Arctic ice melt has weakened the jet stream, and over the last week a low pressure system has been trapped above eastern Britain
— For the last week Britain has been encircled by a gigantic loop in the jet stream, the result of which has been some remarkably wet weather for the east of the country. While welcome for places that had been suffering a long drought, it is a stark warning of weather patterns to come.
The warming Arctic and loss of sea ice has meant that the jet stream does not flow strongly, as it once did, from west to east, pushing weather systems steadily across our shores and onwards into the continent. These days, because there is no longer a stark temperature difference between the Arctic and the Atlantic, the jet stream meanders, causing weather extremes by pushing cold air south and warm air far to the north. This can leave giant high-pressure systems, or in our case last week, a large low, trapped and static between these loops.
Research shows that this is likely to be a continuing pattern in the future, causing extreme weather events in North America and Europe as the Arctic continues to warm. The good news is that the loop over the UK is breaking down today and the jet stream is reforming. Longer term, however, it appears Britain’s benign weather will become more extreme, more often.
by Paul Brown | The Guardian