A rise in Arctic storms has more than doubled the number of winter warming events, which could greatly impede ice growth.
Scientists are no strangers to Arctic winter warming events, winter days during which the temperature in the Arctic is above 14 degrees Fahrenheit. These events are a normal part of the Arctic winter climate. However, a new study from the American Geophysical Union reveals that these warming events have been dramatically increasing in frequency and duration over the past few decades.
The study analyzed winter air temperatures over the Arctic Ocean from 1893 to 2017. Using data gathered from buoys, drifting weather stations, and field campaigns, the study authors discovered that the number of winter warming events in the North Pole more than doubled since 1980. These warming periods also last about 12 hours longer on average now than they did prior to 1980, increasing in length from fewer than two days to almost two and a half days. As a result, the total duration of winter warming events has tripled, from about 7 days per year to around 21 days per year.
The intensification of these warming events is likely due to an increase in major Arctic storms, as each of the warming events that occurred during the past few years was associated with a major storm entering the area. These storms can raise the air temperature in the North Pole by blowing moist, warm air from the Atlantic into the Arctic.
"The warming events and storms are in effect one and the same," explained Robert Graham, the lead author of the study. "The more storms we have, the more warming events, the more days with temperatures greater than minus 10 degrees Celsius [14 degrees Fahrenheit] rather than below minus 30 degrees Celsius [-22 degrees Fahrenheit], and the warmer the mean winter temperature is."
Two more of the study’s authors, Alek Petty and Linette Boisvert, have researched winter storms in the past. By studying one major storm during the winter of 2015-2016, the two scientists gathered new information on the impacts of these storms on the Arctic environment. However, the team argued that the new study on winter warming events provides more insight than ever before.
"That particular cyclone, which lasted several days and raised temperatures in the region close to the melting point, hindered sea ice growth while its associated strong winds pushed the sea ice edge back, leading to a record low spring sea ice pack in 2016," Petty and Boisvert explained. "This new study provides the long-term context we were missing, using direct observations going back [to] the end of the 19th century. It shows that these warm events have occurred in the past, but they were maybe not as long-lasting or frequent as we're seeing now. That, combined with the weakened sea ice pack, means that winter storms in the Arctic are having a larger impact on the Arctic climate system."
The results of the study coincide with other evidence of Arctic warming. In December 2015, researchers in the Central Arctic recorded a temperature of 36 degrees Fahrenheit, the highest winter temperature ever recorded in the area. In 2016, new monthly temperature records were set for four months: January, February, October, and November. Since Arctic sea ice expands and thickens during the winter and fall, warmer winter temperatures could have disastrous impacts on ice coverage in the region. According to Graham, winter storms coupled with rising temperatures could hinder Arctic ice growth and break up ice that is already covering the Arctic Ocean, which would have a devastating impact on the region.