One of the hallmark features of the 2017-18 winter was how the far northern latitude regions of the earth got warm -- not just a little warm, but VERY warm. To give some perspective on the out-of-bounds extremity of this warming, NOAA climate scientist Michon Scott put together the following commentary, which is posted at the NOAA Climate.gov web site.
"Sea ice melts in the spring and summer, and grows in the autumn and winter. Arctic sea ice typically reaches its maximum extent sometime between late February and early April, and since the start of the 21st century, those winter maximums have declined. Although Arctic sea ice in 2018 hasn't broken all previous records for its low wintertime extent, it is still trending well below the 1981-2010 average. But, as researchers watched Arctic sea ice in early 2018, they marveled at the high air temperatures over parts of the Arctic. In late February 2018, at Cape Morris Jesup, Greenland, the weather station closest to the North Pole (maintained by the Danish Meteorological Institute), temperatures climbed 45 degrees Fahrenheit above normal for that time of year.
"Dramatic temperature anomalies can strike anywhere on Earth in any season, but 2018 was the third year in a row to bring anomalously warm temperatures over the Arctic Ocean. At the Cape Morris Jesup weather station, temperatures were above freezing for a total of 61 hours in the month of February, and remained above freezing for almost 24 hours. At their highest, they rose to 43 deg F. That's still fairly chilly, but to put this temperature spike in perspective, imagine the city where you live.
"At the end of February, the normal daytime maximum temperature in Washington, D.C.; Denver, Colorado; Boise, Idaho; and Louisville, Kentucky, is roughly 50 deg F. Imagine all those cities sweating through a 95 deg F daytime maximum before March. Now imagine Miami at 124 deg F at the same time of year.
"Here are some other cities with the same comparison applied:
"Chicago's average February 28 high is 40.0 F. That would soar to 85 F with the Arctic 45-degree jump added. Des Moines, 41.3 average, would be 86.3. Detroit, 39.1, would be 84.1. Bismarck, at 32.6 average, would jump to almost 77.6 for the high. Omaha, 45.0 average, would hit 90 degrees Fahrenheit. Little Rock, 58.8 average, would balloon to 103.8 for the high. St. Louis, average 48.7, would hit 93.7. Oklahoma City, with an average 58.4 Fahrenheit for the Feb 28 high, would instead hit 103.4. Dallas would go from 63.4 average to 108.4 with this Arctic increase applied.
"Bear in mind that, although parts of the Arctic were unusually warm in late February, other areas (parts of Alaska, Greenland, Canada, and the Arctic Ocean) were unusually cold. And, while the North Pole experienced unusual warmth, much of Europe shivered through a deep freeze, with snowfall in Rome. This mix of unusual heat and cold comes down to the jet stream.
"A strong difference in atmospheric temperature between the lower and higher latitudes causes the air current known as the Northern Hemisphere's Polar Jet Stream to flow between the Arctic and the middle latitudes. Sometimes the difference in atmospheric pressure at different latitudes lessens, making the jet stream wavier. Warm air infiltrates the Arctic, and cold air infiltrates lower latitudes. That's what happened in late February.
"Some studies indicate that Arctic sea ice decline increases jet stream waviness by allowing greater heat transport from the ocean to the atmosphere, but National Snow and Ice Data Center Director Mark Serreze says that this hypothesis remains a topic of fierce debate."
The article in full graphic presentation is at this link: https://goo.gl/…
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