Melting sea ice boosts global warming

Friday 07th Sep 2012 by theWeather Club

The loss of Arctic ice is massively compounding the effects of greenhouse gas emissions, according to ice scientist Professor Peter Wadhams of Cambridge University. Arctic white ice is currently at its lowest level in recent history and Prof Wadhams believes that the Arctic ice cap is heading for eventual oblivion.

In 1980, the Arctic ice in summer made up some 2% of the Earth's surface. But since then the ice has roughly halved in area. "Thirty years ago there was typically about eight million square kilometres of ice left in the Arctic in the summer," Prof Wadhams told reporters, " and by 2007 it had gone down to about four million, and this year it has gone down below that".

Added to this the ice is getting thinner. "The volume of ice in the summer is only a quarter of what it was 30 years ago and that's really the prelude to this final collapse," Prof Wadhams continued. Parts of the Arctic Ocean are now as warm in summer as the North Sea is in winter.

The polar ice cap acts as a giant parasol, reflecting sunlight back into the atmosphere in what is known as the albedo effect. But white ice and snow reflect far more of the sun's energy than the open water that is replacing it as the ice melts. For area of over 1% of the Earth's surface, we are replacing a bright surface which reflects nearly all of the radiation falling on it back into space with a dark surface which does the precise opposite by absorbing the vast majority of this heat and which is contributing to warming.

"The difference, the extra radiation that's absorbed is, from our calculations, the equivalent of about 20 years of additional CO2 being added by man," Prof Wadhams said. If his calculations are correct then that means that over recent decades the melting of the Arctic ice cap has put as much heat into the system as all the CO2 we have generated in that time. And if the ice continues to decline at the current rate it could play an even bigger role than greenhouse gases.

Opinions vary on the date of the demise of summer sea ice and Professor Wadhams stresses that there are uncertainties. For example cloud cover over the Arctic could change and help reflect back some of the sun's radiation. But then again methane currently trapped in the Arctic permafrost could be released with warming and make matters worse.

As always very little is simple in the world of the Arctic ice melt. Very little except the need for new data and continuing evaluation as we grope our way to the complex and interconnected effects of our changing climate.