Persistent Arctic Cyclone and The ‘Warm Storm’ of 2013: How Unusual is It? Is Central Ice-Thinning Normal? What are the Worst-Case Scenarios?

(Edited on June 18 due to the availability of new information. I also want to promote two excellent blog posts related to this subject. One, by Neven, over at the Arctic Sea Ice Blog, takes a closer look at the science of Perstistent Arctic Cyclones, the other, posted on the Daily Kos by FishOutOfWater, links PAC 2013 to the collapse of the polar vortex this past winter.)

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Yesterday, two commenters — Sourabh in this blog post and T.O.O. in this blog post — raised some very salient questions about 2013’s Persistent Arctic Cyclone (PAC). These commenters wanted to know how critical to melting is PAC 2013, is this the first time we’re witnessing thinning of the central ice due to a long-period Persistent Arctic Cyclone, and by ‘what conditions could the central ice be expelled from the Arctic Basin?’

I posted a short response to their comments here and here. But I wanted to take the time to explore their questions in greater depth. Hence, this blog post.

Long Duration Summer Cyclones Rare, But Not Unheard of

First, let’s take a look at the current PAC 2013, its forecast duration, and how it compares to other storms. For context, it is important to note that most cyclones in the Arctic basin last for 40 hours or less. By comparison, PAC 2013 began on about May 26th and has remained in the Arctic for about 16 days. Forecasts now show the storm persisting until at least June 21rst. If the storm lasts this long, it will have remained in the Arctic for 26 days.

Another comparison can be seen in the Great Arctic Cyclone of 2012 (GAC). This storm was the 13th most powerful storm ever to impact the Arctic in the modern record. It lasted for about two weeks and reached a minimum central pressure of about 966 mb. The current PAC 2013, while lasting longer (and projected to last much longer) than GAC 2012, reached a lowest central pressure of around 975 mb while averaging in a range of 985 – 995 mb.

It is worth noting that Arctic cyclones are a year-round phenomena. And that more numerous, though somewhat weaker storms, have been noted to appear from May to July. That said, the strongest, longest duration storms usually occur during winter and can last for three weeks to a month or more. During summer, Arctic cyclones are weaker, pack less of a punch, and usually don’t last as long as winter storms. What makes PAC 2013 and GAC 2012 exceptional is the fact that they were both strong, long duration storms occurring during summertime and that they occurred under conditions of record thin Arctic sea ice.

There is some research to show that the strength of summer Arctic cyclones has been increasing since the late 1970s. These researchers show that increasing levels of moisture and higher temperatures around the Arctic during summer time have added fuel to the formation of new storms. Weather records do show the strength of the most powerful summer storms generally increasing with time.

Overall, PAC 2013, though somewhat weaker than GAC 2012 at peak strength, is projected to remain in the Arctic for a very long time. And with lowest pressures rivaling that of a moderate-strength tropical cyclone, it should continue to have substantial impacts — both to Arctic weather and to sea ice.

New Event: Storms that Melt Sea Ice

The Great Arctic Cyclone of 2012 was also unique because it was the first storm to have a major impact on Arctic sea ice. Though researchers have tended to disagree over how pivotal the storm was in reducing ice to the record low values achieved during 2012, it is generally accepted that the storm melted at least 250,000 square kilometers of sea ice during early August.

The storm achieved this feat by mixing the surface ice with warmer waters lying just beneath. Wave action and cyclonic pumping of warmer waters from the depths provided a powerful force for thinning and melting the surface ice. Though no direct research on sea ice volume losses due to GAC 2012 has been published, CICE images before and after the event speak to a major thinning as a result of the 2012 Cyclone.

Before:

GAC2012ThicknessBefore

After:

GAC2012ThicknessAfter

(Images From: US Navy)

Note the large areas of ice thinned into naught by the storm as it plowed through the East Siberian, Chukchi, and Beaufort Seas. A region of central ice was also noticeably thinned during the storm.

We can, therefore, say with some confidence that it is the ice thinning forces of the storm which caused the loss of 250,000 square kilometers of sea ice attributed to its impacts. But we can also say that a visible and, as yet, undetermined volume of ice was also lost and that this loss substantially contributed to 2012’s record low status.

A similar situation is now present during PAC 2013. Substantial thinning is now visible in all the sea ice monitors, especially on the Russian side of the North Pole. But this event is different from GAC 2012 in that is occurring during June, a period of time in which the ice is thicker and more resilient. A period of time when air and water temperatures are relatively cooler. As a result, no where near as much in the way of sea ice area losses can yet be attributed to PAC 2013. I say ‘yet’ because this storm appears determined to stick around for the long haul. So we may see major area losses arise as a result of its action.

In any case, it is worth looking at before and after thickness maps to determine the level of damage caused by PAC 2013.

Before:

PAC2013Before

During:

PAC2013After

After?

PAC2013Jun18

(Images From: US Navy)

As is plainly visible from the above set of images, PAC 2013 has dramatically hollowed out the central sea ice. With at least another ten days of duration expected, we are still just in the preliminary phase of impacts. These should ramp higher as the days continue to progress. (Note, the last image was added on June 18th, two days prior to a possible cessation of the storm).

Both PAC 2013 and GAC 2012 are new events for the reason that they result in melt and weakening of sea ice. This is unprecedented because past storms did not generate measurable losses in summer (You can look at some of this research here and here). To the contrary, it was thought that the cloudier, cooler storms were generally protective. And this was true in a cooler climate. Now, strong storms have a potential to result in losses. And this new feature is an environmental condition brought about by human-caused climate change.

Is This the First Time We’re Witnessing A Summer Cyclone Thin the Central Ice in June?

Now that we have a little background on summer cyclones and how climate change has enabled them to both significantly thin and melt ice, we can confidently answer the question: is this the first time we’re witnessing a summer cyclone thin the central ice in June?

The short answer to this question is: yes.

In the satellite record, there is no precedent for a June storm melting and weakening the ice in the past. Though June storms have impacted and fragmented the ice before PAC 2013, this storm is the first powerful, long-duration event to have such a large, measurable melt effect in early summer. As noted above, past storms were thought to be defensive, resulting in a more resilient ice pack and less melt, overall, come end of summer.

In part, such widespread damage is due to the fact that the area currently influenced by the storm is so large — covering all of the Central Arctic. The other reason is the fact that the ice in this key region is supposed to be the most resilient to late summer losses. Instead, in early summer, we see damage and erosion.

Were the storm to end now, it would leave the central ice thinner and weaker to the assaults of late summer. But the storm hasn’t ended. It continues to churn and thin the ice even as temperatures rise.

It is possible that, if this storm lasts long enough, remains strong enough, and pulls in enough warm air, it could produce a large region of open water at the very center of the ice pack even as it shoves a large portion of the thickest ice toward the Fram Strait. Such an event would not only be unprecedented. It could be catastrophic.

Under What Conditions Could the Central Ice Be Expelled From the Fram Strait? Short Answer: Persistent, Warm Storm

So now we’ll address the nightmare scenario for this particular event. This expose is by no way a prediction. It is just an illustration of what the worst case, in this event, could look like. It is also, by no means, the only way we could lose all or most of the central ice. The ice, for example, could melt out under a sustained assault from the sun. The central ice could take a hit from a swift, powerful storm, then melt as warm air and sunlight moves in behind it. We won’t examine these and other cases. Instead, we’ll take a look at the worst case in the event of a long-lasting Persistent Arctic Cyclone that warms and churns throughout a good portion of summer.

The event could look something like this:

The Persistent Arctic Cyclone that emerged in late May continues on through June and into July. As the Arctic warms, more above freezing temperatures get wrapped into the storm. Eventually, much of the region it covers warms to a range of 0-6 degrees Celsius. Rain becomes a primary form of precipitation in the storm.

The added moisture, warmer cloud cover, and above freezing precipitation create a constant surface stress to the ice. Underneath, the constant churning pushes water temperatures above freezing due to an ongoing mixing of the cold surface layer with deeper, warmer waters. The combined result is an ice melting and thinning machine. By the end of June, a growing region of open water (concentration 20% and less) has emerged.

The open water is a breeding ground for powerful waves and a magnet for sunlight streaming down through periodic breaks in the clouds. This region of warmer water thrashes and bores through the ice as July advances, creating a pheonomena never before seen in the Arctic — a large, central region of open water surrounded by thinning ice. The result is ice edge melt occurring at the same time as central ice melt. From the cored out portion, an arm of open and or nearly open water begins to sweep around the Arctic, clearing away ice in its path. The arm extends to weakest areas of sea ice. A most likely candidate for this arm’s development is the Laptev Sea as there ice there has been weakest since start of melt.

These three factors would be devastating enough. But a fourth factor provides the coupe de grace: Fram Strait export.

The constant counter-clockwise motion of our warm storm has been shoving at the remaining thick ice anchored on Greenland and the Canadian Arctic Archipelago since early June. Increasingly, large volumes of thick ice are flushed out the Fram Strait. By end of June, as much as 10% of the thick ice has been exported. But this is just the beginning.

During late June and early-to-mid July, warm air invasions from the south have melted and thinned the Canadian Arctic Archipelago ice. Now thinning and fractures from this warming have advanced into the thick ice, weakening its anchor. During July, there is less resistance to the storm’s counter-clockwise motion so more and more thick ice ends up meeting its end through the Fram Straight.

By early August, the storm has lasted for an excessive period — nearly seventy days. But it still churns on, fed by an endless procession of storms and injections of warm, moist air from the south. In a final explosion of weather never before seen in the Arctic, much of the remaining thick ice is ejected, melted, or churned beneath a storm-tossed Arctic Ocean. By early September, the storm finally disperses, but little or no ice remains.

Conclusion

The above ‘Warm Storm’ scenario is pure speculation. We have no reason to believe the current PAC 2013 will last so long or will have such powerful effects. More likely, a still damaging but more moderate erosion of central sea ice combined with an enhanced Fram Straight export will occur. Should the storm last until the end of June, these damaging impacts will be more than enough to weaken the ice.

That said, should the storm last longer, then we will have an altogether unwelcome opportunity to test this ‘Warm Storm’ theory.

So we come at last, to answering the first question of our commenters:

How critical to melting is PAC 2013?

And the answer to this question will depend on the duration of the storm, its relative strength over time,  how much warm air is injected into it over the course of its life-span, and how much warm water it is able to dredge up from beneath it. At the very least it has already played a major part in early season melt. Should it last for a long duration, the story of 2013 melt may well become wrapped up into that of this particularly anomalous storm.

Links:

On Persistent Cyclones

Arctic Cyclones

Northern Hemisphere’s Polar Vortex has Collapsed Creating Persistent Polar Cyclone

2012 Arctic Cyclone

GAC 2013: Detachment

The Great Arctic Cyclone of 2012

August Arctic Cyclone was the Strongest Summer Storm on Record

The Summer Cyclone Maximum over the Central Arctic

Dramatic Inter-annual Changes of Perennial Arctic Sea Ice Linked to Abnormal Storm Activity

Powerful Arctic Cyclone Driving Record Sea Ice Melt

Arctic Cyclone Hangs On

The Big Thin Begins

US Navy

410,000 Square Kilometers of Sea Ice Lost in Two Days: Persistent Arctic Cyclone Weakens Heart of Ice, Rapid Edge Melt Devours Fringe

According to Cryosphere Today, Saturday’s Arctic sea ice area measured 10.22 million square kilometers. By Monday, that number had dramatically fallen to 9.81 million square kilometers. This loss of 410,000 square kilometers over the course of two days is extraordinarily rapid, even for a time of year when melt has tended to accelerate. On sea ice area graphs, it makes the last few days look like area numbers fell off the edge of a cliff. (Note that Cryosphere Today area numbers usually lag by a few days. So what we’re actually seeing is area measurements through Friday, June 7th).

Up until recently, sea ice area melt had been relatively moderate. But now, after a week of consistent 100,000+ square kilometer daily losses, and two days of 200,000+ losses, sea ice area is only a smidge above that of record melt year 2012 on the same day in June. In total, more than 800,000 square kilometers were lost over the course of the past week. This melt rate, if sustained, would render the Arctic ice-free by late August. If we look at past records, it is not likely that these rates of loss will continue. But past records may not prove a good guide in the current age of fragile Arctic ice. It is quite possible, given the ice’s fractured, frail, and mobile state, that such enormous melt rates, in the worst case, could be sustained or even exceeded. In this event, we would witness a total collapse of Arctic sea ice by the end of this year. So should current dramatic melt rates be sustained or worsen, we may be upping our forecast chances for near total melt by end 2013 (still at 10%).

In any case, warnings that we were not out of the woods after a slower than expected melt during May, seem to have born out in spades.

Persistent Arctic Cyclone + Rapid Edge Melt = Brutal Combination

The twin forces driving this sea ice loss are the Persistent Arctic Cyclone of 2013 (PAC 2013 — I’ve decided to keep this name. Neven has sanctioned it, even as he playfully recommended calling it Rocky Balboa, which would be entirely appropriate for this dogged storm.), which we began warning about on May 30th in The Big Thin Begins, and a rapid edge melt that also began in early June.

PAC 2013 has, for more than two weeks, been invoking a number of forces detrimental to sea ice in the Central Arctic. It has pulled warmer water up in a column beneath it, melting the bottom ice. It has, through cyclonic action, dispersed the ice away from its center of circulation. And, via energetic storm winds, it has churned and disturbed the surface waters just beneath the ice or at the surface, creating a mixing action that also erodes the ice.

Together, these forces have dramatically reduced the Central Arctic Sea ice. Sea ice thickness, according to the US Navy, after already thinning somewhat, looked like this on May 30th:

CICE2013

Today’s most recent measure shows the central ice pack suffering substantial reduction since that time:

arcticictnnowcastJune9

Note the major thinning in a region of the thickest ice even as thinner regions closer to Siberia ablated further over the past ten days.

Cracks visible in the Lance-Modis satellite shots confirm an increased breaking of the sea ice even just north of the Canadian Arctic Archipelago, where the ice is thickest. Through a combination of bottom melt and sea ice dispersal, it appears that a broad region of this ‘most resilient’ ice lost between .5 and 1 meter worth of sea ice over the past ten days. By June 6th, these losses began to show up in the, less sensitive, Cryopshere Today concentration graphic. By June 8th, a large swath where sea ice concentration had dropped to between 60 and 70 percent was indicated in the region most affected by PAC 2013:

CTconcentrationJun8

(Image source: Cryosphere Today)

Note the large swatch of red running directly through the Central Arctic. That’s a broad region of ice thinned by our Persistent Arctic Cyclone showing up in the Cryosphere Today measure.

Today, the cyclone has shifted toward the Laptev Sea and is dramatically churning the thinner ice there, shifting its special brand of havoc closer to the Siberian coastline. We’ll discuss more about this new development in an upcoming PAC 2013 forecast.

As PAC 2013 churned through the Central Arctic, melt accelerated at the ice periphery. In the Canadian Archipelago, large regions of ice turned a characteristic shade of blue as melt lakes developed and insolation began to do its work there. Both Hudson Bay and Baffin Bay also saw dramatically increased rates of melt. This larger region of the Canadian Arctic saw a powerful influx of higher temperatures. A pulse of warmth that likely pushed melt faster. Temperatures of 10-20 degrees Celsius became a common event near Hudson Bay and southern portions of the Canadian Archipelago. Above freezing temperatures stretched far northward, driving deep into the Beaufort Sea.

Across the Arctic Ocean, the Laptev Sea began to melt at a faster pace even as a region of the Chukchi Sea displayed a dramatic and rapid disintegration of sea ice. You can see this rapid melt by comparing the Lance-Modis image from June 2nd to today’s Lance-Modis shot of the region:

Bering Melt Start

This is what Chukchi Sea ice looked like on the 2nd of June (Image source Lance-Modis).

Bering Melt End

And here is what it looks like today (Image source: Lance-Modis)

Note the clearing of most ice from the Bering Straight even as the ice edge retreated northward toward an increasingly fractured and thinned polar ice cap. As warmer air is expected to enter the Chukchi over coming days, it appears that conditions will continue to favor rapid edge melt there.

Weather model forecasts also show warm air flooding into many regions at the ice edge, growing especially prominent in the Beaufort, Chukchi, and East Siberian Seas. Meanwhile, PAC 2013 is expected to continue to churn through the Central Arctic. These conditions are now projected to persist until at least June 20th, at which point our Persistent Arctic Cyclone will have lasted nearly a month.

As noted above, this combination of conditions: warm air invasion at the ice edge, historically thin, fragile, and mobile sea ice, and a Persistent Arctic Cyclone (PAC 2013) are likely to continue to promote rapid to very rapid melt in the Arctic as June continues to advance. Though 200,000 kilometer per day sea ice area loss is extraordinarily rapid and dramatic, the potential exists for single day losses to exceed even this highly radical number. A sea ice cliff for June 2013, thus, appears to be a distinct potential.

Links:

US Navy

Cryosphere Today

The Arctic Ice Blog

Lance-Modis

 

Persistent Arctic Cyclone of 2013 (PAC) Returns to Trouble Central Arctic, Cloaks Itself in Warmer Air, Strengthens to 975 Millibars

CycloneNorthPoleJune5

(Image source: DMI)

Today the Persistent Arctic Cyclone of 2013 (PAC), re-centered over the North Pole even as it wrapped itself in above-freezing temperatures.

The above image shows a double barrel low roughly centered over the North Pole with a second low adjacent to the Canadian Arctic Archipelago. Lowest pressures remain around 980 mb — a rather potent storm for early June. Though not likely to grow as strong as the Great Arctic Cyclone of 2012 (GAC), this particular storm has now lasted for nearly two weeks and is projected to remain in the Arctic at least until June 15. Such persistence is likely to make this storm a substantial factor in the ongoing melt season.

Yesterday, the storm drew warm air in from the south behind it. This influx of warmer air ran into the Central Arctic beneath a train of cloud over a region near Svalbard and was visible in this Lance-Modis satellite shot. Temperatures in the region of Svalbard rapidly warmed with some regions there reporting 50 degree temperatures today — a virtual heat-wave for Svalbard this time of year. An area of dispersed ice near Svalbard also suffered very rapid melt yesterday, likely a result of this flood of warm, moist air.

Regions near the North Pole now show near freezing and above freezing temperatures. The storm backed into this warmer air, becoming wrapped in it as it returned to the Central Arctic. You can see this plume of warm air on the storm’s right flank in the DMI image below:

ArctictempsDMIJune5

(Image source: DMI)

This above-freezing air now resides over a region where sea ice remains broken and churned by previous passages of this storm. This region is heavily obscured by dense cloud cover. However, we can get a few peeks down through the clouds in the latest Lance-Modis shot of the region. What detailed inspection reveals is the ghostly image of shattered ice with large, dark gaps of ocean water between. These gaps have likely emerged through the physical process of storm winds diverging the ice as cyclonic forces churn the protective, cold top layer of water with warmer layers underneath.

This assault from below is now enhanced by the fact that near freezing and above freezing air has moved in overhead (seawater melts at around 29 degrees Fahrenheit).

A close look at the image below reveals these gaps:

Arctic_June5gaps

(Image source: Lance-Modis)

The clouds in this image are quite thick. However, if you took slightly to the left of direct center, you’ll be able to see ghosts of the fragmented ice and large gaps beneath.

The US Navy’s most recent CICE model run shows the PAC delivering a sustained blow to the thick ice just north of the Canadian Arctic Archipelago (CAA) before impacts are again projected to increase over coming days in the Central Arctic. Note the shifting of yellows and reds to greens and blues near the CAA. This is indicative of a loss of about a meter or more of sea ice thickness in this region. Also note the more wide-spread thinning that is expected to re-emerge near the North Pole as light blues in the model run fade more toward darker blues, showing about an additional half meter loss there.

arcticictn_nowcast_anim30dJun5

(Image source: US Navy CICE)

Confirmation will be necessary both visually and in other measures in order to verify the losses shown in CICE. Early losses were confirmed in Uni-Bremen, Lance-Modis visuals, and JAXA. However, dense cloud cover is currently making confirmation difficult even though some hints of this ongoing damage are visible through the clouds.

As mentioned yesterday, the primary processes for melt occur through divergence of the sea ice as well as via churning, upwelling, and Ekman transport of warmer water up from the depths. Today, melt potential is added via near and above freezing air temperatures over large regions of the Central Arctic. And as we’ve been warning since last Friday, the sustained nature of this storm has the potential to severely weaken the Central Arctic ice just prior to the warmest days of summer.

Since yesterday’s May PIOMAS update we’ve had more news to consider. However, apparent central ice impacts from this storm didn’t begin to seriously ramp up until the start of June. So we may need to wait to end of June for more clarity on total impacts. Nonetheless, all indications are this storm continues to fling the sea ice about quite a bit, with CICE continuing to show significant impacts to central ice thickness.

So, for now, the big thin continues.

UPDATE:

Warm, moist air influx from the south appears to have provided this storm with some added intensity. What, earlier, was a double barrel low pressure system has now combined, drawing warmer air toward its center as its intensity increased to around 975 mb. Now this storm is just about 9 mb shy of the Great Arctic Cyclone of 2012’s maximum intensity. In any case, 975 mb is a very respectable storm.

You can take a look a the latest storm intensity map here:

Arctic Cyclone Intensifies

(Image source: DMI)

UPDATE:

ECMWF weather forecast model runs for June 14 show PAC 2012 deepening to a 965 mb low pressure system. Should this strengthening occur, the system will have become stronger than the Great Arctic Cyclone of 2012. With the storm lasting so long, if it reaches such a strength, we may be dubbing it the Persistent Arctic Megastorm 2013 (PAM). Definitely something to keep an eye on.

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