The team have showed that the combined rate of melting for the two ice sheets has increased during the last 20 years. Together, the two are losing more than 3 times as much ice annually as they were in the 1990s. It was deduced that two thirds of the loss is coming from Greenland in the Northern hemisphere, while the remainder is attributed to the Antarctic in the Southern hemisphere.
In terms of sea level rise, the ice-sheets are now contributing to a rise of 0.04 inches (0.95 millimetres) a year, compared to 0.01 inches (0.27 millimetres) per year in 1990.
The Intergovernmental Panel on Climate Change (IPCC) reported estimates of ice sheet losses back in 2007, however, it was often deemed too broad by scientists and was not clear as to whether Antarctica was losing or gaining ice. These new estimates have doubled the accuracy on ice loss reporting by including significantly more satellite data. It has confirmed that both Antarctica and Greenland are indeed losing ice and have contributed 0.44 inches (11.1 millimetres) to global sea level since 1992.
This increase in global sea level rise accounts for one-fifth of the total rise over the 20 year period. The remainder is accredited to the melting of mountain glaciers and the Arctic ice caps, thermal expansion of an ever warming ocean and groundwater mining.
The study also confirmed that there was a variation in change between the two areas. While both ice sheets are losing more ice now than 20 years ago, Greenland is losing ice at an extraordinary rate, which is reported to have increased five-fold since the mid-1990s. Antarctica however has remained more constant, with a 50% increase in the rate of ice loss during the last decade.
The robustness of this study is attributable to the diversity of research methods employed. The researchers examined previous studies, matching the observational periods. They utilised an array of satellite sensor information including the ESA’s radar missions and NASA’s ICEsat and GRACE satellites. The results, which are the most detailed of their kind, are important for driving environmental policies with clarity and maybe more importantly ending the uncertainties which have been picked on for many years.
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-Photo is of meltwater across the ice surface in Greenland courtesy of Ian Joughin.