Present-day sea-level change:: A review

Understanding of sea-level change has improved considerably over the last decade. Present-day knowledge of sea-level change is derived from tide gauge observations and satellite altimetry measurements. The average rate of sea-level change obtained from tide gauges over the last 50 years is +1.8 +/- 0.3 mm yr(-1). In comparison, altimeter measurements from TOPEX/Poseidon and Jason-1 have shown an average rise of +3.1 +/- 0.4 turn yr(-1) since 1993. It is not clear yet whether the larger rate of rise of the last decade reflects acceleration or decadal fluctuation. The causes of the present-day rate are a combination of increases in ocean temperatures and land ice melt from mountain glaciers, Greenland, and Antarctica. Regional variability in sea-level change, as evidenced by the quasi global coverage of altimeter satellites, appears dominated by non uniform change of thermal expansion. New satellite technologies, such as InSAR, ICESat, and GRACE make significant contributions to understanding sea-level change.