There’s a massive heat dome building over an Arctic sea ice pack that is looking increasingly fragile in both model forecasts and observations. In short, very bad weather for sea ice is rapidly settling in even as the ice pack, despite recent place gains in some measures, is looking increasingly weak.
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First the somewhat good news… Arctic sea ice extent has backed off to about 8th lowest on record. Arctic sea ice area is at about 4th lowest on record. And Arctic sea ice volume, according to DMI, is in the range of 3rd lowest on record (PIOMAS looks even better). This report may sound rather bad, but when compared with late May and early June when sea ice extent measures were at or near new record lows the data could arguably be characterized as an improvement. Yeah, there’s been some big area drops recently, but all in all, not too terrible, right?
Probably wrong… Because the Arctic is gearing up for a very powerful heat wave over the coming week. One that is likely to spike maximum summer temperatures in the High Arctic, a region that seldom shows much variance on the side of hot or cold at this time of year, by 0.5 to 1.5 C above average. A heatwave my somewhat more reserved fellow ice observer, Neven, has called ‘HUGE’ (note that Neven seldom uses caps lock) and is characterizing as something he’s not seen in all of his five years of sea ice observation. From The Arctic Sea Ice Blog Today:
…However, there is one big difference compared to last year and that’s heat. Despite a very cold start, there have been several outbreaks of warm air over the ice, slowly but radically shifting the balance between extent and area data. The impact is felt on the surface of the ice pack, but doesn’t translate directly into a decrease. Not yet. In theory, it should percolate through after a while, especially if the heat persists. And right now the Arctic sea ice pack is undergoing a massive heat wave which shows no signs of letting up.
I find myself in agreement with Neven. The massive heat build in the Arctic predicted for this week is likely to be a significant event with potentially wide-ranging impact. But to understand why, it helps to get an overall picture of the broader context in which this particular heatwave is occurring. And that context includes two other stories as well — the story of human-forced climate change and the story of a still developing and potentially monstrous El Nino.
Ocean Warming Injects Heat into the Arctic
To get an idea how warming in the Equatorial Pacific and over-all greenhouse gas based warming can have such a far-flung impact, particularly on the currently building Arctic heatwave, it always helps to take a look at the behavior of the circumpolar Jet Stream. Large areas of persistently warmed water, like the one we have seen now for two years over the Eastern Pacific, have a tendency to generate high amplitude ridges in the Jet. Ridges that serve as open avenues for heat transport into the Arctic. Specifically yesterday a huge pulse of heat was traveling north along just such a high amplitude and ocean-warmed ridge:
(Amazing high amplitude Jet Stream wave punching all the way through to the High Arctic on the back of the Eastern Pacific’s Ridiculously Resilient Ridge. Image source: Climate Reanalyzer.)
Our particular heat transporter should by now be very familiar — a ridiculously resilient ridge (RRR) — extending northward and buttressed by multiple high pressure cells stubbornly entrenched over abnormally hot water in the Eastern Pacific. Yesterday (Monday, July 6) the ridge elongated. South to north winds over-riding northward flowing warm, salty ocean water. Running up through Alaska, the heat pulse set off all-time daily highs in places like Anchorage (81 degrees and breaking the record set in 1972). The heat then spilled into the Bering, Chukchi and Beaufort Seas where it met with adjoining, though lesser heat pulses over-riding Greenland and the Laptev. A gathering pocket of hot, thick air that is now pooling in the so-called sea ice ‘safe zone’ just north of Greenland.’ A precursor to the very intense high pressure cell we see developing now.
But before we go on to tell the tale of our gathering Arctic heatwave we should first take a closer look at ocean surface temperatures. As these give us a rather clear picture of the Arctic’s current vulnerability — providing for us a hint as to why heat will intensify most strongly to the north of the Canadian Archipelago and Greenland. For it is ocean surface heat that built the road that warm air followed:
(Heat plume running all the way from Equator to Pole clearly reflected in this July 6 NOAA/ESRL SSTA anomaly map.)
Taking a look at NOAA’s July 6 Sea Surface Temperature Anomaly (SSTA) map, we find a massive plume of much warmer than normal (1971-2000) waters extending up from a plainly visible El Nino pattern, all throughout a large sweep of the Eastern Tropical Pacific. Moving northward, these steamy waters spill into two hot blobs off the Mexican, US, and Canadian coasts — a heat pool that again punches up through the Chukchi and Beaufort Seas. An Equator to Pole expanse of ominously hot water that is enabling both sea ice melt in the regions directly impacted as well as a broader invasion of warmth into even the sea ice’s most secure haunts.
Heat Directly North of Greenland, Canadian Archipelago
Warmth that today aided in the formation of an Arctic high pressure ridge hitting significant heights of 1030 to 1035 mb directly between the Pole and Greenland. At 1245 Eastern Standard Time, the ridge had already intensified to 1032 mb. And for at least the next seven days both the GFS and the Euro model shows a 1025 to 1035 mb high pressure cell dominating the same region.
(Left frame shows strong, 1032 mb high pressure system settling in to the region just north of Greenland on July 7. By July 10 [right frame], this ridge is predicted to have greatly warmed the Central Arctic zone between Greenland and the Pole. Image source: Earth Nullschool.)
This persistent ridge will remove cloud cover in a large area between North America and the Pole. Sunlight, at its seasonally most intense, will multiply already widespread melt ponds on the sea ice surface. The combined solar forcing and loss of albedo will push surface temperatures higher as the ridge remains in place. And by Friday a broad band of 2-4 C temperatures is predicted to form in a bulge over the Arctic Ocean north of Greenland and the Pole. Abnormally warm temperatures and direct sunlight that will, over the next week, increase melt pressure over the last remnant of thick sea ice left to the Arctic.
In addition to reducing cloud formation and enhancing the melt-forcing impact of sunlight on the sea ice, high pressure cells in this region will have a couple of further influences. First, they will tend to compact the sea ice overall — drawing in the fringe ice while generating warm water upwelling at the ice edge. And second, the clockwise motion of air circulating around a strong high pressure cell will nudge sea ice out of the Central Arctic toward the gateway of the Fram Strait. Add in the significant impact due to reduced cloud formation allowing sunlight to contact sea ice during a period of peak solar radiative forcing and we end up with a substantial overall blow to the sea ice.
(Extraordinary high temperature anomalies are predicted for the Arctic from July 7-17. A departure more typical for winter when human greenhouse gasses have the greatest heat-amplifying impact. Image Source: meteomodel.)
Taking a look at the meteomodel anomaly map above, we find a very extreme warming of the Central Arctic predicted over the next ten days. A heat pulse to rival 2012 for this period. A melt multiplying heatwave that is predicted to push anomalies for the entire Arctic above +1.5 C beyond the early July average. A polar amplification similar to what is typically a winter manifestation of human emissions-driven anomalous warmth — this time anomalously occurring during a period when heat for the region is approaching peak intensity.
Impacts to Sea Ice Could Be Substantial
In the face of this oncoming weather, ice pack strength would be a deciding factor lending resiliency during melt-promoting conditions or a shift to a much more rapid rate of decline. Though some indicators, including a seemingly slower rate of decline during late June, may point toward more ice resiliency, a growing number of satellite reports and model analysis hint at a general and overall weakness throughout the ice pack.
This weakness can best be described as model indication of thin or low concentration ice, already widespread melt ponding, and visual indication of ice weakness in the satellite shot.
(The US Navy’s GLBb model has always been unfriendly to sea ice. But other models are now starting to agree. Image source: US Navy.)
For low concentration ice, no model is more stark than the US Navy’s experimental GLBb sea ice thickness ensemble. I colloquially think of this as the ‘holy crap’ sea ice model. This label due to the fact that if sea ice state is really as bad as the model indicates, then the ice is basically toast. Starting in June, this model displayed a great overall weakness in the sea ice and, according to its analysis, the situation has progressed from bad to worse with most of the remaining Arctic Ice possessing a thickness of 1.2 meters or less. Easily thin enough for any nudge by weather to really start rapidly bringing the ice down and opening up very large expanses of open ocean.
If the GLBb ‘holy crap’ model were the only sea ice model making us want to say ‘holy crap!’ then we could probably breathe a bit easier. Unfortunately, another US Navy model is now also tending to elicit this response in reaction to its predictions for the next 7 days and more specifically for the next 3 days:
(The US Navy’s ARCc sea ice concentration model predicts a very rapid rate of sea ice decline over the next few days. Image source US Navy.)
The top image in this up and down comparison shows the US Navy’s ARCc model’s interpretation of sea ice concentration for July 6 of 2015. Note the extensive green regions showing a 40-50 percent sea ice concentration. It’s a huge swath of ice including large sections of the Chukchi, the Beaufort the ESS, the Laptev, as well as remaining ice in the Kara Sea, and Baffin and Hudson Bay. Now watch what happens to those large sections of lower concentration ice from July 7 to July 10 in the ARCc model 30 day history and forecast summary. Almost all that green is wiped off the map. It’s like losing about 1 million square kilometers of extent and 600,000 kilometers of area in just 72 hours. Or about 10,000 square kilometers of ice per hour. A precipitous fall that would mark an extraordinary and likely unprecedented rate of loss should it emerge as the Navy model predicts.
But you know what they say about models — no model is perfect and every model ends up wrong in some manner or another. So the question here is — how likely is it that the Navy models could be correct or incorrect this time?
To try and tease this answer out we could also look at other sea ice concentration maps. Notably all the major ones including Cryosphere Today, Uni Bremen, and NSIDC currently show sea ice looking either thin or very thin. Specifically, Uni Bremen has shown some amazing contrast over the past 48 hours:
(AMSR2 model analysis of sea ice surface state shows very rapid thinning in the Beaufort and Chukchi Seas during the past 24 hours. Image source: Uni Bremen)
The left image in the above comparison is from the AMSR2 model analysis for Arctic sea ice concentration on July 5. The right image is the same analysis but for July 6. Note the substantial change in the sea ice concentration for the Beaufort and Chukchi seas over just one day. A change that is consistent with the pulse of warm air and water riding up through the Eastern Pacific and through Alaska, the Bering and the Chukchi. Another holy crap moment, and not at all of the good variety. To say the least, a similar response north of Greenland and the CAA would be devastating.
Moving away from models and back to observations we find that from the satellite vantage the entire Arctic Ocean displays an ice pack in various shades of azure. By color analysis alone we can readily see that the 2015 ice (July 6 MODIS image) is far more melt pond embedded than 2014 or 2013. 2012 is a tough comparison due to NASA-MODIS’s format change from that year. But the widespread melt ponding alone hints at a reduced resiliency for the ice when compared with recent years.
(Arctic sea ice turns blue color characteristic of widespread proliferation of melt ponds on July 6. Also note very thin and diffuse sea ice in the Beaufort and Chukchi. Image source: LANCE-MODIS.)
Turning to the Chukchi and Beaufort, we see a visible confirmation of the weakness indicated in the US Navy and Uni Bremen models. Beneath the smoldering outflow of the Alaskan fires we can plainly see the decayed state of ice. The floes greatly disassociated with widening gaps appearing between diminishing ice clusters.
As satellite gives us an overall view of the Arctic from above, local observations can help provide a sense of the sea ice state at the surface. During recent years, cameras mounted on buoys throughout the Arctic have provided us with a first-hand account of the story of Northern Hemisphere sea ice decline. And during recent days almost every camera-based buoy has shown an extensive expansion of melt ponds and open water. (Extensive melt ponding extends as far north as the Pole).
In the swiftly thinning ice pack of the Beaufort even the contrast of a single day can be quite stark.
(Warm storm kicks up under the gradient imposed by a building heat dome of the Arctic. Top and bottom frame provides a stark tale of impacts in just one 24-hour period. Image source: USIABP.)
In the above top-bottom comparison of RACS#2 ice buoy photos we find that wide but placid areas of sunlit open water in the Beaufort Sea on July 6th (top frame) have rapidly transformed to wind-driven 1-2 foot waves whipped up by 15-25 mile per hour winds on July 7th (bottom frame) in association with a tightening gradient around the strengthening high pressure in the Central Arctic. Waves of this kind can deliver a significant amount of melt forcing to the ice — mixing cooler surface waters with warmer waters below as well as rocking through the ice floes with a rain of incessant, ice-breaking blows.
Conditions in Context: Rapid Melt Likely On the Way
Increasing model agreement indicating rapid sea ice melt, observations of sea ice weakness via satellite and buoy based systems throughout the Arctic, and predictions of a substantial Arctic heatwave all point toward a high and rising risk of rapid sea ice melt. Larger global trends, particularly heat transport from the Equatorial Pacific all the way to the northern Polar zone through the mechanisms of El Nino, human based greenhouse gas heat forcing, and the associated Ridiculously Resilient Ridge, heighten this risk even further. Finally, a wide array of observations indicate that such rapid melt is already starting to set in. Given this increasing agreement and confluence, it appears that the late June ice dispersal is likely over and that serious trouble for Arctic sea ice has now set in and will remain in play for at least the next seven days.
The Arctic Sea Ice Blog
The Polar Science Center
Hat Tip to Neven
Hat Tip to Frivolous
Hat Tip to Jim Hunt
Hat Tip to Climate Hawk