Nunatsiaq Online
NEWS: Climate Change July 14, 2017 - 8:00 am

Arctic warming events are more frequent and last longer, report says

But according to data collected, freak winter warmth in the Arctic is not unprecedented

STEVE DUCHARME
A graphic from the National Snow and Ice Data Centre in Colorado which shows the lowest ever maximum sea ice extent, which occurred this past March 2017. The Orange line shows the median, ice edge from 1981 to 2010. That means half of ice extent values for that time period were greater than that line, and half were smaller.
A graphic from the National Snow and Ice Data Centre in Colorado which shows the lowest ever maximum sea ice extent, which occurred this past March 2017. The Orange line shows the median, ice edge from 1981 to 2010. That means half of ice extent values for that time period were greater than that line, and half were smaller.

Mid-winter Arctic warm spells, like when temperatures hovered near freezing at the North Pole in December 2015, will likely be more common in future, but are not entirely unprecedented, a new report suggests.

In a new study, published in May in Geophysical Research Letters, a team of international scientists, including researchers from NASA, say it is “becoming more common to have at least one extreme winter warming occurring during the month of December in the [North Pole] domain.”

The study based its results on weather data collected by late-nineteenth century explorers, manned Soviet Union weather stations at the North Pole, and modern weather databases.

A “winter warming event” was defined in the study as any Arctic weather event where temperatures rose above -10 C between December and March, and an “extreme winter warming event” was when temperatures closed in on 0 C.

Temperatures in the Arctic during those months are typically colder than -30 C.

Simulations and historical weather data compiled by the researchers suggests that there is, on average, an increase both in the frequency of winter warming events, as well as in their duration, the report says.

Individual warming events are increasing at a rate of about 1.7 events per decade, the report concluded, with the average duration of the warm spell increasing by five additional hours over the same time.

The maximum duration of these events is also rising by 24 hours per decade, on average, but the report acknowledged the “large variability” within individual seasons over the past 100 years.

The inspiration for the study stemmed from the strange and widely-reported warming of the North Pole in December 2015 when the temperature rose to 0 C—briefly rivalling the temperature in Vancouver the same day.

The event symbolized a generally warmer winter that year, throughout the Arctic, which scientists say was caused, in part, by a “split tropospheric vortex.”

That vortex sucked warm air and moisture from the Atlantic Ocean into the North Pole which helped to disrupt traditional weather patterns across the circumpolar world that winter.

But not everyone benefitted from the warmer temperatures.

In fact, the eastern Canadian Arctic and Northern Greenland experienced a colder-than-usual winter in 2015 as warm high-pressure zones further east and north keep cold air trapped over that region for most of the winter.

But while the 2015 warming event at the North Pole has been classified as a rare occurrence, precedents for that kind of freak warm Arctic weather go back decades, the report noted.

Winter heat waves warmer than -5 C were observed during more than 30 per cent of all Arctic winters between 1954 and 2010, according to data collected by Western North Pole buoys and manned Soviet weather stations.

And temperature events above -10 C occurred at least once during 60 per cent of the winters between 1951 and 1991, according to another set of data cited in the report.

All that data will prove invaluable for researchers as the climate continues to change in the Arctic, with temperatures increasing twice as fast as the global average, the report said.

The most rapid Arctic warming has been recorded during the winter months—and the 2015-16 winter was the warmest winter since comprehensive data collection began in 1950, the report said.

As well, “the winter maximum sea ice extent in March 2017 was the lowest in the 38-year satellite record,” the report said.

March 2016 and March 2015 tied for lowest sea ice extent, prior to that.

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