Terry, Nice work but I think you make a mistake here: "In the months when freezing now occurs from October through to March the lack of ice would mean no change of phase. Without the phase change temperatures would be colder, but since this will only occur in warmer conditions the phrase "Arctic ice keeps winters warmer", while accurate probably conveys the wrong message." As long as there is a combination of ice and water the temperature nearby, air and water, remains at the freezing point. If there is no ice it will remain above the freezing temperature, that is, warmer, than it would be if there were ice.

What about the quality of the ice? i have seen a lot of stories about rotten ice. Volume is, after all, a proxy for ice mass. Today's ice is not your daddy's ice, or does winter repair all that rotten ice and make it solid again??

Modeling can certainly never establish causality for a particular event, though it might suggest a cause for a type of event.

The logic of the concept of causality prevents us from finding the cause of a particular event. Causality can only be determined scientifically for a type of event. Thus the inevitable frustration in this endeavor. We find a cause of an event by repeating the conditions minus a factor to see if the event still occurs. Repeatability is only possible with types of things.

R. Gates Yes you are of course quite right that most of the heat is in the deep ocean, but does the proportion in the deep ocean and that available change. If this proportion remains constant then the amount unavailable to melt ice is irrelevant to my argument. Yes, Neven I wondered about this negative feedback a long time ago but can't remember anyone coming up with an answer. But I assume that it won't change the imbalance of the heat budget. If it did the earth would stop warming and the deniers would be right. And no, volume does not decline linearly, because there certainly iss some variation in the surplus heat retained each year. But heat always moved from hot to cold and therefore into the arctic. It can only leave the arctic if it leaves the planet, to space, even colder than the arctic. However, not all heat goes into raising the temperature. Melting ice and evaporating water take heat without raising temperature. But any additional heat must do one of these three things for the most part, though there are, of course other things that use heat in small amounts.

Since the theory of Global warming comes to this: the earth's heat budget is out of balance, with more heat due to insolation arriving than escapes through infrared radiation. Given this more ice volume is a peculiar phenomenon. For since the budget is out of balance the earth should retain more heat this year than last, and lst years heat is still around. As this budget has become further and further out of balance in the last decade it rarely happened. It can only have a few causes. 1) The sun got dimmer either because of what happened on the sun or because of particulate matter in the atmosphere. But this would have to be a large effect actually pushing the budget in the other direction rather drastically. Neither of these things happened. 2) Arctic ice volume ceased to be a proxy for global warming. Glaciers calved so gigantically that the calves became significant in the measurement of arctic ice volume. Don't think so. 3) The ice became so rotten that ice volume was no longer a proxy for ice mass. So that even though ice volume increased, ice mass decreased. It's hard to imagine this happening in the winter.

What do people think the volcanic activity in Siberia will do to this years melt?

What happens when a drilling rig meets a meethane plume?

Open water allows better absorption of high frequency radiation in the summer and better emission of infra-red low frequencyfradiation in winter. So the two processes are quite different. I wonder what depth of the water is heated in summer as compared to the depth cooled in winter. If the winter water near the surface can cool sufficiently to freeze without too much transfer of heat from deeper water, then a skin of ice could limit further cooling.

Does anyone have an explanation for the consistent big dip in area anomaly in October. Since this is a consistent anomaly, it most reflect a consistent change in something, a change that, one would think, has to do with global warming. And since it is consistent it can't be about random weather changes.

How does late open water affect heat loss in the Arctic Ocean? Isn't it really a negative feedback?

But the question is, "how many nuclear reactors are without power?"

Is anyone else having nightmares about kilometer thick chunks of Greenland Ice sheet calving off under the pressure of torrential melt water and crashing into the ocean to produce multiple tsunamis. No? Good

Is anyone else having nightmares of kilometer thick chunks of Greenland ice sheet breaking off under torrents of melt-water that washes them into the ocean where they make a whole series of tsunamis. No? Good.

Does anyone know how what looks to me to be large arctic sea temperature anomalies compare with other recent years? http://ghrsst-pp.metoffice.com/pages/latest_analysis/sst_monitor/ostia/anom_plot.html?i=17&j=1

As a mathematician wholly ignorant of the arctic except for what I have been able to gather here and elsewhere on the web, I perhaps have a different perspective that some might find of value. Imagine the arctic as a glass of water with an ice cube in the sun. Let's further assume there are no currents in the glass and no breezes to disturb the air above the glass. Then there would be a lens of water and a certain amount of air that would surround the ice cube and remain at the freezing point. The ice itself might start out at a temperature considerably below freezing, but it too would have a margin that was just at the freezing point. The glass would heat up because of insolation, and cool down because of radiation. But temperatures would remain pretty much the same. The expansion and contraction of the ice cube, alternately taking up and giving off the heat of fusion, would act as a thermostat. Cold drinks on hot days. The difference between insolation and radiation would be almost perfectly reflected in the growth or shrinkage of the ice cube. Now of course things get more complicated in the real world. But whether the ice is growing or shrinking still depends in a large part on just the difference between insolation and radiation. The seasonal variations are by far the largest. Most of the other factors, to the extent that they are what they have been in the geological past, have not changed that much. The new blanket of greenhouse gases have their effect in decreasing radiation. Now in our ice cube analogy, the ice cube is the coldest thing in the environment. But since the water has a lower albedo than the ice, the insolation-radiation difference becomes minus sooner in the water than on the ice. As days get shorter, ice's higher albedo makes less and less difference to insolation, as there is less and less insolation to reflect. But since a good absorber of light is a good emitter, the radiation from the water will be far larger than that of the ice. With the water already at its coldest beside the ice cube, the ice cube will expand when the water loses so much heat that it “threatens” to go below freezing. Such expansion will release the heat of fusion, mostly into the water, and warm it. Since the less ice area there is the more exposed water and so the sooner insolation/radiation will tip towards refreeze in the autumn in the arctic as a whole. This might account for the peculiar fact that there does not seem to be a trend towards later and later minimum dates. Now as soon as a patch of water is covered in ice it radiates less heat. The ice is not as good a radiator as open water. Thus the water below the ice loses less heat then open water. So ice will form in open water before the already formed ice will thicken. Ice will form as a thin sheet over the whole surface first before the water below the ice can begin to cool. Of course this does not take into account all the many other local factors. But in general the larger the area of open water to refreeze, the thinner the first year ice will be because it will take more of the winter to cover the open water. Thus the large anomalies of ice thickness we see in October, as first year ice expands across the arctic. Much of the extra heat is trapped under the thin ice. Now the arctic is not a glass of water surrounded by air. Russia and Canada are its borders. These land masses with a low albedo, can get cold a lot more quickly than the ocean. There is no transfer of the heat of fusion here to control temperature. So these land masses can cool the air which can in turn cool the ocean and it's ice. Ice will form not only around the already existing ice, but near the land as well. This too might account for the stability of the minimum date. But this effect is soon minimized when the land is snow covered. The snow raises the albedo very high, reducing heat reflection from the land. The all time record low snow cover this year might encourage a quick refreeze, unless snow cover quickly increases this fall.

When a denialist insists that warming is the result of "natural cycles" why not ask him what he thinks is the cause. After all, natural cycles such as ice-ages and El Nino have causes too. Denialists think that their claim of "natural cycles" lets them think warming must be causeless.

What can they do if they wake up? Surely it's too late now.

Because the room is warmer than the ice cube.

As a pure amateur I might be totally wrong about this, but here goes. The arctic is like an ice cube in a glass of water in a warm room. That ice cube cannot grow by giving up heat to the room. It can only grow by giving up heat to space through infra red radiation. Thus refreeze is entirely dependent upon greenhouse gas concentration over the arctic. If this were to remain constant the total volume of recovery would remain constant, but unless it declines the volume of recovery cannot increase. And if concentration increases that volume can only decrease. On the other hand the ice cube can gain heat not only from insulation, but also from the rest of the “room" through ice being removed (driven through the straits), and warm air and water infiltration. Thus volume declines, in propitious years, can not be recovered unless there is a decrease of greenhouse gases over the arctic.

I don't know if anybody pointed out yet that any ice driven through the Fram strait to melt in the Atlantic in effect transports the heat of fusion into the arctic. That is 80 calories per gram.

Yeah, I had forgotten this.

This thread is beginning to sound like Slim Pickens riding the bomb in "Dr. Strangelove."

How can that area in Beaufort be second year and older ice? It's all cleared out already. Does that much old ice drift in there?

It's interesting that by knowing that no first year ice can survive a summer we can say that the amount of ice can no longer increase. The years where the minimum seems to recover do not indicate that there is more ice, but are artifacts of what we measure. Obviously extent can grow without any new ice, and so can area if old ice breaks up into thinner pieces. Even volume is inaccurate because the same volume of ice can be hard and dry or like a snow cone. But what cannot rise is the actual mass of ice that has actually frozen and absorbed the heat of fusion. And that is pretty much a game-ender. When a year propitious to melting comes along it lops off big chunks of old ice which can never recover.