Can you really detect a 0.7-inch rise in global sea level?
The media release and abstract are below.
Sea-level rise between 2005 and 2011 was predominately caused by the melting of mountain glaciers and polar ice sheets, reports a paper published online this week in Nature Geoscience. The findings suggest that sea level rose by 2.4 mm per year over this period.
Jianli Chen and colleagues used gravity data from the GRACE satellites to estimate changes in ocean mass between 2005 and 2011. They show that the ocean mass increased over this period, resulting in a 1.8 mm rise in sea level per year, largely due to the melting of ice sheets in Greenland and Antarctica, and mountain glaciers. In addition, they assessed changes in ocean density using data from a network of ocean floats. They estimate that a reduction in density over the same period led to a sea-level rise of 0.6 mm per year. Total sea-level rise obtained from these two techniques provides independent support for the estimate of 2.39 mm per year derived from satellite altimeters.
Changes in global mean sea level primarily reflect the sum of a three contributions: water mass changes in the oceans, water density changes, and variations in the volume of the ocean basins. Satellite altimetry data suggest that sea level rose by about2.39±0.48mmyr−1 between 2005 and 2011. However, previous estimates of sea level rise from density and ocean mass changes were lower than the altimeter data indicate. Here
we show that the gap in the sea level budget disappears when we combine gravity data from the GRACE (Gravity Recovery and Climate Experiment) satellite mission and temperature and salinity observations from the Argo programme collected between 2005 and 2011. The Argo data indicate a density- driven sea level rise of 0.60 ± 0.27 mm yr−1 throughout this period. To estimate ocean mass change from the gravity data, we developed a forward modelling technique that reduces the bleeding of terrestrial signals into the ocean data. Our reassessment suggests an ocean mass contribution of 1.80 ± 0.47 mm yr−1 , for a total sea level rise of 2.40 ± 0.54 mm yr−1 , in agreement with the altimeter-based estimates. On the basis of the GRACE data, we conclude that most of the change in ocean mass is caused by the melting of polar ice sheets and mountain glaciers. This contribution of ice melt is larger than previous estimates , but agrees with reports of accelerated ice melt in recent years.