Hubbard glacier calving as it reaches the sea

Melting ice fields contributing to climate change

Patagonian iceberg off the coast of South America/Science Photo Library, Javier Trueba

Recent studies in both the Northern and Southern hemispheres have shown ice fields to be melting at a rate that is much higher than previously predicted.  White ice reflects sunlight, helping keep the atmosphere cool, but as it melts, a vicious cycle is created as more sunlight is absorbed and the air temperature increases further.

In the Southern hemisphere, scientists have been monitoring the North and South Patagonian ice fields in the Andes Mountains.  A new study by researchers at Cornell University has shown that glacial thinning has increased by 50% since the millennium, compared to the previous thirty years.  Until 2000, the average contribution to rising sea levels from both ice fields was about 0.042mm each year, but this has since increased to an average of 0.067mm. In fact, the amount of water lost from the Southern Patagonian Ice field alone over the last twelve years can submerge the United States in 2.7cm of water, and if we were to include the melt from the Northern Patagonian Ice field, this figure rises to 3.3cm.

Whilst warming air temperatures contribute directly to glacial thinning in the highest and coldest regions of the ice fields, the real danger is the increasing chance of rain, as opposed to snow, as the climate warms up.  The concern now is that with the twofold threat of increasing air temperatures and more rain, the amount of water underneath the glaciers could increase, reducing the friction beneath them and causing them to move faster into the sea.

Meanwhile, in the Northern hemisphere, the Arctic ice fields are also melting at a rate far higher than previously predicted.  In 1980, the arctic accounted for 2% of the world’s surface area; a figure which has since halved.  The remaining ice is also thinner than it has historically been, and this summer, the volume of ice in the Arctic is just a quarter of what it was thirty years ago.

Scientists are now predicting that melting ice fields could become a more significant factor to global warming than greenhouse gases.  In an occurrence known as the albedo effect, melting sheets of white ice, which reflect the sun’s rays back out of the atmosphere, helping to keep the air cool, are giving way to dark water, which is absorbing this heat.  The increase in global warming as a result of the thinning ice fields is predicted to be as much as 20 years’ worth of carbon dioxide emissions.  In addition, as the arctic heats up, the course of the jet stream, which is determined by the temperature difference between here and the tropics, could change.  This could lead to wet summers in Northern Europe, and hot dry summers further south.  It could also steer storms over the UK, leading to more wet summers like the one we’ve been having this year.

The future is still very unclear, but studies such as those in the Andes are essential in building up a model that can be used to predict the thinning of icefields across the world.  Opinions on the Arctic vary, but the Met Office does not predict an ice-free summer until after 2030.


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