Arctic Ice Melt May Shift Jet Stream South, Cause Rainy UK Summers

A new study published in the journal Environmental Research Letters suggests that a loss of Arctic sea ice caused the jet stream to shift further south, thus contributing to an extraordinary run of wet summers experienced by Britain and northwest Europe between 2007 and 2012.

University of Exeter scientist James Screen uses a computer model to investigate the wet weather and whether it was linked to the melting of sea ice in the Arctic.

Screen's study "compared weather patterns during low sea ice conditions as seen in recent years to weather patterns during high sea ice conditions typical of the late 1970s." Other studies have suggested that warming Arctic waters have played a role in Britain's wetter summers, but Screen suggests it's likely a combination of many factors that have led to the undue wetness.

"The results of the computer model suggest that melting Arctic sea ice causes a change in the position of the jet stream and this could help to explain the recent wet summers we have seen," he said. "The study suggests that loss of sea ice not only has an effect on the environment and wildlife of the Arctic region but has far reaching consequences for people living in Europe and beyond."

Because Screen's model did not use estimates of how much sea ice there will be in the future, the study cannot predict future weather. The results do suggest, however, that if sea ice loss continues as it has over recent decades, the risk of wet summers may increase.

Weather systems and the rain within them are steered by the jet stream -- currents of strong wind high in the atmosphere.

Typically the jet stream lies between Iceland and Scotland during the summer and weather systems pass north of Britain, but a southerly shift can bring unseasonably wet weather to Britain, which can be unwanted by local farmers and summer tourists in Britain.

"The model suggests that while summer rainfall increases in northwest Europe, Mediterranean regions will receive less rain. The effects are not limited to Europe -- weather systems as far as North America could also be influenced," the University of Exeter said in a statement.

The research team reported that the average extent of Arctic sea ice is declining by about half a million square kilometers per decade, an area equivalent to almost twice the size of the UK.