Great Arctic Cyclone of 2016

August 17, 2016

arcticcyc16a

Bob Henson in WeatherUnderground:

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 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, a low that bottomed out at 966 mb on August 6. This was the lowest pressure analyzed across more than 1600 August cyclones in the Arctic since 1979, according to a 2012 study by Ian Simmonds and Irina Rudeva (University of Melbourne).

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 occurred in August and September was 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.

https://twitter.com/StuOstro/status/765718203859210240

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.

arcticice081616

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 model’s 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.

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2 Responses to “Great Arctic Cyclone of 2016”


  1. I posted a comment on both the Arctic Sea Ice blog and Dot Earth several days ahead of the GAC of 2012 predicting huge losses in ice extent due to the storm, predicting a new low sea ice minimum. After the event, I expected several years of recovery before such an event would hit again.

    My basis: Detailed analysis of sea ice extent in the Beaufort sea region in the last half August of 2011, when hundreds of kilometers of sea ice disappeared essentially overnight when a cyclone rolled through the Beaufort region. The data was confirmed by video imagery from the USCGC Healy which traveled north right through the area hit by the cyclone, and showed very little leftover ice up to almost the 80N latitude in the Beaufort after the storm; prior to the cyclone, ice floes covered the entire area. The Austrian who runs the Arctic Ice Blog, Neven, called the event a “flash melt”. These observations proved vital in estimating the impact of the big storm the following year (2012).

    Normally, only 1-2 cm of ice per day melts off an ice floe. But in a storm, due to the increased heat transfer, a floe can melt at the rate of 50-80 centimeters per day. Any floes with less than a meter of ice thickness can disappear in just a day or two. The top 50 meters of the Arctic overturns (Ekman pumping), providing stored heat to melt the ice pack. The cap normally has a colder fresher lens under the ice that isolates and slows the bottom melt. A storm would normally pass over a relatively contiguous ice cap without effecting this ice/lens. When the cap weakens by melt and breaks into smaller ice floes, with open water in between, the storm can churn up the water, causing heat transport from warmer deeper saltier water. In order to melt a meter of ice on the surface, the top 50 meters cools about 1-2C, and this uses up all the thermal energy available in this layer. Clearly the heat transport mechanism is a key factor in setting the bottom melt rate, and a storm increases the heat transport rate.

    After a flash melt event due to a storm, the upper 50-100 meters of ocean cools in the aftermath, and in a severe event like the GAC of 2012, the resultant cooling should lead to several years of lower ice bottom melt. But as Arctic Amplification keeps driving warming of the Arctic ocean, eventually the water under the cap circulates recharging this layer, and setting the stage for another event.

    I predict that the current storm will have a similar impact to the GAC of 2012.

    In 2012, I made one further speculative prediction; that the resulting damage to the ice cap, would result in a massive amount of thermal energy release back into the atmosphere in the Arctic during the refreeze, and this would disrupt the jet stream and cause some extreme weather events somewhere in the NH during the period from October to March.

    At the end of October, Hurricane Sandy rolled up the East Coast, was stopped from heading out over the ocean by a blocking high stalled in the N. Atlantic, and veered west in a highly unusual path for a hurricane. The United States was hit with the worst storm damages in history.

    I speculate that similar extreme or unusual weather events are likely for the NH mid-latitudes resulting from the ice cap damage caused by this current storm.

  2. MorinMoss Says:

    Page below has a nice animation from NASA for this year’s melt since March

    http://www.nasa.gov/feature/goddard/2016/nasa-monitors-the-new-normal-of-sea-ice

    Direct YouTube link: https://www.youtube.com/watch?v=_qhpxvRt6tY


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