Meltwater runoff from the Greenland ice sheet, which covers 80% of the country, is a major contributing factor to global sea level rise. The processes by which melting water reaches the ocean is still a subject of research, with most studies focusing on large chunks of ice that break off the ice sheet forming icebergs, or on large lakes which can abruptly drain. Recently, a study lead by Dr Laurence Smith, Professor and Chair of Geography, and Professor of Earth, Planetary, and Space Sciences at University of California revealed that the network of 523 rivers and streams flowing on top of the Greenland ice sheet may be draining as much – if not more meltwater through sinkholes, than the other two processes combined.

The research team utilised remote sensing, remotely controlled boats equipped with specially designed instruments, and helicopter flyovers to map the network of rivers and streams, and collect data on water flow.  Alongside the importance of rivers and networks, the study also indicated that discharge from the Isortoq River, one of the largest rivers on the ice sheet, is lower than expected given the amount of water flowing down it.  Where and how this ‘missing’ water is being captured under the surface is not yet understood, but is contrary to models used by the Intergovernmental Panel on Climate Change, which assumes all meltwater goes into the ocean.  The study will help researchers refine climate models, ultimately developing better global sea level rise projections.

The paper which was published in PNAS is open access.