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Putting the recent Antarctic snowmelt minimum into context

Filed under: — eric @ 27 October 2009

Guest Commentary by Andrew Monaghan and Marco Tedesco

Our study published in mid October in Geophysical Research Letters (Tedesco and Monaghan, 2009) documents record minimum snowmelt for Antarctica during austral summer 2008-2009 and lower-than-normal melt for several recent years, based on a 30-year satellite microwave record. Numerous blogs have cited the results as a challenge to previous studies reporting Antarctic warming, while also steadfastly ignoring other studies with similar results (e.g. Barrett et al., 2009). They have overlooked that these studies show that Antarctic warming has occurred mostly in winter and spring, whereas melting of course occurs in summer. And they oversimplify the causality and hence confuse our prediction for the future. We found that the same mechanism that has primarily caused low snowmelt in recent years will likely change in a manner that will enhance snowmelt in forthcoming decades. A brief summary follows.

Map of Antarctica showing number of melting days in summer 2008-2099.
Map of Antarctica showing number of melting days in summer 2008-2009.

Our study demonstrates that low melt years during the 1979-2009 satellite record are related to the strength of the westerly winds that encircle Antarctica, known as the Southern Hemisphere Annular Mode (SAM). When the SAM is in a positive phase – meaning that the belt of winds is stronger than average – it has a cooling effect on Antarctic surface temperatures. The SAM was especially strong in austral spring and summer 2008-2009, and subsequently the 2008-2009 snowmelt was lower than normal. During the past 30-40 years, the SAM has gradually strengthened during austral summer (Marshall 2003), due mainly to human-caused stratospheric ozone depletion. In turn, the increasing SAM has weakened longer-term summer warming over Antarctica. The SAM index is not strongly positive every year of course, and particularly when combined with other atmospheric circulation changes (e.g. a strongly positive Southern Oscillation Index (SOI) – indicative of La Nina conditions) may contribute to anomalously high or low summer temperatures in any given year. The figures shown in our Supplementary Material section in our original paper illustrate this point nicely (below):
1998 Summer1999 Summer
Monthly averaged December-January surface temperature anomalies (K) for 1998 (left, strong negative SAM and SOI) and 1999 (right, strong positive SAM and SOI).

The ozone hole is projected to recover significantly during the next 25 – 50 years due to the Montreal Protocol, which limits ozone-depleting substances used in industrial and household applications. As the ozone hole ‘heals’, the increasing summer SAM trends are projected to subside. As this happens, it is likely that summer temperature increases over Antarctica will become stronger and more widespread because the warming effect from greenhouse gas increases will no longer be kept in check by the dynamic
cooling impact of the SAM.

Therefore, the linkage between the SAM and snowmelt leads to our key conclusion: that enhanced snowmelt is likely in Antarctica as the SAM trends subside during the 21st century and summer temperatures become warmer. Our results agree with studies that have noted cooling and/or slower warming during the past three decades due to increasing SAM trends over the same period. Additionally, our conclusions do not contradict findings showing strong regional warming on the Antarctic Peninsula and in West Antarctica for the past 50 years, and warming over the entire continent for the past century. Our record is limited to the satellite era only, during which ozone depletion has dominated Antarctic summer temperature trends, and as already noted above, the observed warming in the last 50-100 years has occurred mostly in winter and spring. This context is important.


92 Responses to “Putting the recent Antarctic snowmelt minimum into context”

  1. 51
    Mark says:

    “There may be grain of possibility there?. Whichever way you cut it..still comes back to climate change doesn’t it!”

    I was more concerned with the “therefore this can’t be climate change, can it” statement.

    It wasn’t supported by the statements used to proffer it as fact.

  2. 52
    Mark says:

    “28: Mark. It’s unique in respect that the sediment shows an unbroken linear timeline back 200ky. ”

    This didn’t appear in the paper presented.

  3. 53
    Mark says:

    “The original station was much lower at sea level, knowing inversions Clyde’s temperature record should not to be used ! and again, in the late 80’s the station moved to the airport!”

    Maybe surfacestations has something disavowing this station as representative.

    Chip can then pop over to WUWT to discuss it.

  4. 54
    JCH says:

    I do hope Eric reads the paper and makes comments. The skeptics really think they have easily debunked this paper, which, because the lakebed is unaltered deep into the geologic past, seems to be a pretty important line of evidence for the current warming not being due to natural variability.

    I mentioned this paper and the skeptic claims on another thread a week or so ago, and somebody pointed out that skeptics need to explain why DDT only killed off the cold-adapted. On ice loss on Baffin Island, they may have some ‘splainin’ to do.

  5. 55
    CM says:

    Theo (#49), here’s a layman’s take — I’m happy if anyone will correct me:

    The westerly winds that circle the Antarctic are stronger in the Antarctic winter when the air over the pole is colder and there’s lower pressure aloft. The ozone hole means ultraviolet is not absorbed by ozone to heat the stratosphere as it used to in the Antarctic summer. Therefore the circumpolar winds are stronger for longer, and as this belt of wind keeps out warmer air from higher latitudes, this affects Antarctic surface temperatures.

    [Response: Pretty good. See also this post which was one of the first we ever did. - gavin]

    Note it is actually the absorption of visible and infrared, not so much ultraviolet by ozone that warms the stratosphere (and hence cools it when there is less ozone).–eric]
    [err, um, actually correction to my correction. Ozone does absorb in the visible, but not much. The relevant absorption is in the relatively low frequency UV. See e.g. here: (http://www.atmosphere.mpg.de/enid/208.html). Amazing what a quick google search gets you. Easier than going through my file drawers.--eric]

  6. 56
    Hank Roberts says:

    > 43, Wayne Davidson, 28 October 2009 at 11:58 PM, station moved twice
    But has anyone got _pictures_ of the three different stations?

  7. 57
    Timothy Chase says:

    Theo Hopkins wrote in 49

    Maybe I missed it, but what has ozone got to, do one way or the other, with antarctic temperatures? Can someone point me to an answer.

    In the upper stratosphere the cooling trend is due mostly to the reduced amount of infrared radiation reaching it as the enhanced greenhouse effect renders the troposphere more opaque to infrared radiation. But in the lower part of the stratosphere the cooling trend has been more due to the depletion of ozone than to enhanced greenhouse effect. Ozone is semi-opaque to ultraviolet radiation — but like carbon dioxide and water vapor are opaque to infrared, although ultraviolet radiation is of sufficiently high energy that it will split ozone.

    The stratosphere is lower at the poles, and likewise, much of Antarctica is at a fairly high altitude. So as the ozone layer is depleted this lowers the temperature of the lower stratosphere — and by lowering the temperature of the lower stratosphere it increases the temperature differential between the surface of Antarctica (particularly towards the pole), and this increases air circulation between the stratosphere there and the troposphere, resulting in a cooling effect at the surface.

    You can see that here:

    [Antarctica: Cooling at the Center, Warming Outside the Polar Front]
    http://rst.gsfc.nasa.gov/Sect16/antarctic_temp-AVH1982-2004.jpg

    from:

    Earth Systems Science: Evidence for Global Warming
    http://rst.gsfc.nasa.gov/Sect16/Sect16_2.html

    As the ozone layer heals this will warm the ozone layer, weakening the winds that cool the polar Antarctic surface, and thus reducing the cooling effect that a weakened ozone layer has had upon Antarctica.
    *
    One more detail regarding the image of warming and cooling in Antarctica shown above…

    The polar front that encircles much of Antarctica in essence shelters it from the rest of the warming that is taking place throughout nearly all of the rest of the troposphere. This is one of the reasons why the southern pole is so sensitive to ozone depletion. However, the polar front is at roughly 67° latitude south, so its most of the West Antarctic Peninsula lies outside of polar front and therefore isn’t protected by it. Thus the West Antarctic Peninsula is already seeing the same sort of polar amplification that we are seeing in the Arctic.

  8. 58
    Timothy Chase says:

    CORRECTIONS to 57

    [Oh dear lord...]

    Third sentence of first paragraph:

    Ozone is semi-opaque to ultraviolet radiation — but like carbon dioxide and water vapor are opaque to infrared, although ultraviolet radiation is of sufficiently high energy that it will split ozone.

    Third sentence of last paragraph:

    This is one of the reasons why the southern pole is so sensitive to ozone depletion. However, the polar front is at roughly 67° latitude south, so its most of the West Antarctic Peninsula lies outside of polar front and therefore isn’t protected by it.

    PS

    First and last paragraphs are those that are most likely to be remembered — given the mechanics of human memory. So of course they are where you are more likely to have mistakes — in the first paragraph because you are just winding up and the last paragraph because you are already winding down.

  9. 59
    Deamiter says:

    #49 — Theo: Check out the links in Eric’s response to comment 18.

  10. 60
    CM says:

    Re my #55 above: Yes, I should have remembered ozone was not just absorbing ultraviolet. Thanks.

    [Response: actually, you're more right than I was .. Look at my correction to me correction, above. O3 does absorb in IR of course -- and in the troposphere it acts as a greenhouse gas -- but its the absorption of sunlight (in the low-freq UV) that results in warming of the stratosphere in the presence of O3. Absorption in the visible is not very important, though non-zero.-eric]

    Also, when referring to the ozone ‘hole’ cooling the stratosphere I should have spoken of (austral) *spring*, though the effects drag on through summer.

    And, ehem, where I said “higher” latitudes, I obviously meant “lower”.
    (Well, on my map the South Pole is *down*, so everything else has to be *higher*, right? :-) )

  11. 61
    tharanga says:

    How well do models handle the interplay of the SAM, ozone depletion and Antarctic temperatures? Can anybody recommend a good review paper on the topic?

    [Response: (Cough). - gavin]

  12. 62
    David Wozney says:

    The averaged trend of the Antarctic sea ice extent shows an increase from 1979 to 2009. The Antarctic sea ice is about 90% of the world’s ice.

    [Response: No it isn't. You are confusing the ice sheet (on land) with the sea ice (on the sea). This post is about the ice on land. - gavin]

  13. 63

    # 56 Hank, Google earth Clyde River Nunavut… The near extreme West 2 small buildings next to extreme West black roof top building was the second station and garage. Across the Bay due East find the circle by the road , that was about the first station. They removed the buildings, further North a few Kilometers up road I met a huge polar bear who luckily preferred a beach whale Carcass than me. Finally, on village side of Bay follow the road much further North, the current station is there. By one of the buildings is an auto weather system and CARS community Radio operator observer installation. Before anyone quotes mysterious weather events at one location, please study hard, and eliminate
    other plausible explanations. Its warming Up Here in the Arctic! You Don’t have to take my word for it, take the satellite view:
    http://www.esrl.noaa.gov/psd/map/images/rnl/sfctmpmer_30a.rnl.gif

  14. 64
    CM says:

    Re ozone absorption spectrum, some more googling: Ozone absorbs in the visible at the 602 nm “Chappuis band”.
    http://disc.sci.gsfc.nasa.gov/oceancolor/additional/science-focus/ocean-color/ozone.shtml

    There’s a neat solar spectrum graph at GlobalWarmingArt, which compares the incoming at TOA and sea-level to give a broad-brush impression of how much energy is absorbed by what in which parts of the spectrum (averaged over the U.S. – I guess it could be pretty different over the Antarctic?).
    http://www.globalwarmingart.com/wiki/File:Solar_Spectrum_png

  15. 65
    Mark says:

    “The Antarctic sea ice is about 90% of the world’s ice.”

    And if there’s only antartic ice left because it’s all melted elsewhere, it will have 100% of the world’s ice.

    But how does that prove it’s cooling?

    (the earlier part is forgivable: I’d not made that connection either, but that 90% is irrelevant hence needs walloping).

  16. 66
    Hank Roberts says:

    >62, 65, “sea ice”
    See Gavin’s inline reply correcting the gross error in 62

  17. 67
    Hank Roberts says:

    “Ozone (O3) is the only naturally occurring atmospheric gas that absorbs visible light appreciably. An acrid gas, ozone is blue because it absorbs orange light…. The amount of ozone in the atmosphere is tiny—about 1 part per 2 million—so if it were all brought to sea level, it would form a layer only about 3 millimeters deep, on average.

    These 3 millimeters of ozone absorb about 1.5 percent of the orange light (and none of the blue or violet light) in a sunbeam or moonbeam that reaches ground level when the sun or moon is directly overhead, but more than 25 percent of the orange light when the moon or sun is at the horizon because of the long, oblique path. Ozone absorbs enough orange light to keep the zenith sky blue at sunset and sunrise. Without ozone, the zenith sky would be almost white at sunrise and sunset! And as we are about to see, absorption of orange light by ozone can also turn the moon blue.”

    http://www.weatherwise.org/Archives/Back%20Issues/2009/Sept-Oct%202009/full-Gedzelman.html
    (A wonderful, illustrated read on sky color, aerosols and much else.)

  18. 68
    Hank Roberts says:

    Too good not to quote more. Mark your calendars, USAians!

    “… The next total lunar eclipse will not occur until the winter solstice, December 21, 2010, … total and visible (provided the sky is clear) anywhere in the 50 states. Furthermore the blue fringe should be deeper blue than normal because the sunlight reaching the northern part of the umbra will pass over the high northern latitudes of Earth, where ozone content is generally high.”

    http://www.weatherwise.org/Archives/Back%20Issues/2009/Sept-Oct%202009/full-Gedzelman.html

  19. 69
    Mark says:

    Hank @66.

    “What does 90% ice is irrelevant” have to do with whether it’s 90% of sea ice or 90% of land ice? Or, indeed, any other fraction not 90% of either?

  20. 70
    Lawrence Coleman says:

    69 Hank! All sea and land ice is relevant! The ocean currents circulate the cool water around the sea ice packs and keep the current flowing north by thermohaline circulation..vise-versa for the arctic regions. And the land and sea ice especially at higher altitudes chills the air and keeps the world tolerably cool. That’s what I’m always saying..what happens when the arctic sea ice is gone for most of the year..what helps cools the air then let alone the sea( N.A. thermohaline conveyor)? Only the mountains in greenland, Ellesmere island and parts of northern canada..that aint enough! Missing that vital 10% will alone cause catastrophic change to the world’s climate..mark my words!

  21. 71
    scott putnam says:

    This comes from a non-scientist, a real estate lawyer who reads this site with great interest. Recent posts have discussed an apparent slowdown in the rate of growth of temperature readings around the world. Also discussed has been the diminishment of the arctic ice cap. Is it possible that these are connected? When we toss an ice cube into a glass of room-temperature water, the cube melts and the whole glass cools down some. Can this be happening on a global scale?
    Sorry if this is unbelievably elementary, but I just had to ask.

    [Response: Good question, but not really valid. The amount of ice loss (from arctic sea ice, and from ice sheets/mountain glaciers) is a very small number (someone care to do the maths?) is large, but the energy involved is small compared to the energy needed to heat or cool the planet. The dominant effect of ice loss would be the increase in energy fluxes into the system because of the decrease in albedo. - gavin]

  22. 72
    Karsten Johansen says:

    “Climate sceptics” recently have been very active here in Norway. Two professors (Ole Humlum and Ole Henrik Ellestad) on 16. october in the newspaper “Aftenposten” (see: http://www.aftenposten.no/meninger/debatt/article3323704.ece ) said, without naming any precise sources of any kind, that 1) “The UN environmental organization” (?) now have “admitted”, that “it is wrong that temperatures in the last hundred years have been rising sharply”, and 2) “the medieval warm period was far warmer than it is now, and it was global”. Could someone help clearing up what they may be referring to?

    Ellestad and others also have some somewhat enigmatic curves in “Teknisk Ukeblad” (“Technical Weekly”) on 21. october: http://www.tu.no/natur/article226175.ece – the figures occur a bit down in the article, one claiming to show the “surface temperature of the Greenland Ice Sheet” (but no mention of exactly where!), and the other claiming to combine “observed facts” with the “IPCC calculations”. No precise sources for the figures are given. A third figure is claiming to show “antarctic snowmelt”, and is referred to Marco Tedesco, Earth and Atmospheric Sciences, City College of New York and Andrew J. Monaghan, National Center for Atmospheric Research. I sure would like some comments.

  23. 73
    CM says:

    Karsten (#72), re question (1), why don’t you write to them and ask? And report back if you get an answer, it might be fun (my best guess is they totally misread an incident with a graph in a recent UNEP compendium on climate science). Re the last question, the above article by Tedesco and Monaghan puts the graph into context.

  24. 74
    G. Karst says:

    Here is what October looks like:

    October (month end averages) NSIDC (sea ice extent)

    30 yrs ago
    1980 Southern Hemisphere = 18.9 million sq km
    1980 Northern Hemisphere = 9.5 million sq km
    Total = 28.4 million sq km

    Recorded Arctic min yr.
    2007 Southern Hemisphere = 18.6 million sq km
    2007 Northern Hemisphere = 6.8 million sq km
    Total = 25.4 million sq km

    Last yr.
    2008 Southern Hemisphere = 18.1 million sq km
    2008 Northern Hemisphere = 8.4 million sq km
    Total = 26.5 million sq km

    This yr.
    2009 Southern Hemisphere = 18.5 million sq km
    2009 Northern Hemisphere = 7.5 million sq km
    Total = 26.0 million sq km

    ftp://sidads.colorado.edu//DATASETS/NOAA/G02135/Oct/S_198010_extn.png
    ftp://sidads.colorado.edu//DATASETS/NOAA/G02135/Oct/N_198010_extn.png
    ftp://sidads.colorado.edu//DATASETS/NOAA/G02135/Oct/N_200710_extn.png
    ftp://sidads.colorado.edu//DATASETS/NOAA/G02135/Oct/S_200710_extn.png
    ftp://sidads.colorado.edu//DATASETS/NOAA/G02135/Oct/S_200810_extn.png
    ftp://sidads.colorado.edu//DATASETS/NOAA/G02135/Oct/N_200810_extn.png
    ftp://sidads.colorado.edu//DATASETS/NOAA/G02135/Oct/S_200910_extn.png
    ftp://sidads.colorado.edu//DATASETS/NOAA/G02135/Oct/N_200910_extn.png

  25. 75
    Hank Roberts says:

    Yup. And you can look this stuff up, if you’re curious about what’s going on and want more than a snapshot comparison of a few handpicked instants.

    http://scholar.google.com/scholar?q=%22antarctic+sea+ice%22
    for example
    http://cat.inist.fr/?aModele=afficheN&cpsidt=2831504
    Abrupt mid-twentieth-century decline in Antarctic sea-ice extent from whaling records

    and moving to contemporary work
    http://www.sciencedaily.com/releases/2009/04/090421101629.htm
    “ScienceDaily (Apr. 22, 2009) — Increased growth in Antarctic sea ice during the past 30 years is a result of changing weather patterns caused by the ozone hole, according to new research. Reporting in the journal Geophysical Research Letters, scientists from British Antarctic Survey (BAS) and NASA say that while there has been a dramatic loss of Arctic sea ice, Antarctic sea ice has increased by a small amount as a result of the ozone hole delaying the impact of greenhouse gas increases on the climate of the continent…..”

  26. 76
    Mark says:

    Ice extent does not equal ice volume.

  27. 77
    Mark says:

    PS even by your figures, we’ve lost 500,000 square kilometers of ice extent.

    At that rate, there will be no ice at either pole in 52 years.

    How does this prove there is no global warming?

  28. 78
    G. Karst says:

    Hank Roberts and Mark:

    I don’t post my ice report to prove or disprove anything. It is posted for information purposes only.

    Another blogger asked me if I thought this year’s seasonal ice recovery (extent 1st month ice growth) appears sluggish or lagging? I thought the following might help answer the question:

    1980 Northern Hemisphere (Oct.) = 9.5 million sq km
    1980 Northern Hemisphere (Sept) = 7.8 million sq km
    Delta Sept\Oct Extent = +1.7

    2007 Northern Hemisphere (Oct.) = 6.8 million sq km
    2007 Northern Hemisphere (Sept) = 4.3 million sq km
    Delta Sept\oct Extent = +2.5

    2008 Northern Hemisphere (Oct.) = 8.4 million sq km
    2008 Northern Hemisphere (Sept) = 4.7 million sq km
    Delta Sept\Oct Extent = +3.7

    2009 Northern Hemisphere (Oct.) = 7.5 million sq km
    2009 Northern Hemisphere (Sept) = 5.4 million sq km
    Delta Sept\Oct Extent = +2.1

    1979-2000 mean (Oct.) = 9.3 million sq km
    1979-2000 mean (Sept) = 7.0 million sq km
    Mean Delta Sept\Oct Extent = +2.3

    So in the Arctic, the first month freeze-up ice growth (+2.1) is comparable to the mean first month growth (+2.3). Beyond this… we just have to wait and see. GK

    [Response: GK, thanks. Useful and interesting. Still, I feel compelled to remind readers that this post was not about sea ice!--eric ]

  29. 79

    Karsten,

    Here are some studies that say it was NOT warmer during the Medieval Warm Period than it is now:

    Bradley, R.S., Hughes, M.K., and H.F. Diaz 2003. “Climate Change in Medieval Time.” Science 302, 404-405.

    Goosse H., Arzel O., Luterbacher J., Mann M.E., Renssen H., Riedwyl N., Timmermann A., Xoplaki E., Wanner H. 2006. “The Origin of the European ‘Medieval Warm Period’.” Clim. Past, 2, 99–113.

    Osborn, Timothy J. and Keith R. Briffa 2006. “The Spatial Extent of 20th-Century Warmth in the Context of the Past 1200 Years.” Science 311, 841-844.

  30. 80
    jyyh says:

    putting it in context might include the fact that the northern hemisphere ice area, according to Cryosphere Today anomaly plot, hasn’t been on the positive side after 2003 spring. let’s see if this winter makes an exception.

  31. 81

    OK, the artice is not about ice extent. However, ice extent measurement is the best proxy to test AGW hypothesis against. There is no missing data subject to “creative” methodologies, temperature “reconstruction”, etc. The ice cover data is pure and relatively untampered indicator of global temperature, (expecially considerting that according to AGW hypothesis it is the poles that are expected to warm the most).

    [Response:Actually any losses (or gains) in Antarctic sea ice there have to do with the winds, not the temperature. Temperature is almost irrelevant for Antarctic sea ice. For the Arctic, it's much more important. But in general if you want temperature, use a thermometer.--eric]

    Now getting back few posts (#74), we have roughly 2.4 (=28.4-26) ice loss, or about 10% for the 30 year time period. How can #77 assert with straight face that the poles would be ice free in 52 years?

    [Response: Neither of you is making very sensible statements. The ARCTIC may be ice free IN SUMMER in a few decades or less. The Antarctic will continue to have substantial ice in summer for some time to come, I am sure. Both regions will continue to have substantial sea ice in winter indefinitely.--eric]

  32. 82
    Hank Roberts says:

    Tegiri, from the looks of your weblog, it might be better for people to answer you over there, rather than try to sort out and cite all the assumptions you seem to make. Ahem.

  33. 83
    Mark says:

    “Now getting back few posts (#74), we have roughly 2.4 (=28.4-26) ice loss, or about 10% for the 30 year time period. How can #77 assert with straight face that the poles would be ice free in 52 years?”

    By showing that 26million sq km left and 0.5 million sq km having gone in the past year, the ice COULD be free AT BOTH POLES by 2060.

    And most of that ice is in the South, so the North Pole should disappear earlier.

    NOTE: This is as rigorous a mathematical treatment of the data as you have done, so should be equally valid.

  34. 84
    Brian Dodge says:

    “The amount of ice loss (from arctic sea ice, and from ice sheets/mountain glaciers) is a very small number (someone care to do the maths?)” -gavin

    9.162969e+12 m^3 melt total 2009 , (assuming 1 meter thickness)
    307195000 J/m^3 to melt ice
    2.814818262e+21 Joules total to melt Arctic sea ice
    1.66 w/m^2 forcing from anthropogenic CO2 cdiac.ornl.gov/pns/current_ghg.html
    5.10072e+14 m^2 area of earth wikipedia
    2.6702146783e+22 watt-second, or Joules/year forcing
    10.541542914 percent of forcing required to melt total arctic sea ice loss in 2009 , not just the increase in loss(calculated to a ridiculous number of significant figures – even when I set the number of places to zero in Appleworks, they reappear when cut and pasted). Prior to ~ 1950, the annual melt was about 5e+12 m^3 (assuming 1m thickness), so the amount absorbed by the INCREASE in ice melt would be even less. http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seasonal.extent.1900-2007.jpg
    Most of the ice that melts is first year ice(ice that formed since the last summer minimum), and most of the first year ice is around 1-2 meters thick, but winds change the area and thickness of sea ice, resulting in large uncertainties in calculating the volume of sea ice melt from the extent (but not enough to make up an order of magnitude).
    We also have to remember that the freezing in the fall gives back most of that heat absorbed by melting the previous spring & summer, or to put it another way, some of the Joules put into the system as visible radiation are stored in melting ice for a while, before being returned by the heat of fusion from re-forming the ice and ultimately radiated away as thermal infrared radiation. The joules of energy that the change in melt of ~4e12 m^3 of ice(give or take a factor of 3?) represents have taken from about 1959 to accumulate.

    One years worth of the current anthropogenic CO2 forcing would result in 4.9e-4 deg C rise if distributed throughout the 1.3e+19 m^3 of the ocean.

    5.23e+11 m^3 Greenland ice melt
    (www.interscience.wiley.com) DOI: 10.1002/hyp.7354
    ‘Greenland Ice Sheet surface mass-balance modelling
    and freshwater flux for 2007, and in a 1995–2007
    perspective” Mernild et al

    1.0 e+11 m^3 glacial melt
    http://www.eoearth.org/article/Observed_Impacts_of_Climate_Changes

    so they are another order of magnitude away from having a measurable impact.

    [Response: Just to be clear here, you are calculating the amount of cooling effect on the ocean from dumping cold ice into it, right? That was Gavin's question but it wasn't worded clearly. Note that your figure of 0.0004 for the entire ocean would be about 0.02 for the mixed layer only (the upper ~75 of the ocean). That would actually seem significant except that as you point out it is a seasonal, not a mean annual value, and has no bearing on the trend.--eric]

  35. 85
    G. Karst says:

    Brian Dodge #84:

    I don’t see a calculation for sensible heat that is required to raise ice from (-30?) to the melting point or did I misunderstand?

  36. 86

    On a tangentially related topic, according to the IJIS sea ice extent data, November 5, 2009, had the lowest extent for that date ever. Or, to put it another way, the sea ice extent trace for 2009 crossed below the record-low 2007 values, as it’s been threatening to do for about two weeks.

    I wouldn’t make too much of it–sea ice extent is volatile and variable, and there’s an excellent chance that 2009 won’t stay the lowest for long, as 2006 had exceptionally low values for early December. But if someone starts spouting off about “recovery,” there’s a rather sharp rejoinder available at the moment!

  37. 87
    Brian Dodge says:

    @ G. Karst 6 November 2009 11:12 AM
    Since the question was about how much heat was absorbed by melting, I ignored the additional amount for thermal capacity. ice heat capacity ~2 J/g-degC, heat of fusion ~335J/g, so the additional heat from -30 to 0 would be less than an additional 20%. Also, the top surface of the sea ice may be -30C, but the bottom will be ~-2C.

    according to Appl Environ Microbiol. 2004 January; 70(1): 550–557. doi: 10.1128/AEM.70.1.550-557.2004
    Bacterial Activity at −2 to −20°C in Arctic Wintertime Sea Ice, Junge et al
    “Arctic wintertime sea-ice cores, characterized by a temperature gradient of −2 to −20°C, were investigated…” so we’re probably talking about an average ice minimum temperature of around -11C.

    @ Kevin McKinney — 6 November 2009 5:26 PM The “recovery” this year was still below the long term OLS trend – see http://www.arctic.noaa.gov/reportcard/figures/seaice2009fig2-sml.jpg. Note the 90-92 recovery – at least it ended above the trend.

  38. 88

    Brian, you don’t have to tell me!

    But I can’t guarantee that there won’t be someone on a newsblog out there somewhere who’s foolish enough to claim otherwise.

  39. 89
    jyyh says:

    The probability to hit the low mark this late in the year in such a dataset is about 1 to 18, if the ice extent was a totally random number. So, this is not a very remarkable year in this respect. However, some previous years are, and they’re located on the latter half of the dataset, so I’d say there is a trend in the ice extent, and it is down, as the cumulative ice extent anomaly, since the beginning of the dataset, appears to be negative. But what happened before this, is another matter as far as this dataset is concerned. (I’m assuming the IJIS dataset is robust and well-documented, up to the spectrographic instruments, in the stable orbit, that are being used to obtain this data.) But of course this is trivial.

  40. 90
    jyyh says:

    And one might want to calculate the correct value before posting a reply to the prev post.

  41. 91

    Ice loss in the Antarctic is not only from melting in situ. If you do a Google Scholar search on antarctic ice sheet ice stream velocity you get some interesting results.

    Here’s one of interest that for once is not paywalled:
    Bell et al. Large subglacial lakes in East Antarctica at the onset
    of fast-flowing ice streams
    , Nature 445, 904-907 (22 February 2007).

    [Response: Indeed! Ice loss from Antarctic is virtually not at all from melting! I don't recall the numbers off hand but is is probably > 90% from calving.--eric]

  42. 92
    Hank Roberts says:

    Eric, do you have any idea if outburst floods could occur from under an ice stream like those in Antarctica that are long enough to reach the sea and be calving? I’m thinking of events like the Channeled Scablands flood or floods, which happened from under ice very far inland, very late in deglaciation.

    I’m also wondering whether the ANDRILL work has come up with any indication of that kind of rapid event.

    Bits and pieces of vaguely related stuff found at http://climatechangepsychology.blogspot.com/2009/07/subglacial-hydrology-basal.html


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