© Downs Matthews/Polar Bears International
7/7/2020 11:19:11 PM
State of the Arctic in 2020
By Dr. Zachary Labe
Yet again, it is another year of extremes around the Arctic Circle. For everyone monitoring our rapidly changing Arctic, we are certainly getting used to hearing those words – extreme event.
This winter’s maximum Arctic sea-ice extent was the 11th lowest in the satellite record. While not as dramatic as previous years, it remains consistent with the long-term trend. In particular, this winter’s weather was influenced by an unusually strong stratosphere polar vortex and a positive phase of the Arctic Oscillation (AO). The polar vortex is a band of intense westerly winds in the upper atmosphere (stratosphere), which are similar to a low-pressure system. In contrast, the Arctic Oscillation also characterizes a low-pressure pattern, but it is found in the lower atmosphere. A stronger polar vortex and positive Arctic Oscillation have the tendency to lock colder air in the Arctic due to a faster jet stream.
However, a positive Arctic Oscillation also contributes to an acceleration of sea ice movement from near the Siberian coast to the North Atlantic – known as The Transpolar Drift Stream. This can reduce the amount of thicker and older sea ice in the Arctic Ocean, especially near Siberia. Observations of sea-ice thickness found in this region were up to 1 meter (about 3 feet) below average this winter. Polar bear habitats are particularly sensitive to younger and thinner Arctic sea ice. Climate model projections of future winter Arctic sea ice continue to show a dramatic thinning of ice over the 21st century.
Figure 1: Daily sea-ice extent along the Siberian coastline of the Arctic (East Siberia, Laptev, and Kara Seas) for 2020 (red line) and throughout the satellite era (purple  to white  lines). The record low sea-ice loss year in 2012 is also highlighted in yellow. Data is from the NSIDC Sea Ice Index v3.
As spring progressed, temperatures surged in parts of the Arctic Siberia and were up to 10°C above average. This remarkable warmth has continued all the way through June. In fact, the average December 2019 to May 2020 temperature over Western Siberia crushed the previous record by about 2°C. The thinner sea ice resulting from this winter’s positive Arctic Oscillation, a lack of spring snow cover, and the record Siberian warmth all contributed to the dramatic decline in Arctic sea-ice extent over May and June. A powerful high-pressure system formed over the Arctic this spring, which contributed to sunshine, warmth, and the formation of melt ponds over the central Arctic. This early loss of sea ice around Siberia is unprecedented, and it will have large impacts on the terrestrial and marine ecosystems of the region (Figure 1). Widespread wildfire conditions in Siberia are also expected to persist through July.
Figure 2: Daily Arctic sea-ice extent in 2020 (blue line) compared to average (yellow line). Data is from the NSIDC Sea Ice Index v3.
As we close the first week of July, total extent of Arctic sea ice has fallen to near a record low, which is more than two standard deviations from average (Figure 2). In addition, there has been a substantial loss of sea-ice volume in response to the warmth and high-pressure system (Figure 3). While the latest probabilistic outlook from the Sea Ice Prediction Network does not indicate 2020 falling below 2012’s record low sea ice minimum, we will need to monitor conditions closely given the recent anomalous weather pattern.
Figure 3: Daily Arctic sea-ice volume simulated for each year from 1979 [blue line] to 2019 [red line]. 2020 is indicated in yellow. Data is from the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS).
From my perspective as a climate scientist, this year’s extreme warmth in Siberia is not too surprising. The significant warming of the region – known as Arctic Amplification – increases the risk for these types of polar heat waves. Data sets from scientific institutions around the world all show that the current rate of warming in the Arctic is unparalleled in our observational record (Figure 4). This warming is already substantially impacting indigenous communities and ecosystems around the Arctic Circle. Unsurprisingly, 2020 is consistent with these trends.
Figure 4: Surface air temperature anomalies (departure from average) for each year from 1900 to 2019 over the Arctic Circle. Each solid line uses a different type of data set.
Although it’s very concerning, we have the opportunity to largely lower the risk of future warming in the Arctic by spreading awareness and systematically reducing our greenhouse gas emissions. This will decrease the probability of a future ice-free Arctic summer and help to preserve polar bear habitats.
Dr. Zachary Labe is a postdoctoral researcher in the Department of Atmospheric Science at Colorado State University. Follow him on Twitter at @ZLabe and learn more about his work via his website.