NORTH POLE UNDER WATER
by Neven / July 08, 2013
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 Cryosphere Today sea ice area (SIA) and IJIS sea ice extent (SIE) numbers, which I compare to data from the 2005-2012 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 of particular interest.
July 8th 2013
Here’s another rehearsal for when I grow up and make good videos with a title roll and background music and everything. By the way, I make a big mistake as I go along. Can you hear what it is?
This update should actually be called ‘Bye bye, Beaufort and Chukchi’, but it doesn’t sound as good. As announced in the previous ASI update the trend lines on various graphs have started to drop precipitously, with thin ice on the fringes (Hudson, Baffin, Kara) disappearing fast. Despite a slow start unlike any other in recent years, which I described in this recent blog post, 2013 is still hanging in there, slowly leaving the less aggressive melting seasons behind and moving towards the record years of 2007, 2011 and 2012. The question now is how things will proceed, as the amount of easy-to-melt ice is starting to run out. Even though this year’s ice pack consists of a record amount of first-year ice, the weather still plays an important role. The interesting thing about last year’s melting season was that decrease rates slowed down somewhat when the weather turned bad in July, but didn’t stall, like they did in previous years under similar circumstances. I think the same will go for this year as well, also because area/extent numbers are quite bit higher, and thus still a lot of melting potential. But there’s no telling what could happen if the weather is very conducive to melting/ compacting/transport for a week or two, and it looks like we’re having some of that up ahead.
Sea ice area (SIA)
July is a month where trend lines on the Cryosphere Today sea ice area graph get divided in the two camps of winners and losers, with 2010 moving from one to the other. Because of steady, substantial drops since the last week of June the 2013 trend line has slowly started to move from one camp to the other. Here’s the graph based on the latest data:
At one point 2013 was trailing 2012 by an incredible 1.1 million km2, but the difference has been reduced to 781K km2. When it comes to century breaks, there have been just as many this melting season as last year’s: 32 (with 2010 in third spot with 31 CBs). If 2013 doesn’t falter, it could come a bit closer still until the month is done. Here’s the link to my updated CT SIA spreadsheet. The SIA anomaly has been hovering around the -1 million km2 mark:
Sea ice extent (SIE)
On July 2nd IJIS reported a drop of 208K km2, which is the largest daily drop for July in the 2005-2013 period. Starting the month with 6 century breaks in 7 days, 2013 has finally left that last spot and could very well be in at least 4th position by the end of the month if some of this momentum is maintained. The 9 million km2 mark has also been passed today:
Here’s the link to my updated IJIS SIE spreadsheet.
Cryosphere Today area per IJIS extent (CAPIE)
Because extent has dropped just as fast or even slightly faster than area,
CAPIE has been decreasing much slower than in previous years:
Just a reminder of what CAPIE tells us:
When trying to determine how much sea ice extent (SIE) or sea ice area (SIA) the ice pack covers, scientists divide the Arctic up into grid cells. They then look at what the sea ice concentration is within those grid cells. When the concentration is above the 15% threshold, the whole grid cell is counted as 100% ice-covered for SIE. However, for SIA it’s the percentage that is counted, which can be anything between 15% and 100%. For both metrics a sea ice concentration below 15% is counted as zero. This means that SIA will always be lower than SIE, as for instance holes within the ice pack get counted for area, but not for extent (unless they are really big and cover a whole grid cell, or several grid cells). When we divide Cryosphere Today SIA data by IJIS SIE data, we thus get a percentage that tells us something about how much divergence (in other words: holes) there are within the ice pack when the percentage is low, or how much compaction there is when the percentage is high (ie the difference between SIE and SIA is smaller). See this blog post from 2010 to understand how we got to develop this crude metric and have been using it ever since.
At first I was baffled that CAPIE for this year has been so high so far, because the recent persistent cyclone – or PAC-2013 – caused a lot of divergence within the ice pack, showing holes that haven’t been witnessed during the satellite era, at least not that early in the melting season. But the answer was rather simple: because of the generally cold conditions this melting season, there has been less melt pond formation. Now, melt ponds can fool the satellite sensors into thinking there is open water where there isn’t, which gets recorded for SIA and not for SIE, causing SIA to drop faster than SIE, and thus CAPIE to go lower as well. This, by the way, is the main reason why scientists prefer SIE over SIA as a measurement, but most of the amateurs here and elsewhere prefer SIA, because melt ponds eventually get drained or frozen over. That leaves the open holes, a more and more common feature of the Arctic sea ice pack, which are better reflected better in SIA data. A lot of text, but I want to make sure that people understand what CAPIE is: a crude, but useful tool to determine how compact or not the ice pack is, compared to previous years.
Here’s the link to my updated CAPIE spreadsheet.
Regional SIE and SIA
Regional graph of the week, taken from the Regional Graphs page:
Arctic sea ice virtuoso Wipneus has made me a map (based on data by Uni Hamburg, see blog post here) showing the differences that have taken place since the previous ASI update. Red = ice two weeks ago, open water now; blue the other way around:
Now the MASIE product disagrees with me, but I’m under the subjective impression that there is very, very little ice off the east coast of Greenland. I think the Uni Bremen sea ice concentration comparison page for July 7th on the ASIG (Arctic sea ice graphs page) is showing the same. Except for perhaps 2009, no year in the 2006-2013 period has had as much open water in this particular region. The reason for this is probably two-fold: warm sea surface temperatures (see further below), and either less transport of ice from the Arctic Basin through Fram Strait, or transport of thinner ice that melts out easier. It’s difficult to tell what the exact situation is down on the ground, because clouds have been in the way for quite some time now, maybe fooling sensors into thinking there is ice, where there isn’t. Last week one could peek just a bit through the clouds and that’s when I noticed how dispersed the relatively small amount of ice floes were (image courtesy of Arcticio):
If the – now very blue – fast ice comes loose, SSTs remain high in the region, and transport is low or consists mostly of thin ice, there could be a lot of open water here in August. We’ll see what happens.
Sea Level Pressure (SLP)
It’s time for yet another animation of Danish Meteorological Institute SLP images for the last two weeks:
With PAC-2013 gone nothing out of the ordinary has been transpiring in the Arctic in the past two weeks. In fact, this is what I referred to as the ‘neither fish nor flesh’-setup of atmospheric patterns in my recent blog post comparing this year’s patterns with those of previous years, which is actually the set-up that is least conducive to melting/compaction/transport (MCT). It is also reflected in the AO Index, where a negative AO is a sign of high pressure areas dominating the Arctic (usually the best set-up for MCT) and a positive AO is a sign of lows dominating the Arctic (a slightly worse set-up for MCT, except when a Great Arctic Cyclone comes along):
Although the AO Index has been mostly neutral or slightly positive (cyclones dominating) since May 1st, the rate of ice loss has increased in the past week, mostly because of all that melting potential on the fringes coming to fruition. All bad starts come to an end. And that brings us to the most interesting of all graphs and maps, the 6-day weather forecast by the ECMWF model (click for a larger version):
This is the big one, this is the ideal set-up for large ice loss, this is the rationale behind this update’s subtitle (in case anyone was puzzled). It was in the works for a couple of days already, but the forecast needs to be consistent from day-to-day, and now it shows a huge high-pressure area over the Chukchi and Beaufort Seas. Especially the latter region is what separates 2012 and this year (see, again, the Uni Bremen sea ice concentration map for July 7th). Because of last year’s good start to the melting season with lots of clear skies over the Beaufort Sea, there was a lot of melt ponding there that was a prelude to the big crash in June and July. This year the ice was supposed to be thinner than ever, with hardly any multi-year ice to keep things together. I think most of us expected the retreat to be very fast this year, especially after the bigcracking event in February and March, but the Arctic is known for doing counterintuitive stuff, and thus the cracking event may actually have let a lot of heat escape that helped make the ice more sturdy. As it stands, the Beaufort region is still almost completely covered with sea ice. This might now change in the 7-14 days to come. One week at least of maximum insolation seems feasible, as ECMWF has 10 days of 1025-1030 hPa over the Chukchi, Beaufort and Central Arctic regions. The Chukchi looks especially vulnerable to lots of sunlight. To quote Frank Zappa: Here comes the ice pick in the forehead!
We’ve almost reached the midline of the bell on the DMI 80N temp graph, but air temperatures north of 80 degrees northern latitude still haven’t gone above average (only 2009 looks similar in the last 13 years):
Compared to two and a half weeks ago sea surface temperatures have gone down considerably in the Bering Strait, but up considerably in the Kara and Barentsz Seas. There’s some more orange in the Laptev Bite, and a hint of red on the Beaufort coast:
Still looks pretty benign compared to last year.
2013 has started to catch up, and although the easy ice has almost melted out on the fringes, some perfect weather in the coming 7-14 days is probably going to maintain the pace for a while longer. The Chukchi Sea will melt out, there might very well be a total crash in the Beaufort Sea as well, Nares Strait is about to open up, the ice in the Northwest Passage is about to break and melt in situ (just like last year), the Laptev Hole is getting bigger every day and could eventually connect to that huge region of low concentration slush, that extends from the middle of the ice pack all the way to Franz Josef Land. It looked for a while as if 2013 was out of the running and wouldn’t be able to rival last year’s record bonanza. That’s only logical after such a bad start to the melting season. But this year’s upcoming and first streak of weather that is super conducive to melt, compaction and transport might change all that. The next two to three weeks could be incredibly important in determining where this melting season is going to end up and this might teach us more about the million dollar questions: How far has the shift in the division of power between weather conditions and ice thickness/volume progressed? Is a slow first half of the melting season enough to cause a (temporary) plateau or even a recovery? Or doesn’t the ice give a damn?
by R. Gates / July 10, 2013
It’s been a while since we’ve looked at methane trends in the Arctic atmosphere (just a little under a year in fact). This important greenhouse gas has been on the rise over the past several decades, though that rise has not been nearly as steady as CO2. What’s worrisome to those who follow methane is the return to higher growth rates of the gas over the past few years. This chart shows the atmospheric measurement of methane at Point Barrow cover the last 2.5 years. First, the horizontal red bar shows the lowest boundary of the yearly methane measured a few weeks ago. Methane always hits a low annual concentration at Point Barrow around the middle of the year, usually in June as part the natural fluctuations. This year we saw the highest low point ever recorded. This is significant because it shows the underlying long-term growth rate. If you compare this year’s low point to last year’s, you get a sense of the upward turn in the atmospheric methane concentrations. At the top of this graphic in the large red circle are several “anomalous” readings that were recorded over Barrow last year just about the time that GAC-2012 was hitting. These are huge outliers, but because there were several of them occurring all about the same time, we can also assume they were valid data in the sense that it was really being recorded properly. In direct email discussions with staff at Barrow station at the time, they characterized these as “likely” local anthropogenic sources, i.e. outgassing from drilling rigs, etc. Note the word “likely”. These samples are sent back to a lab for analysis that can better describe the sources. My hunch, and again, this is only a hunch, is that GAC-2012 or simply the very low ice levels of last summer or some combination, may have brought up more methane and caused these very high anomalous readings. It is also important to note that all the data points in the graph that are orange have yet to be fully validated– though they are in the vast majority of cases.
Finally, in the small red circle is one the latest readings from Barrow. It continues to show the higher long-term upward trend is accelerating and also shows the remainder of 2013 should be interesting to watch, as it will likely show the strong growth rate of methane in the Arctic atmosphere. Though the level will oscillate up and down a bit between now and its annual peak in early 2014, we should monitor the rest of the summer Arctic melt season for the kinds of “anomalies” that we saw last year. I will especially look for a period of anomalously high levels should another large cyclone hit in August or even September when sea ice is at its lowest. The bottom line of all this is that methane levels remain an important metric to gauge both current and potential future changes in the Arctic climate, and the trends should be of great concern.
Addendum by Neven
Thanks go out to R. Gates for his update on methane. I’m taking the opportunity to draw attention to this effort to get methane levels back to 1250 ppb, much like the 350 movement is doing for CO2: 1250now.org
There is also a very cool interactive website that allows one to track methane in the atmosphere everywhere on the planet: Methane Tracker. The site is still in the pre-alpha phase, but when it’s finished, it’ll be announced here in a separate blog post.
Differences between MODIS data retrieved from the Terra and Aqua satellites
by Omar Cabrera / 7/3/2013
Terra’s and Aqua’s orbits will display different cloud covers for the same location, given its orbits. Terra crosses the equatorial line at approximately 10:30am, and Aqua crosses the equatorial line at 1:30pm. This means that either satellite may be the best one for a specific time and location, depending on your needs. I would suggest you to :
– If you’re studying an Aqua or Terra data layer that shows vector data, I would suggest to narrow down your search “Per via di levare” by checking both data layers, Aqua and Terra, for a timespan of at least three days, and then uncheck either one to see which data appears to be more complete, and then narrow the time span on the Google Earth plugin until it displays the data you’re looking for.
If you’re studying an Aqua or Terra data layer that shows images (either png or jpg) like the ones under “Corrected and Surface Reflectance”, the best approach is “Per via di porre”. Pick just one date, and check one of the satellites and then the other, and then select the one that has the clearest view for your purposes. If you’re visualizing methane using the “Individual Methane Layers” functionality and are attempting to view exact conditions for a given time, the best approach is to visit the websites that have their orbit tracks for every day, and pick the best time for the event you’re studying. Their links are included below:
Ice-free Arctic in two years heralds methane catastrophe – scientist
by Nafeez Ahmed / 24 July 2013
A new paper in the journal Nature argues that the release of a 50 Gigatonne (Gt) methane pulse from thawing Arctic permafrost could destabilise the climate system and trigger costs as high as the value of the entire world’s GDP. The East Siberian Arctic Shelf’s (ESAS) reservoir of methane gas hydrates could be released slowly over 50 years or “catastrophically fast” in a matter of decades – if not even one decade – the researchers said. Not everyone agrees that the paper’s scenario of a catastrophic and imminent methane release is plausible. Nasa’s Gavin Schmidt has previously argued that the danger of such a methane release is low, whereas scientists like Prof Tim Lenton from Exeter University who specialises in climate tipping points, says the process would takethousands if not tens of thousands of years, let alone a decade.
But do most models underestimate the problem? A new paper in Proceedings of the National Academy of Sciences (PNAS) projects that the Arctic will be ice free in September by around 2054-58. This, however, departs significantly from empirical observations of the rapid loss of Arctic summer sea ice which is heading for disappearance within two or three years according to Nature co-author and renowned Arctic expert Prof Peter Wadhams, head of the Polar ocean physics group at Cambridge University. If Prof Wadhams is correct in his forecast that the summer sea ice could be gone by 2015, then we might be closer to the tipping point than we realise. To get to the bottom of the scientific basis for the Nature paper’s scenarios, I interviewed Prof Wadhams. Here’s what he had to say:
Q: How long do we have before the Arctic summer sea ice disappears?
A: Given present trends in extent and thickness, the ice in September will be gone in a very short while, perhaps by 2015. In subsequent years, the ice-free window will widen, to 2-3 months, then 4-5 months etc, and the trends suggest that within 20 years time we may have six ice-free months per year.
Q: Why do the climate models not match empirical observations – and why is your estimate of the Arctic sea ice disappearance so different from most model projections?
A: The modellers did not pay sufficient regard to observations, especially of ice thickness. They considered certain physical processes in the model, then when the rate of retreat greatly outstripped the predictions of the model, they ignored the observations and stuck with the model. A very great physicist, Richard Feynmann, said that when a model comes up against measurements that contradict it, it is the measurements that must be preferred and the model must be abandoned or changed. Scientists who have a lot of their credibility bound up in a model are reluctant to do this. Then there are a number of key processes that can only be represented if the model has a very fine grid scale, such effects as the break-up of ice due to waves generated in the large areas of open water that we now have in summer; or the additional weakening of the ice by meltwater pools that melt their way right through the ice sheet. A modeller who represents all these fine scale processes is Wiselaw Maslowsky (Monterey) and his models agree with my empirical predictions.
Q: Our global emissions trajectory is already on track to breach 2C in coming decades. What does a 2C world imply for the Arctic melt and the potential for methane release?
A: We are already in a 2C world in terms of the heating potential of carbon dioxide that we have already put into the atmosphere. The heating will reach 2C before 2050 and will then go on to 3-4C globally by the end of the century. Even a 2C world involves the probable loss of Arctic sea ice for much of the year (and 4C for most of it), which will ensure maximum methane release from the exposed shallow seas of the continental shelves.
Q:What does the loss of the Arctic summer sea ice mean for the climate? How will this impact on society and the economy?
A: Our own model shows that the methane release from the ice retreat will add about 0.6C to global warming by 2040. Adding on the faster sea level rise, and trend towards greater extremes in weather (due to jet stream displacement) means increased risk of catastrophic floods in less developed countries and a decrease in food production at a time when world population is rapidly increasing.
Q: What is the link between permafrost melt, methane release and the loss of the Arctic sea ice? After 2015, if the Arctic becomes ice free in the summer, is there a heightened danger of methane release?
A: The loss of sea ice leads to seabed warming, which leads to offshore permafrost melt , which leads to methane release, which leads to enhanced warming, which leads to even more rapid uncovering of seabed. If a large release has not occurred by 2016 the danger will be continuously increasing. It is thought that at 2-3C of global warming, which means 6-8C of Arctic warming, methane release from permafrost on land will be greatly increased.
Q: Some people say that a catastrophic methane release over 10 years – your worst-case scenario – is a very low probability event and we don’t really need to worry about it. What’s your response to that?
A: Those who understand Arctic seabed geology and the oceanography of water column warming from ice retreat do not say that this is a low probability event. I think one should trust those who know about a subject rather than those who don’t. As far as I’m concerned, the experts in this area are the people who have been actively working on the seabed conditions in the East Siberian Sea in summer during the past few summers where the ice cover has disappeared and the water has warmed. The rapid disappearance of offshore permafrost through water heating is a unique phenomenon, so clearly no “expert” would have found a mechanism elsewhere to compare with this.