After I have just written the article about the use of satellite missions in monitoring the polar ice caps, I just came across the news that satellite measurements show a much faster sea-level rise than previous models have suggested. Satellite altimetry, such as the ICESat mission is the most common method used to monitor sea-level height changes over time. The study, by the German oceanographer and climatologist Stefan Rahmstorf, found that sea-levels are rising at an annual rate of 3.2 mm, which is 60% faster than the best estimate of 2 mm.
At the same time I found another article that has been just published, using the GRACE space mission, saying that ice sheet melting has been massively overestimated. Improved measurement analysis of the GRACE data suggest that the Greenland ice sheet is melting at a lower rate than expected, and is predicted to have melted completely in about 13,000 years (at the earliest) and to cause a global sea-level rise of 5 cm by the year 2130.
Now, just a day later, a new paper has been published with the news that Greenland is melting five times faster than it was in the 1990s. 47 scientists from 26 key labs have contributed to this study, using results from 10 different satellites. Their estimations are named to be the most reliable to date, providing the clearest evidence of polar ice sheet losses.
The amount of data that has contributed to the latest paper and the results that sea-level rose much faster than predicted leads to the assumption that the latter paper is more reliable on the results of ice sheet mass loss.
However, the errors on the estimated values still remain large and it actually is possible that the ice is decreasing more slowly than most scientists think. That in turn would rise the question; what other factors contribute to the intense sea-level rise? Could it be thermal expansion, as is suggested in the article?
After all, the publications just show once again how difficult the issue of ice mass loss and sea-level rise is and how important it is to undertake more research, especially with the study of polar ice sheet mass balance.