ESA has a short movie of the calving – worth a look, Anthony
From the European Space Agency: Greenland glacier gives birth to giant iceberg
Envisat has been observing a rare event in the Arctic since early August – a giant iceberg breaking off the Petermann glacier in North-West Greenland.
The Petermann glacier is one of the largest glaciers connecting the Greenland inland ice sheet with the Arctic Ocean. Upon reaching the sea, a number of these large outlet glaciers extend into the water with a floating ‘ice tongue’.
The ice tongue of the Petermann glacier was the largest in Greenland, with an extension of about 70 km until early August. This tide-water glacier regularly advances towards the ocean at about 1 km per year. During the previous months, satellite images revealed that several cracks had appeared on the glacier surface,suggesting to scientists that a break-up event was imminent.
In the Envisat radar image taken on 3 August, the ice tongue was still intact but, on 4 August, a large part of the floating ice tongue was separated from the glacier, giving birth to what is currently the largest iceberg in the northern hemisphere. Such a process of detachment, called ‘calving’, occurs regularly on the Petermann glacier, with smaller calving events in summer 2008 and 2009. However large calving events are rare, with the last such significant event being documented in 1991 by ESA’s ERS-1 satellite.
The animation [below] was created by combining three Advanced Synthetic Aperture Radar (ASAR) acquisitions (31 July, 4 August and 7 August 2010) taken over the same area. The breaking of the glacier tongue and the movement of the iceberg can be clearly seen in this sequence.
HI-RES GIF (Size: 1820 kb)The detached iceberg is now about 30 km by 14 km in size with an area of about 245 sq km. It is floating away from Petermann glacier and will enter into the Nares Strait, which separates Greenland from the Ellesmere Island in Canada.
The Nares Strait connects the Lincoln Sea and Arctic Ocean with the Baffin Bay. The strait is usually navigable by icebreakers during August/September, when sea ice extent is at its minimum after the summer melt period. Envisat ASAR images will be used in the coming days to monitor the movement of the giant iceberg in support of icebreaker navigation.
The radar imaging system used by Envisat and other satellites is particularly suited to observe polar areas, as it can acquire images through cloud or fog, and night and day.
“”” tty says:
August 9, 2010 at 1:11 pm
nandheeswaran jothi:
The movement is probably mostly wind-driven. A large ice-cap like Greenland acts as a permanent high-pressure area, so on average wind blows away from it more often than towards it. You can see on the radar that the sea ice is drifting even faster. “””
“”””” so on average wind blows away from it more often than towards it. “””””
So “on average”, what is it that happens when ALL of the air has blown away from Greenland; on average of course ?
Do Kirchoff’s laws (circuit theory) not apply to Greenland ? Next time I need to defrost my Freezer; I’ll just blow on it; on average of course !
There’s an interesting tale from the early 1950s of the USAF using an ice island as a research platform. Might have been hard to track in those pre-satellite days.
Around Pole on Iceberg
http://newspapers.nla.gov.au/ndp/del/article/27133618
Judging by Google Earth, it looks like a disaster movie writer would have quite a tough job coming up with a scenario where this giant ice-berg collides with a monster hurricane in New York Harbor.
George, step back and think a moment. A high pressure area is caused by air descending from higher in the atmosphere, so of course air will move in to replace it at the top of the column. A high pressure area creates winds away from itself at the base of this high-pressure column of air.
Now I understand the process would work something like this: the ice-cap cools air over it, causing it to shrink, which brings more air in to the column; that creates a high-pressure zone. The air will move outwards from this high-pressure zone, at the base, on avarege, most of the time. In layman’s terms, at ground level, at levels that matter to our perception of events around this glacier, the air moves away from greenland on average most of the time.
In your haste to snark you’re not actually understanding what you read.
<blockquote cite="Fred says:
August 9, 2010 at 12:14 pm
We are watching a Fiord being created . . "
A “Fjord”? Well, when the next big chunk comes off in perhaps ten years, perhaps it will be a “Chevy” (if Government Motors is still in business by then :^)
Impressive Synthetic Aperture Radar images and a lot more impressive than the normal calving of glaciers that drop a building-sized chunk every half-hour or so. http://tvpclub.blogspot.com/2010/08/three-times-size-of-manhattan-and-it.html
Maybe the ice huggers should fly their flags at half mast and get their loony left wing majority in congress to declare a national day of mourning.
That’s quite an optimistic use of ‘movie’ – three frames that don’t link through persistence of vision. 🙂
“”” Archonix says:
August 9, 2010 at 2:27 pm
George, step back and think a moment. A high pressure area is caused by air descending from higher in the atmosphere, so of course air will move in to replace it at the top of the column. A high pressure area creates winds away from itself at the base of this high-pressure column of air.
Now I understand the process would work something like this: the ice-cap cools air over it, causing it to shrink, which brings more air in to the column; that creates a high-pressure zone. The air will move outwards from this high-pressure zone, at the base, on avarege, most of the time. In layman’s terms, at ground level, at levels that matter to our perception of events around this glacier, the air moves away from greenland on average most of the time.
In your haste to snark you’re not actually understanding what you read. “””
What is your evidence that I snarked in haste ? Actually I snarked quite leisurely; and only after understanding fully what I had read; namely that the winds blow towards Greenland, on average more often than they blow away from Greenland; and now you have introduced a set of winds that is blowing mostly on average towards Greenland; rather than away.
So which is it; is there an assymmetry or do the winds blow towards Greenland just as much as they blow away from Grteenland; in order that the place not run out of air.
And if in fact the winds do blow mostly away from Greenland (I’m always willing to learn) how the heck does all that ice and snow end up on Greenland; with the wind always or mostly blowing away from the island ?
Looking at that photo I’m reminded of my last kidney stone…
George, what he’s trying to explain to you is called the katabatic wind system
Here’s a link to a picture of it:
http://explorersweb.com/sitemedia/TSthumbs/20090630katabaticemirates.jpg
“Katabatic winds exist thanks to the huge piece of ice on top of Greenland. That ice cap is at places more than 3000 meter thick, which forms a vast plateau 3000 meter above the main sea level. The air mass on top of this plateau becomes extremely cold, and cold air is very dense, which means it is much heavier than the relatively warm air along the coasts of Greenland. Due to gravity the colder air starts rolling down from the high plateau towards the coast. This movement of cold air, which happens only in the lowest hundred meters of the atmosphere, is called ‘katabatic’ wind.”
”The wind direction of the katabatic wind is, at one point, nearly always the same: it blows from the interior of Greenland to the coast and almost perpendicular on the elevation contours. The speed depends mainly on the angle of the slope, the steeper the slope the stronger the katabatic wind. At some places it is not exceptional that this wind blows with a speed of 40-60kt and this for several days in row.”
Ken Hall says:
August 9, 2010 at 12:11 pm
I read somewhere that there was a 5.0 earthquake in the area of this calved ice island. Does anyone know if this is true, or was it a sceptical person making it up?
If true, it could explain why it cracked and broke off.
says nothing in Greenland or near for the past 7 days
Paul Hildebrandt,
From your source: Greenland area quake. August 5th.
Fred and Ira,
The Fjord would have been created during some previous glacial period when the water level was lower and the ice was scraping and gouging the sides and bottom of its valley. In our present time the valley is flooded and the tip of the glacier would be floating. Otherwise it could not “sail away” as an ice island after it fractures from the ice up-valley (or up-Fjord).
Cool!
Hey, now that this “chuck of ice as big as Manhatten” has broken away from its glacier ice roots and is moving towards the sea ice trapped near the fjord’s outlet, can we get it added to the AMSRE sea ice extent list and move up the mid-September sea extent margin a bit?
I don’t see the ice melting. I see it breaking. And that is not unprecedented. It’s called calving; you can even find it in the dictionary. Calving of ice is normal. What would be unprecedented is if ice didn’t calve.
I wonder what it sounded like?
Something quite interesting is happening at the NOAA pole cam I think?
The pictures are showing the melt ponds fully frozen over, its been snowing and the snow is not melting now. NOAA is not showing external temperatures on its pictures only the internal temp which as we know has internal heating powered by solar cells, is the external sensor broken or has NOAA disabled it?
The melt ponds should not be freezing over this early if past years are anything to go by and it may be that the melt season is winding down earlier than past years. Of course the melt may resume and its open season on the probability but it would help if we knew what the actual temperatures are through the day and night.
The disappearance of the melt ponds may signify nothing but then again…interesting times ahead for watchers of the NOAA pole cam eh?
I can imagine a writer imaginatively describing this event, “With a sound like 100,000 screaming new-born cattle and the growls of 10,000 polar bears, the huge glacier began slowly to break apart from one side to the other …”
I bet if you had a satellite video showing calving events over the past 500 years compacted into 30 seconds you would not see anything unusual or ‘rare’. Human time V nature time. Arctic ice extent comes to mind. :o)
George E. Smith writes:
“So “on average”, what is it that happens when ALL of the air has blown away from Greenland; on average of course ?
Do Kirchoff’s laws (circuit theory) not apply to Greenland ? Next time I need to defrost my Freezer; I’ll just blow on it; on average of course !”
It does, but a high pressure area is a high pressure area because the air is sinking, so the air over the icecap is replenished from above, and blows away to the sides. Conversely in a low pressure area the air is rising. That is why it rains a lot more from low pressure areas than high pressure areas.
Incidentally the many storms off the icecap were already known back in the Middle Ages. They are mentioned in the 13th century Norwegian böok “Kónungs skuggsja”.
Just a thought ~ With regards to the idea of an earthquake causing this calving; wouldnt the calving itself (the sudden freeing of an island of ice) create the release of enough energy to cause a fair sized earthquake?
The U.K. Daily Mail, which has been reasonably sceptic seems to have fallen for this big time. Their Science editor Michael Hanlon reports from “The crack in the roof of the world”, and says “Yes, global warming is real – and deeply worrying”.
Unfortunately he’s rather inconsistent, first we get emotive stuff like: “This river runs deep, possibly 13ft. Not a speck of dust, mud, weed or debris pollutes its flawless, azure depths. ” Then further down we suddenly find: “Minute specks of black airborne dust – a mixture of desert sand blown thousands of kilometres from the south, soot particles from power stations and microscopic algae and bacteria – settle on the ice and, being dark, absorb the sun’s rays, magnifying their heat like a spyglass onto the ice. ”
http://www.dailymail.co.uk/sciencetech/article-1301713/The-crack-roof-world-Yes-global-warming-real–deeply-worrying.html
Smokey says:
August 9, 2010 at 7:38 pm
Totally missed that.
Thanks.
Ken Hall says:
August 9, 2010 at 12:11 pm
I read somewhere that there was a 5.0 earthquake in the area of this calved ice island. Does anyone know if this is true, or was it a sceptical person making it up?
If true, it could explain why it cracked and broke off.
…and…
Smokey says:
August 9, 2010 at 7:38 pm
Paul Hildebrandt,
From your source: Greenland area quake. August 5th.
The quake was a 4.4 and was over 650 miles from Petermann Glacier. I doubt very much if it had an effect.
There are ‘Good’ Witches at East Anglia and there are ‘Bad’ Witches there too. This was done by one coven or the other, though it’s hard to tell at this time which. If the shelf ice had melted and shrunk, I’d have thought it was the Bad Witches. If the shelf ice had continued to grow and didn’t break, I’d have thought the ‘Good’ Witches did it. But since the shelf did grow and break, there must have been a great competition between the two sides, on brooms of course since they left no prints in the snow. I know some think Harry Potter and all that stuff was just a fairy tale but it wasn’t. EAU is actually called Hogwarts Academy by many who have been there.
And one would expect an advancing glacier to be calving ice, while a retreating glacier would be …. not calving? (not that either have anything/much to do temperature).