Previously on WUWT we discussed the media’s fascination with “melt” when it comes to ice shelves cracking off. Then there’s also this picture that keeps getting recycled.
http://www.ogleearth.com/wissm.jpg
It is clear from the photo above that we see a stress crack, not a melt. Now we have a time lapse satellite photo series of the Wilkins ice shelf that shows the process of currents and winds causing those stresses.
Mike McMillan writes:
Fox News is reporting that the Wilkins ice shelf bridge that’s been eroding has finally collapsed.
http://www.foxnews.com/story/0,2933,518374,00.html
I went back to the old ESA sat photos and noticed something interesting. I downloaded the gif animation and did some highlighting.
In the upper area, the shelf was previously fractured, then glued together by new ice. I highlighted a string of drift ice in green to show what the currents were doing during the previous collapse. The current runs down from the top, compressing the fractured shelf and likely busting up the new ice glue. The current then reverses, pulling the fractured shelf ice out to sea. The green drift ice looks almost like a fingertip crunching into the shelf, and clearly shows the compression.
A different process works on the lower side of the ice bridge. A gyre pulls
off chunks of unfractured ice. I’ve highlighted a chunk of non-edge ice in
pink, and we can watch it tumble out along with a companion berg. Note the
sea immediately refreezes in the open areas. One of the gif frames shows the
gyre swirling the new ice, and I’ve enlarged the frame.
http://i40.tinypic.com/erg287.jpg
UPDATE: I slowed down the original animation to 1 frame per second, with a 2 second pause at end, per requests in comments. -Anthony
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Phil,
please explain why the breakup of floating ice is a problem. Isn’t it because you ASSume that warming is melting the glacier itself?? Doesn’t pay to believe junk science like Steig et. al. If the whole peninsula melted there would be little world wide effect. Of course, with the recorded temp trend there, it isn’t happening for hundreds of years!! The weather cycles will change many times during that period.
Also, let us know your thoughts on the latest reports from Greenland where the Galloping Glaciers have dropped back to their normal walk!! It really sucks to be a warmist when all the data points are turning against you!!
It’s a pleasure to see the high level of the discussion here and the high standards for the arguments put forward. So much better than the hysterics nearly everywhere else about how the Republicans and SUV drivers are wantonly destroying the earth one melting glacier/drowning polar beat at a time.
Two-and-a-half questions:
1. Regarding the Wilkins ice shelf – since the story about the collapse suggests warming is the cause, do we know the trend in water temperature around the shelf? I ask because one post here said the highest recorded temperature in Antarctica was 17 deg F, and it seems to this non-climatologist that an increase in spring temps. from, say, -5 deg F to 5 deg F wouldn’t start “melting” ice. So
1A. Is it true, as the link http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/current.anom.south.jpg suggests, that total Antacrtic sea ice is more than 1 million km^2 above the 30-year mean? If so, why isn’t the purported rise in surface temperatures reducing overall sea ice, rather than just ravaging the Wilkins shelf?
2. What are the facts behind Pres. Obama’s assertion that “during the summer, there won’t be any ice in the Arctic”? Is complete disappearance imminent, or even an anomalous decrease from recent norms?
kuhnkat (21:00:44) :
Phil,
please explain why the breakup of floating ice is a problem. Isn’t it because you ASSume that warming is melting the glacier itself??
There’s no glacier, any melting would be at the base of the sheet ice as I explained earlier.
Doesn’t pay to believe junk science like Steig et. al. If the whole peninsula melted there would be little world wide effect. Of course, with the recorded temp trend there, it isn’t happening for hundreds of years!! The weather cycles will change many times during that period.
Also, let us know your thoughts on the latest reports from Greenland where the Galloping Glaciers have dropped back to their normal walk!! It really sucks to be a warmist when all the data points are turning against you!!
Does it? I wouldn’t know.
David (21:11:50) :
1. Regarding the Wilkins ice shelf – since the story about the collapse suggests warming is the cause, do we know the trend in water temperature around the shelf?
I guarantee it’s above the melting point of sea water.
1A. Is it true, as the link http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/current.anom.south.jpg suggests, that total Antacrtic sea ice is more than 1 million km^2 above the 30-year mean?
And a couple of months ago it was below the 30-year mean, big deal!
We think the Antarctic never rises above freezing. But there are also very few data points collecting real temperature data down there. Wave action plays a large part in ice breakup. There is a lot of info on this link about the disagreement as to whether it is warming or cooling. It appears to me that the center of Antarctic is cooling, and the edges (where these ice bridges exist) are warming. It is also mentioned that climate models actually predict that there will be more than enough snow over the next 50 years to counter-act Antarctic ice loss, particularly since the hole in the ozone down there helps to keep it cooler. The Antarctic is supposed to remain frozen for a long time.
http://en.wikipedia.org/wiki/Antarctica_cooling_controversy
Regarding Obama’s concern about the Arctic, I found the following interesting link. Even though the ice extent appears “normal” right now, they believe it is thinner than normal, and therefore is more susceptible to melt this summer. The summer melt has begun and won’t be done until September. So we will see some real measurable results in just a few months. This will be fun, won’t it?
http://nsidc.org/arcticseaicenews/
Pete
Sir
I and a a friend who has experience at aerial analasys took a good look at the original Wilkins affair and it was obvious that movement of a big ice mass was responsible for the accident to the glacier which was rammed and shattered .The cracks from the shock wave were evident in the photos as was the displacement of the floating ice to the North which was moved about 5kms what is happening now is the ongoing history . As the Atlantic Ocean temperature is rising the warmer water circulating in the Southern Ocean is going to make it’s effects known .This Peninsula is a very prominent piece of land and ice
I’ve assembled the recent Wilkins aftermath shots into an animation. Pretty boring.
The old ice bridge is overlaid on the first frame, and the islands are underlaid into the missing data regions to make it easier to follow.
http://i42.tinypic.com/e9da2d.jpg
Hi Anthony,
Great blog… stupid question.. how can I subscribe? 🙂
Thanks, couldn’t see anywhere to do so…
Cemanthe
David (21:11:50) :
“2. What are the facts behind Pres. Obama’s assertion that “during the summer, there won’t be any ice in the Arctic”? Is complete disappearance imminent, or even an anomalous decrease from recent norms?”
David – there are no facts. This is one of the most uninformed and ridiculous statements made by an American president in my lifetime (and I am 47 years old). In fact, you should read the president’s statement in its entirety here:
http://tomnelson.blogspot.com/2009/04/missouri-april-29-2009-president-obama.html
One more point – the fact that the scientists in the AGW establishment have NOT come out and corrected and/or “clarified” the president’s remarks speaks volumes about their integrity…
I personally do think that people are responsible for global warming and it is a real concern but know matter what anyone thinks about it can anyone really disagree with the solutions. More green spaces, less dependence on fossil fuels, renewable resources, and more efficient forms of transportation. How can anyone not be in favor of these solutions. Even with out global warming in the equation are not these ideas beneficial to the world as a whole. Waywardwind
We can do something from our own side to reduce the generation of CO2. For example, you can walk rather than drive if the way is not so far.
I did find some information in the following link regarding what air temperatures are usually like in the Antarctic. You need to keep in mind that 0C is the temperature that clean water freezes. Salt water doesn’t freeze until something like -4C?
http://en.wikipedia.org/wiki/File:Antarctic_surface_temperature.png
Thank you for this… I appreciate the work. I am going to show this to everyone!
People need to realize that “global warming” is just as big of a “pandemic” as the “Swine Flu.” Ridiculous!
NASA’s “Image of the Day” website is today (May 1, 2009) featuring a photo of the Wilkins Ice Shelf taken from NASA’s Terra satellite:
http://www.nasa.gov/multimedia/imagegallery/image_feature_1341.html
Paul
Good link Paul. Thanks. The winter cycle has just begun down there, and it is freezing back over again. It will be interesting to see how far back it recedes next summer.
I think the real newsworthiness of the Antarctic ice bridges is that climate models had predicted that the Antarctic ice would initially cool and increase in volume while the rest of the earth warmed. They are now being forced to re-evaluate this prediction since the Antarctic air temperatures over the last 20 years indicate a warming trend over most (but not all) of this continent. I suspect they underestimated the warmth coming from the oceans, but that is just my uneducated guess.
Pete
I’m leaving another comment so that I can subscribe to your blog… I’m still new to WordPress and didn’t realize that you had (or could) click to subscribe when you were posting a new comment…
LOWER LEFT AREA, relatively open to the sea
Your color photo might also represent a stress crack that is due to melting underneath. With less ice to provide flotation, the breakaway ice separates and falls down.
Your argument might be better made on the 03-05-2008 photo. There, in the
lower left corner of the photo, notice the right end of the ice shelf bridge. There the separation is apparently occurring away from the water’s edge. And those long straight lines suggest that there are other things happening.
But, otherwise, the separations are generally parallel to the face (the line of contact with the water). And this is what would be expected if there were melting below. With less flotation holding it up, the block falls down.
The shear face might occur at a pre-existing weakness in the ice; i.e., where it is (or has been) under stress.
UPPER RIGHT AREA, protected
There are no new separations to see on the bridge itself.
For the loose ice, the major breaks are parallel to the contact with the water. Which suggests melting below. But, its hard to visualize just how the warm water would act…behind all the ice in front.
So, anyway, I couldn’t say that it was only warm water that broke up all this ice. But, it would suffice.
Dave the Denier (19:45:42) :
I am curious to know how high above the water is the sheet edge that starts in the bottom-right of the color photo and extends to the middle of the photo. Also, about how long are the sheets in the picture. I am clueless as to their scale. Can anyone help me on that? Thanks!
A neighborhood guess would be around 65 to 80 feet high, 20 to 25 m. The animation is oriented north/south, so if the photo is indeed of the bridge area, with the sun off to the left, the icebergs would be cracking off the south (swirly) side of the bridge.
I think the photo was taken prior to the animation period, when the bridge was wider.
For scale, the pink iceberg in the animation is 6½ miles long by 1½ miles wide, 10½ x 2½ km.
Always these close-up views of the Wilkins Ice Shelf area.
Next time there’s coverage of such a story, and to put it in a larger context, how about using an NSIDC image of Antarctic sea ice extent. Even now, while the extent hasn’t reached its max, the area of Wilkins is laughably miniscule:
http://nsidc.org/data/seaice_index/images/daily_images/S_daily_extent_dthumb.png
http://www.ft.com/cms/s/2/75f9cea6-3669-11de-af40-00144feabdc0.html
This article is from the Financial Times (UK). I just thought it would be rather
thought provoking for you. Degrees in ‘Climate Change’ !! Wow!! Whatever next?
Hey ya’ll, the wilkins ice shelf melting is just the beginning! but what are we really going to do about the environment when no one has the money/concern to fix non-economic things? http://www.flypmedia.com/issues/29/#2/1
check it out!
anquan