No mention of missing “M’s” here in this press release from University of Melbourne
Melting sea ice has been shown to be a major cause of warming in the Arctic according to a University of Melbourne study.
Findings published in Nature today reveal the rapid melting of sea ice has dramatically increased the levels of warming in the region in the last two decades.
Lead author Dr James Screen of the School of Earth Sciences at the University of Melbourne says the increased Arctic warming was due to a positive feedback between sea ice melting and atmospheric warming.
“The sea ice acts like a shiny lid on the Arctic Ocean. When it is heated, it reflects most of the incoming sunlight back into space. When the sea ice melts, more heat is absorbed by the water. The warmer water then heats the atmosphere above it.”
“What we found is this feedback system has warmed the atmosphere at a faster rate than it would otherwise,” he says.
Using the latest observational data from the European Centre for Medium-Range Weather Forecasting, Dr Screen was able to uncover a distinctive pattern of warming, highly consistent with the loss of sea ice.
“In the study, we investigated at what level in the atmosphere the warming was occurring. What stood out was how highly concentrated the warming was in the lower atmosphere than anywhere else. I was then able to make the link between the warming pattern and the melting of the sea ice.”
The findings question previous thought that warmer air transported from lower latitudes toward the pole, or changes in cloud cover, are the primary causes of enhanced Arctic warming.
Dr Screen says prior to this latest data set being available there was a lot of contrasting information and inconclusive data.
“This current data has provided a fuller picture of what is happening in the region,” he says.
Over the past 20 years the Arctic has experienced the fastest warming of any region on the planet. Researchers around the globe have been trying to find out why.
Researchers say warming has been partly caused by increasing human greenhouse gas emissions. At the same time, the Arctic sea ice has been declining dramatically. In summer 2007 the Arctic had the lowest sea ice cover on record. Since then levels have recovered a little but the long-term trend is still one of decreasing ice.
Professor Ian Simmonds, of the University’s School of Earth Sciences and coauthor on the paper says the findings are significant.
“It was previously thought that loss of sea ice could cause further warming. Now we have confirmation this is already happening.”
Tim Clark says:
April 30, 2010 at 11:40 am
Tim, GHG induced warming is different from a surface albedo feedback affect. These are not the same things, so until you can understand the difference between a surface feedback affect and that from changes in atmospheric GHGs or changes in atmospheric circulation, you will not be able to understand the paper. Perhaps a crash course on physics and energy balance will help.
“”” Study: Melting sea ice major cause of warming in ArcticPosted on April 29, 2010 by Anthony Watts “””
Well my cut and paste doesn’t preserve the formatting; but it preserves the erroneous word order; so herewith, the hand done correction:-
Study: Warming in Arctic major cause of melting sea ice Posted on April 29, 2010 by Anthony Watts.
There now, isn’t that much better ?
There’s an actual reason why they have all that sea ice up there in the first place; it’s cold up there; and it’s cold up there because they don’t get much solar irradiance up there. And that ice is also cold, so it doesn’t radiate thermal LWIR at the same rate as the tropical oceans do, so it doesn’t warm the atmosphere via GHG as much as happens in the tropics.
Also because of those lower water and ice temperatures, and air temperatures; the humidity tends to be lower and the total atmospheric water vapor content tends to be lower, so the atmospheric GHG warming is also lower than in the tropics.
But then you have these ocean currents from the tropics; that bring warmer surface waters up into the arctic ocean; where we are told they cool, and sink so the water can return to the equatorial regions along the cold bottom. One of the reasons for that cooling up there is that you have all that ice floating in the surface water, and most of the ice volume is actually under the water; and the total ice surface area in contact with the water, is greater than the ice area in contact with the air. Air is a much better thermal insulator than water is, so the conduction of “heat” from water to ice is vastly greater than from air to ice, so the warmer surface waters can melt ice better than the air can; and all that latent heat comes out of the ocean; not the air. Hey not all of it, but most of it.
Well then there’s the sun. Hey you can’t have it both ways. No fair crediting the ice for the earth albedo; while at the same time blaming it for melting the ice. Either it bounces off to albedo purgatory, or it is absorbed to melt ice.
One effect you don’t hear much about results from the obliquity of the solar input in the arctic.
My IR Handbook gives a proposed standard Solar Spectral Irradiance with a peak of 2074 W/m^2/micron for air mass zero (extraterrestrial). I should caution this is for an older TSI value of 1353 W/m^2; which is the value I grew up with in high school. Ac ouple of graphs in the handbook place the air mass one peak at 75% of the AM-0 value; but I don’t have tabulated values. For AM-2. Now for an atmospheric height (H), and a sun altitude angle (A), corresponding to a surface incidence angle (90-A), the slant range is H/Sin(A); so Air mass two corresponds to a sun altitude of 30 degrees.
My Mercator maps generously put the perimeter of the arctic ocean at 70 deg north, which skirts the top of Alaska, but most of greenland and a lot of Canada, and Siberia protrude even north of that. So at the Equinox in September; when the refreeze starts, (A) is zero at the pole; so it would be 20 degrees at the perimeter of my ocean. At the Summer Solstice we would get another 23 1/2 deg or 43.5 deg solar Altitude, which presumably is the maximum. That would give us a minimum of AM 1.45 at the edge of the Arctic ocean, versus 2.92 at the Equinox.
the Handbook gives a peak of 1215 W/m^2/micron, for the AM-2 spectral Irradiance; but for some unexplained reason this value is for a TSI of 1322 W/m^2; so that presumably was some sort of Neanderthal observation, peeking out of a cave somewhere.
So bear in mind these are spectral peak values not integrated totals, and they need to be factored by the current TSI value of 1366 W/m^2; but you get the point; the ground level insolation in the arctic ocean is greatly reduced by Air mass absorption, and then by the ground obliquity factor; that’s why they have ice up there. Note that the AM factor results in an increase in the direct solar atmospheric heating; because of the increased slant path length. To some extent the outgoing (albedo) reflection also undergoes an increased outgoing pathlength so even on the outgoing, the solar heating of the atmosphere is increased. it’s nearly impossible to compute, because the outgoing albedo component is going to be highly scattered since the surface is not a flat optical surface with the ice there; but can be moreso, with the open water.
But in the end; all that solar warming of the atmosphere, results in a reduction of the surface level insolation which is what would be available to melt surface ice.
For some reason; the solar heated atmosphere, wants to expand, and thereby transport itself via the process of convection, to higher altitudes, where it tends to get lost to space. So don’t count on the solar heated atmosphere being responsible for very much conduction heating of the ice surface. It will of course give an LWIR component of radiative heating; but that will be very much a “skin effect” heating due to the huge absorption coefficient of either ice or water at those wavelengths. And no I don’t believe either the ice or the water has an actual “Skin”; just the IR heating is confined to the top few microns of the surface; which tends to promote either evaporation or ablation as the case may be; so not much in the way of melting.
Now I agree that with less sea ice, and more open water, you get more evaporation into the air; which transports a whole lot of heat to the atmosphere; something like 540-590 calories per gram. I really have to convert those numbers to Joules; and commit them to memory; since htese daya a calorie is a quantity of food.
But I am much more ready to believe that it is the melting ice in the arctic that is leading to the warming up there, than I am to believe the opposite.
I’ve flown over the Arctic Ocean in daylight precisely once, going from SFO to London, and it was choc-a-bloc wall to wall ice. That would have been round about this time or a bit earlier in 1979-80 (when is the Pentecostal Weekend in Europe). So that would have been about the time when the Arctic ice reached its all time, never exceeded, maximum extent, that yielded those great pictures that Nobellist AlGore took back then, to show how bad it was going to look in 2007.
I don’t know enough about what is going on up there or how it all works; and I certainly have no prediction for this September’s minimum ice extent; but I am currently not alarmed by what I keep reading and seeing in photos.
When Svend Hendriksen decides to leave Greenland for a safer place; then I might get alarmed.
Well this ended up getting shaggy dog like; but maybe I got my points across.
“”” FerdinandAkin says:
April 30, 2010 at 11:13 am
Dr James Screen of the School of Earth Sciences at the University of Melbourne has found NCAR scientist Kevin Tenberth’s “missing heat”. The answer is as plain as day: The missing heat is hidden in the Arctic Ice! As the ice melts, it releases the heat to the atmosphere over the Arctic. This is a positive feedback loop that will continue until the Arctic is ice free, probably in the year 2013 or even sooner. “””
Not so, I’m afraid; the vast majority of that latent heat comes OUT OF the ocean water. Where on earth did you get the idea that ice gives up “heat” when it melts ? Do you put ice cubes in your Coke/Pepsi or maybe Scotch in order to WARM your drink, or to COOL it ?
Just for laughs have your kids do this in the kithcen. Take two equal amounts of water. Freeze one to make ice cubes; let them stabilize in the refrig. at about zero deg C. Then heat the second equal mass of water to +80 deg C; using the family Centigrade thermometer to check the temperature.
Add the ice cubes to the +80 deg C water, and record the temperature as the ice warms up the water with all that heat it gives up.
Don’t worry if some of the ice melts during this process; that is sort of inevitable. If at the time the ice all disappears, your thermometer reads zero deg C; do not panic ! Take two Aspirin, and then post a report here at WUWT.
The notion that the melting ice warms the air is becoming increasingly difficult to observe as real scientists start making observations in the Arctic.
skye says:
April 30, 2010 at 11:58 am
Tim, GHG induced warming is different from a surface albedo feedback affect. These are not the same things, or changes in atmospheric circulation, you will not be able to understand the paper. Perhaps a crash course on physics and energy balance will help.
Oh wow, what a smackdown.
From the paper:
Increased concentrations of atsmospheric greenhouse gases have driven Arctic and global average warming…. … The Arctic region has long been expected to warm strongly as a result of anthropogenic climate change…………In the Arctic, this greenhouse effect dominates during autumn, winter, and spring.
I’m not really interested in your labile physics knowledge. The assertion in the paper is that increasing greenhouse gases initiate the amplification affect. If the original assumptions used to make ther argument are invalid, the paper is useless. In the modern record, the 30’s and 40’s centered on 1939 are the hottest in the Arctic record, citation above. Explain to me how the Arctic in the 60’s and 70’s cooled,/b> while [CO2] exploded. Where was this alledged amplification then. If this amplification existed as a result of [CO2], then the Arctic ice would be gone, zip, nada, post 1939. I suggest that “understanding the difference between a surface feedback affect and that from changes in atmospheric GHGs” doesn’t mean squat until you can correlate [CO2] with Arctic temperature, or else it’s just weather, move along.
J. Newman says:
April 30, 2010 at 9:31 am
The atmospheric CO2 increase has almost certainly increased the freezing temperature of water because ice continues to build and there is celarly alot of hot air in the arctic.
Global Warming increases the melting point of water, yes, that’s publishable. Go for it.
Well I wouldn’t put much stock in anything coming out of Melbin; those Ausies are nutz. Hell I just saw a news Bulletin that one of my colleagues received from down there. Seems like the Ausies aren’t happy with the number of holidays they get to drink Fosters; which they will tell you in their own words, is Australian for beer.
So the crazy buggers decided to invade their southern nieghbor to establish a new victory holiday date that they could drink to.
Wow what a mess that turned into; you ever seen an Abo Canoe; well we Kiwis know canoes; just ask our Maori
Cobbers about canoeing; and damn good sailors they are too; so the Aussie Navy was totally outclassed. So then they resorted to their Air Force; hey; earth to Oz, Kiwis don’t fly; Moas don’t fly; Wekas don’t fly; what the hell was it you expected to run into in the air over there; well of course there is always Aotearoa; land of the long white cloud. Well that cloud of course hides a lot of Cumulo-Granite; some of it high enough to have ice on it. Height is not a concept that is understood in the land of Oz where it is all at about sea level; so there was a lot of bent aeroplanes, and not much bang from the AAF.
Fionally it got down to the hand to hand ground fighting, and the outclassed diggers, all got tossed into a big tank of Stein Lager. Well, poor chaps couldn’t drink fast enough to keep their heads above water; and they all drowned.
Hey Earth to Australasia; both of you blokes don’t know anything about Beer. Lager is a Ladies drink, and real men don’t drink lager. We have the same problem here in Colorado; where they make a lot of lager; comes naturally, because evidently nobody ever warned them about eating yellow snow.
So the two of you oughta just kiss and make up; and take a trip to Bavaria, where they also have snow and ice; but they know something about Beer.
Talk about mayhem over there on the other side of the pizza; both of you lot oughta be ashamed of yourselves.
Besides when was the last time you actually waited for a beer to cool down before you drank it , anyway.
I don’t think your arctic thesis is gonna work out for you; try studying poisonous snakes, and spiders; that’s more up your alley !
Tim Clark says:
April 30, 2010 at 1:33 pm
Sorry Tim, but that is not what the paper is saying.
If you want to assume that the decline in the summer sea ice cover is linked to rising GHGs, then you could indirectly say that GHGs are responsible for the amplified Arctic warming observed in autumn.
I am surprised that you don’t understand that open water absorbs more of the sun’s energy than sea ice. Do you understand the differences in the reflective properties of ice versus water? You can look at the graph of September ice extent and that reduction you see in the ice cover must correspond to an increase in the amount of open water. Water absorbs more solar energy (albedo near 0.1) than ice (albedo for snow-covered ice is 0.8 and for bare ice is 0.6). If the oceans are not warming because of the absorbed solar energy, it has to release it back to the atmosphere. It is basic energy balance physics. Something that most high-schoolers understand.
What the paper shows is that heat is being released from expanding open water areas in autumn when the ice cover reforms. It has to, the heat has to someplace. If you want to go further and make GHGs responsible for the decline in the summer ice cover, then you can link GHGs to amplified warming (which is what climate models do). The planet is warming right now…what is not quantified is how much of the warming is a result of natural variability and how much is a result of human activity.
This paper is an example of a feedback affect in motion. that is all.
Skye: Let’s keep the eye on the ball. If Screen and Simmonds don’t even know that arctic warming is more than a century old why bother with irrelevant details they bring up. The warming is best documented by Kaufman et al. in Science 325:1236-1239. Their field work uncovered a two thousand year old cooling trend that ended abruptly when the twentieth century began. From that point on their curve turns up and looks very much like a hockey stick only this time it is real. The warming itself has lasted, with an interruption in mid-century, to this day. The interruption was from 1940 to 1960 and brought some cooling. The warmest period in the twentieth century was in the thirties and this level of Arctic warmth was not reached again until 2003. So what do the authors themselves think of it? Just what you would expect a real warmist to say: “This shift correlates with the rise in global average temperature which coincided with the onset of global anthropogenic changes in global atmospheric composition….warming in the Arctic was enhanced relative to global average, likely reflecting a combination of natural variability and positive feedbacks that amplified the radiative forcing.” A wonderful concatenation of global warming mantras, all wrong. First, global average temperature did not increase at the start of the twentieth century but decreased according to temperature graphs from NOAA and the Met Office. Second, at the start of the twentieth century the greenhouse effect from all sources was only twenty percent of what it is today. In addition, published curves of carbon dioxide abundance in air show that it took no notice of the passing of the century. This fact alone tells us that it is impossible for carbon dioxide to have had anything to do with that warming. And that is because laws of physics demand that its partial pressure should have simultaneously taken a jump, and this did not happen. Which leaves us looking for a cause that can act suddenly and massively and be capable of affecting Arctic temperatures over a wide geographic area. And be flexible enough to retract temporarily as it did in mid-century and then resume its influence. Eliminating the sun, carbon dioxide, and volcanoes leaves just one possibility: it must be ocean currents. We know that the Gulf Stream today delivers huge amounts of warm water to the Russian Arctic. But what do we know of its history? If a rearrangement of North Atlantic Ocean currents directed the Gulf Stream to its present northerly course at the turn of the twentieth century this would explain the sudden start and the present course of Arctic warming. Together with additional currents entering through the Bering Strait this can account for all the observations of Arctic warming now and in the past. Neither the greenhouse effect nor a hypothetical “Arctic acceleration” can do that and must be rejected as causes of warming.
The Albedo of open ocean water increases exponentially as the incidence angle of the Sun increases.
Once the Sun is at 10 degrees, (September 21st at 80N), the Albedo of open ocean water is not much different than sea ice (open ocean 0.350 reflected: average sea ice conditions on September 21st 0.450).
Now factor in the average 65% cloud cover (with an average Albedo of 0.5) and there is actually not much difference during the height of the melt season between open ocean and ice cover in the Arctic. There is more difference in early to mid-August.
So the ice-melt-Albedo-feedback issue (in the Arctic) has been way over-blown versus reality. The Albedo-feedback does not start to become important until we are talking about lower latitudes like 60NS and 50NS.
Bob Kutz says:
April 30, 2010 at 9:25 am
Allow me to explain the real situation.
You see, what we need to do is create a new tax. That tax will be on everything. This is because it will mainly target energy use and that is pretty much tied to everything we produce.
That tax will, in and of itself, prevent all these nasty earthquakes and even volcanoes, along with the HGW (Hidden Global Warming) that causes every one of these nasty things to disturb our otherwise perfect and completely stable environment.
Nothing to do with sheep’s bladders, you see?
[/sarc off (again)]
Bill Illis says:
April 30, 2010 at 4:25 pm
Now, I’ve been reading such things for a while. There is also the strong possibility that reduced ice cover allows heat to be lost from the warmer water, thus cooling it and providing a negative feedback.
Are there any studies (peer reviewed, preferably, to gag abusive AGW chicken littles) that have examined either of these situations?
If not, is there any way we could justify spending any money on daft research like thus until those two basic questions have been laid to rest?
Hey everbody.
Please calm down.
This paper was not just from Melbourne,
It was printed by NATURE
so it must have been PEER REVIEWEd
by real EXPERTS in their field.
So wot’s this Latent Heat of thinagdy,
What’s he kow aboit it anyway.
It must be right.
It’s in Nature,
and so on and on and on.
(some of the spelling errors in this post were intential,
some were mine).
Bill Illis says:
April 30, 2010 at 4:25 pm
Bill do you have a reference for your albedo values? Because those are not what have been measured in the field. Not only does water reflectance increase with solar zenith angle, so does snow and ice reflectance. New snow has an albedo of nearly 0.9, and by September it is likely snow is falling on the ice again. The ice albedo feedback is real. I have measured it myself in Greenland. I have measured the reflectance of snow-covered ice, bare ice, and melt ponds. I’m sorry but your values are not correct.
Arno Arrak says:
April 30, 2010 at 3:06 pm
Arno, I think you are confusing annual temperature variations with seasonal temperature changes. BTW…look at Steve’s other post where he shows UAH temperature trends. Notice first off warming in all seasons (this was not the case in the 1930s-1940s warming). Nor was the 1930s-1940s warming widespread in the Arctic, it was on the Eurasian side. Unfortunately there are not Arctic wide observations of sea ice from that time-period, so the link between any autumn warming during that time and sea ice cannot be examined. But it can be examined today using 30+ years of satellite observations.
Again, it seems that the basic energy balance of surfaces is not being understood by many of the posts I see. The amount of energy absorbed by the surface depends on the surface albedo. If you have a surface with a lower albedo (such as water), you will absorb nearly 90% of the incoming solar radiation. This will cause a warming of the ocean. Air temperatures in autumn are much colder than the ocean, thus there is a heat transfer from the ocean back to the atmosphere. That is all this paper is saying. It is not necessarily anything groundbreaking, it is exactly what one would expect given the ice extent trends. You all are making a much bigger deal out of this paper than it merits.
BTW…many seem to be missing the fact that the authors state in their paper that the winter warming (not the autumn which is a result of the ice-albedo feedback), appears to have a atmospheric circulation signal (i.e. transport of warm air into the Arctic).
Also note all trends in air temperatures in the Arctic are positive (for all months, all seasons). But different processing are responsible in different seasons.
Platitudes. Is this all that is left of mainstream climate science? What a bunch of boring mush. I’m picking up a Jack Russell tomorrow and the biggest concern I have is cold tolerance so I can walk with him in the other 6 months of the year up here. That means a rough coat. Let’s see what happens in Greenland over the next 30 years.
JER0ME: OR just press the Control (CTRL) button and spin the mouse wheel, for those of us in the 21st century…
You can write but you cannot make them read… Your sarcastic comment is wrong. That only changes the web site you are looking at. If you change the about:config parameter layout.css.devPixelsPerPx as I said it changes the size of ALL websites AND the menu and icon bar. It magnifies everything. Not the same thing as you are saying.
I can only see one thing thats common with the sea ice (and all ice). That is the sun . When you get up to 6 months of light the ice melts and when you get up to 6 months no sun light you get more ice growth .So in 2007 was there more sun shine hours recorded than normal in the Artic?.
Ref – UK John says:
April 30, 2010 at 8:51 am
“This young man comes from East Anglia, it is very flat, very rural, little to do.
Inbreeding!”
___________________________
You know in all my time (too short) in East Anglia I never picked up on that phenom. What brand/type of folkmeter are you using? Do you use the Cambridge Sliding Scale or the Lakenheath Fixed Point Metric. I prefer a quite new, though untested, version (3.01.1a) of the Ipswich Wetbulb Sliding Fixed Point Fahrenheit Scale.
PS: I’ve noted to my chagrin that people are the same everywhere, only more or less so in most places due to local culture. The measured differences on a continental scale amount to miniscule fluctuations of +/- .00003%. It’s a lot like global monthly temperature variation put out by UAH. Detecting something so small on a daily basis can give one a headache;-)
skye:
Melt ponds and the melt-back of the snow means that the Albedo of sea ice falls quite a bit during the melt season (when open ocean water starts to appear). In normal conditions, there is not much difference in the Albedo between frozen sea ice and open ocean at this time of the year.
Here is the annual cycle of Albedos for different areas/regions in the Arctic from 1982 to 1999. Note that Greenland has a fairly high number throughout the year but the sea ice has quite a drop-out during the melt season.
http://journals.ametsoc.org/action/showFullPopup?doi=10.1175%2FJCLI3438.1&id=_e8
From Lindsay and Rothrock: Our friends at the Polar Science Cetnre at the University of Washington.
http://psc.apl.washington.edu/lindsay/pdf_files/albedo_from_avhrr_jclim_1994.pdf
From 1980 before anyone was concerned about Arctic ice melting. The average surface albedo at 80N (where the ice does not really melt out yet) is 0.508 in August. The only way that number can occur is for sea ice albedo to be relatively low at the height of the melt season.
http://climate.rutgers.edu/stateclim_v1/robinson_pubs/refereed/Kukla_and_Robinson_1980.pdf
Even our own Judith Curry has written two papers about it here.
http://curry.eas.gatech.edu/currydoc/Curry_JC5.pdf
http://lightning.sbs.ohio-state.edu/geo622/paper_ice_Curry1995.pdf
Bill, if the albedo of open water is the same as that of ice, then tell me, what are the dark areas in MODIS images from the Arctic Ocean (http://rapidfire.sci.gsfc.nasa.gov/subsets/?mosaic=Arctic.2010121.terra.4km).
Sea ice albedo does drop off strongly during the melt season, see the many publications by Don Perovich at CRREL. This is related to melting the snow off the ice and the development of melt ponds. So if you take a satellite pixel say from AVHRR (like you Lindsay and Rothrock linked paper), you are averaging over at least 1.1 square km, so for August, you will be averaging melt ponds and bare ice into that 0.47 value quoted in their abstract. Also, the Lindsay and Rothrock 1994 paper was one of the earlier attempts at deriving sea ice albedo from AVHRR, and the BRDF correction they apply to the AVHRR data (remember, ice does not reflect equally in all directions), is very inaccurate, so the absolute magnitude of the albedo is a bit in error. Field measurements by Perovich would be a better reference to use.
Note also your Kukla and Robinson reference shows the albedo value for mixed pixels (again, ice and melt ponds are mixed together to give the 0.508 albedo you quote for August). And they are not using actual data, but assuming values from literature and applying them to latitudinal bands.
And your first link is also for mixed pixels.
But again, I will let the visible satellite imagery speak for itself. If water had the same reflectance as ice, you wouldn’t be able to see the difference between the two in the imagery. But, you do.
From AlanG on April 30, 2010 at 11:07 pm:
JER0ME: OR just press the Control (CTRL) button and spin the mouse wheel, for those of us in the 21st century…
You can write but you cannot make them read… Your sarcastic comment is wrong. That only changes the web site you are looking at. (…)
Errrrrr! (annoying buzzer sound)
AlanG, as mentioned here, you are giving Firefox advice. What versions are you giving advice for? With the pointer in the area displaying the site, the advice given by JEROME works on the latest versions, with the caveat that you shouldn’t spin the scroll wheel but slowly turn it a click at a time. I tried a big turn when I read that advice on the “New Theme” thread and my P4 machine w/ on-board graphics hung for a bit processing all the view changes. The ctrl-dash(minus sign) and ctrl-plus sign (or = without shift if using the key next to the backspace) combos also work to go smaller/larger.
And here is the whole Arctic (covering about 55/60-90N);
On September 10th, 2009 (the peak of the ice melt last year).
http://rapidfire.sci.gsfc.nasa.gov/subsets/?mosaic=Arctic.2009253.terra.4km.jpg
Versus yesterday:
http://rapidfire.sci.gsfc.nasa.gov/subsets/?mosaic=Arctic.2010120.terra.4km.jpg
There isn’t a lot of difference from 75-90N between the two.
And here is the box covering approximately 80-90N on September 10th, 2009.
http://rapidfire.sci.gsfc.nasa.gov/subsets/?subset=Arctic_r04c03.2009253.terra.2km
From skye on May 1, 2010 at 8:27 am:
(…) (http://rapidfire.sci.gsfc.nasa.gov/subsets/?mosaic=Arctic.2010121.terra.4km).
(…)
But again, I will let the visible satellite imagery speak for itself. If water had the same reflectance as ice, you wouldn’t be able to see the difference between the two in the imagery. But, you do.
Such wonderful imagery looking straight down!
Now post some pics showing what it looks like at the small angles, let us see what the reflectance looks like as incoming light from the Sun would actually “see” it.
After all, people on this site are likely aware that a body of water can appear dark looking straight down into it, but as you look out over the water it doesn’t look so dark, and as you look further out it isn’t “dark” at all since you’re seeing reflections. At the small angles is there really a great difference between still water, smooth shiny ice, and a mirror?
So let’s see the pics (and measurements) based on the actual “solar view” of the Arctic, rather that comparisons in ways that don’t matter since those conditions don’t happen.
PS to my previous post:
Don’t forget, the ice floats above the water. You can clearly see the assorted spaces (leads etc) from that straight down view. But as the angles get less than 90deg (perpendicular to ground), that shiny ice starts blocking out the view of that dark water. From the “solar view” there is lots less dark water visible, thus calculations based off a simple area ratio of open water to ice would overestimate how much solar radiation can be absorbed.
You can see this effect for yourself, just lay some dominoes or Lego’s on your desk while sitting down, then look at them from the side as you rotate your head while lowering it to desk, until you’re resting the side of your head on the top of the desk, then close your eyes and think of the significance of your new observations…