According to a new study the Greenland ice sheet is possibly more vulnerable to the temperature increase of global warming than previously estimated.
According to the study, conducted by scientists from the Potsdam Institute for Climate Impact Research (PIK) and the Universidad Complutense de Madrid and published in the journal Nature Climate Change, the temperature threshold for a complete melt of the ice sheet is in the range of 0.8 to 3.2 degrees Celsius, with a best estimate of 1.6 degrees increase above pre-industrial levels.
Already the region has experienced a global warming increase of 0.8 degrees.
“The more we exceed the threshold, the faster it melts,” says Alexander Robinson, lead-author of the study.
According to the study, a ‘business-as-usual’ scenario of greenhouse gas emissions would see a long-term global warming temperature increase of 8 degrees Celsius, resulting in one fifth of the ice sheet melting within 500 years and a complete loss within 2000 years.
“This is not what one would call a rapid collapse,” says Robinson. “However, compared to what has happened in our planet’s history, it is fast. And we might already be approaching the critical threshold.”
However, if the global warming temperature rises could be curbed at 2 degrees Celsius a complete melting of the Greenland ice sheet would not occur for 50,000 years. That being said, this new study has already reduced the threshold from 1.9 to 5.1 degrees with a best estimate of 3.1 degrees Celsius down to 0.8 to 3.2 degrees Celsius, with a best estimate of 1.6 degrees increase above pre-industrial levels.
“Our study shows that under certain conditions the melting of the Greenland ice sheet becomes irreversible. This supports the notion that the ice sheet is a tipping element in the Earth system,” says team-leader Andrey Ganopolski of PIK. “If the global temperature significantly overshoots the threshold for a long time, the ice will continue melting and not regrow – even if the climate would, after many thousand years, return to its preindustrial state.”
This threshold is linked directly to the idea of ‘climate feedback’ between the climate and the ice sheet.
For example, because the ice sheet is over 3000 metres thick and thus elevated into higher altitudes, it can stay cooler. But as it melts, the surface level will retreat into warmer temperatures, thus increasing the melt speed.
Another example is that of albedo, the amount of light that a bright surface can reflect back into the atmosphere. The more ice that melts the darker the surface are will get as earth underneath is revealed. As this happens, less sunlight is reflected and now absorbed by the ice sheet, again increasing the melt speed.