NASA: Warm Ocean Currents Cause Majority of Ice Loss from Antarctica

Breaking news from NASA and the ICEsat team, that’s their headline, not mine.

This really makes all the hype over the now discredited Steig et al. paper, which attempted to establish an air temperature warming trend as one of the possible causes for “Antarctic melting”, only to have the Mannian PCA math they used shot down in flames for smearing data from the Antarctic Peninsula all over the continent, look even weaker.

Click for a larger image or visit the video animation page here

WASHINGTON — Warm ocean currents attacking the underside of ice shelves are the dominant cause of recent ice loss from Antarctica, a new study using measurements from NASA’s Ice, Cloud, and land Elevation Satellite (ICESat) revealed.

An international team of scientists used a combination of satellite measurements and models to differentiate between the two known causes of melting ice shelves: warm ocean currents thawing the underbelly of the floating extensions of ice sheets and warm air melting them from above. The finding, published today in the journal Nature, brings scientists a step closer to providing reliable projections of future sea level rise.

The researchers concluded that 20 of the 54 ice shelves studied are being melted by warm ocean currents. Most of these are in West Antarctica, where inland glaciers flowing down to the coast and feeding into these thinning ice shelves have accelerated, draining more ice into the sea and contributing to sea-level rise. This ocean-driven thinning is responsible for the most widespread and rapid ice losses in West Antarctica, and for the majority of Antarctic ice sheet loss during the study period.

“We can lose an awful lot of ice to the sea without ever having summers warm enough to make the snow on top of the glaciers melt,” said the study’s lead author Hamish Pritchard of the British Antarctic Survey in Cambridge, United Kingdom. “The oceans can do all the work from below.”

To map the changing thickness of almost all the floating ice shelves around Antarctica, the team used a time series of 4.5 million surface height measurements taken by a laser instrument mounted on ICESat from October 2003 to October 2008. They measured how the ice shelf height changed over time and ran computer models to discard changes in ice thickness because of natural snow accumulation and compaction. The researchers also used a tide model that eliminated height changes caused by tides raising and lowering the ice shelves.

“This study demonstrates the power of space-based, laser altimetry for understanding Earth processes,” said Tom Wagner, cryosphere program scientist at NASA Headquarters in Washington.” Coupled with NASA’s portfolio of other ice sheet research using data from our GRACE mission, satellite radars and aircraft, we get a comprehensive view of ice sheet change that improves estimates of sea level rise.”

Previous studies used satellite radar data to measure the evolution of ice shelves and glaciers, but laser measurements are more precise in detecting changes in ice shelf thickness through time. This is especially true in coastal areas. Steeper slopes at the grounding line, where floating ice shelves connect with the landmass, cause problems for lower-resolution radar altimeters.

ICESat was the first satellite specifically designed to use laser altimetry to study the Earth’s polar regions. It operated from 2003 to 2009. Its successor, ICESat-2, is scheduled for launch in 2016.

“This study demonstrates the urgent need for ICESat-2 to get into space,” said Jay Zwally, ICESat project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md. “We have limited information on the changes in polar regions caused by climate change. Nothing can look at these changes like satellite measurements do.”

The new research also links the observed increase in melting that occurs on the underside of a glacier or ice shelf, called basal melt, and glacier acceleration with changes in wind patterns.

“Studies have shown Antarctic winds have changed because of changes in climate,” Pritchard said. “This has affected the strength and direction of ocean currents. As a result warm water is funnelled beneath the floating ice. These studies and our new results suggest Antarctica’s glaciers are responding rapidly to a changing climate.”

A different picture is seen on the Antarctic Peninsula, the long stretch of land pointing towards South America. The study found thinning of the largest ice shelf on the peninsula can be explained by warm summer winds directly melting the snow on the ice shelf surfaces. The patterns of widespread ocean-driven melting and summer melting on the Antarctic Peninsula can be attributed to changing wind patterns.

The study was carried out by an international team from the British Antarctic Survey, Utrecht University in Utrecht, Netherlands, the University of California in San Diego and the non-profit research institute Earth and Space Research in Corvallis, Ore.

For more information about ICESat and ICESat-2, visit:

http://icesat.gsfc.nasa.gov

==============================================================

I have the paper:

Antarctic ice-sheet loss driven by basal melting
of ice shelves
H. D. Pritchard, S. R. M. Ligtenberg, H. A. Fricker, D. G. Vaughan1, M. R. van den Broeke & L. Padman

doi:10.1038/nature10968

And I’ll be posting more on it later, for now, here is the summary:

To summarize, we find thinning attributed to ocean-driven basal melt on 20 of 54 ice shelves, with the most widespread and rapid losses (up to ~ 7m yr -1) on the coast of West Antarctica, where warm waters at depth have access to thick ice shelves via deep bathymetric troughs. There is evidence that changes in wind forcing explain both the
increased oceanic supply of warm water to thinning West Antarctic ice shelves, and the atmospheric warming on the Antarctic Peninsula that caused the loss of Larsen A and B and now dominates the thinning of Larsen C. That is to say, both processes are ultimately linked to the atmosphere. Both mechanisms imply that Antarctic ice shelves can respond rapidly to Southern Hemisphere wind patterns that vary on
timescales of years to decades.

We find that ocean-driven ice-shelf thinning is in all cases coupled with dynamic thinning of grounded tributary glaciers that together account for about 40% of Antarctic discharge and the majority of Antarctic ice-sheet mass loss2. In agreement with recent model predictions, we conclude that it is reduced buttressing from the thinning
ice shelves that is driving glacier acceleration and dynamic thinning.

This implies that the most profound contemporary changes to the ice sheets and their contribution to sea level rise can be attributed to ocean thermal forcing that is sustained over decades and may already have triggered a period of unstable glacier retreat.

And just in case people forget, the sea-ice trend in Antarctica is positive:

http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seaice.anomaly.antarctic.png

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82 thoughts on “NASA: Warm Ocean Currents Cause Majority of Ice Loss from Antarctica

  1. I have not read the paper. However it sounds like they measured – for the first time – the rate at which floating ice was melting from below. That sounds useful. We always knew ice melted from below but it is useful to quantify that.

    However what puzzles me is how they can state that the rate of melting from below is accelerating since they have just got done with measuring it for the first time. The link to changing current patterns also seems a bit of a stretch. People have been looking at these currents for … how long? How can anyone realistically say they have changed?

    It looks like a good bit of experimental measurement has been sexed up with a bunch of alarming and unjustified speculative statements to make it more appealing to a political rag like science.

  2. Clearly no-one has done any engineering calculation of the enthalpies involved.

    The real heating will be from reduction of cloud albedo due to phytoplankton blooms.

  3. just to say that, regardless of the scientifico/politico conclusions, that that is a beautiful picture of an unknown region of our planet.

  4. I suppose what they are saying is the volume of ice is less, not the surface area of ice. What’s the purpose of showing the 2D surface area when the paper is discussing the 3D volume?

  5. Well floating ice melts and contributes nothing to sea level rise. If what we are dealing with is a migrating glacier which is what they do, how does the ocean speed it up? The glaciers moving into the ocean cause sea level rise their melting just makes them less obvious.

  6. The BBC tonight showed a programme of the Old Pulteney expedition to row to the magnetic pole as it was in 1996. Readers of this blog will know of this trip as it was followed on-line at the time. The thing that amused me was how they always seemed suprised when they came up against pack ice. Who would have thought it?

  7. The Russians just bored thru 4,000 meters of ice into the fresh water Lake Vostok. This 14,000 sq km lake is the size of Lake Ontario, with an average surface temperature of -50F and 50 times the ambient dissolved Oxygen of typical fresh water lakes. Please, how did human Carbon Dioxide redirect OLR to keep this lake melted ? Maybe the HEAT, the fresh WATER and the free OXYGEN all come from BELOW !

    See…. http://www.thelivingmoon.com/41pegasus/02files/Lake_Vostok02.html

    ….and then engage “brain”.

  8. So sea ice cover measurably increased over the chosen time period but they used models to “prove” that the ice got thinner. Please explain how the warm currents managed to thin the ice without effecting it’s coverage.

  9. From NASA and published in Nature. It’s got be right. Right? With that off my chest I’ll go read it anyway.

  10. I have a simple experiment I would recommend to anyone who has doubts about how Antarctic ice sheets “melt”.

    You need a stop watch, and a thermometer that includes zero deg C on its scale, and you need to find something like a mid west or similar cold lake that gets ice on it in winter. Night time is preferred to eliminate spurious “heat” sources like the sun.

    So part one of the experiment requires waiting for a wind free night, with the air and water Temperature at the lake right at zero deg C, so there should be chunks of ice floating on the water.

    You srtip down to your pre-natal suit, and start the stop watch as you stand alongside the lake shore.

    Time how long it takes for you to freeze to death, or preferrably abandon this phase of the experiment, before that time.

    Phase two of the experiment is identical to phase one, with one slight experimental difference in procedure.
    Before you start the stop watch, as in phase one, go and jump in the lake.

    Record the new time to expiration.

    Then write a short essay, on the relative thermal conduction of air and water.

    [Moderator's Note: George, while there is a certain elegance to this experiment, don't you think, maybe, you might have suggested that no one try this at home? -REP]

  11. “We can lose an awful lot of ice to the sea without ever having summers warm enough to make the snow on top of the glaciers melt,” said the study’s lead author Hamish Pritchard of the British Antarctic Survey in Cambridge, United Kingdom. “The oceans can do all the work from below.”

    I pointed out recently that the Antarctic Peninsula warming causing glacier/floating icesheet melt claim was fraudulent, because all the warming was at night, and night time temperatures hardly ever get above zero C.

    The not warm enough to melt the snow on top claim, appears to derive from this point, but otherwise not based on any data.

    Snow and ice can ‘melt’ from the top when temperatures are below zero, by sublimation, and increased solar insolation (from decreased clouds) will cause increased sublimation. Perhaps they have excluded this mechanism as the cause of icesheet melt, I can’t say from Anthony’s summary above.

  12. WASHINGTON — Warm ocean currents attacking the underside of ice shelves are the dominant cause of recent ice loss from Antarctica,

    “ATTACKING” for gosh sakes!!!! attacking….

    Who wrote this? What an A-hole.

    Besides this ATTACK has been under way for 10,000 years….The BS never ends does it?

  13. Ah, now I understand! The missing heat was hiding under Antarctica, wringing its hands together and laughing to itself with all the devious intent of a silent film villain!

    need I say /sarc?

  14. Ice floats. If it melts, total water level stays the same. If it doesn’t melt, water level stays the same. Middle school science. What a bunch of clowns to even go there.

    Maybe I will pull the ice above the glass bar trick on them, and bet it doesn’t overflow!

    “C’mon—Double or Nothing, professor!”

    This is one of the useful properties of water that enables life on the planet.

  15. That’s one for the history books surly? NASA in 2012 announces that they have discovered that Ice melts. (Yea of course, “and don’t call me surly”).

    The usual culprits will have headlines like,
    “ocean driving Antarctic ice loss”.
    “Antarctic Ice Melting From Warm Water Below”.
    “Warmer seas behind Antarctic ice shelf melt, study finds”

    The spin on ice melting is very much on Que at the end of this this summer in the SH.
    I wonder why? (hmm… scratches chin!)

  16. I’m not sure how going from radar to laser helps you measure the removal of the underside of the ice.

  17. And to pre-empt some of the icesheet -sea ice confusion. On the east side of the Antarctic Peninsula, where the Larsen icesheets are, you can see from the graphic below that sea ice extends far beyond the icesheets (300+ kms) even at this time year, the late Austral summer.

    You can also see ice free areas along the coast, so warm ocean upwelling along the coast is certainly occuring. The question is whether it has increased.

  18. [Moderator's Note: George, while there is a certain elegance to this experiment, don't you think, maybe, you might have suggested that no one try this at home? -REP]
    >>>>>>>

    But he did. He said go to a lake. And to jump in it.

  19. So… ocean currents have changed, bringing more warm water to the ice sheet, causing it to melt from below. Assuming that is correct:

    1. Where did the warm water originate from?
    2. What replaced the warm water? Presumably less warm water from somewhere else?
    3. Since the warm water left where it was, and was replaced by other presumably colder water, did some area of earth experience cooling as a consequence?
    4. If the volume of water melting from the ice sheet is in fact large enough to cause a measurable rise in sea level, then the obvious question is, where does that water go once it melts? Being at freezing point, it would be colder than any other water it flowed toward.

    So, unless the study can show corresponding cooling to account for the change in warm water currents and the results of new cold water entering the ocean in vast quantities, all they’ve shown is…that something changed. Oh my. Like that’s never happened before.

  20. But…but…the antarctic sea ice extent is above average right now

    and actually the arctic sea is pretty much at the historical average

    So…uh melting…ice free arctic…global warming…abnormal…catastrophic…I just don’t get it…

  21. Whoops my second plot above one should be …

    Just “kissing” the historical average too. Go, baby ice, go!

  22. Thanks Anthony, a most interesting read, in a world where 70% of the surface area is water, to be precise.

    Antarctica, is a rather unique continent, with it’s very own current, which flows around the continent, unlike all other continents, as this diagram clearly shows :- http://en.wikipedia.org/wiki/File:Conveyor_belt.svg

    So, by what mysterious mechanism are the oceans heating up again, since the initial around the world voyage of the oceanographic research vessel, the HMS Challenger, in 1873?

  23. It’s Nature. I hate to ad hom, but in this case the stain on the rep is inky extreme. Lie to me a few hundred times, and I tend to lose confidence.

    The floating ice is melting! It’s melting! Oh no!!!!!

    Yeah, well, as the Award Winning Best Science Blogger points out: Antarctic ice mass in total is increasing. Good thing if some of the edge ice melts. There’s way too much ice in Antarctica anyway.

    Ice is death. Nothing alive in frozen H2O, because Life requires liquid water. Anarctica is a Continent of Death. We pro-lifers (as opposed to pro-deathers) are not happy about that. What the Big World Gummit types ought to be doing is bombing the ice shelves and towing the bergs to places that could use it. Circulate and melt that dead ice. Do something useful with it.

    WARMER IS BETTER. FIGHTTHE ICE.

  24. I don’t see a problem……Even where they were screaming “it’s breaking” is frozen over 10 times

  25. So, the inference is that CO2 is now causing changes in winds. I am assuming less wind (exception would be Al Hansen). This is back to the old El Nino/CO2 connection that has already been shown to be FALSE.

  26. A warmist talking point, clearly: oceans are warmer because of CO2 warming the air-water interface, causing the breakup of Antarctic ice shelves, which relieve the pressure on the inland glaciers, which then rush to the ocean and raise sea levels.

  27. In the graphic above colour represents ice thickness, not as you might assume ocean temperature or ocean temp change.

    Having read the NASA PR. There is no mention that they measured increased warm water upwelling.

    The logic is icesheets are melting, warm water is upwelling, therefore upwelling warm water has caused the icesheet melt (in the sense of icesheet retreat).

    Either the press release is badly written or the claim is junk.

  28. Athelstan. says:
    April 25, 2012 at 3:57 pm

    Gawd sakes, whatever next – Earth discovered to be in heliocentric orbit?

    Seconded.

    DaveE.

  29. ICESat was the first satellite specifically designed to use laser altimetry to study the Earth’s polar regions. It operated from 2003 to 2009.
    =======
    This is one of the biggest problems with any science that depends on nature cooperating….
    They based everything on the info they have from 2003 – 2009….
    ….by the time they get their paper out there
    it’s changed……

  30. Predictions and WAGS about ice melt cause and effect are fraught with danger. For example, in March the powers that be said this about March’s Arctic ice extent:

    “The ice that grew late this winter is quite thin, and will melt rapidly as the sun rises higher in the sky and the air and water get warmer.”

    It does not appear to be melting rapidly yet. In fact, it seems to be hardly melting at all. It must really suck to say something in a published article, and to say it with such “we know about this stuff, you don’t” confidence, then have your boss tell you to quietly publish ANOTHER article about current conditions now, winking that you should never refer to how wrong you were last month.

  31. I do not think the warm water is “attacking” the ice (warm water bad, ice good). I think the ice is sucking heat out of the warm water that innocently drifts by (ice bad, warm water good).

    If these silly “scientists” can engage in asinine anthopomorphisms to suit their politics, so can I.

  32. Did they really need a satellite and an army of PhD-candidates to figure this out? Some of these ice cakes have been watched for decades, with the expectation that they would eventually break away. The photographs show the whole story. Glacial ice pushed out far enough into the Antarctic Ocean until the stress on the land connection could no longer remain intact, and the ice cake broke away. Recon photos showed this gigantic ice cake was loose, and the warmists went into cardiac arrest over the whole situation.

    The photos showed the surface of the ice cake was absolutely flat. That tells you that the top was not melting. The ocean water was slightly warmer than the ice. That is why it is water and not ice…….get it? It spent years melting off the underside of the ice cake until the lowering of the cake broke the land connection. And it does take a long time for water which may be only one degree warmer that the ice to remove the latent heat from the ice and turn some of the under surface into water.

    If a 10th grade general science student could not figure this out he should be required to repeat the course.

  33. I don’t imagine that the same authors are responsible for this other paper published at the same time (well the names are exactly the same).

    “Corrected ICESat altimetry data, surface mass balance, and firn elevation change on Antarctic ice shelves”

    http://doi.pangaea.de/10.1594/PANGAEA.775982

    Of course, the ICESat data needed to be corrected for … “We have modified the original ICESat data by applying an improved tide model (CATS2008a) as well as the recommended corrections for saturation and surface air pressure (the inverse barometer effect). … The original reported elevation relative to WGS84, as defined …. “

  34. “Studies have shown Antarctic winds have changed because of changes in climate,” Pritchard said. “This has affected the strength and direction of ocean currents. As a result warm water is funnelled beneath the floating ice. These studies and our new results suggest Antarctica’s glaciers are responding rapidly to a changing climate.”

    I have no science qualifications at all but the above seems to say that climate change is driven by climate change.

  35. Rushing – so have not had time to read all comments BUT…… could this melting ice have anything to do with all the undersea vents and volcano’s being discovered? Oceans warming….. from hot steam etc. Wondered also if these undersea activities which are spewing heat and chemicals into our ocean could be responsible for the die offs we are experiencing with dolphins etc…….

  36. “Most of these are in West Antarctica, where inland glaciers flowing down to the coast and feeding into these thinning ice shelves have accelerated, draining more ice into the sea ”

    Glaciers “flowing down” = growing glaciers

    “draining more ice into the sea” = there is more sea ice, not less

    “thinning ice shelves” … how can they be thinning if there is more ice?

    Nature + NASA = Idiots

  37. … ocean thermal forcing … may already have triggered a period of unstable glacier retreat

    Man, I hate this kind of mush-mouthed, cowardly speculation that seems to be a climate scientists specialty …

    w.

  38. As I recall under the Antarctic peninsula (where all of Steig’s Heat was plastered over the whole of Antarctica comes from, there are quite powerful volcanic vents that spew out boiling water continuously (I haven’t got a clue how much this would heat up the water if at all)

  39. looks like real-science.com is out of commission once again….

    [Reply: Works for me. ~dbs, mod.]

  40. Willis, could this be the beginning of a runaway …ocean thermal forcing.. effect? where the Ice acts as a blanket around the warm oceans reflecting back radiation? /jk

  41. “Studies have shown Antarctic winds have changed because of changes in climate,” Pritchard said. “This has affected the strength and direction of ocean currents. As a result warm water is funnelled beneath the floating ice. These studies and our new results suggest Antarctica’s glaciers are responding rapidly to a changing climate.”

    A different picture is seen on the Antarctic Peninsula, the long stretch of land pointing towards South America. The study found thinning of the largest ice shelf on the peninsula can be explained by warm summer winds directly melting the snow on the ice shelf surfaces. The patterns of widespread ocean-driven melting and summer melting on the Antarctic Peninsula can be attributed to changing wind patterns.
    =

    In what is it different? It’s the winds and really too bad for warmists, from Antarctica the number of depressions below 980hPa coming out is increasing and the depressions are deeper -i.e. associated anticyclones are more powerful-… Leroux, Dynamic Analysis of Weather and Climate, Springer 2010 figures 14.10 and 14.11 and page 350 the conclusion is “the warming of the Antarctica peninsula is of dynamical origin”. Intensification of meridional exchanges causing transfer of additional warm, moist air to the Pole as a result of reinforced MPHs. This dynamic is precisely the opposite of what a global warming world should create. What the satellite offers is a confirmation and a precision on the various processes at work, not at all any confirmation of CO2 induced warming… quite the opposite!

  42. Re Lake Vostok being liquid, can I ask again please, why are deep ocean waters so close to freezing point? The have a source of heat below (geothermal) and a source of heat above (the Sun). Until someone can explain why the ocean deeps are not as warm as the surface, I shall regard any global hypothesis about temperature, water and ice with great suspicion. When was the whole Ocean mass so cold before (if it was) and what caused the cooling?

  43. “”””” Geoff Sherrington says:

    April 25, 2012 at 10:04 pm

    Re Lake Vostok being liquid, can I ask again please, why are deep ocean waters so close to freezing point. “””””

    What is the big mystery ? sea water of greater than about 2.47% salinity, increasess in density right down to its freezing point , and since it is denser when colder it sinks below warmer waters, so the deeper waters tend to be colder, until you get down to where the internal heating from the mantle, takes over and the cooling stops.

    No mystery at all.

  44. Geoff Sherrington says:
    April 25, 2012 at 10:04 pm

    Re Lake Vostok being liquid, can I ask again please, why are deep ocean waters so close to freezing point? The have a source of heat below (geothermal) and a source of heat above (the Sun). Until someone can explain why the ocean deeps are not as warm as the surface, I shall regard any global hypothesis about temperature, water and ice with great suspicion. When was the whole Ocean mass so cold before (if it was) and what caused the cooling?

    First, the geothermal heat is generally small, on the order of a few hundredths of a watt per square metre. Yes, there’s more at the suboceanic vents that make such great TV … but in the immensity of the ocean floor those are few and far between.

    Second, the oceans are constantly being fed very, very cold water from the poles. The water there is cooled. When it is cooled it sinks, and over time spreads across the bottom of the ocean. Here’s a cross-section:

    “NADW” is North Atlantic Deep Water. “AABW” is Antarctic Bottom Water. Both sink because they are cold, with the AABW being the colder of the two. As a result, it ends up below the NADW.

    And because the oceans are thermally stratified, warmest at the top and coldest at the bottom, the sun never gets to warm the bottom waters …

    w.

  45. “Studies have shown Antarctic winds have changed because of changes in climate,”

    Or;

    “Studies have shown Antarctic winds have changed the local climate,”

  46. What is surprising to me is the amount of bedrock below sea level in Antarctica, seen here. Compare this image with the header image and the idea of a solid, roughly round, Antarctica disappears. There are plenty of basins that would provide relief from ‘warmer’ currents.
    The WA area was mentioned as having

    …..warm waters at depth have(ing) access to thick ice shelves via deep bathymetric troughs.

    OK, what temperatures are we talking about here, and what flow rates, for how long?
    The impressive 80mb video seemed to show an irregular wind driven pattern of surface water movement that may not indicate subsurface direction, certainly does not look like the circumpolar current, and, if Tom Rude is correct,(above) warm moist Peninsular air will deposit as snow on this area, adding to the glacial flow.

    What is it with Antarctica ?, do they think that this ‘unknown’ continent brimming over with scientists is their domain only and we will accept anything they say because of its remoteness?

  47. Steve from Rockwood says:
    April 25, 2012 at 4:20 pm
    I’m not sure how going from radar to laser helps you measure the removal of the underside of the ice.

    You use a blue-green laser.

    It’s amazingly accurate — if you sit on the bottom of the ocean and aim upwards…

  48. “We’ve looked all around the Antarctic coast and we see a clear pattern: in all the cases where ice shelves are being melted by the ocean, the inland glaciers are speeding up. It’s this glacier acceleration that’s responsible for most of the increase in ice loss from the continent and this is contributing to sea-level rise.”

    Is there any solid evidence to back up the lead author’s statements that (1) “inland glaciers are speeding up” and (2) the continent is losing ice overall and “contributing to sea-level rise”?

  49. @Willis Eisenbach
    Don’t consider this as a critique, just as some additional thoughts. As we have seasonal ice-free areas close to the Antarctic coast, I think it is reasonable to infer some “warmer” upwelling areas. If so, the age of the water should be an inateresting topic.
    If this water can be identified (e.g isotope-ratio) as being a part of the meridional overturning, I would expect the eventual warm water to be very old. Very old means way older than the human output of CO2 (i.e. on a millennial scale.

    Cassanders
    In Cod we trust

  50. I must confess that I never really understood how ‘warm’ air, which is below (and usually very much below) freezing could be driving ice sheet melt. Same point applies to the Himalaya Glaciers.

    Given that approximately 90% of ‘floating’ ice is below water, the obvious candidate for melting ice sheets would be a trend in slightly warmer water temperatures.

  51. George E. Smith; says:
    April 25, 2012 at 4:06 pm
    ////////////////////////////////////////////
    Similar risky experiment.

    Use a metal (not plastic) kettle to boil water. When boiling place your hand about 1 inch above the top of the kettle (not spout) and feel the 100 deg C heat being radiated from the meatl top to your hand. You can keep your hand about 1 inch or so above the kettle for quite some time without problem.

    Now move your hand over the spout and into the steam. Within a fraction of a second, you feel the heat on your hand and by reflex action you are forced to move your hand away.

    This shows the difference in energy content between relatively dry air and very moist air at the same temperature.

    So climate science which at its heart is concerned with energy imbalance uses land based temperature data that does not measure energy content. Whilst I am sceptical of the land based temperature data sets, it is noteowrthy that no attenpt is being made to assess what change in atmospheric energy content has taken place these past 30 or 40 years.

    The fact that they do not even measure the right metric tells you everything you need to know about the quality of science being undertaken.

  52. I put ice in my whiskey (a) to melt the ice or (b) to cool my drink? Drinking faster and replacing that Whiskey by new Whiskey from the bottle will make the ice melt faster. The question is : when do I start the stop watch ? and will I be able to stop the stop watch?

    ps I am not standing near a lake.

  53. “First, the geothermal heat is generally small, on the order of a few hundredths of a watt per square metre. Yes, there’s more at the suboceanic vents that make such great TV … but in the immensity of the ocean floor those are few and far between.”

    One vent could easily be on the order of a few MW. So, one vent could have more energy flux than square kilometers of the conductive flux.

    IMO, the average geothermal flux entering the oceans (~100 mW/m2) is underestimated.

  54. As has been stated by others, melt floating ice and it has zero effect on the level of the water it was floating in. Melt ice that is grounded and the ice below water level will have a net *negative* effect on the water level.

    As for why warmer water currents have moved closer to the shores of Antarctica? The decreasing tilt of Earth’s axis, duh. I did a quick google but wasn’t able to find anything like a timeline of the axis angle change over any period of time.

    Such a chart would be interesting, especially from the past 100 years or however far back precision measurements of the angle have been done. So would a calculation of the total area of the bands covered by the theorized maxima ans minima of the Arctic and Antarctic circles. (Theorized because they’ve never actually been measured as they happened.)

    But of course there’s always the nutbars that get it backwards. http://www.newscientist.com/article/dn17657-global-warming-could-change-earths-tilt.html

    Blaming the effect for the cause = Science!

  55. This study to me appears akin to population censuses focussing on the fast-breeding immigrant population and extrapolating to the whole population. When 80% of the population aren’t breeding enough, that’s a fairly silly thing to do.

    By all means study the Western Antarctic Ice Sheet, which is known to be anomalous compared to the rest of the Continent.

    But to imply that what is happening there represents the totality of what is happening in Antarctica is somewhat unscientific, to put it diplomatically…….

  56. WOW! just to think i got banned from the climate forum on Netweather for suggesting such a thing with out putting links up!! who’d a thunk

  57. richard verney says:
    April 26, 2012 at 1:38 am

    I must confess that I never really understood how ‘warm’ air, which is below (and usually very much below) freezing could be driving ice sheet melt. Same point applies to the Himalaya Glaciers.

    Given that approximately 90% of ‘floating’ ice is below water, the obvious candidate for melting ice sheets would be a trend in slightly warmer water temperatures.

    The sea ice page shows Arctic mean temperatures below freezing until May while winter ice peaks in March and then starts its inevitable melt – a full 30-60 days before air temperatures are above freezing. Why does the ice start melting when air temperatures are still below freezing? Is it warmer water or does the ice sublimate as the sun returns to the Arctic?

    What does “slightly warmer temperatures” mean? Above freezing? Or from -2 to -1.5?

  58. Let’s hope the old icebridge between Antarctica and South America never materializes again. The ice extent is way out there right now but fortunately East of the strait. If that same broad tongue of extent were IN the strait, more of the circumpolor current of cold water would be pouring into the Atlantic instead of harmlessly circling the Antarctic continent.

  59. And because the oceans are thermally stratified, warmest at the top and coldest at the bottom, the sun never gets to warm the bottom waters …

    Ahhh, Willis, IIRC while they are thermally stratified, that stratification all occurs in the top 1 km, or even the top 500 meters. Underneath that the water temperature is a nearly uniform 4 degrees C, is is not?

    Not that this makes your point incorrect. Below roughly 200 meters, it is very, very dark. And many wavelengths (as has been pointed out in other threads) are absorbed almost entirely in the top centimeter of water — IR in particular. Visible light penetrates much farther and warms as it does, but its significant heat content is probably absorbed in the top few tens of meters.

    This does raise an interesting point re the article. Earth’s “climate” arguably consists of self-organized patterns of circulation that are all driven by thermodynamic forces that change the efficiency of the Earth at losing its dynamic energy input. That is, the bulk of the Sun’s energy is absorbed during the day, by the oceans, in or near the tropical band around the equator, simply because the Sun doesn’t shine at night, the Earth is 70% ocean, and the tropics are precisely the band of latitudes where the sun is directly overhead (incident at 90 degrees upon the surface of the land or water) at least once during the year, maximizing the flux of the Poynting vector through/into any given patch of surface.

    Moving the heat around changes the rate at which the Earth cools, given any input. Because outgoing radiation intensity from the surface in the water window bands scales roughly like surface temperature T^4 (in Kelvin) plus radiation from in the IR bands from top of troposphere CO_2 and other GHGs at much cooler and much more globally uniform temperatures, and because radiated power scales like the area, the rate at which energy is lost is greater when the daily dose of heat is spatially concentrated. When the tropics are warmer and the poles are cooler, the planet should maintain an average temperature that is colder than it is when the surface temperature is more uniform. The moon is an extreme case of this (although not usually a very good/comparable one as it doen’t rotate as fast as the Earth does and has no thermal “ballast” comparable to the ocean of water or air quite outside of transport issues) as it is much hotter where it is hot, rapidly cools to much cooler as it cools, and has in the end an average surface temperature that is much less than Earth’s.

    The efficiency of the transport of heat from the equators to the poles might well be the primary factor responsible for determining the Earth’s mean temperature once the basic balance of the GHE is taken into account. It could even be a major factor in stabilizing interglacials in the current (Pliestocene) ice age. When heat transport to the poles is slowed, not only do the poles cool but on average, so does the entire planet because the tropics only have to warm a little to compensate for a lot of temperate zone/polar cooling due to the T^4. They have a much larger surface to radiate from, and the poles are already much colder, on average, so cooling them has a much smaller marginal impact on global heat loss rates.

    When heat transport to the poles is enhanced, the planet warms because the tropics comparatively cool. If the tropics cool (on average) by a small temperature shift $\Delta T$, the poles have to warm by a much larger shift in order for total outgoing radiation to still balance incoming radiation.

    Note the positive feedback that can maintain ice age/glacial conditions. In an interglacial, the glaciers melt (decreasing albedo) and surface temperatures become more uniform, with enhanced transport from equator to poles. This improved heat transport is itself equivalent to degrees of “global warming” as the more uniform surface temperature has to be, on average, higher to maintain balance from an also higher net insolation due to the reduced surface albedo. When an ice age/glaciation period cometh, “something” changes conditions and tips the balance towards a lower mean (something possibly being the sun, possibly being some mix of Milankovitch/Precession/Obliquity, possibly being the appearance and disappearance of oceanic circulation modes as the continents drift around and eventually move enough that a major current “suddenly” changes and alters the poleward transport of tropical heat). As the poles get colder, the tropics might even actually get a bit warmer but the average decreases. Albedo increases, net surface insolation decreases, and if there is any feedback that further slows heat transport, one can get kicked over into a protracted cold phase.

    That’s why this paper is indeed very interesting. We already know that there are strong correspondences between decadal oscillations and surface temperature. The connection between transport efficiency and mean temperature is a possible explanation — when the phases are such that they improve transport from tropic to poles, the poles warm, the tropics cool, and the planet warms a bit on average. When they reduce the net transport from equator to poles, the poles cool, the tropics warm, and the planet cools a bit. In general, when the Earth exhibits maximum thermal inhomogeneity it cools most efficiently, and when it is most thermally homogeneous it cools less efficiently and hence has to be slightly warmer, on average, in order to maintain energy balance.

    Polar heat transport is highly multimodal, of course. Ocean currents are a huge factor. Decadal atmospheric circulation is a huge factor. The moisture content of the transported air is a huge factor — droughts in the tropics reduce the heat content in the transported air and are net cooling (a conclusion that I think has good empirical support) — it not only cools the poles by reduced transport but causes the tropical land surfaces to quickly lose at night most of the heat they gained during the day, increasing the temporal diurnal inhomogeneity (net cooling). And somewhere on top of all of this (quite literally) one has modulation of surface radiation due to cloud albedo and the GHE due to humidity, cloud albedo, and complex feedbacks associated with e.g. ENSO — the decadal oscillations not only affect polar heat transport but vertical heat transport and the height of the tropopause.

    Finally, everything is coupled in nonlinear ways. A pretty problem! But this paper points to a piece in the puzzle. Net growth in Antarctic ice suggests reduced polar transport in the southern hemisphere, net cooling. For a while — perhaps 30 years — northern polar ice has been diminished, suggesting net warming of the northern hemisphere. However, the PDO has changed phase, and its effect was quite manifest this winter with Alaskan sea ice strongly increased and much colder temperatures in the West/Northwest continental US. The NAO has not yet shifted phase — and is much more irregular so we don’t really know when or if it will — but if/when it does it may well reduce heat transport to the Atlantic side of the Arctic. Or a fluctuation of any one of several Arctic currents might manage it even before that. And behind all of this is the “something” — all of the factors that somehow drive the entire system inexorably into an instability region where feedbacks back to glaciation become positive and we tumble back down to ice.

    Personally I think that it is very likely that we have already turned the corner on the Holocene. The LIA was reportedly the coldest century since the Younger Dryas ended, suggesting that “something” is moving us to where cold phase fluctuations are enhanced and prolonged, a probable precursor of cold phase shift. We should be so lucky as to stabilize warm phase for another few hundred or few thousand years, but the Earth’s climate is really remarkably headstrong and responds to something that sets the thermostat in a way that resists natural variability far greater than anything anthropogenic.

    It might be nice to eventually understand that something.

    rgb

  60. rgbatduke says:
    April 26, 2012 at 7:31 am

    And because the oceans are thermally stratified, warmest at the top and coldest at the bottom, the sun never gets to warm the bottom waters …

    Ahhh, Willis, IIRC while they are thermally stratified, that stratification all occurs in the top 1 km, or even the top 500 meters. Underneath that the water temperature is a nearly uniform 4 degrees C, is is not?

    Thanks, Robert. Not as far as I know. Why would it be uniformly 4°C?

    Some folks claim that the bottom of the ocean is all at 4°C because that is the point of maximum density for fresh water. But salinity changes the picture:

    SOURCE (see page 3)

    As long as the salinity is above 25 psu (which is all of the ocean), density increases with falling temperatures right down to the freezing point. That’s why, in my graphic above, the AABW water flows under the NADW … because it’s colder, and thus denser.

    w.

  61. “”””” richard verney says:

    April 26, 2012 at 1:52 am

    George E. Smith; says:
    April 25, 2012 at 4:06 pm
    ////////////////////////////////////////////
    Similar risky experiment.

    Use a metal (not plastic) kettle to boil water. When boiling place your hand about 1 inch above the top of the kettle (not spout) and feel the 100 deg C heat being radiated from the meatl top to your hand. You can keep your hand about 1 inch or so above the kettle for quite some time without problem. “””””

    Good point Richard; may I suggest a similar and quite safe; but highly instructional experiment, that can be performed without any special equipment while yakking around the typical office coffee pot; you don’t even need a thermometer.

    Hopefully your office coffee haunt, has one of those nifty cool/hot water gizmos for those who believe bottled water is clean.

    Then you need one of those modern super light paper thin drinking water bottles; the type that are so thin, that they crush easily with very little finger pressure. Failing that availability, any plastic water bottle will do, but the thin ones are more illuminating.

    So again , a two part A – B experiment.

    Part 1 (A) having emptied the water bottle (12 oz size is good), you grasp it lightly near the wide part at the top, between your thumb and forefinger. A “Coke” bottle shape is ideal, as you can hold it with virtually no finger pressure at all.
    So you hold the bottle lightly under the blue ice water spigot, and let some ice cold water into the bottle.

    You will immediately notice that absolutely nothing happens; and you feel nothing at all, even though you now have some bloody cold water in the bottom of the bottle. That paper thin plastic bottle wall, is a lousy thermal conductor (along the surface); so you feel nothing.

    As you add more water, the water level eventually will reach the level of your fingers. (Trust me on this; I have actually done this so I know what I’m talking about !).

    Now for extra credit; don’t look at the bottle while you are filling it. Believe me; you WILL know when the water level reaches your fingers; it will start sucking heat out of your thumb and forefinger, the instant the water is on the other side of the plastic from your finger, and it will get cold.

    Isn’t that amazing; with a half inch of ice water in the bottle, you don’t feel a darn thing; but the instant it reaches finger level you get cold. Think about thermal conduction, along versus through the bottle skin.

    Now for the big encore; far more amazing than Experiment A.

    Part B. Empty out the ice water, before your fingers freeze to the bottle.
    Now repeat the first part of the experiment; but this time turn on the (hopefully) MacDonald’s Hot red water spigot, intead of the cold blue one.

    Wow !!*%&$ ; what a difference . Before you even get a half inch of water in the bottle, your thumb and forefinger will be screaming stop ! Well I exaggerate a little; it is QUITE SAFE, and you won’t get burned, but you WILL feel the heat immediately.

    So what the hey ! A thermos bottle keeps the hot liquid hot, and it keeps the cold liquid cold; but how do it know ? !

    This plastic bottle is evidently a lot smarter than a thermos bottle; because it do know the difference.

    So what happened, is that as soon as you got some nice hot water into the bottom of the bottle, some of it evaporated and created some hot steam in the bottle, and the steam immediately rises to escape from the bottle; but along the way, it encounters the cold surface of your thin bottle, and it condenses on the bottle; and right about where your fingers are, and along with the 80 deg C or so Temperature of the water, it also dumps out the latent heat of evaporation, right where your fingers are.

    The “heat” (conduction) has barely started to creep up your paper thin bottle skin, but the “heat” (convection) arrives quickly at your fingers, and then the “heat” (phase change latent) really dumps on you.

    It takes about 100 Calories of “heat” to raise the ice cold water(one gram) to near the boiling point. The latent heat of evaporation is about 590 Calories per gram; six times the heat due just to the Temperature.

    You should have your kids do this experiment; just to impress on them, how potentially dangerous steam burns are, so they don’t mess around, with things they don’t understand.

  62. The concern here is that loss of the ice shelves will reduce their butressing effect on inland glaciers, and hence accelerate the flow of inland glaciers into the sea.

    I can see how grounded ice shelves provide buttressing, but not how floating shelves do.

    To take a classic example, Notre Dame Cathedral in Paris has vaults that exert a diagonally downward thrust that has both a vertical and a horizontal component. The walls hold up the vertical component just fine, but without buttresses, the walls would be pushed over by the horizontal component of the vault thrust. The flying buttresses come up at an angle and are anchored solidly in the ground, and hence provide the required horizontal component at the base of the vaults, offset by their horizontal thust in the opposite direction at ground level.

    But now if each flying buttress were set on a pontoon, and the level of the Seine raised until the pontoons were just floating, the buttresses would no longer provide the required horizontal thrust, and would just slide out, allowing the walls to topple.

    The grounded portion of the shelves drags against the ocean floor, and hence provides back-thrust to hold the inland glaciers in. But since it is the floating shelves that are affected by warm currents, it is hard for me to see how their reduction would significantly reduce the buttressing of the inland glaciers.

    Of course, melting the floating ice by itself would have no direct effect on sea level. There might be an indirect effect via ocean temperature, but I think that would be small.

  63. “”””” Hu McCulloch says:

    April 26, 2012 at 2:00 pm

    The concern here is that loss of the ice shelves will reduce their butressing effect on inland glaciers, and hence accelerate the flow of inland glaciers into the sea. “””””

    It’s the same principle as how the ships parked at the SF docks prevent all the buildings on Nob Hill from sliding down into San Francisco Bay . Quite simple really.

  64. And I thought my “jump in the lake” experiment would adequately demonstrate why, when the floating sea ice melts, the sea level will FALL !.
    The 80 Cal per gram latent heat of freezing, comes right out of the ocean, and cools an astronomical amount of sea water, causing it to shrink. If you assume that the coefficient of expansion of sea water, is independent of Temperature near zero (which it isn’t), then it is a trivial exercise to prove that the change in sea level is independent of how the heat gets distributed. you either cool a lot a little or you cool a lot a little; or somewhere in between.

  65. “This study demonstrates the urgent need for ICESat-2 to get into space,” said Jay Zwally, ICESat project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md. “We have limited information on the changes in polar regions caused by climate change. Nothing can look at these
    changes like satellite measurements do.”

    http://news.nationalgeographic.com/news/2007/12/071212-AP-arctic-melt.html

    Jay Zwally said in 2007 that the ice in the Arctic could be gone by 2012. These are the geniuses?

    How can you believe anything that these people say?

  66. Regarding oceanic temperature:

    http://www.windows2universe.org/earth/Water/temp.html

    http://www.onr.navy.mil/focus/ocean/water/temp3.htm

    It isn’t quite uniform, but it is a very slowly varying function below the thermocline and stops well short of 0C everywhere but in the very deepest of trenches. I agree that it isn’t just a matter of density — salinity is a more important aspect of density than temperature. Also, this profile depends on latitude — in polar regions the 4K zone can extend up to very close to the surface and can even invert. Either way, the average temperature of the ocean is roughly 4C. This was discussed fairly extensively on one thread or another last year, I believe.

    Personally, I think that this remarkably low average temperature is very intimately connected with episodic glaciation. The oceans are a heat and CO_2 reservoir in addition to being a major heat redistribution mechanism via thermohaline circulation (the “conveyor belt”). The entire Holocene has likely had little impact on the mean ocean temperature, given that is probably “pinned” between 4 C and 0 C (if it were much colder, the ocean would start freezing from the bottom up and interglacials might never thaw the deep ocean floor). The entire Younger Dryas episode near the beginning of the Holocene is hypothesized as being due to a “sudden” alteration in thermohaline circulation that diverted the polar movement of heat, which (as I point out above) increases tropical temperatures but at the expense of lower average global temperatures with positive feedback from glaciation. The possibilities of modulation of e.g. atmospheric CO_2, water vapor, circulation patterns, and more in very long period chaotic cycles with multiple nonlinear feedback loops are mind boggling — it isn’t just the case that nobody understands this, it is that we can’t even get our heads around all of the factors well enough to construct a nontrivial model.

    rgb

  67. Is the lazer measuring just a single spot? I noticed the data was gathered from both poles. Is there lazer data from the North Pole? Is the lazer beam continuous, and able to measure the swift peaks and then dips caused by passingh over a pressure ridge? Or does it just take a shot every now and again, and therefore likely miss the pressure ridges? How exactly does the gizmo work?

  68. rgbatduke says:
    April 27, 2012 at 9:50 am

    Regarding oceanic temperature:

    http://www.windows2universe.org/earth/Water/temp.html

    http://www.onr.navy.mil/focus/ocean/water/temp3.htm

    It isn’t quite uniform, but it is a very slowly varying function below the thermocline and stops well short of 0C everywhere but in the very deepest of trenches. I agree that it isn’t just a matter of density — salinity is a more important aspect of density than temperature. Also, this profile depends on latitude — in polar regions the 4K zone can extend up to very close to the surface and can even invert. Either way, the average temperature of the ocean is roughly 4C. This was discussed fairly extensively on one thread or another last year, I believe.

    Umm … well … man, I hate to say it, but hardly any of that is true.

    First, temperature varies quite a bit, both below and above the thermoclines. Here’s the monthly profiles (marked from I to XII) at Ocean Station “P”, in the mid-latitude North Pacific.

    As you can see, it is neither uniform nor slowly varying.

    Next, in the polar regions, it’s well below 4°C up to very close to the surface.

    Panel “a” is mid latitudes, “b” is low latitudes, and “c” is high latitudes. Note that at high latitudes the entire water column is well below 4°C.

    Finally, it does not “stop well short of 0°C everywhere but the deepest trenches.” Here’s the T-S diagram of the Southern Ocean …

    Note that the majority of the temperatures in the Southern Ocean are below 4°C., and many are below 0°C.

    Personally, I think that this remarkably low average temperature is very intimately connected with episodic glaciation. The oceans are a heat and CO_2 reservoir in addition to being a major heat redistribution mechanism via thermohaline circulation (the “conveyor belt”). The entire Holocene has likely had little impact on the mean ocean temperature, given that is probably “pinned” between 4 C and 0 C (if it were much colder, the ocean would start freezing from the bottom up and interglacials might never thaw the deep ocean floor).

    I see no reason to invoke the glacial periods. The ocean is constantly being fed with very, very cold water from the poles. This seems quite adequate to maintain a very low average temperature, with no glaciers required. In addition, the overturning time for the entire ocean is thought to be on the order of a few thousand years, so if there were such an effect, it would be mostly gone by now.

    Next, I don’t see how it is possible for the ocean to freeze from the bottom up … where would the latent heat go? Even in the bottom of the ocean, if you drill down a few hundred metres the earth’s temperature is warm, so the heat can’t go down. And if it is freezing from the bottom up as you hypothesize, the layer of water above the putative ice would be warmer … so with warmer layers above or below, what would impel the ocean bottom to freeze?

    Note, for example, that the T-S diagram shows that the water at the bottom of the Southern Ocean (third graph above) is just a few tenths of a degree above freezing … but it doesn’t freeze from the bottom up.

    The entire Younger Dryas episode near the beginning of the Holocene is hypothesized as being due to a “sudden” alteration in thermohaline circulation that diverted the polar movement of heat, which (as I point out above) increases tropical temperatures but at the expense of lower average global temperatures with positive feedback from glaciation. The possibilities of modulation of e.g. atmospheric CO_2, water vapor, circulation patterns, and more in very long period chaotic cycles with multiple nonlinear feedback loops are mind boggling — it isn’t just the case that nobody understands this, it is that we can’t even get our heads around all of the factors well enough to construct a nontrivial model.

    The curse of the climate scientist … as the musician said, “so many drummers … so little time”.

    All the best,

    w.

  69. The newspaper alarmists have said this melting will cause sea levels to rise. Have they never tried the famous experiment of putting some ice cubes to float in a glass of water and watching them melt without any rise whatoever in the level of the water?

  70. There’s a similar recent paper covering the arctic. It covers the Barentz Sea which is responsible for much of the fall in extent in the arctic of the past couple of decades. In this case the warming is coming from the Atlantic. It makes you wonder about just how significant the role of internal ice feedback are.

    Abstract here

    http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-11-00466.1

    The following looks like a preprint although some of the language has changed.

    https://bora.uib.no/bitstream/1956/5126/1/Barents%20Sea%20ice%20cover%20reflects%20Atlantic%20inflow.pdf

  71. Did anyone notice how dishonest the video is? The red is the thickest ice shelves.

    “The shelves are indicated by the rainbow color; red is thicker (>550m), while blue is thinner (<200m)."

  72. ““This study demonstrates the urgent need for ICESat-2 to get into space,” said Jay Zwally, ICESat project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md.”

    Now there’s a surprise! /sarc

  73. Bob Tisdale has had a word recently about the Southern Ocean temperatures, he is talking about the circumpolar current below 60deg South.

    Image : http://bobtisdale.files.wordpress.com/2012/04/figure-82.png

    His comment on the graph :

    The Southern Ocean (90S-60S) is the ocean “basin” that surrounds Antarctica. It has cooled over the 30-year term of the Reynolds OI.v2 dataset. See the graph here from this post (above), link here. Since January 1995, the rate at which it’s cooling is even stronger. The difference between the rate that it’s cooling and the rate the climate models say it should be warming is 0.14 deg C/decade.

    Nice codicil to the banner “NASA : warm ocean currents cause majority of ice loss from Antarctica”……..the argument seems to disappear.

  74. Lets see, we’ve had two satelites crash and burn. How convenient. I wonder what the odds are of a third one crashing. Probably directly proportional to the thickness of the ice at the polar caps.

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