The ice cover in the
In recent years, satellite images have shown large variations in the ice cover around the North Pole. The images have also shown that the ice cover in the
Climate change or other causes?
The media regularly cite sources who believe that it is now only a matter of decades before climate change results in a totally ice-free
How much of the change in ice cover is caused by dramatic changes in the climate, and how much is the result of other factors? And what is causing the ice cover in the
The Arctic climate paradox
A few years ago, US researchers discovered what they termed the “Arctic climate paradox”. Since 1980, the researchers had been observing a decrease in ice cover. They explained this through a slow process of climate change combined with fluctuations in patterns of atmospheric pressure and air currents over the
The AO is normally influenced by three pressure systems located over the Azores,
Instead it accelerated.
When the Norwegian researchers began their work, they noticed in particular a dramatic change in the weather pattern in the Arctic beginning about the year 2000. The change corresponded to the point in time when the reduction of ice cover in the
The answer is blowing in the wind
The researchers began to analyse the circulation patterns over the
“We found that these patterns can explain in large part why the ice cover decreased so much more rapidly after 2000. Wind patterns depend on the position of major high-pressure and low-pressure systems. We discovered that months with very little ice cover and high temperatures corresponded with crucial variations in the wind patterns,” explains Mr Sorteberg.
“Up until 2000, the Arctic Oscillation (AO) had the greatest impact on the winter ice cover in the
Ice is pushed away
“We have now managed to document what has occurred in connection with this change,” says Mr Sorteberg.
The changed wind direction pushes large ice masses away from the Arctic and down along the eastern coast of
Extent of ice a poor indicator
The conclusion from this research is that we should be cautious about using the extent of the ice cover as an indicator of the ice’s climatic “state of health”.
The extent of the ice cover is highly dependent on the wind direction, and short-term changes in the ice cover give very little indication of whether climate change is occurring in the
“The dramatic changes in the extent of Arctic sea ice in recent years have mainly been caused by atmospheric circulation patterns that have tended to reduce ice cover, combined with a slow process of climate change. Variations in the circulation patterns are part of the natural fluctuations in the weather. In certain periods these fluctuations will reinforce manmade changes, while at other times they will mask them,” says Mr Sorteberg.
Climate change leads to thinner ice
Mr Sorteberg believes we should be cautious about interpreting the dramatic decrease in Arctic ice cover in the past decade as an indication that the
However, he emphasises that he and his colleagues do not reject the assertion that climate change is affecting Arctic ice cover or that the IPCC is wrong when it states that the
“There is no doubt that the Arctic sea ice has become thinner in recent years. The thickness of the sea ice is a much better indicator than the extent of the ice cover if we want to study how climate change may affect the ice in the