As of Tuesday, the deepest cyclone in the Northern Hemisphere wasn’t anywhere near the tropics--it was spinning in the central Arctic Ocean. A surface low located near 83°N, about 500 miles from the North Pole and about 1000 miles north of Barrow, Alaska, deepened to a central pressure of 968 millibars (mb) at 2 am EDT Tuesday morning, August 16. This is on par with the central pressure you might find in a moderately-sized Category 2 hurricane. Such lows are a common feature of Arctic climate, but they rarely gain such intensity in the middle of summer. The only deeper Arctic cyclone on record in August is the Great Arctic Cyclone (GAC) of 2012. According to a 2012 study
by Ian Simmonds and Irina Rudeva (University of Melbourne), this low bottomed out at 966 mb on August 6, yielding the lowest pressure analyzed across more than 1600 August cyclones in the Arctic since 1979. The cyclone's minimum pressure was even lower--963 mb--in the real-time analyses produced by Environment Canada while the storm was raging
. The Arctic cyclone was analyzed with a central pressure of 968 mb at 06Z (2:00 am EDT) Tuesday, August 16, 2016. The central pressure had risen to 971 mb by 12Z (8:00 am EDT). Image credit: tropicaltidbits.com
. Surface analyses over the Arctic Ocean show the Great Arctic Cyclone of 2012 at its deepest (left, at 06Z August 6, 2012) juxtaposed with the current cyclone (right, as of 00Z Tuesday, August 16, 2016). The initial Image credit: Environment Canada.Wind, waves, and ice
The GAC of 2012 churned across the Arctic for ten days while its central pressure was below 1000 mb. The cyclone had major effects on the distribution of regional ice and appears to have played at least some role in that summer’s record depletion of Arctic sea ice. Normally, low pressure near the North Pole causes ice to spread out (as surface waters and sea ice move to the right of the surface wind). Yet the intensity and duration of the 2012 cyclone’s winds and waves appears to have more than compensated for that effect, leading to an overall loss of ice extent. The extent plummeted in August 2012
en route to a record-low extent in September
A study in 2013
led by Jinlun Zhang (University of Washington) found that the GAC quadrupled the melting of sea ice from below by pushing warm surface water against the bottom of wind- and wave-tossed ice floes. However, because much of the Arctic ice was already thin and compromised, much of the extent loss that would occur in August and September was already baked into the system when the cyclone came along. Zhang and colleagues estimated from a model simulation that the record September minimum was only about 4% lower as a result of the GAC of 2012.The kind of ice-breaker we don’t need
It’s too soon to know exactly how this year’s storm--let’s call it the Great Arctic Cyclone of 2016 for now--will affect the Arctic. However, according to polar researcher James Screen (University of Exeter), “This certainly has the potential to be an interesting event and possibly have a big influence on whether or not we see a new record sea ice minimum next month.” As many reports have noted in the last few years, the Arctic’s summer ice pack is in the midst of a dramatic long-term decrease due to global and regional warming. However, there remains a good bit of year-to-year variation in the ice extent. Each summer’s ice pack has a different character in terms of the area it covers, its thickness, the extent and location of surface melt ponds, and so on. This means the impacts of a strong August cyclone in the high Arctic could be quite different from one year to the next. The current cyclone is located near a zone that separates relatively thick, dense ice to its east (north of the Canadian Archipelago) from thinner, more dispersed ice extending from the eastern coast of Siberia all the way up to near the North Pole (see Figure 4 below).Figure 3.
Near-surface circulation around the low in the central Arctic as of early Tuesday, August 16, 2016. Sustained winds of at least 30 mph appear to be affecting a large area. Image credit: earth.nullschool.net
Sea ice concentration across the Arctic as of August 15, 2016. The approximate location of the strong Arctic cyclone as of Tuesday, August 16, is shown by the large L. Image credit: University of Bremen
. Largely due to incredible winter warmth, temperatures averaged north of the Arctic Circle for the period January through July were far higher this year than in any year since records began in 1948. Image credit: Zach Labe, UC-Irvine, @ZLabe
As of early August, the Arctic’s sea ice extent was among the four lowest on record
since satellite monitoring began in 1979. Temperatures across the Arctic for the year thus far have been far above record levels (see Figure 5), so there is concern that the ice pack may be weaker than satellite measurements and models imply. We can expect some dramatic changes over the next few days, as winds and waves break up ice and churn up relatively warm water from below. Much will depend on the exact track of this Arctic cyclone and how long it persists as an intense low.
Remarkably, the most recent runs of the ECMWF and GFS keep the current low and/or subsequent lows spinning across the Arctic Ocean for at least the next week--perhaps at pressures below 990 mb for much or most of the time. The models even flag the possibility of another unusually intense cyclone at some point next week. One caution from polar scientist Steven Cavallo (University of Oklahoma): “There is not really much skill in the forecast models accurately predicting the strength of an Arctic cyclone more than 3 days ahead of time.” However, if the models' overall message of unusually persistent and strong low pressure in the central Arctic verifies, there could be very significant impacts to the sea ice pack extending through the rest of the melt season.Will climate change lead to more Great Arctic Cyclones?
Given the amount of change occurring to the state of summer sea ice in the Arctic, it’s natural to wonder if there might be a change in the upward-pointing influence on atmospheric circulation. “An interesting question is whether the long-term loss of ice (and increased heat and moisture fluxes) is making Arctic cyclones more intense,” Screen noted. “The jury is still out on that one, but if that was the case, we could expect GAC-type events to occur more frequently.” A 2009 modeling study
led by Yvan Orsolini (Norwegian Institute for Air Research) estimated that the number and strength of summertime Arctic cyclones would increase slightly through the 21st century. Over the long term, “we do expect a lowering of the mean sea level pressure over the Arctic with sea ice loss," says climate modeler Clara Deser (National Center for Atmospheric Research]. "To to the extent that this signal reflects cyclone behavior, I would concur that under climate change, it might be the case that cyclones would intensify. However, attribution of the extent to which the Great Arctic Cyclone of 2016 is a result of the loss of sea ice is more challenging, since internal variability may also contribute."
For deep coverage of the deep Arctic cyclone, check out the dedicated post
at the Arctic Sea Ice Blog, as well as recent entries in “The 2016 melting season” at the Arctic Sea Ice Forum
.Elsewhere on the blog
Jeff Masters filed an update earlier Tuesday on the devastating floods in southeast Louisiana
, which have now inundated some 40,000 homes, and on the current state of Invest 98L, which is likely to become a tropical depression in the next day or two. We’ll be back with our next post by Wednesday.
Bob HensonFigure 6.
Sea ice across the Arctic experienced a major decline in extent and concentration during the first few days of August 2012, as the Great Arctic Cyclone of 2012 churned across the area. Image credit: National Snow and Ice Data Center