Mass and volume contributions to twentieth-century global sea level rise

Abstract

The rate of twentieth-century global sea level rise and its causes are the subjects of intense controversy. Most direct estimates from tide gauges give 1.5-2.0 mm yr(-1), whereas indirect estimates based on the two processes responsible for global sea level rise, namely mass and volume change, fall far below this range. Estimates of the volume increase due to ocean warming give a rate of about 0.5 mm yr(-1) (ref. 8) and the rate due to mass increase, primarily from the melting of continental ice, is thought to be even smaller. Therefore, either the tide gauge estimates are too high, as has been suggested recently, or one (or both) of the mass and volume estimates is too low. Here we present an analysis of sea level measurements at tide gauges combined with observations of temperature and salinity in the Pacific and Atlantic oceans close to the gauges. We find that gauge-determined rates of sea level rise, which encompass both mass and volume changes, are two to three times higher than the rates due to volume change derived from temperature and salinity data. Our analysis supports earlier studies that put the twentieth-century rate in the 1.5-2.0 mm yr(-1) range, but more importantly it suggests that mass increase plays a larger role than ocean warming in twentieth-century global sea level rise.

Impact of global seismicity on sea level change assessment

“…This value is reduced by more than an order of magnitude if the effects of the giant thrust earthquakes of the last century are not considered (i.e., adopting the CMT catalog). Since sea level rise rates associated with climatological factors (water volume increase due to ocean warming and mass increase from ice melting) are estimated to be at most 1/1.5 mm/yr [Levitus et al, 2000;Miller and Douglas, 2004], the average contribution to RSL coming from seismic activity is not negligible with respect to the climatological factors. Moreover, in regions with strong seismotectonic activity the seismic contribution amounts to several mm/yr, representing a major contribution to RSL.…”

“…[6] Estimates of sea level rise coming from water volume increase due to ocean warming give a rate of about 0.5 mm/yr, while the rate due to mass increase from ice melting is highly controversial; recent estimates range from less than 0.5 to 1.5 mm/yr [Levitus et al, 2000;Miller and Douglas, 2004]. Therefore the average contribution to RSL coming from seismic activity may be comparable to estimates of individual climatological factors and, in regions with strong seismotectonical activity, may represent locally a major contribution to RSL.…”

Century-scale relative sea-level changes in West Greenland — A plausibility study to assess contributions from the cryosphere and the ocean

“…The broad pattern and magnitude of these changes is also reflected in a later 64 ATM study spanning the period of 1998-2004(Thomas et al 2006.The geometry of these mass 65 changes is typical of an ice sheet reacting to a warming climate -warmer temperatures at lower 66 elevations lead to increased thinning compared to other areas on the ice sheet and can force a 67 positive feedback cycle of decay. Also, warmer temperatures increase moisture supply to the ice 68 sheet, allowing the central regions to thicken (e.g.…”

“…Oceanographic Atlas (WOA) data to reduce any bias that may have been introduced during the 349 interpolation process (Miller and Douglas, 2004). The location and maximum depth of 350 measurements of the temperature and salinity profiles used are detailed in Fig.…”

“…For the calculation of steric height trends only Ocean 346 Station Data are used since this instrument type has the longest continuous record of data in this 347 area. We use raw oceanographic profiles from the WOD05 in preference to interpolated World 348Oceanographic Atlas (WOA) data to reduce any bias that may have been introduced during the 349 interpolation process (Miller and Douglas, 2004). The location and maximum depth of 350 measurements of the temperature and salinity profiles used are detailed in Fig.…”