Ice caps are miniature ice sheets, covering less than 19,305 square miles. They form primarily in the world’s polar and sub-polar regions that are relatively flat and high in elevation (think Iceland).
A ice sheet is defined as being greater than 20,000 miles and these massive chunks of ice naturally flow downward and are funneled to the ocean by glaciers (think Greenland and Antarctica).
The Institute for Marine and Atmospheric research Utrecht - IMAU, in a new finding reveals that the natural capacity of Greenland ice caps to contain and refreeze meltwater broke down around 1997, when – due to rising temperatures - the thick snow cover on the ice caps became completely saturated with refrozen meltwater. Since then, the rate of mass loss of the ice caps has accelerated and has become practically irreversible, the authors write in the article published today in Nature Communications.
Brice Noël, PhD candidate at Utrecht University and lead author of the publication, expects that the meltwater run-off will only increase the coming years. “The highest ice caps are still relatively healthy at the moment. However, we see melting occur higher and higher. That’s a big problem, because that ‘melting line’ is moving towards the altitude where most of the ice mass is.”
Noël also analysed a number of variables which influence the underlying causalities of ice loss. The researchers found that the mass loss correlates directly with meltwater run-off, which is in turn directly influenced by an increase in temperature.
The findings show that until 1997 Greenland’s ice caps were able to contain and refreeze enough meltwater to remain stable, even with temperature fluctuations. In summer, a healthy ice cap is able to absorb meltwater in the tens of metres of tightly packed snow layer on the ice. Meltwater refreezes during winter, causing the total mass of the ice cap to remain more or less stable from year to year.
However, rising temperatures have so much increased the amount of meltwater that the snow layer is completely saturated with refrozen meltwater. Having crossed this tipping point, new meltwater cannot be absorbed by the snow anymore and causing it to run off into the sea.
The Researchers note that Greenland’s ice caps represent the largest ice masses on earth apart from the large ice sheets of Greenland and Antarctica. The ice caps around Greenland’s edges may lose one fifth to one quarter of their volume by the year 2100, which would add an extra 1 ½ inches of sea level rise.
This phenomenon is also happening on Ellesmere Island in Canada.
Acquired on August 15, 2015, this animation shows the shrinking extent of ice caps on Ellesmere Island. Mark Serreze, Director of the National Snow and Ice Data Center (NSIDC) at the University of Colorado-Boulder, has observed the disappearance of these ice caps with particular interest. NSIDC reports:
As a young graduate student, Mark Serreze spent the summers of 1982 and 1983 studying two ice caps near St. Patrick Bay on Ellesmere Island in Nunavut, Canada. These ice caps have dramatically shrunk over the past 50 years and are likely to soon disappear entirely. Their imminent demise has hit Serreze, now NSIDC Director, at a personal level. Serreze reflected on his time there, and said, “I knew every quirk, nook, and cranny of those little ice caps. I had a very personal relationship with them.”
The rate of retreat has accelerated sharply since the turn of the 21st century. Serreze says that we may now be witnessing the ice caps’ final days.
ACTION
Scientists will march on April 22, 2017.
The Peoples Climate March will be on April 29th, 2017.
Both of the above events will be held in Washington DC. For local action, contact Indivisible and find a protest and march near you