measured, see our links below).