Arctic ice loss could be making Britain's winters colder and snowier

  • 28 Feb 2012, 14:45
  • Verity Payne

Credit: NASA Earth Observatory

You've probably heard a lot in recent years about how Arctic sea ice is melting. So what's the big deal? After all, the Arctic's a fair distance away and you're not a polar bear.

Scientists worry that changes in the Arctic will have knock-on effects in other parts of the world, including closer to home. This includes on our winter weather, with three separate scientific studies published this year linking the loss of Arctic sea to cold and snowy winters here in Europe.

The most recent of these studies, published in the journal Proceedings of the National Academy of Sciences, comes from a team of researchers (incidentally including well-known blogging scientist Judith Curry) from Georgia Tech University, the Chinese Academy of Sciences and Columbia University.

The team used observational data along with climate models to examine whether there was a link between Arctic sea ice loss and the unusually large snowfall in Northern Hemisphere winters over recent years. 

The research showed that when Arctic sea ice melt is unusually high in summer, the Arctic Ocean, Greenland, and northeastern Canada have a warmer winter, while northern North America, Europe, Siberia, and eastern Asia cool down and experience above average snowfall.

How could sea ice loss make a cold snowy Europe?

Arctic sea ice changes seasonally, growing in winter and melting in summer - this is why graphs of sea ice over time show an up-and-down cycle. But at the same time sea ice is in decline - over the past 40 years ice area or 'extent' has declined by around 12 per cent per decade as shown in the graph below:

NSIDC Sept sea ice

Source: NSIDC

Scientists think that when Arctic sea ice melts more than usual in summer it takes longer for the sea ice to regrow in the autumn, leaving the ocean uncovered by ice for longer than normal.

Because sea ice reflects some of the sun's energy, more uncovered ocean means the ocean warms more. In turn, this heat escapes from the ocean into the atmosphere, warming the air up and reducing the temperature difference between the Arctic and lower latitudes.

This affects weather systems, allowing more 'blocking patterns' to develop - where high pressure air masses sit over the European continent, 'blocking' other air masses and bringing cold, snowy conditions to the continent.

It was a large 'blocking pattern' that is thought to have caused the unusually cold and snowy weather experienced by much of Europe at the start of February 2012, neatly shown in this satellite image:

NASA Cold snap over Europe 12

 Cold snap key

Source: NASA Earth Observatory

These changes could also lead to more snowfall, as the study's lead author Dr Jiping Liu, a senior research scientist in the School of Earth and Atmospheric Sciences at Georgia Tech, explains:

"We think the recent snowy winters could be caused by the retreating Arctic ice altering atmospheric circulation patterns ... and increasing the amount of moisture in the atmosphere. These pattern changes enhance blocking patterns that favor more frequent movement of cold air masses to middle and lower latitudes, leading to increased heavy snowfall in Europe and the Northeast and Midwest regions of the United States."

The link between Arctic sea ice loss and winter conditions in the Northern continents has also been proposed by other two other research papers published this year, in the journals Tellus A and Environmental Research Letters.

It's even been suggested that conditions in the Arctic might be linked to weather conditions in the mid-latitudes during summer. A paper in press in the journal Geophysical Research Letters suggests that Arctic warming slows weather patterns, increasing the chance of extreme weather in the mid-latitudes, including drought, flooding, cold-spells, and even heat-waves.

Outlook for European winter weather uncertain

Climate model projections indicate that the Arctic ocean is likely to continue to lose sea ice, with some suggesting ice-free summers in a matter of decades. So as the Arctic warms, are we going to see more severe winter weather here in the UK?

Well, it's complicated, because sea ice extent is not the only thing affecting Northern Hemisphere winters. Solar activity might play a role in determining Northern Hemisphere winter conditions, particularly for Britain. There's also the Arctic Oscillation to consider - a natural regional climate cycle that has a big role in controlling winter conditions.

Dr Lau told the BBC News:

"It's possible that future winters will be colder and snowier, but there are some uncertainties."

Whether we're in for more snow or not, this kind of research does lend weight to the argument that the loss of sea ice in the Arctic isn't just of interest to climate scientists or shipping companies. There are also likely to be impacts on the climate of the rest of the world.

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