We average weather for 30 years to get climate. Over a 30 year period, the difference between PIOMAS and Satellites does not matter. Does anyone here doubt that in 20 years, the amount of residual sea ice will not matter? Which is not to say that there will not be a lot of ice around the Arctic from Greenland glaciers. Look at the winds hitting Greenland from the (open) Greenland sea over the last 3 months. Those winds have carried more heat than the direct solar radiation absorbed by the ice.

Looks like we have indeed reached the point where latent heat in the atmosphere and ocean heat from below dominate over direct solar heating in sea ice volume/extent melt.

Perhaps; the recent and current conditions in the Arctic take some of the "Great" out of the 2012 august event. Perhaps 8/12 was only the first of of a new class of weather events? E.g., more water vapor and heat in proximity to sea ice drive more interesting wind events.

My guess is that global atmospheric circulation patterns have changed in the last few years. Now, some of the summer heat that conventional wisdom expects to go north, is now going south to Antarctica. One driver of the change in circulation is the additional latent heat in the atmosphere over the Arctic allowed by water vapor coming up through cracks in the sea ice. This inhibits the kind of circulation patterns that we saw in 2007. I think we are starting to see warm continent/cold ocean driven cyclones. In short, I think that over the last couple of years, we have seen the primary driver of Arctic cyclones change. My view remains that sustained, warm winds are the key mechanism that will bring a blue Arctic. When we get the winds, we will lose the ice. Ultimately, I also expect more heat transported from south to north across the equator via ocean currents. This will affect local heat balance for the North Atlantic drift and Greenland. More heat in the system means larger heat flows, everywhere.

I do not fear rain at the poles, so much as more water vapor in the air. Whenever, the dew point is above 0C, the water vapor is melting the snow and ice. Water vapor allows the rest of the world to collect heat, and rapidly transfer that heat to the poles via the atmosphere, rather than by the slower ocean currents. Suddenly, heat in the atmosphere can rival direct radiation from above for melting snow and ice. Water vapor alone can melt 28 cm of ice in a day. It is hard for direct solar radiation to melt that much ice, that fast. Water vapor and solar radiation can melt more ice. And, water vapor in the atmosphere helps hold energy near the surface so it can melt ice, rather than being radiated into space. Lighting is just an indicator that there is a great pile of water vapor in the local atmosphere. Thunder in the Arctic is the Death Knell of ice.

You may also want to consider forecast potential rain/ latent heat coming ashore on southeast Greenland over the next few days. http://cci-reanalyzer.org/WeeklySummary/ suggests inches of rain. That much rain could easily disrupt the stability of the 'aquifer' (supercooled water in firn) sitting on top of the ice. When that aquifer starts leaking, it will release a good bit of potential energy, and possibly take the ice under it out to sea as it drains.

Tom, Fully concur that ocean heat drives everything. However, some of that heat is advected into the the ocean by surface water and even deep plumes of permafrost melt.

Thank you very much. I had thought about this, and it is very nice to see that others get the same answers. Um, does the rapidly moving keels of thin ice stir the fresh water lens more than the slowly moving keels of thick ice? That is, with increased continental melt has the fresh water lens gotten thicker and more stable?, Or, less stable? I tend to think that thinner ice allows more light in, warming the top of the lens, and heat from the mid-waters warms the bottom of the lens making it over-all warmer, lighter, and more stable, but less protected from cyclones. I still think that the sea ice will continue to diminish as long as the fresh water lens is intact. Then, when a cyclone drives deep mixing, the Arctic will go abruptly blue.

TennyNaumer, I concur. I think the 2015 ice was porous and weak. There might have been a volume volume of ice in 2015, but it contained a lot air so the mass of ice was much lower than indicated by the volume. It floated high and fooled the eyes in the sky. We all wanted ice recovery, and some allowed themselves to be fooled. Speed of ice drift has been increasing showing the ice is weaker. And this spring, it burst open. In 2007, the ice was still competent enough to tolerate some wind.

Regarding Ian Eisenman, Non linear feedback systems almost always have tipping points. See the early work of Ed Demming on industrial statistics. This has been very well validated by computer models of industrial systems. The problem with Arctic ice is estimating what "abrupt" means. On the other hand, once the ice has tipped (gone out of control in Demming's terminology) it is not going back. A PDF of Eisenman's paper is at http://eisenman.ucsd.edu/papers/Wagner-Eisenman-2015b.pdf I think his problem is that his noise function needs to simulate noise from El Nino and PDO cycles.

Most of the heat trapped by AGW goes into the oceans. In the past, that heat was carried north in the North Atlantic drift, and the heat radiated off through the very dry Arctic Atmosphere. The momentum of the North Atlantic drift, acting on the sea ice in the Greenland Sea, helped keep the sea ice across the Arctic, compressed with pressure ridges for mechanical strength. Under compression, the ice was more likely to overlap to become thicker, and stronger than to thin, spread out, and become weaker. Loss of the Greenland Sea ice, meant there was nothing for the North Atlantic Drift to push against, and contributed to the thinning and mechanical weakening of sea ice across the Arctic. And, with more water vapor in the atmosphere, heat from the North Atlantic Drift is more likely to go to warming existing ice, than be radiated into space. The 2007 Greenland Sea melt event was a precondition for the the Beaufort Gyre cracks and holes. It was a "tipping point". That is the BG defects could not exist when there was pressure from the North Atlantic Drift compacting Arctic sea ice. These days, the extra heat in the North Atlantic Drift and increased level of greenhouse gases in the Arctic result in the melting of sea ice, rather than the extending and compressing of sea ice. While the Arctic has gone from year-round sea ice to ice free (or vice-versa) many times before, it has never before done it in a single human lifetime. In some ways, it is the difference between a mule and a jet plane. It is neat to see grand geology unfold in a single lifetime.

This group likes to watch real time events. The real time event that NOBODY is talking about is CH4. In real time, CH4 is the equivalent of 86 units of CO2. With CH4 now around 1.8 ppm, that means for this summer's melt, it is the equivalent of 154 ppmv of CO2, and adding in the real CO2, we have something over 558 CO2 ppmve. Talking about CO2 at 409 ppmv, or rising by 3, or 10 ppmv per year, or per decade, misses the full physical reality of greenhouse gases affecting the Arctic Sea Ice in 2016.

If the rich and idle cared about the Arctic (or the Earth) we would not be in this situation. This is conspicuous consumption to demonstrate their status, not an interest in the environment. Since they want to be "high status", I do not feel bad about blaming the whole situation on them - Much is expected of of those to whom is given. AGW will eat great wealth and all of its trappings as easily as it eats permafrost on the Alaskan shore.

I would cheerfully bet a yellow snow cone that this year's sea ice is the weakest and most rotten in the record, and thereby it tends to float higher, thereby distorting the volume estimate. I also expect that there has bee more snow fall this year, so some of what is considered sea ice is actually snow. Thus, I expect a sudden drop in volume as the melt season begins.

There was a time when continuous and competent Arctic sea ice separated the Arctic atmosphere from the Arctic ocean. From continent to continent, the atmosphere was cold and dry, allowing heat to radiate off freely. Greenland was also cold and dry. Now, the diminished and cracked sea ice allows water vapor (latent heat) to move into the Arctic atmosphere. This reduces the amount of heat radiated off, so that heat from the Arctic Ocean is trapped. A warmer Arctic means that latent heat from the south is not condensed and radiated off. Water vapor in the Arctic atmosphere changes the density of the air, impacting global atmospheric circulation patterns. Loss of sea ice is long process of partition and equilibrium. The effects began when ice began to diminish and crack, allowing water vapor into the atmosphere. Increasing water water vapor in the Arctic atmosphere changes our weather. Today most our infrastructure was designed using engineering standards based on the climate of 50 years ago. Cracks in ice affect people, NOW. Some horses can get out of a barn if the barn door is closed, but not latched. Measuring whether the barn door is 12 feet open or a full 16' open does not really tell you much whether your animals can get out of the barn. At this point the Arctic barn door (ice separating air and water) is open enough that all the “weather animals” can come and go as they please. As a result, for the last few years we have seen weather patterns never before seen, and which were not included in our engineering basis of design. The 4 options are about measuring the width of the barn door opening as the horses come and goes. The important question about sea ice is, “Can water vapor move from the ocean to the atmosphere?” At this point, the ice is both diminished and fractured, and water vapor can move from the Arctic Ocean into the Arctic Atmosphere. AGW unlatched the Arctic Barn Door at least 20 years ago. More water vapor in the Arctic atmosphere means more precipitation on Greenland. In 1970, rain on Greenland was almost unknown. Starting in 2002, I tracked rain on Greenland for for 60 consecutive months, and rain was reported somewhere on Greenland every month. If it is raining, then there is water vapor in the air, and water vapor melts ice. Long story, short: There is excellent observational evidence that loss of sea ice competence affects GL melt. A fractured tea cup is not a “tea cup”, and fractured sea ice does not behave as traditional competent sea ice.

It is a mile post on a journey. Before circa 2000, the jetstream intruding into the Arctic was rare. By 2007, the jet stream crossing the Arctic was common. By 2009, we could associate the path of the jetsream across the Arctic with exceptional Atlantic seaboard weather events. Now, there is no longer (cold) enough sea ice between Greenland and Norway to cool and condense all moisture out of low level intrusions of warm, moist air. Thus, warm moist air can blast into the Arctic proper. This is a sign of things to come. A cold, dry Arctic with cold, competent sea ice drives one kind of jet stream behavior, while fractured sea ice with atmospheric water vapor in equilibrium with liquid water at 0C drives another kind of jet stream behavior. In short, the mile post tells us that we are very close to having Greenland as the Northern Cold Pole, setting up very intense local heat gradients that will drive atmospheric behaviors that we have never seen before

1) A gram of water vapor condensing on the surface of the GIS melts 7.5 g of ice resulting in 8.5 g of melt water on top of the GIS. 2) Water falling down a moulin converts its potential energy to kinetic energy, and then to heat. The water is at 0C because it has been transferring its energy to the ice around it. 3) Large ice sheets are complex structures subject to huge gravitational forces. Suddenly form a cylinder of ice a kilometer tall, and the ice at the base would explode. This does not happen in ice sheets because the ice at the base is under compression supplied by an infinite series of buttresses formed by ice at lower elevations. As moulins perforate the buttresses this support is lost. 4) Ice sheets are not designed by engineers with some margin of safety. They are at structural equilibrium. Suddenly formed holes (moulins) in the foundation disrupt that equilibrium. 5)Once the potential energy of a column of ice exceeds the compressive strength of the ice structure at the base of the column, the ice structure at the base of the column fails rapidly. This adds to the stress on the ice structure at the base of adjacent columns of ice; they fail, and so forth. 6) The difference between a structurally competent column of ice and one that fails is likely a fraction of a degree in temperature. Once a progressive structural failure begins, it can propagate into colder, stronger ice. Rate of propagation is a function of the total energy of the ice column. The higher the total energy, the faster the propagation. 7)Water/ice slurry from ice sheet collapse cuts its own channels. Current fjord system under the GIS was likely formed this way. Such deep fjords dug by solid ice would be wider. No, those channels were dug by cavitation in water as a walls of ice collapsed into them. I do not much worry about the kind of slippage we see in mountain glaciers. Nor, do I worry much about plastic flow as the ice warms and softens.

I would say that the Arctic has changed since 2005. Now, it has more water vapor over the region. The water vapor rises, condenses, and when the sun is low in the sky (spring & late summer) the clouds are warmed by sunlight. That warming drives a stable spring and late summer low. I doubt if this bit of geometry is in your climate texts. In the old days, the air over the Arctic was dryer and colder. Snow and ice tended not to absorb sunlight. Lows were driven by other mechanisms. Heat from direct insolation in this process is trivial compared to the amount of latent heat advected into the region from the south by this circulation. Thus, a bit of heat from sunlight on the sides of the cloud column results in circulation patterns and substantial sea ice melt. This is a powerful feedback from additional moisture in the Arctic atmosphere.

My expectation is that the Arctic will move to a regime of two, large, stable cyclones per year; one in spring, and one in late summer. I think a naming system based on year and season (or day of the year) would be convenient for historical records. Then somebody reading this history in 20 years does not have to find a separate list of storm names and dates.

1 M km^2

Global warming has been acting on the Arctic for a long time. The difference between the cold, dry environment of an Arctic cyclone in 1920 [320 ppmv CO2] and the almost as cold, almost as dry environment of an Arctic cyclone in 1960 [350 ppmv CO2] was small, but real. However, by 2012 [397 ppmv CO2], an Arctic cyclone was in a much warmer, much wetter environment. GAC-2012 was a different kind of storm. Serreze & Barrett, 2008) describe an intermediate form of Arctic storm in intermediate conditions. To rank Arctic cyclones strictly on the basis of central pressure is like comparing desert dust devils to real tornadoes, and tornadoes to hurricanes. These are three different phenomenon that occur in three different environments. The Arctic "then" is not the Arctic "now". The Arctic now is warmer, wetter, and produces different kinds of atmospheric phenomena. GAC-2012 and PAC-2013 are different from the Arctic cyclones from before 2005, when the Arctic was drier and colder. If you remember, more than a year ago I predicted that in 2013, a large Arctic cyclone would fracture the ice this year. One could not make such predictions about traditional Arctic cyclones. They were too small and localized to cause wide spread ice fracturing and movement. They were fueled by one lobe of the 500 mb jet stream coming across Siberia. Today's, Arctic cyclones suck in latent heat from both the North Atlantic and the Pacific (across Alaska) at the same time. This is a sea change from the kind of storms that Serreze & Barrett,(2008) address. Further, I predict that PAC-2014 will be larger and more stable. GAC/PAC are more closely related to polar vortex and global circulation phenomena than to the traditional Arctic cyclones. In the past, latent heat from the oceans had a more zonal flow at the southern edge of the Arctic. Now, that latent heat from the North Pacific and North Atlantic is transitioning to a more meridional flow into the Arctic. I expect more persistent Arctic cyclones are a part of what is driving increased meridional atmospheric circulation. Ultimately, meridional atmospheric circulation will drive additional meridional ocean circulation. This additional meridional ocean circulation will carry a good deal of heat into the Arctic. Such enhanced ocean circulation is the pathway to a year-round, sea ice free Arctic. I suggest that GAC-2012 and PAC-2013 mark the trail head to a sea ice free Arctic.

Less than 1 million km^2 average ice extent for month of Sept. 2013. That is functionally 0 for critters like polar bears, walrus, & seals. Large areas will have dispersed ice that will not register as ice extent, e.g., ice will remain a hazard for shipping. This estimate is based on sustained low pressure in polar region continuing to drive the polar cyclone that pulls latent heat from the south. Thus, ice melt is based on hemispheric heating, rather than on direct local solar heating. The latent heat then condenses on the ice, thereby keeping local atmospheric pressure low, and driving the cyclone. (I do know that wind driven by phase changes in water is not part of the conventional wisdom on weather. See for example; Makarieva, A. M., Gorshkov, V. G., Sheil, D., Nobre, A. D., and Li, B.-L.: Where do winds come from? A new theory on how water vapor condensation influences atmospheric pressure and dynamics, Atmos. Chem. Phys., 13, 1039-1056, doi:10.5194/acp-13-1039-2013, 2013) I suggest that the slow start of the melt season is the result of warm/weak ice spreading out across the surface of the water. That increase in area of ice detected fools PIOMAS into overstating current volume.

My feeling is that the Arctic cyclones that formed a few years ago over intact/competent sea ice are inherently different from the current generation of Arctic cyclones that are occurring over fractured sea ice, and thereby have access to more water vapor. The practical impact is that Arctic cyclones are getting larger, more powerful, and more persistent.

The cyclone is breaking the ice, and then banging the pieces together, forcing spray into the air. The spray wets the ice, so sublimation is not required to move water vapor into the atmosphere. The wet ice has a lower albedo than ice covered with snow or frost. Sublimation occurs in dry conditions, cooling and hardening the ice. I wish this were the case.

A "Polar Vortex" is driven by cold, dry air. This "cyclone" is mostly driven by water vapor. If I am correct, you will always see a leg of "jet stream" at 300 mb over the Arctic, near the top of the cyclone. That is, the segment of jet stream and the cyclone are two aspects of the same circulation, rather than the jet stream blocking surface weather. As long as we have large patches of sea ice surrounded by water vapor, such cyclones are likely to be stable and persistent, with any highs that intrude into the space tending to be transitory. Lack of snow at the perimeter of the circulation helps supply water vapor to drive the circulation. I strongly agree that the negative snow anomaly is part of the system generating the cyclone(s). This summer, I do not see "blocking" so much as "stranding". The jet stream no longer moves and transports weather systems as it did in the past. If the metaphor is a conveyor belt, then with blocking, the conveyor belt is running, but the blocked weather system is not on the conveyor belt. With stranding, the conveyor belt is broke. The foundation for a working jet stream is cold, dry, and competent Arctic Sea Ice. These days that occurs only in the winter. In coming summers, I expect regional geographic features drive regional circulation patterns (and weather) that generates segments of jet stream flows rather than a global jet stream that transports a sequence of weather systems over regional features. My view is very different from a global circulation that generates Rossby waves.