‘Too soon to tell …’
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FRISCO — There’s been lots of speculation and some early research on a possible link between soaring temperatures in the Arctic and extreme weather in North America and Europe, but the jury is still out, according to scientists with the National Oceanic and Atmospheric Administration.
NOAA’s James Overland was part of an international team that took a close look at possible connections and concluded that more research is needed.
“We are in the pre-consensus stage of a theory that there are links between the rapid warming of the Arctic and some severe weather events since 2007,” said Overland, lead author of the new study, “The melting Arctic and Mid-latitude weather patterns: Are they connected?”
“New studies on the changing Arctic together with additional Arctic observations will improve our ability to make long-range forecasts for the mid-latitudes, helping millions of people better plan for the future and take steps to be more resilient in the face of severe weather,” Overland said.
Arctic temperatures are increasing two to three times faster than those at the mid-latitudes. Some scientists have theorized that warming Arctic temperatures and melting ice and snow contribute to weaker upper level westerly winds and a wavier jet stream in some years.
The jet stream is powered in large part by the temperature and air pressure gradients along the boundary of cold Arctic air masses. If those differences decrease, it could slow the jet stream and cause it veer much farther north and south, even getting stuck at times.
The new study says it’s still a dotted line from Arctic warming to the destabilized or wavier jet stream and severe cold outbreaks. What’s missing is long-term observational data, the authors concluded, adding that tropical energy, varying sea surface temperatures and regional and chaotic effects also play major roles in driving extreme winter weather events.
The research does show evidence of Arctic/mid-latitude weather linkages in eastern Asia. Loss of sea ice and warmer temperatures north of central Asia increase the intensity of the Siberian high pressure system. This system, in turn is the source region for cold storms that can reach Japan, South Korea, and parts of China.
By contrast, a wavier jet stream over North America can have multiple causes, but its intensity can be reinforced by a regionally warm Arctic.
The way to advance these theories from a pre-consensus stage is to increase investigations of the fundamental atmospheric circulation features such as the jet stream that meanders, and the connection between the warmer Arctic and the negative phase of the Arctic Oscillation, an index of the dominant pattern of sea level air pressure in the Arctic.
“We are where other major theories such as plate tectonics and El Niño were before they were accepted,” said Overland, who works at NOAA’s Pacific Marine Environmental Laboratory in Seattle. “We need a Grand Science Challenge with more observations and research to advance forecasting abilities. This will help NOAA give communities, both within and outside of the Arctic, the improved information they need to be ready, responsive and resilient to severe weather and long-term environmental change.”