Glaciers & Global Warming
Experts believe that global warming is responsible for the retreating glaciers, but scientists also know that periods of global warming have happened before. Evidence from ice cores has revealed variations in average temperatures around the world going back hundreds of thousands of years. This tells us that natural events can lead to the planet becoming warmer or cooler, but global warming today seems to be a combination of natural and man made causes.
Athabassa Glacier, Canadian Rockies
Glaciers are very sensitive to small changes in temperature and a one-degree change from 0 to -1 or to +1 degrees can mean the difference between a glacier growing, or melting.
Scientists generally agree that almost all glaciers in Europe have been retreating during the last one hundred years and they expect that the retreat will continue.
As glaciers melt, they release fresh water. That may sound like a good thing, and it would be if we could send the water to the places that need it. But unfortunately, almost all the fresh water will go into the oceans and this is where the problems start.
An obvious result of more water in the oceans is that sea levels will rise. That's not good news for low-lying countries and for people living on lowland coasts. There are scientists who believe that many cities will be threatened by flooding in the next 100 years.
Fresh water is different to salt water - it is less dense. That may not sound like much of a problem but actually, it might prove to be more worrying than sea level rises. The world's weather patterns are controlled by ocean currents that move billions of litres of warm water from the equator towards the poles, and cold water from the poles towards the equator. The movement of heat through ocean currents explain why Canada freezes solid every winter whilst the British Isles remain much warmer.
If you add too much fresh water to salty seawater, you change its density, making it less dense and less likely to sink. If the amount of fresh water became enough to stop the warm water from sinking, the entire ocean current system could stop working. While the subsequent changes in climate cannot be calculated at the moment, we do know that the whole planet would experience enormous problems such as hotter weather at the equator, which would in turn lead to drought and crop failure.
Perito-Moreno Glacier, Argentina
In 2005 the first comprehensive study of glaciers around the coast of the Antarctic Peninsula revealed the real impact of recent climate change.
Results from the study by researchers at British Antarctic Survey (BAS) and U.S. Geological Survey (USGS) show that over the last 50 years 87% of 244 glaciers studied have retreated, and that average retreat rates have accelerated.
Byrd Glacier by Landsat
BAS and USGS analysed more than 2000 aerial photographs dating from 1940, and over 100 satellite images from the 1960s onwards, to calculate the position of glacier fronts along the coast of the Antarctic Peninsula. These historical records revealed previously unknown patterns of change.
Fifty years ago, most of the glaciers were slowly growing in length but since then this pattern has reversed. In the last 5 years the majority were actually shrinking rapidly. The retreat began at the northern, warmer tip of the Antarctic Peninsula and, broadly speaking, moved southwards as atmospheric temperatures rose. This region has shown dramatic and localised warming – around 2°C in the last 50 years – but this is not the only factor causing the changes. It’s a complex picture.
On average the glaciers studied retreated by 50 m per year in the last five years, faster than at any other time in the last fifty years. However 32 glaciers go against the trend and are showing minor advance. Had BAS and USGS not studied such a large number of glaciers they may have missed the overall pattern. It’s the change from advance to retreat that suggests warming is the key cause, but these glaciers clearly show a more complex response than neighbouring ice shelves.
These glacier retreat patterns combined with dramatic ice shelf break-ups leave scientists at BAS and USGS in no doubt that the Antarctic Peninsula ice sheet is extremely sensitive to recent warming. What they still need to determine is whether or not the warming in this area has its roots in human-influenced global warming. Either way, continuing retreat of glaciers in this area is important because it could allow more ice to drain from further inland and contribute to sea level rise. The current effect may be small in global terms, but this research takes scientists a step closer to understanding the cause and predicting the future.
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