While the retreat of Arctic and Antarctic ice sheets has been widely reported, the disappearance and breakup of these sheets are occurring much faster than anticipated. As surface snow melts on the ice flows of the Arctic and Antarctic, the resulting water flows through cracks in the ice sheet to its underlying base. If sitting on land, this water acts as a natural lubricant increasing the movement of the ice into the ocean. On floating ice sheets, these fissures weaken the larger structure and hasten its breakup. Scientists watching these effects over time are alarmed by the accelerating disappearance of these ice sheets.
Based on recent studies of both the Arctic and Antarctic ice flows, scientists are convinced a number of factors are speeding up these breakups. As an example, researchers who studied the 2002 collapse of Antarctica’s Larsen B Ice Shelf have identified the cause as the rapid and unpredicted draining of the more than 2750 lakes that had accumulated on the surface of the glacier. They now understand the draining of the majority of these lakes led to the collapse of the ice shelf into thousands of icebergs over the course of just a few days.
The study’s author, Alison Banwell, a glaciologist at the University of Chicago described the situation as follows, “Our suggestion that the drainage of one single ‘starter’ lake can produce multiple fractures that are able to drain hundreds of surrounding lakes through a chain-reaction process is, therefore, of crucial importance. We argue that it was this chain-reaction process which contributed to the abruptness of the explosive disintegration of the Larsen B Ice Shelf.”
Another factor identified is the disappearance of snow cover on the ice sheets. The theory is that a sufficiently thick layer of surface snow will allow water to sink into the snow and refreeze. As the climate warms up however, melt water increases making the snow layers progressively thinner. If the melt water cannot refreeze and there are huge lakes that form on the ice, the water can drain into cracks and faults in the ice shelves causing them to widen. They become so wide and deep that the entire ice shelf collapses.
According to Dr. Kuipers Munneke of the British Antarctic Survey, “If we continue to burn fossil fuels at the current rate, almost all ice shelves in the Antarctic Peninsula will be under threat of collapse in the next 200 years.” This conclusion is not the result of a model that scientists have devised but rather conclusions drawn from satellite measurements of the thickness of the ice shelves.
Climate scientists must now update their forecasts of the increasing ocean water levels not only in its timing but in the degree of rising water. They say these findings confirm a much higher range of sea level rise than has been predicted before. Some respected scientists have now dubbed the disappearance of these ice sheets irreversible. While the net changes may take hundreds of years, there appears to be no reason that more acceleration will not occur.
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