During the melting season I'm writing (bi-)weekly updates on the current situation with regards to Arctic sea ice (ASI). Central to these updates are the daily IJIS sea ice extent (SIE) and Cryosphere Today sea ice area (SIA) numbers, which I compare to data from the 2005-2011 period (NSIDC has a good explanation of sea ice extent and area in their FAQ). I also look at other things like regional sea ice area, compactness, temperature and weather forecasts, anything that can be of particular interest.
Check out the Arctic Sea Ice Graphs website
for daily updated graphs, maps and live webcam images.
* There are still two weeks left to vote on the polls in the right hand bar.
One is for Cryosphere Today minimum daily sea ice area, the other for NSIDC minimum monthly sea ice extent (the one that is used for the SEARCH SIO projections). More info in this blog post.
June 15th 2012
When even odd man out Arctic ROOS - popular in certain quarters during certain seasons - says that 2012 currently has the lowest sea ice extent and area, then you know we're talking business. Since the last ASI update things started out slow at first, but then trend lines dropped off a cliff, on some graphs even approaching vertical conditions, century breaks everywhere you look. Practically all graphs are in agreement, except for one.
So what is causing the Arctic to scream extra loud (just in case somebody out there is still not hearing it)? There are two obvious reasons. First of all, the easy ice is going. All that extra ice that gave rise to the late and relatively high maximum, was wafer-thin. The second reason is that prolonged clear skies, especially over the Beaufort Sea, has caused a lot of melt ponds to form. These cause satellite sensors to see open water where there actually is none.
This 'goodbye, easy ice, hello, melt ponds' theory explains a lot, but I don't think it tells the whole story. There are other factors as well. Either way, it's one hell of a start to the melting season. But will it last?
Sea Ice Extent (SIE)
So if even the Arctic ROOS graphs indicate that 2012 has the smallest ice cover for this time of year, which graph could possibly be disagreeing? Why, it's our beloved IJIS SIE graph that hasn't quite come around yet:
It's getting there, but it still has 2012 in third position. Maybe this is because of the switch from AMSR-E to WindSat, I don't know, and it doesn't really matter either in this phase of the melting season. Nevertheless, 2012 had the highest daily SIE decrease for the last 9 days, a series including 6 century breaks.
The current difference between 2012 and other years (without the unrealistic last data point that gets revised upwards) is as follows:
- 2005: -373K (-57,531)
- 2006: -217K (-59,609)
- 2007: -475K (-63,328)
- 2008: -489K (-58,500)
- 2009: -651K (-55,938)
- 2010: +24K (-74,120)
- 2011: +47K (-66,010)
Between brackets is the average daily SIE decrease for the month of June. 2012's average daily SIE decrease for June is currently -87,344 km2 per day. It's almost as if July has already started.
Sea Ice Area (SIA)
Fasten your seat belts for this one. The Cryosphere Today SIA graph has the 2012 trend line going through the basement, leaving all the other years in dust and debris:
7 century breaks in a row (of which two double centuries), and counting. Amazing stuff. I mean, look at that graph.Of course, SIA anomaly is also showing something we have not yet seen before around this time of year:The current difference between 2012 and the other years is as follows:
- 2005: -1,178K (-93,233)
- 2006: -570K (-88,414)
- 2007: -525K (-101,301)
- 2008: -674K (-86,647)
- 2009: -1,181K (-86,332)
- 2010: -522K (-105,310)
- 2011: -549K (-101,230)
Between brackets is the average daily area decrease for the month of June. We're halfway through the month and 2012's average daily area decrease for June is currently -117,737 suare km per day. This is obviously the SIA's month of mega-melt (it's July for SIE).
Regional SIE and SIA
Regional graph of the week:
Sea ice area in the Beaufort Sea has taken a second nosedive and is very low for the time of year (also see the MASIE graph for this region on the regional graphs page). This has come as a great surprise, at least to me. Like I've written ever since the 2011/2012 Winter Analysis post, I was under the impression that, whereas the Siberian and Atlantic side of the Arctic looked pretty vulnerable (confirmed now), the ice on the Pacific and Canadian side of the Arctic had grown quite a bit thicker because of low temperatures and winds pushing the ice across from the Arctic Basin.
This seems not to be the case for the Beaufort Sea, as corroborated by data from the IceBridge mission and of course satellite images. A huge polynya has opened up due to a persistent high-pressure system over the area, with the Sun beating down on the sorry looking ice floes. Remember, we are approaching the Summer Solstice, which means there is a huge amount of insolation there, more than anywhere on the planet (edit: almost as much as in the Sahara).
In its latest monthly analysis the NSIDC also drew attention to the situation in the Beaufort Sea:
Although ice extent has remained high in the Bering Sea, open water areas have developed in parts of the Arctic Ocean, notably along the coasts of the Beaufort and Laptev seas. These openings are largely driven by winds pushing the ice away from fast ice, ice that is attached to the coast and that does not move with the winds. That the open water areas have not refrozen points to the relatively warm conditions over the Arctic, particularly in the Beaufort Sea.
The ice cover in the southern Beaufort Sea is also substantially broken up, with many individual ice floes instead of a consolidated pack. This makes the ice in this region vulnerable to enhanced melt during summer, as the sun rises higher in the sky and the dark open water areas between the floes readily absorb solar energy.
But of course, this isn't the only reason SIE and SIA have been dropping like rocks. The easy ice vanishing from the Bering Sea (last week's regional graph of the week), melt in Hudson Bay getting underway, and the carnage in the Siberian regions also have a lot to do with the big decreases.
Cryosphere Today area per IJIS extent (CAPIE)
With IJIS still wavering a bit, and CT SIA going down like crazy, we can all guess what the effect on the CAPIE graph has been:
This is one of the indications that there is quite a bit of melt ponding going on, just like in sunny 2007. All of these melt ponds get counted as open water for sea ice area, but not for sea ice extent where there is a threshold of 15% in a given grid cell. There have to be a lot of big melt ponds in a grid cell for it to be counted as open water. For this reason SIA goes down faster than SIE, and that's why the percentage drops. The fact that it drops so much more than other years, looks to me like a confirmation of melt ponding.
Sea Level Pressure
The Danish Meteorological Institute has solved its technical issues and so their excellent daily updated maps are online again.Let's have a look at what happened in the last two weeks:
There we have our culprit. That big yellow, orange and then red high-pressure system that positioned itself over the Beaufort Sea, intensified and then stayed there for a while, has caused open skies on the one hand, and also blew open that large polynya off the Canadian coast and caused the Beaufort Gyre to start churning that ice towards the Central Arctic.
However, towards the end of the animation we see the yellow disappear and a big blue low-pressure system forming over the Canadian Archipelago. This was predicted by the ECMWF weather forecasting system, so let's have a look at the 6-day panel to see what's next in store:
It looks like we're going to see the exact opposite conditions in the coming week, with that low staying put over the Beaufort Sea and bringing the Beaufort Gyre to a halt. According to melting-season-rules this should slow down SIE and SIA decreases considerably, but at the same time I can't help but wonder what those cyclonic winds are going to do the ice pack. Never mind the fact there is a serious high forming over the Siberian regions, right around the time of the Summer Solstice. Open water + 24 hr Sun = mucho heat accumulation.
It's still anomalously warm over Siberia, and it will probaby get warmer with those forecasted highs. The rest of the Arctic doesn't look very warm right now (two weeks ago Hudson Bay and the Canadian Archipelago looked a tad warmer):
The big orange blotch of warm SSTs that we saw in the Barentsz Sea two weeks ago has subsided a bit, but now we see red spots all over the Arctic, in Baffin Bay, in polynyas, even in Bering Strait:
That red can start to fade from one day to the next, but other SST graphs on the Arctic Sea Ice Graphs website show it too. We'll have to keep an eye on that, as it will play a determining role in the second part of the melting season.
The easy ice has almost melted out, but at the same time polynyas on both sides of the Arctic are getting bigger, with the Kara and Laptev Seas losing ice at record speed. Add to that the formation of melt ponds on the ice in the Beaufort Sea, and it's no wonder trend lines have been plummeting every which way you look.
The question now is: Will the conditions that were so conducive to melting have an inertia-like effect on the SIE and SIA numbers? And what is that big low going to do? Will it tear up the ice pack so we get to see the holes we did in the 2010 melting season? And how about those highs over the Siberian coast during Summer Solstice?
A lot of questions. Answers coming soon.