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.
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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.
July 28th 2012
I'm basically going to say the same thing as I did in the last ASI update: Weather patterns haven't been conducive to sea ice decrease, trend lines on graphs should be stalling, but they don't. As I've shown in yesterday's blog post comparing this year's weather patterns in June and July with previous record years, the decrease should have slowed down significantly like it did in 2010 and 2011, but it didn't. The 2012 SIE trend line shouldn't follow 2007 so closely, but it does. The 2012 SIA trend line shouldn't lead, but it does.
Now air and sea surface temperatures are higher than in previous years, but does that explain all of it? Personally, I don't think so. I think ice thickness is playing a big part in all of this. One of the conclusions I found most important last year, was that, yes, the weather is still dominant and determines whether a melting season will see a new minimum record or not, but only as much as ice thickness will allow it. There comes a point when large parts of the ice pack become so thin that it doesn't matter what the weather does. Sure, ideal conditions will cause a nosedive, but the train keeps chugging along, even when the weather isn't so great for melt, transport and compaction.
I believed I saw that in September 2011. I believe I'm seeing it now too,
4-6 weeks earlier. Maybe my eyes deceive me.
Sea Ice Extent (SIE)
In the last ASI update I was wondering whether the 2012 trend line
on the IJIS SIE graph would veer off to the right towards big staller 2010:
But it didn't. Especially in the last couple of days the 2012 trend line has decided to track new leader 2007, after following 2011, which had a brake put on its decline in mid-July. 2007 had a very strong first week in August, so it will be interesting to see whether 2012 can keep up or not.
The current difference between 2012 and other years (without the unrealistic last data point that gets revised upwards) is as follows:
- 2005: -593K (-83,709)
- 2006: -608K (-70,025)
- 2007: +198K (-98,608)
- 2008: -683K (-81,260)
- 2009: -371K (-92,127)
- 2010: -376K (-62,601)
- 2011: +90K (-83,473)
Between brackets is the average daily SIE decrease for the month of July. 2012's average daily SIE decrease for July currently is -87,101 km2 per day, which is quite a bit less than 10 days ago, but given the circumstances quite high. One would have expected it be more like 2010's average of -63K, but it's actually third highest.
Sea Ice Area (SIA)
Despite a couple of slow days in the past week, the situation on the Cryosphere Today SIA graph is basically the same:
Here we see the difference between area and extent at work. The slowdowns in 2010 and 2011 are less apparent here because of melt ponds and holes within the ice pack. This year there are a lot of holes on the Pacific side of the Arctic, these get counted for SIA, and so the 2012 trend line is still leading, and has been for almost a month now. Despite today's uptick I think 2012 will stay in the lead until the end of the month.
As we saw in this blog post, the CT SIA anomaly graph broke through the 2 million km2 barrier earlier than ever this year. It has shot back to 1.8 million, but given the fact that the long-term average decline is going to slow down, I wouldn't be surprised if it dips below 2 million some more before the period of re-freeze:
The current difference between 2012 and the other years is as follows:
- 2005: -857K (-76,120)
- 2006: -939K (-77,397)
- 2007: -218K (-91,629)
- 2008: -797K (-89,552)
- 2009: -867K (-99,165)
- 2010: -465K (-73,502)
- 2011: -111K (-91,469)
Between brackets is the average daily area decrease for the month of July. 2012's average daily area decrease for July is currently -86,335 square km per day. That's a big drop compared to two weeks ago (-105K), but still a lot higher than 2010, the year that also had anti-melt weather patterns in July.
Cryosphere Today area per IJIS extent (CAPIE)
CAPIE has been low, supporting the satellite images showing holes in the ice pack. These holes get counted for sea ice area, but not for sea ice extent, so if you divide the one by the other, you get a CAPIE or compactness percentage that tells you something about how patchy or Swiss-cheesy the ice pack is compared to previous years. Here's the graph:
With extent going down a bit faster in the last couple of days, and area going slower, CAPIE has gone up a bit again, but it's still really, really low for the time of year.
Percentages for July the 26th:
- 2005: 69.70%
- 2006: 71.04%
- 2007: 68.56%
- 2008: 68.64%
- 2009: 72.27%
- 2010: 66.78%
- 2011: 66.09%
- 2012: 63.44%
Regional SIE and SIA
Regional graph of the week:
I'm guessing this graph will be Regional graph of the week in more updates to come, as this is one of the few regions left that still have ice in them, together with the East Siberian Sea, Canadian Archipelago and Greenland Sea (where there's always ice because of transport from the Arctic Basin). In fact, the Arctic Basin is the biggest and most important region of all. This is where we expect the last of the ice to be, by the time the Arctic is coming close to becoming ice-free.
The trend line on the Arctic Basin SIA graph has dipped below 3 million km2, a recurring feature since 2007. Judging by this MASIE extent graph it seems to be going down faster than other years, which is hardly surprising with those holes showing up all over the place:
Most of the regions on the Regional Graphs page are practically empty of ice. The nosedive I expected on the East Siberian Sea SIA graph came about, and the Canadian Archipelago (where a lot of ice is melting in place, instead of being transported to warmer waters) is going down hard as well.
Sea Level Pressure
As usual I start with an animation of SLP images from the Danish Meteorological Institute to see what has happened in the past two weeks:
The lows dominating the Arctic, churning up and diverging that ice for the first 10 days since the last ASI update, can clearly be seen. Much of the transport towards Fram Strait was cut off, but at the same time those lows didn't move over the Canadian Archipelago either, so these effects perhaps cancelled each other out. Towards the end of the animation we see a weak high taking over and then moving in the direction of Canada. Basically things are at a standstill right now, due to a lack of intensity of both high- and low-pressure systems.
Maybe the weather forecast by the the ECMWF forecast model can tell us whether the weather will stay like this:
I would say it does seem like it will stay like this. Highs remain dominant on the American side of the Arctic, lows on the Siberian side, but I don't see anything intense that either spurs or slows the decline. For a fast decrease you need a strong high in the 1025-1035 hPa range, preferably over the Beaufort Sea. Or a nice cyclone in the 985-995 hPa range to stir things up and cause some of that flash melting that we love so much on the ASI blog because it looks so awesome.
Actually, we have been seeing some flash melting already, without that cyclone, but more on that some other time.
A bit more yellow and green air temperature anomalies in Siberia, a bit less in Alaska, northern Canada and Greenland, compared to two weeks ago:
When it comes to sea surface temperature anomalies (as calculated by DMI), things look again much worse than the image I posted two weeks ago for the previous ASI update:
There's significantly more red in the Laptev Sea, the red in the Kara and Barentsz Seas grew and intensified some more, and it's growing in the Beaufort Sea as well. Luckily, it seems to have cooled down a bit in the Chuckchi Sea and Bering Strait.
I'm getting increasingly worried about this. 4-5 °C warmer than on average in so many parts of the Arctic. I wonder what that will bring come September and October. If it stays like this, of course.
With ice that doesn't seem to care what the weather does and warm temperatures in many places above and below the ice, it's no wonder that SIE and SIA keep decreasing steadily. This melting season doesn't resemble 2007 in any way really, but 2012 is keeping up with the tempo easily. The longer the weather stays like this, the stronger the evidence becomes that the ice is thinner than it has been for a long, long time. If it doesn't stay like this and weather patterns start to move towards something that made 2007 so formidable, we will need a word that surpasses 'formidable'.
The weather is neither fish nor flesh right now, but the ice pack keeps getting smaller, from within and without. We will know more in two weeks.