Is melting Arctic sea ice shifting the jet stream?

Is melting sea ice shifting the jet stream?

Study finds robust link between Arctic ice decline and severe Eurasian winter weather

Staff Report

FRISCO — If you feel like you’ve been on a weather roller coaster, maybe it’s because the jet stream has been behaving like one more and more often in recent years.

Instead of flowing around the mid-latitudes of the northern hemisphere with a few ripples, some years, the high-altitude river of air has been more like a writhing, out-of-control fire hose, snaking and looping, carrying huge surges of warm air north and cold. polar air south. At times, the jet stream has been getting stuck in that pattern for longer stretches.

Climate research is starting to show that melting Arctic sea ice is driving the changes in the jet stream, leading to the chance of more extreme winter weather. The National Snow and Ice Data Center discussed the scientific question in its most recent Arctic ice update, describing how research is focusing on how the extra heat stored in ice-free areas of the ocean during recent summers is released back to the atmosphere as the ice begins to re-form, leading to amplified warming in the Arctic atmosphere.

While there is no single smoking gun study to show the link, a new Japanese research effort looked at the observed trend of more frequent severe winters in Eurasia — despite  increasing global- and annual-mean surface air temperatures.

In their study, the scientists used a huge data set to model any connection between declining Arctic sea ice and mid-latitude weather, finding “robust” signs of the link. In fact, their results suggest that sea-ice reduction in the Barents–Kara Sea doubles the probability of severe winters in central Eurasia.

The study was careful to account for changes in other hemispheric patterns, particularly the Arctic Oscillation, a regime of contrasting pressure areas known to influence the jet stream. Even with the oscillation factored in, the study found the atmospheric response to sea-ice decline is approximately independent of the Arctic Oscillation.

The model suggests that sea-ice decline leads to more frequent Eurasian blocking situations, which in turn favor cold-air advection to Eurasia and hence severe winters — but that pattern may not continue for long in a generally warming climate.




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