Gosh, we in North Florida only have about two weeks per year of 91F maximums. But we also get a couple weeks at 92, a couple at 95 and maybe a week at 100+ (13 weeks worth of 90+ is average, per the statisticians.) :)

3.15 M km^2 NSIDC mean September 2013 extent. (M = million, in case my mother is reading) I visualized a point on the graph Larry Hamilton posted based on the following: Extent will go down as I expect volume and area to continue to decline (despite PIOMAS virtually duplicating recent years in the current season). A lot of rotten ice and slush will be counted as ice. September mean extent will decrease only a little because leads or polynyas north of 80 or 85 N will freeze over quickly once the sun goes down, and there will be more high latitude open water than ever before at minimum extent. (I’m not sure how wide a lead or polynyas needs to be before being counted as water, but I think some will be big enough.) This northern most area will only be ice-free for a brief time; the water will not have much time to absorb solar radiation (nor mix with deeper water) that would delay re-freezing, and the month average will be rather larger than the minimum. September cyclones, however, would speed melting and delay refreezing. The southern areas of the Arctic will continue to melt when the northern most areas start to refreeze, but there won’t be much ice in southern areas. If PIOMAS volume is currently about the same as it was a year ago, and more area is covered by <2 meter thick ice, then >2 meter thick ice needs, on average, to be thicker than last year’s, and most of this (extent-wise) will stay around into another freezing season (whence some of it will be exported out the Fram). I expect average September Arctic ice extent to go below 1 M km^2 about two years after minimum ice area and volume crash below 1 M km^2 and 0.75 M km^3, respectively. Increased methane will cause the Siberian Arctic to melt faster; Mt. Cleveland’s eruption may slow down Canadian Arctic melting that would otherwise melt faster with all the relatively thinly iced leads (re Cracks of Doom). My mom always uses “M” for thousand (from Roman numerals). I hope Espen is using this nomenclature when he guesses “3,014.699 M km2” or, as a European, uses a comma for the decimal point.

I talked to some folks at a party a few weekends ago about Arctic sea ice projections (“Neven's cadre”) vs. models (“the professionals”). My wife twice, in the following few days, berated me for talking about what “nobody is interested.” In polite society, apparantly, climate change is in the same category as sex and religion. (She did allow that the geologist daughter of our host was possibly actually interested.) I regularly post short articles on a bulletin board in the hallway where I work (often from Grist or Climate Progress). The shelf-life of these articles seems to be much shorter than "free kittens" or "subs with free ice tea" flyers. Although it is a science-friendly environment with lots of engineers, biologists and geologists around, there are many outspoken Biblical creationists, too, who believe in "fire next time". Someday soon, I hope, these neighbors of mine (whom I count as friends) will realize that Anthropogenic Global Warming is that fire.

Thin Ice: the inside story of climate science "In recent years climate science has come under increasing attack, so geologist Simon Lamb took his camera to find out what is really going on from his climate science colleagues." Just the trailer is available now at http://thiniceclimate.org/ The full length will be available April 22-24 (NZ time) - Earth Day.

Sorry, Lodger, but I made no reference to, and implied nothing about, what had happened this past winter. I only reflected on the trend associated with the current wind map and forecast for the next few days for "thickest ice" (intending to mean >2 year old ice). In addition, a certain amount of the December 2 eastern bulge that is missing in your March 28 map moved westward to replace ice that is now in the Beaufort Sea. The only thing I wrote that would definitely put crow on my plate (yuck, I'm a vegetarian!) is if the ice just above Greenland and the Canadian Archipelago moves as fast as ice has been moving in the Beaufort Sea. I do appreciate your showing how much multiyear ice (at least 2 years old) north of Fram Strait has been moved this winter. Your map shows that there is now relatively little MYI in the area most likely to be exported during this melting season. As long as the Beaufort Gyre is supported by high pressure over the Arctic Basin, most of the remaining MYI will stay in the Arctic. The "goat's head", in my opinion, has roughly equal chances of getting exported or moving south, then west.

Projected ice movement, per the ARC ice speed & drift maps (on Daily Graphs page) have winds nudging much of the thickest ice westward - toward the Beaufort Sea - over the next 5 days. The recent cracking just north of Greenland and the Canadian Archipelago will allow the ice to actually move. It won't move 1/2 km/hr, but it'll move. There is hardly any fast ice left. (Well, it is now "fast" in a different way.) When I first started watching (several years ago) some of it seemed so robust! No more. This movement trend will lead to less thick ice going out the Fram. It will just melt in the Arctic Ocean over the next few summers. (Plenty of other ice will go south, probably keeping up with the historical volume of export through Fram Strait.)

Another great presentation, Jim! I noticed today that there is not a PIOMAS wikipedia article, although PIOMAS is mentioned in the article "Measurement of sea ice". I imagine someone at the Polar Science Center (PSC) could write one. The article on PSC's website answered all my questions about how the model works.

Jim, I like your graph "Arctic Sea Ice Volume - Annual Maximum and Loss, and Ice Remaining at Minimum" because it uses two sets of data to show what is happening. If extended, what do the two curves (Yearly ice max and Yearly ice loss) project for 2013 and beyond. (The curves' formulas would do.) And thanks, Neven, for digging in the trash!

Crandles, I'm curious about the Central Arctic Basin - how its sea ice volume growth/shrinking has been changing, per the PIOMAS model. Unless all that ice flushes out Fram Strait or is moved towards Siberia (to melt there), the "last stand" will be in the CAB. Thanks for all your work on this. That quote from Laxon, et. al. (2013) is a reminder that each data system we look at is useful for internal comparison purposes and not as absolutely correct numbers.

Way to write, Terry and sigmetnow! Here are some scriptural possibilities: You must provide for the redemption of the earth. (Lev. 25:24) The earth withers, ...for they have transgressed (Isaiah 24:4-5) You cannot serve both God and mammon. (Luke 16:13) Do not follow the crowd in doing wrong. (Exodus 23:2)

Whoops: I wrote about stacked FYI getting over 2 m think in Open Thread #1, which probably belongs here.

I wonder if some definitions and assumptions concerning first year ice (FYI) and multi-year ice (MYI) need to be revisited. (2nd year ice being separately identified is a different consideration.) It is easy to understand that Arctic sea ice less than about 2 (or 2.5) m thick in April is FYI. I'm not, however, certain what portion of ice over 2 m in April is MYI. I have repeatedly read that wind packs sea ice against the Greenland and Canadian Arctic coasts. Much or most of this packing is of relatively thin FYI, so some of the thick ice in April is composed of the same 'high' salt content ice as is FYI. Such young thick ice may, however, have similar surface texture to true MYI. I do not have any expertise as to how new thick ice will differ from true MYI in its response to the influences of wind, solar radiation, air temp, water temp, ocean currents, etc. I believe, however, that soon, most of the existing ice over 2 m thick in April could be melted (or transported out of the Arctic and melted), and the next April have about the same amount of similarly thick sea ice.

Very interesting map, Wipneus! You deserve to be proud. As idunno inquired, when (approximately) is the 10^6 km^2 area crossed, according to these 'cell' projections? As Tommi K noted, melted-out areas will surely accelerate neighboring ice-coverred areas, as areas next to open water are more prone to melt than are areas far from the melt edge, and much of the CAB has never been near ice-free sea.

Chris's graph showing Arctic sea ice area declining at a slower rate than is volume may explain something. Scientists who watch "only" area see Arctic sea ice lasting much longer (ice-free Arctic by "mid-century") than those who watch mostly volume (ice-free later "this decade"). I expect crandles is on the right path concerning ice: when it breaks up from wave action, pieces fall over, so that area declines more slowly than does volume. This happens at the ice edge more than in the middle of the ice pack, although we have seen much more sloppy ice soup these last two years. When most of the Arctic sea ice becomes an expanse of "slush puppy" melange in September, perhaps then new data points on Chris's graph will trend toward [0,0]. But I fear there might be only one or two years of such an environment before we have a functionally ice-free Arctic (< 10^6 km^2 area).

A plot of Area against Year has melting season data sets for each selected day-of-year (I used 5-day intervals) suggests a slope change in the late 1990s or earliest 2000s for the various data sets. The slope change is quite small early in the melt season (e.g. Day #150 has line and 2nd order polynomial best-fit curve that aren't far different from each other) to noticeably larger by Day #215. Day #250 (last day with near-continuous melt-season data over the satellite record) was graphed with all data, the last ten years of data, and the last five years of data. The best-fit lines for 10 years of data (actually 9 years of day #250 with one year’s day #247 – 2005’s min.) and 5 years of data are virtually collinear. Best-fit line and 2nd order polynomial curve for the entire Day #250 data set show that the data earlier than about 2003 isn't anything close to collinear with the last 10 years. Projecting Day #250’s last 10 years (or 5 years) line forward, 1 million sq. km. (“ice free”) will be reached in 2019 or 2020. These best-fit lines suggest 2013 will reach 2.35 M km^2 about on Day #250. Because of Arctic ice volume declines (or just because I’m pessimistic), I rather suspect an "ice-free" Arctic will be seen prior to 2019.

I’ve been playing with the CT area data at http://arctic.atmos.uiuc.edu/cryosphere/timeseries.anom.1979-2008, organizing it in different ways, having been inspired by a graph by Seke Rob. I plotted Melting Season Day-of-Year against First-Day-Below-X-million-Sq.-Km., with a data set (zig-zag quazi-linear line) for each year. The graph shows that melting (area reduction) is slowest at the beginning and at the end of the melt season, and fastest in between: third order polynomial best-fit curves approximate the data with R^2 values on the order of 0.99 (according to Excel). Visually, however, the minimum extent/last days of melt data points usually indicate slower melting than the curves would ‘predict’. Using linear projections of these data sets clearly do not provide a good basis for extrapolating phantom 1M sq. km. points, as I had done earlier this year from the data organized in a different way. I've never learned how to put a graph onto a web page, so cannot link to one here.

Wipneus and others, Thanks for keeping up the data and remarks in this thread, even if it does take several clicks and several scroll downs to reach it. Two days of increase - is that a trend? I daren't express an opinion!

There is a transition between "full melt" mode and "full freeze" mode. (For example, small northern ice-free areas freeze over while southern ice edges continue to melt.) Area increasing while extent continues to decrease is one way of noticing this. Volume decreasing while area increases would be another. Might Arctic MODIS show this, ever? Are there other indicators? Is there a graph showing this? I'm thinking, Delta Area vs. Delta Extent or something.) A year ago I postulated that the melting season would extend into earliest October because of all the warm water around. I was wrong. I've noticed a comment or two this year with that same prophecy. Has the environment changed to make this more likely? Or did I just have "bad luck" last year, or are a bunch of us overly pessimistic?

Seke Rob, That's an interesting alternative to "no step". I'm sure, however, it would be easily misunderstood or worse. I'm very happy to wait for the calm after the "Is this the minimum?" storm that is sure to arise after every reported increase (or rumor of an increase). (Remember the "Surely, THIS is the maximum" earlier this year?)

Seke Rob, Neven gave me the perfect "in" with his "What a loss" theme. What a loss it is on your "ASI Extent Max/Min Day & Days taken scaling 16-4M km2 marks" graph that all previous years show "No Step" when every year could show a "Last 10 days km2 Ave" (or 15 days - 1/2 mo. - if you prefer). We can calculate the current Step Day Ave for previous years, but it is not so obvious what the current rate was in previous years, especially early and late in the year. (And before max and after min, the 10 day average will just go positive.) There is a moderate consistency over the decades on how fast or slow ice melts on a particular week. As examples, the date of ASI max and min are remarkably stable, the first full 1M drop has usually taken a month or so, and the fewest number of days to drop 1M has generally occurred during the month around Day 190. I so appreciate this and other graphics you make available. I am in your debt! (If I ever get the time, I'll continue my exploration associated with that other graphic presentation of yours I like so much.)

Arctic volcanic eruptions do happen - see here - but do not melt sea ice. From this 2008 NYT article by Andrew Revkin (not my first choice of authors) I quote Jamie Morison (Univ of Washington): "It occurs to me that we have primary evidence that heat from the bottom is not reaching the ice. Temperature profiles from virtually everywhere in the Arctic Ocean display a maximum temperature at a depth from 200-400 [meters]. This is associated with the Atlantic Water entering the basin from the Norwegian Sea. Fundamental laws of physics require that below the depth of this maximum, the heat flux is downward. Very near the bottom temperatures have been found to increase with depth indicating a small upward heat flux from geothermal sources, which help to heat only the very deepest water."

I have the privilege of finding #4! I am happy, however, to have Anu's idea highlighted.

A month ago, both before and after the Kane Basin ice bridge collapsed, I reported ice moving in a gyre within the Kane Basin (southward on the west side). After the bridge broke, but while ice was basically blocked from exiting by a large floe temporarily caught in the Kane Basin gyre (at the Basin's mouth), I noticed (not reported because clouds prevented certainty) that ice was not particularly accumulating in the Kane Basin, and possibly melting in situ. I'm interested to hear that the Kane Basin gyre is part of a larger Nares Strait 'flowing both north and south' and others perceiving in situ melting. The 2012 Petermann Ice Island is slowly moving toward Baffin Bay (southward) on the Canadian (west) side of Nares Strait.

Besides CT's AB referenced above, this year CT's Barents Sea area anomaly approached the 2006 anomaly record. The CT Kara Sea 2012 anomaly probably set a record; the 2006 "record" looks decidedly suspect on the graph - I'm sure the area did not plummet to zero for a day. All the other CT areas have not shown spectacular early melting this year, based on the anomaly graphs.

I was referring to what Cryosphere Today calls the "Arctic Basin"; I looked at their anomaly graph here. "Central Arctic Basin" can refer to areas with different boundaries, unless, I suppose, one refers to CT's Central Arctic Basin (sic).