I was looking at the surface wind forecast for the next week, http://globalweatherlogistics.com/seaiceforecasting/gfs.1000mb.vectors.arctic.html What do you make of it? The lines seem close together which means high wind speeds, but everything seems very cyclonic in shape. It might always look this way and I didn't notice but I am not sure so I am asking, is the pro or con for the compaction effect?

For some reason I can never remember if Positive or Negative AO is the one that encourages more ice to flow out through the Fram Strait. Thus I don't know if the building negative AO value will increase the transport rate or slow the transport rate down to a lower value. Right now the current 2015 CIA reading from the Cryosphere Today web page is below the seasonal minimums for all years before 2007 as well as 2009, 2013 and 2014. The next records to be passed will be 2010 with 3,072,130 km^2 and 2008 with 3,003,560 km^2 I think it is highly probable 2015 will pass both of them in the next 20 days but I am not a climate scientist, just as interested observer trying to figure things out with the data available for free online.

Do we have any data on how far back into the ice sheet the next grounding line is if this one gets melted past?

Okay this is probably a dumb question, but why doesn't everyone use a universal orientation for the Arctic on maps? I love maps and I figure them out, but for the casual viewer having some random location being at the top and bottom of each map depending on the publisher is just confusing. My suggestion would be to use 0 Longitude at center bottom and 180 Longitude at center top. These lines are internationally recognized for map use and would cause all polar maps to be displayed in the exact same orientation making comparison between visual data sets much much easier.

It never ceases to amaze me, the number of people who can't grasp the fact that Antarctic Sea Ice is nearly all thin first year ice and as a consequence it nearly all melts away each and every year. Comparing that with the Arctic where up until 2005 over half of the sea ice was 5 years old or older is like comparing Lake Eire and the Black Sea. Yes both are large bodies of water, after that pretty much everything is different.

Jim I was thinking in the context of standard hull cargo ships being able to pass through with an ice breaker escort that doesn't have to break them a pathway at any point in the journey. I think it would be foolish to take a standard hull ship through without an escort and if you go around that side Russia demands an escort be along in case of trouble. Not too long ago China, South Korea and Japan were exploring regular transits as a way to save time and money on shipping to Europe. China even went so far as to send their own icebreaker through the passage to gain real world experience.

Does anyone have a list of dates for when the Northern Sea Route has gone ice free? I don't have a source handy but IIRC the first time in recent history it opened up a completely ice free passage was 2007 and the pattern has repeated in some of the years since then but not all. It looks to me as if an ice free pathway is about to open and I wish to compare dates over the last decade for when this has taken place.

Colorado I have long argued with certain people who insist it will take a Millennium for Greenland to melt if it ever does. All it would actually take is for a warm wet Atlantic hurricane to dump torrential rains on it every year or so. The speed with which even 5 C rain can erode ice is simply astonishing. Drop a meter of 5C rain on the GIS every summer around August 1 and the effects would stun anyone who has not spent much time thinking about it. It is not just surface melt either, the large volume of rain would create scores it not hundreds of fresh Moulins that would bore through the sheet raising the internal temperature softening the ice while at the same time the base pressure would lift the sheet allowing it to flow much faster for a week or two.

Bill you said [quote]However, the North Atlantic Drift Current does eventually sink way up there, and, as it does so, it feeds into and becomes the North Atlantic Deep Water. My (very limited) understanding is that, having travelled up from the Gulf of Mexico, and having been subjected to evaporation for the whole way, the NADC is just about the densest, saltiest surface water anywhere. As it cools, it gets even denser, eventually ending up as NADW. Therefore, every joule that it picks up from insolation whilst flaffing about up there prior to actually sinking, finds itself getting buried into the deep ocean, hence extracting "heat energy" which would otherwise help to melt the ice from underneath. This, so I understand, is what helps provide the thermal inertia. [/quote] In the deep past this was true, however in the current climate regime the North Atlantic Drift does not sink because of higher salinity like the waters of the Mediterranean Sea do. What happens under the current climate is the NADC encounters and mixes with fresher surface waters as it travels north. When it reaches the point where its temperature is low enough to make it denser than the surface waters it sinks, but it only sinks a few hundred feet at first. The salinity at that point is only slightly higher than that of the water at about 100 meter depth so it sinks to about that level. As it gradually cools it sinks further and further until it reaches the sea floor a long distance south of where it initially sank below the surface. The Arctic Basin is actually fairly sharply stratified by temperature and salinity. So long as the inflowing surface Atlantic Drift gets diluted significantly before sinking the Arctic Bottom water is stable and remains in place in perpetuity. In the distant past this was not the case. When the Arctic Basin was ice free surface evaporation outpaced fresh water influx from rivers and this resulted in highly saline water eventually sinking. Because of the high salinity it would sink all the way to the bottom of the basin displacing the deep Arctic Bottom water and forcing it over the sill to flow out into the Atlantic deep basin. After many years a circulation would be set up like that in the current Mediterranean Sea with relatively warm highly saline water filling the bottom water portion of the basin and then itself exiting over the sill into the Atlantic basin. Here are a couple links about the stratification as it stands today, https://upload.wikimedia.org/wikipedia/commons/thumb/c/c1/BrnBld_BeringToFram.svg/1280px-BrnBld_BeringToFram.svg.png http://www.amap.no/documents/doc/a-schematic-representation-of-the-three-layer-structure-of-the-arctic-ocean-with-the-arctic-surface-layer-above-the-atlantic-water-and-arctic-deep-water-the-residence-time-for-the-different-water-masses-are-also-shown/442

Verg I am with you on this one. I grew up close enough to Lake Erie that many times in my life I have seen it go from thick enough to support ice shanties and snow mobile traffic to spongy ice/open water a week later. The thinnest ice areas in the Arctic Sea mass now is under 2 meters thick and as you pointed out it lacks snow cover and is getting 24/7 sun at low angles. A sunny period can make that thin dark ice melt out far quicker than intuition leads people to believe. A lot of people in this discussion both here and in other places I frequent point to 2007 and say it was a perfect melt year weather wise. Indeed it was, but the erosion of hard ice in that banner year has never been replaced. The ice is now much thinner and becomes 'rotten' much more easily because one warm wind storm early in the season sharply reduces the snow cover that insulates the surface from direct sunlight.

I wonder about the melt pond logic for one simple reason. When melt ponds form on floating ice shelves like the Larsen B they can grow to be a dozen meters deep before they breech and drain. On 3 meter thick floating sea ice it seems logical that cracks would allow drainage to occur before the ponds get very deep at all. If the ponds are always easily draining through cracked thin ice you won't get massive ponding even as the sun melts the ice from above.