Climate Science

All Rise

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Science  25 Jun 2004:
Vol. 304, Issue 5679, pp. 1877
DOI: 10.1126/science.304.5679.1877d

The rise in sea level is one of the most important impacts of global warming, but the exact rate of rise is still poorly known. Direct measurements indicate that it has been 1.5 to 2 mm/year over the past century, but that figure is based on data from tidal gauges, which are known to have an uneven global distribution and to be affected by postglacial rebound of coastal regions. Other methods are needed to improve both the accuracy and precision of this value, and one alternative is to adopt a reductionist approach.

Sea level rises by two mechanisms: steric, which is due mostly to the thermal expansion of the oceans; and eustatic, which comes largely from the increase in ocean volume due to melting of continental ice. Wadhams and Munk estimate the size of the eustatic contribution from measurements of the decrease of global seawater salinity. Correcting published values for the effects of melting sea ice (which freshens the ocean but does not affect sea level), they find that glacial melting is causing approximately 0.6 mm/year of the observed sea level rise. Adding that to the generally accepted value of the steric contribution, 0.5 ± 0.2 mm/year, they infer a total rate of 1.1 mm/year. — HJS

Geophys. Res. Lett. 31, 10.1029/2004GL020039 (2004).


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