Wobbling Arctic Jet Stream Pushing Already Record Greenland Melt Into Unknown Territory
Extraordinary melting in Greenland's ice sheet last summer was linked to warm air delivered by the wandering jet stream, a phenomenon that scientists have increasingly tied to global warming. This interplay of climate phenomena, described in a new study in the journal Nature Communications, is more evidence of the complex ways in which the Arctic's climate is heading for "uncharted territory," said the study's lead author, Marco Tedesco.
The study adds to an emerging theory on the effects of the pronounced warming of the Arctic, where temperatures are rising faster than in more temperate zones, as models have long predicted. Known as "Arctic amplification," this moderates the normal temperature incline that drives the jet stream. If it makes the jet stream wobble, as some scientists suspect, it would suck warm air up into the Arctic—as was observed in Greenland last year.
The new study analyzes the severe shift in wind patterns last July that transported huge masses of warm, moist air from the Atlantic to the Arctic, dramatically melting the northern reaches of the ice sheet. Never before has the jet stream been seen to intrude so far into the Arctic during the summer, the scientists reported.
Accounting for these shifts is crucial to being able to model how much sea level will rise and how fast. Greenland's melting is one of the biggest contributors to rising seas, and if its ice were to disappear completely it could raise global sea level by as much as 20 feet. "The models are not capturing these extreme events like the July melting," said Marco Tedesco, the study's lead author. "If we are changing the atmosphere in a way that has not been happening before, with greenhouse gases, then even if we have the tools to make projections based on observations, we won't know how to model for the future." Tedesco is a geophysicist with Columbia University's Lamont-Doherty Earth Observatory.
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http://insideclimatenews.org/news/08062016/greenland-arctic-record-melt-jet-stream-wobbly-global-warming-climate-change
