Stronger winds explain puzzling growth of sea ice in Antarctica
From University of Washington press room by Hannah Hickey
Much attention is paid to melting sea ice in the Arctic. But less clear is the situation on the other side of the planet. Despite warmer air and oceans, there’s more sea ice in Antarctica now than in the 1970s – a fact often pounced on by global warming skeptics. The latest numbers suggest the Antarctic sea ice may be heading toward a record high this year.
While changes in weather may play a big role in short-term changes in sea ice seen in the past couple of months, changes in winds have apparently led to the more general upward sea ice trend during the past few decades, according to University of Washington research. A new modeling study to be published in the Journal of Climate shows that stronger polar winds lead to an increase in Antarctic sea ice, even in a warming climate.
“The overwhelming evidence is that the Southern Ocean is warming,” said author Jinlun Zhang, an oceanographer at the UW Applied Physics Laboratory. “Why would sea ice be increasing? Although the rate of increase is small, it is a puzzle to scientists.”
This mixture of different types of Antarctic sea ice was photographed Oct. 13, 2012, by a NASA aircraft flying over the Bellingshausen Sea.
His new study shows that stronger westerly winds swirling around the South Pole can explain 80 percent of the increase in Antarctic sea ice volume in the past three decades.
The polar vortex that swirls around the South Pole is not just stronger than it was when satellite records began in the 1970s, it has more convergence, meaning it shoves the sea ice together to cause ridging. Stronger winds also drive ice faster, which leads to still more deformation and ridging. This creates thicker, longer-lasting ice, while exposing surrounding water and thin ice to the blistering cold winds that cause more ice growth.
In a computer simulation that includes detailed interactions between wind and sea, thick ice — more than 6 feet deep — increased by about 1 percent per year from 1979 to 2010, while the amount of thin ice stayed fairly constant. The end result is a thicker, slightly larger ice pack that lasts longer into the summer.
“You’ve got more thick ice, more ridged ice, and at the same time you will get more ice extent because the ice just survives longer,” Zhang said.
When the model held the polar winds at a constant level, the sea ice increased only 20 percent as much. A previous study by Zhang showed that changes in water density could explain the remaining increase.
“People have been talking about the possible link between winds and Antarctic sea ice expansion before, but I think this is the first study that confirms this link through a model experiment,” commented Axel Schweiger, a polar scientist at the UW Applied Physics Lab. “This is another process by which dynamic changes in the atmosphere can make changes in sea ice that are not necessarily expected.”
The research was funded by the National Science Foundation.
Still unknown is why the southern winds have been getting stronger. Some scientists have theorized that it could be related to global warming, or to the ozone depletion in the Southern Hemisphere, or just to natural cycles of variability.
Differences between the two poles could explain why they are not behaving in the same way. Surface air warming in the Arctic appears to be greater and more uniform, Zhang said. Another difference is that northern water is in a fairly protected basin, while the Antarctic sea ice floats in open oceans where it expands freely in winter and melts almost completely in summer.
The sea ice uptick in Antarctica is small compared with the amount being lost in the Arctic, meaning there is an overall decrease in sea ice worldwide.
Many of the global climate models have been unable to explain the observed increase in Antarctic sea ice. Researchers have been working to improve models to better reproduce the observed increase in sea ice there and predict what the future may bring.
Eventually, Zhang anticipates that if warmer temperatures come to dominate they will resolve the apparent contradiction.
“If the warming continues, at some point the trend will reverse,” Zhang said.
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The polar vortex that swirls around the South Pole is not just stronger than it was when satellite records began in the 1970s, it has more convergence, meaning it shoves the sea ice together to cause ridging.
This makes me wonder if this isn’t one of the reasons that the “ozone hole” continues, despite CFC reduction schemes. Of course the study is all model based, so it may not represent reality.
Perhaps the addition of 49 gt/yr of ice on the continent over the last decade is causing more to be pushed out to sea as well?
The NSIDC Arctic and Antarctic graphs are misleading. The Arctic is scaled from 2-12 and the Antarctic is scaled at 0-20. This gives the impression that the Antarctic gains are puny relative to the Arctic losses. In reality, the current aggregate of both extents is roughly half a million km shy of the 30 year mean. The current aggregate extent is 19.351 million sq km. using a quick and dirty rough estimate; 1 million sq km is equal to the 5% of the total extent. Essentially, the current global extent is 2.6-2.7% below the 30-year mean.
The truth of the matter is things are not nearly as dire as the individual graphs would lead you to believe. The aggregate NSIDC sea ice extent provides a clearer picture of what is, and most importantly, what isn’t happening.
http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/global.daily.ice.area.withtrend.jpg
Will people give over with these ‘modelling studies’!
Do they think people are stupid?
Computers aren’t like the ones on Star Trek, you can’t just ask them a question and get an answer. Computers know jack..!
If you want an answer, you have to tell it what the answer is in the first place!
These herberts took two observed things… one that Antarctic ice has increased and two that winds have increased a bit in that area. They then TOLD the computer that the second was causing the first and also in-putted the parameters for how much. They might as well have told it that the increased ice was causing the increased wind.
Brilliant!
That is proof of nothing, other than the stupidity of the ‘modellers’. Two things that happen at the same time are automatically correlated in their idiotic La La land.
Don’t anybody tell them that pirates have also increased during the period of increasing ice and increasing winds or we will have another computer ‘study’, proving something or other, coming round the corner soon!
Alan
RobRicket says:
September 19, 2013 at 8:44 am
No, it’s actually worse than you think!
See, the recent “losses” of Arctic sea ice extent are trending towards “zero.” (And, in fact, they can never go below “zero” so there is a finite bound to the “loss of Arctic sea ice problem”. It can never get worse than zero (effective zero, since “sea ice extents” includes areas of as little as 15% sea ice cover.)
Regardless, sea ice minimums could continue to decline – and that decline (from 4,000 Kmm^2 to 3,000 Kkm^2 to 2,000 Kkm^2 to 1, 000 Kkm^2 to “ZERO!”) will get ever larger and larger “percent losses!”
Can’t you see the CAGW headlines in Nature, Scientific America, and National Geographic” each year?
“25% of Sea Ice Now Threatened by Global Warming”
“Arctic Loses 33% of Sea Ice!”
“Scientists Predict 50% Sea Ice Loss!”
“Global Warming to Cause 100% of Sea Ice Loss”
But these very real (potential) sea ice losses are ALL at 81, 83, and 85 degree latitude! They occur when the sun is at most between 4 and 8 degrees above the horizon – and that for only 4 hours a day. The rest of the time, the sun is either even lower (near sunrise or sunset) or completely below the horizon. Not only is the albedo of open water 4 to 8 times higher than at temperate latitudes of most areas of the earth, but the atmospheric attenuation at 80 and 85 degrees north is 4 to 12 times higher than at more normal latitudes. There simply is no solar radiation to be absorbed by the “exposed Arctic Ocean” when sea ice is at low levels in mid-September.
And, the make it even worse than you think: the Arctic ice that is melting is increasingly “dirty” and is itself absorbing more heat energy. Thus, the “dirty” and pond-covered Arctic sea ice that is melting in August and September has a much lower albedo than the pristine new snow-covered sea ice in October, January, or early May. Net? The sea ice albedo in September is even closer to the albedo of the open ocean in September. When September or August sea ice does melt, there is little difference in direct radiation albedo.
Now, diffuse albedos are significantly different (for diffuse radiation, open ocean absorbs much more energy than even dirty sea ice). But – since the Arctic clouds CAUSE the diffuse radiation, if there is diffuse radiation to be absorbed, more than 70% of the potential diffuse radiation has already been reflected from the ocean by the clouds that caused the diffuse radiation. Net? Even under clouds, the open Arctic Ocean at times of minimum sea ice extents lose more heat than they gain from either direct or diffuse radiation.
Essentially no radiation gets through to “heat” the Arctic ocean when the sea ice melts up there from today’s minimum extent levels. If all of the sea ice did vanish one year, there is a ever-larger increase in heat losses from the ocean waters, and little heat gain in the Arctic, and thus the planet cools.
Not so in the Antarctic. There, the increasing levels of sea ice reflect much more light energy at ALL times of the year – at sea ice minimum (2,000 to 3,000 Kkm^2) and at all times up to sea ice maximum (19,000 Kkm^2 to today’s records of 19,600 Kkm62. But notice the propaganda “gain”! That is, that a “gain” of only 500 Kkm^2 is “only” 500/19,000.
With this CAGW logic, even a gain of 1,000 Kkm^2 in the Antarctic can be dismissed as “only” a 5% change! But remember, the Arctic “lost” 50% of its sea ice!
Yet that 500,000 km^2 “gain” (because the 19,500,000 “record Antarctic extent” is at latitudes far closer to the equator than the 85-86 north latitude of minimum Arctic sea ice extents: at minimum Antarctic sea extent, the sea ice is at latitude 70 south: closer to the equator than Arctic sea ice is at its MAXIMUM extents. (Hudson Bay, Bering Straits, the Baltic are exceptions to this 70 degree latitude “rule” – but those are “arctic waters” that melt every year anyway. Pretending that they do not already melt, or that they change the earth’s heat balance when they melt is incorrect.) At today’s 19,500,000 Antarctic sea ice extents, the reflecting edge – the new sea ice – is at latitude 60 degrees south. Closer to the equator than the south tip of Greenland, than southern Alaska. At those latitudes, every sq km of new sea ice IS reflecting significant amounts of solar energy – thus cooling the planet even more.
Looking at ” total sea ice” as you did hides the gain even more effectively because it assumes that Arctic sea ice is reflecting as much solar energy as Antarctic sea.
And, if you are tricked into “adding” a 500,000 km^2 “gain” of sea ice to a 1,100,000 “loss” of sea, you merely confuse the reader into conceding that there is still a “loss” of sea ice – which is the intent after all of the whole conversation. But the “balance” is wrong – dead wrong. The “loss” is at high latitudes where solar energy cannot be gained, and the gain is at significantly lower latitudes where there is solar energy to be reflected.
RACookPE1978 says:
September 19, 2013 at 11:01 am
Excellent, simple analysis.
Why do CACA advocates supposedly worry about sea ice? Polar bears thrive even in the absence of Arctic sea ice, so no worries there. That leaves albedo, unless you know of some other alleged concern.
And as you correctly show, expanding Antarctic sea ice produces far more allegedly beneficial reflectivity than could possibly be lost by retreating Arctic ice.
Less Arctic sea ice in summer would be a blessing to humans & other living things, but sadly its extent is probably going to start waxing again.
RACookPE1978,
Good information to chew on. Clearly, there must be enough energy reaching the Arctic ice to cause summer melting. Since the albedo of dirty ice is superior to water, I don’t see the logic in saying: ” Even under clouds, the open Arctic Ocean at times of minimum sea ice extents lose more heat than they gain.” What of periods of less cloud cover…if ice is melting, we can hardly say there is a net heat loss.
Having said that, the info regarding the relative differences in ice extent lattitudes is appreciated.
So the growth in Antarctica has at various times been placed on ozone hole more winds, then snow, then melting ice, then lighter winds and now stronger winds. Plus this post now says they don’t know what is causing the “southern winds have been getting stronger”. Could it be they just don’t know?
Jimbo says:
September 19, 2013 at 12:58 pm
Also has been blamed on fresh melt water from the EAIS, which isn’t melting.
Western Antarctic ice sheet is back up again to date. I wonder why it was down in the last couple of years. Ahhhhhh less wind. 🙂
http://ice-glaces.ec.gc.ca/prods/CVCHACTWA/20130916180000_CVCHACTWA_0007271338.gif
Not only that but Dronning Maud Land, in the Atlantic sector of East Antarctica, has experienced some extreme snowfalls (as predicted by the IPCC) but the extent is up (not predicted by the IPCC but the opposite for the 21 century). Warmists are desperate to see the total meltdown of Antarctica. All we sceptics can do is wait, observe and point out issues.
http://onlinelibrary.wiley.com/doi/10.1002/grl.50559/full
Jimbo says:
September 19, 2013 at 1:11 pm
And from the WAIS, where there might be some water-lubricated glaciers, the supposed cold freshwater hasn’t caused sea ice growth as great as from the much more extensive EAIS.
Dilemmas & conundra multiply for CACA WAGs on all continents, oceans & in the air. Mother Nature likes to slap down liars, frauds, rogues & charlatans.
Jimbo says:
September 19, 2013 at 1:11 pm
Abstract from your cited study:
“Enhanced snowfall on the East Antarctic ice sheet is projected to significantly mitigate 21st century global sea level rise. In recent years (2009 and 2011), regionally extreme snowfall anomalies in Dronning Maud Land, in the Atlantic sector of East Antarctica, have been observed. It has been unclear, however, whether these anomalies can be ascribed to natural decadal variability, or whether they could signal the beginning of a long-term increase of snowfall. Here we use output of a regional atmospheric climate model, evaluated with available firn core records and gravimetry observations, and show that such episodes had not been seen previously in the satellite climate data era (1979). Comparisons with historical data that originate from firn cores, one with records extending back to the 18th century, confirm that accumulation anomalies of this scale have not occurred in the past ~60 years, although comparable anomalies are found further back in time. We examined several regional climate model projections, describing various warming scenarios into the 21st century. Anomalies with magnitudes similar to the recently observed ones were not present in the model output for the current climate, but were found increasingly probable toward the end of the 21st century.”
Maybe the authors should have considered running a cooling scenario.
But to their credit they appear to recognize that climate didn’t suddenly start changing without precedent in 1979, having been static for the prior four billion years.
So in 2012 easterly weak winds explain puzzling lows of sea ice in Antarctica?
It is amazing to watch the warming crowd contort themselves to defend the indefensible.
Jim Steele: Sept 18 @7:33
That is an informative essay on Antarctic vs Artic sea ice formation you posted on your blog
RobRicket on September 19, 2013 at 12:24 pm
RACookPE1978,Good information to chew on. Clearly, there must be enough energy reaching the Arctic ice to cause summer melting. Since the albedo of dirty ice is superior to water, I don’t see the logic in saying: ” Even under clouds, the open Arctic Ocean at times of minimum sea ice extents lose more heat than they gain.” What of periods of less cloud cover…if ice is melting, we can hardly say there is a net heat loss.Having said that, the info regarding the relative differences in ice extent lattitudes is appreciated.
The factor missing in your reasoning is water temperature and heat. If Arctic melt is at least partly from warm water input, then there can be heat loss even during melting.
It is considered that ENSO heat especially from el Ninos is transported to the poles taking a decade or more to get there. Thus ocean heat is continually delivered to the Arctic, at a varying rate depending on ocean oscillation cycles such as PDO and AMO.
Ice loss begins before air temperature increases above zero in summer and continues in September after it goes below zero. When air temperature is below zero at the sea surface there must always be heat loss from the water.
If poleward transport of heat is considered, then the poles must be continually shedding heat from the oceans.
RGB
What many people do not realize is that the Earth can warm or cool significantly due to NOTHING BUT alterations in global transport of heat.
Amen brother! An important fact missed entirely by those who seek some distinct atmospheric driver (CO2, soot, volcanoes, ozone etc..) for every inflection and wiggle in the temperature record.
But this fact is well understood by the ocean circulation modelling community, but fails to be communicated beyond it. This parochialism and territoriality is a major failure of the scientific community and process.
milodonharlani says:
September 19, 2013 at 11:14 am (replying to)
RACookPE1978 says:
September 19, 2013 at 11:01 am
(and)
phlogiston says:
September 19, 2013 at 9:10 pm (replying to)
RobRicket on September 19, 2013 at 12:24 pm
There are several simultaneous, but not mutually contradictory, heat flows going on at the same time up there (or down under in Antarctica) that oppose each each other. And, heat transfer being an instantaneous event, the opposing heat fluxes can actually reverse each other at different times of the same day, or, at the same time at the same day, oppose each other at different latitudes.
The top of the surface water will be slightly above freezing all the time: But it changes as currents flow under the ice (the water getting colder the longer it is under the colder ice), and getting warmer (up to 4 or 5 degrees C several hundred km ‘s away from the edge of the ice fields. The AVERAGE surface air will vary from -20 C to -25 C (mid-November to mid-March) but will oscillate greatly down around that level. Look at the DMI 80 north latitude air temperatures: Over the summer months, the average air temperature will go up to +3 degrees C – NEVER HIGHER! Over 50 years, the average summer air temperatures have never varied, but are slowly decreasing as ice extents have decreased. Regardless of “why” or how long this trend may continue, the average air temperature over the Arctic Ocean has NOT been increasing, and has very, very small standard deviation. (Winter standard deviations are very, very large. Annual “arctic air temperatures” ONLY have been increasing if the winter (non-solar radiation temperatures!) are used.
Now, over each 24 hour period, the actual air temperature will vary +/- 6 to 10 degrees around this slowly changing daily average air temperature. So the actual air temperature right above the ocean (or the ice) will vary over a 8 to 12 degree range: Sometimes each day ( in summer) the air temperature is higher than the water temperature, sometimes it will be lower over each sq km at each latitude. In the winter, the air temperature is always lower than the water temperature, but there is seldom very much open water in the Arctic each winter. Sensible Heat Transfer is always from water to air in winter, but the amount varies each day and each hour. In summer, sometimes heat transfer is one way, sometimes it is the other. Latent heat transfer (change of phase) is the same differences.
Now, over ice, the top of the ice will be “almost” the same as the air temperature. But down under that 1 or 2 meters of ice, the water will be always be warmer than the ice. So, again, the heat will flow in different directions each hour of each day: Sometimes freezing more water into ice at the bottom, sometimes melting ice into water at the bottom of the ice. Through all of this phase changes and salinity changes right in the same little band where the ice and water are mixed. But there is nothing contradictory about the changes: What is hotter at this given minute? How saline is the water at this minute at this given sq meter of under ice surface?
Is the sun shining above through clouds this minute? What about the previous minute? Energy absorbed can – and does – change minute-to-minute as the sun comes in and out of clouds, as clouds change the diffuse radiation levels, and as the solar elevation angle of the sun changes each hour. Clouds cover the arctic about 83% of the time in the summer, but only about 40% in March, April, and May. So direct radiation is more likely in early spring, less likely in late summer when the “melt season” is high gear. But the almost continuous cloud cover reflects 30-70% of the inbound radiation. Still a lot: it is enough to melt some of the ice from above. Not all. Slits and opening in the ice will re-freeze at night, and the sun does NOT stay continuously high in the sky at all locations up north. As it gets later in the July and august and September, even the far north sees less and less solar radiation.
BUT – the long wave radiation heat transfer depends on the surface temperature of the radiating surface (to the 4th power actually) if the two emissivities are the same, right? . (And water and ice do have nearly the same emissivities.) So, where the open ocean is present, more long wave radiation is emitted to space (remember than open ocean is ALWAYS warmer than ice-covered surfaces), more evaporation losses are present when the open ocean is present (no evaporation losses at all if it is ice-covered actually), and sensible heat transfer through convective is higher when the open ocean water is present. And, in contrast to the ever-diminishing solar exposure, the open ocean areas in the Arctic are always evaporating, always radiating long wave radiation, and always convecting more heat away into the cold arctic air.
So, over any 24 hour period, any open ocean in the Arctic above 80 degrees north always loses more energy from mid-August through late September than ice-covered waters do.
There are other winds to take into account. Strong “katabatic” winds blow down from the Antarctic continental interior to the coast, bringing a load of snow and tending to drive the sea ice away from shore, producing open water.
Gil Dewart says:
September 20, 2013 at 11:58 am
And, if open water is produced by such kakabatic winds, the openings are right around the continent edge at about 70-71 latitude. The actual antarctic sea ice edge is 10 degrees further north at between 61 to 60 south latitude.
You would be claiming that sea ice in east Texas is moved by winds blowing in Denver, if katabatic winds were the only explanation. .
RACookPE1978 says:
September 19, 2013 at 9:54 pm
Many thanks for the useful explanation of Arctic sea ice surface heat dynamics. Open water in the Arctic in late summer = heat loss, as you conclude. However increased open water is there due to heat input to the Arctic. Therefore the inescapable conclusion is negative feedback. Some folks don’t like to hear this.
Here’s a thought experiment. Imagine the Arctic ocean / sea is static and stagnant, no water movement at all at any depth. (Assume also no undersea volcanoes.) What is the average air temperature over the whole year at the Arctic? From your data, it must be somewhere in the -10C – -20C range. Well below zero. So our imaginary static Arctic ocean would be frozen solid from surface to sea floor. Only at latitudes where the annual average temperature increases above zero, would liquid water be found.
Therefore the presence of liquid water in parts of the Arctic where annual average temperatures are less than zero is simple proof that there is continuous import of heat into the Arctic in ocean currents.
Where does this heat go?
The ice mass is accreting that is a fact that the wind is doing it is a sidebar. Is the wind not a part of the climate ?
phlogiston says:
September 21, 2013 at 10:49 am
I’d rather not use a ‘flat plate” thought experiment, since the heat transfer changes across the Arctic from March 20 through September 20 are due to rotation and inclination: The math is not trivial, but it is simple if you use a globe instead of the CAGW’s prefered Hansen-NASA-GISS Mercator-projected flat plate insulated-ice-cube-in-space.
To begin with, they use a very simplified – but equally inaccurate – albedo summary chart like that in the Wickedpediafiles, then compare their assumed ocean albedo to the “classic” laboratory Fresnel equations for reflection of a laboratory perfect, pure water, pure atmosphere pure light wave reflecting off of a perfectly stable perfectly flat pool of water. Obviously, such a perfection is ridiculed as false (“oceans have waves” for example, as I have read here many times) but then the approximations and simplifying assumptions on their side multiply ad infinitum.
So, with your permission, can I expand on those albedos?
Most assume “pure ice”,
but the real world has “dirty” Arctic ice with many melt ponds that is actually much darker June-July-August-September than under fresh snow in January,
Most assume “pure water” under direct single-wave radiation as a incorrect albedo for water,
but the real world has “open ocean” with wind and turbidity, and that “real world water” reflects diffuse light and direct light very, very differently. Real world, measured albedos must be used.
You’ll want to look up these papers on the web:
Richard Payne, 1972: “Albedo of the Sea Surface”.
Use Figure 4 for direct radiation (clear skies.)
Use Figure 5 for diffuse radiation (cloudy skies); those two are the best.
Journal of the Atmospheric Sciences.
Now, Payne measured his albedos from Buzzards Bay, Mass over a 4 month period.
Charles Rutledge, P5.17 Multi-Year Observations of Ocean Albedo From A Rigid Marine Ocean Platform, 2006 did a longer study over a greater range of solar elevation angles.
Use his Figure 4 in this web page for both clear skies (red, direct radiation) and cloudy skies(blue dots, diffuse radiation) to see the very striking difference between the two forms of solar radiation hitting sea water.
Scott Pegau, 2001, Albedo of Arctic Leads In Summer, doesn’t find strikingly different results from Payne or Briegleb, but his plots confirm their experimental values for the Arctic Ocean in “real world” melting Arctic waters up in and around the sea ice. Most importantly, Pegau expands on Briegleb’s equation for open ocean albedos at varying solar elevation angles by adding a wind speed correction term. So, add Pegau’s Figure 3 (albedo of direct beam radiation vs solar elevation angles at various wind speeds from 0 to 20 meters/sec.) Essentially, that replaces the “theoretical lab values” of the Fresnel equation – while confirming their ultimate form! – with actual field-measured albedos from the Arctic Ocean.
Briegleb’s paper is 1986, Journal of Climate and Applied Meteorology – it is harder to use compared to either Payne or Pegau’s papers and had fewer easy-to-use figures since he prefers to plot albedos vs the cosine of the solar zenith angle. Skip it unless you really, really want to feel utter pain for several hours.
So, what will you find when you replace these open ocean experiment values into the CAGW’s assumed Wickedpediafiles figures?
1. Up in the Arctic Ocean above 80 north latitude, the sun will be at high angles for long period of time only during June and July. By August, it will be very low in the sky, and be above the horizon fro increasingly shorter amounts of time each day. Because it’s solar elevation angle is much lower in the sky, two things happen: The first is that the sun’s light must penetrate increasingly larger amounts of atmosphere to get to the surface of the Arctic ice. The second thing is that, once that much-weakened beam of direct solar energy does get down to the Arctic’s ice surface, it hits the ice (or the open arctic ocean water) at increasingly smaller and smaller solar elevation angles. There, it hits with a much higher albedo, and more energy is reflected from the open water. Use the NOAA’s solar elevation calculator to see the impact of a 8 or 10 air mass value on penetration coefficients!
2. On the other hand, if that direct beam of sunlight does get through the ever-thickening atmosphere and if does hits the arctic ice in mid July, August or September, the ice it hits is “dirtier” and has a much lower albedo than what is drawn above. (Instead of “clean ice” of albedo of 0.83 to 0.85, July and August sea ice is only 0.55 to 0.60 albedo. ) Thus, what little direct sunlight that does get through is absorbed into the sea ice only slightly less than it is absorbed into the open ocean in July and August! (June and very late May are different stories: more radiation does get through at longer durations each day at higher solar elevation angles in June than in early May or late July. then again, that is why those are the melt seasons.)
3. But, direct solar radiation is only 1/2 the story: and, to tell the truth, actually about 1/7 the story. The skies in July and August are very cloudy, with only 1 in 7 days being clear with near-theoretical amounts of direct radiation getting through the clouds to strike the surface. Under those 6 out of 7 days when conditions of clouds and diffuse radiation dominate the Arctic, the albedoes change.
4. Sea ice albedo under diffuse radiation remains about the same: 65% reflected, 35% absorbed.
5. Open water albedo under cloudy skies in lower: 6.6% is reflected, 93.4% is absorbed are the usually an accepted values, and these values do not vary much as solar elevation angle changes. However, those same clouds that lower albedo also reflect so much radiation from above that the satellites measuring outbound energy cannot distinguish easily between cloud reflections and ice reflections. In total, only about 33% of the potential solar radiation gets through the clouds (the rest is reflected into space) and is available to be absorbed into the water.
So, if the energy does get through the atmosphere, just about equal amounts are reflected as absorbed; and it it diffused through the atmosphere, only 1/3 gets through to be potentially absorbed into the Arctic Ocean.
Net – as your thought experiment shows for a “flat plate, solid water” Arctic, the total outbound radiation will always – over the year – cool the Arctic.
RACookPE1978 says:
September 21, 2013 at 11:44 pm
phlogiston says:
September 21, 2013 at 10:49 am
So correct analysis of albedo with real world values of actual Arctic surface conditions comes to the same conclusion from the other side – an in an impressive and cool way. Surface radiation heat flux at the Arctic goes just one way – “to infinity and beyond”.
It seems that the modelling of all this should be done in true explicit 3D. In the Arctic every component such as diffuse as opposed to direct insolation has completely different geometry.
Oh no. It’s still worse than you think. 8<)
See, the real world, 3D model of the inbound (heating) solar radiation shows that the solar radiation always has to fight its way through a ever-thicker atmosphere and an ever-lower solar elevation angle to get to the surface. Thus, in the early morning and late afternoon hours of each day, every day of the year, the inbound solar energy will be attenuated to get through 2, 3, 4 up to 11 or higher atmospheric "thickness". Then, as above, when that light energy does get to the earth's surface, the surviving light energy is reflected off of the surface (water or ice) by ever-increasing albedos. (It is only at that one minute, during those few fleeting seconds around local apparent noon that both atmospheric attenuation and albedo are both minimum for that one day. And, every day further from June 22's solar maximum, the daily radiation decreases as well. So, 364 days of the year, inbound radiation is less than the maximum.
Outbound radiation? Well, outbound long waver radiation is perpendicular to the earth's surface every minute of every hour of every day of the year. Outbound (cooling) long wave radiation always needs only penetrate 1.0 atmosphere thickness .. And, once out of the atmosphere, the outbound radiation immediately hits the infinitely cold temperature of space. (Inbound longwave radiative flux will vary based on atmospheric temperatures and relative cloud cover.)
Evaporation heat losses from theopen ocean? 24 hours per day, increasing as wind speed increases.
Convective heat losses? 24 hours per day. Increasing as wind energy increases.
Increasing as air temperature decreases.