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.
July 15th 2012
Two weeks have passed since the last ASI update. At the time the weather forecast for the Arctic showed things that pointed to a (possibly big) nosedive on sea ice extent and area charts. The forecast became even worse, showing a very big, very strong high-pressure area over the Beaufort Sea and low- pressure systems on the Siberian side of the Arctic. In other words, a hefty Dipole Anomaly, that we saw so much of in 2007.
But none of it came about. The weather forecast completely changed its tune and instead was showing a low-pressure area taking over things. Which did come about. So the nosedive didn't really live up to its weather forecast potential, and I was expecting a lull, a stalling, a levelling off of trends on graphs, but this hasn't really come about either! In the end nothing much has changed when it comes to the graphs in the past two weeks.
If the weather forecast had come about, 2012 would have undoubtedly taken a big lead, but as we say in Dutch: If my aunt had had a dick, she'd be my uncle! Instead, 2012 keeps steadily ploughing towards the minimum (two months from now), still battling it out with the big boys, apparently not much perturbed by atmospheric patterns that brought a stop to the 2010 and 2011 marches for melting season glory. Although that stop could still be coming about in the next week.
I hope I can shed some light on the how, why, and whence from here, but sometimes I feel as if all I've learned in the past two years has already turned obsolete.
Sea Ice Extent (SIE)
We can clearly see how 2010 levelled off when the weather switched at the beginning of the month. The same thing happened to 2011 when the weather switched halfway through the month. And maybe we are seeing the start of a similar situation for this year, now that the string of century breaks has been followed by two daily decreases of just 58 and 57K km2.
The current difference between 2012 and other years (without the unrealistic last data point that gets revised upwards) is as follows:
- 2005: -761K (-83,709)
- 2006: -354K (-70,025)
- 2007: +1K (-98,608)
- 2008: -816K (-81,260)
- 2009: -692K (-92,127)
- 2010: -305K (-62,601)
- 2011: +261K (-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 -97,020 km2 per day, just a tad lower than 2007's daily rate.
Sea Ice Area (SIA)
The Cryosphere Today SIA graph also surprised me a bit with another century break streak in the past couple of days, noting the second highest daily decrease of the year at 240K. This has had consequences:
The 2012 trend line took a bit of a nosedive, despite weather conditions that on the look of it aren't conducive to big decreases. It could be because of the holes in the ice pack that keep popping up here and there, or new melt ponds forming. Either way, after the CT SIA anomaly graph went up again from the 1.905 million square km of two weeks ago, it has dropped back to 1.938 million square km, so we're still very close to the minus 2 million square km anomaly mark:
The current difference between 2012 and the other years is as follows:
- 2005: -853K (-76,120)
- 2006: -698K (-77,397)
- 2007: -436K (-91,629)
- 2008: -902K (-89,552)
- 2009: -1,123K (-99,165)
- 2010: -549K (-73,502)
- 2011: -480K (-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 -104,821 square km per day. That's pretty high for this month, and one would expect it to come down in the coming two weeks.
Cryosphere Today area per IJIS extent (CAPIE)
Like I wrote above, this could be caused by holes in the ice pack that get counted for area, but not for extent. Or it could be some more melt ponding throwing off satellite sensors, to which SIA is more sensitive than SIE. And it could be due to IJIS switching to WindSat, after the demise of AMSR-E. Probably a bit of everything, but I think the first reason plays the biggest part, considering low sea ice concentration on the Pacific side of the Arctic.
Either way, the difference is marked:
- 2005: 73.06%
- 2006: 76.56%
- 2007: 72.15%
- 2008: 70.72%
- 2009: 74.10%
- 2010: 71.32%
- 2011: 75.01%
- 2012: 66.94%
Regional SIE and SIA
Regional graph of the week:This is the most important region after the Arctic Basin, holding a rather large amount of sea ice compared to other regions adjacent to the Arctic Basin, and melting out as the last of those regions (Greenland Sea doesn't melt out because of ice transport through Fram Strait). The reason I chose this region as regional graph of the week, is that those lows that are currently dominating the Arctic (more on that below), are causing winds that blow the sea ice away from the shores of the East Siberian Sea. Not that this ice looks particularly strong; it looks mushy and grey. Those winds will speed up the opening of the final stretch of the Northern Sea Route. I've got a hunch that we will see the trend line on this graph take a nosedive in the coming 10 days.
Most of the regions of the Regional Graphs page are close to melting out completely, except for the Chukchi Sea (see blog post). Pretty soon it will all be down to the Arctic Basin, the East Siberian Sea and the Greenland Sea. If you want to compare regions with how they looked in previous years, I advise you to make use of the Concentration Maps page on the ASI Graphs page.
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:
During the first week of July we see that high coming in (yellow colour) from the American side of the Arctic and spreading out all over the Arctic Basin. But despite the weather forecast this high never really intensified. There aren't many isobars either, which is a sign that the pressure gradient didn't lead to strong winds. So basically all this high did was provide cloudless skies for some extra insolation.
We do get to see more isobars during the second week of July when a low takes over. And because that low stays in the center of the Arctic, but doesn't move over the Canadian Archipelago, those isobars are ideally placed for winds to push the ice out of Fram Strait. Which they did a fair bit. At the same time the low-pressure system pushed ice away from the Siberian coast - which has started to show up on sea ice concentration maps - and pulled in warm air (and smoke!) from Siberia. This could be the reason that we didn't see that levelling off on SIE and SIA graphs. Despite a dominating low, there might enough movement for a relatively big ice decrease to continue.
Either the situation stays like this, or a high takes over again, or that low is going to move some more and cause that stalling like we saw in 2010 and 2011. Here's the panel of the ECMWF weather forecast for the coming 6 days:
It seems things are going to stay the way they are in the coming days, with lows dominating, but not moving into North America. Isobars still point towards ice transport through Fram Strait and further clearing of the Siberian coast. We will probably keep seeing holes in the ice through holes in the clouds on satellite images. I'm not really sure what the effect on SIE and SIA decrease will be, but my gut echoes the title of this ASI update: steady as she goes.
Either that or a type of lull we saw from July to mid-August 2010, mid-July to August 2011, and mid-June to July 2012.
Still nothing spectacular going on with regards to air temperatures, that's to say no oranges and reds we're so accustomed to seeing during winter, just the regular 5-10 degrees warmer than normal:
Things are relatively warm over Greenland, as we saw in yesterday's blog post. The Canadian Archipelago is warm, which will probably translate into effects that will lead to another ice-free Northwest Passage. And we see anomalous warmth over eastern Siberia, that might get sucked over the ice in the East Siberian Sea by those dominating lows.
With sea surface temperatures the story is quite different. Again, things look much worse than the image I posted two weeks ago for the previous ASI update:
We now have red in the polynya in the Laptev Sea, the red intensified and grew in the polynya in the Beaufort Sea, all of the orange went out of Baffin Bay, there's red and orange showing up at the edge of the ice in the Greenland Sea and between Svalbard and Franz Josef Land, and even the waters in the Bering Strait seem to warm up. Only the anomalies in the Kara and Barentsz Seas more or less look the same. Ain't that a relief!
Things look a bit like they did in 2010 and 2011 when the rapid decline came to a grinding halt, but so far trend lines continue to go down steadily. This could have something to do with the position of low-pressure areas that refuse to replace the high-pressure areas on the American side of the Arctic. Or it could have to do with the fact that there is enough weak ice left for weather patterns not to matter as much. As we saw at the end of this update SST anomalies are all over the place, attacking the ice from all sides.
I'm not sure what to expect in the coming two weeks. We're going to have lows continuing their domination over the Arctic for a while longer. They might slow things down, or they might not. But once weather patterns switch to something that looks and smells like a Dipole Anomaly, 2012 will be a serious contender for the minimum record championship. It's still very low for the time of year, and the ice doesn't look so great in many places.
We will look and then see.