Greenland and Antarctica are home to most of the world's glacial ice – including its only two ice sheets – making them areas of particular interest to scientists. Combined, the two regions also contain enough ice, that if it were to melt all at once, would raise sea levels by nearly 215 feet (65 meters) – making the study and understanding of them not just interesting, but crucial to our near-term adaptability and our long term survival in a changing world.
When warm summer air melts the surface of a glacier, the meltwater bores holes down through the ice. It makes its way all the way down to the bottom of the glacier where it runs between the ice and the glacier bed, and eventually shoots out in a plume at the glacier base and into the surrounding ocean.
The meltwater plume is lighter than the surrounding ocean water because it doesn't contain salt. So it rises toward the surface, mixing the warm ocean water upward in the process. The warm water then rubs up against the bottom of the glacier, causing even more of the glacier to melt. This often leads to calving – ice cracking and breaking off into large ice chunks (icebergs) – at the front end, or terminus of the glacier.
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 22.214.171.124.0