Earth from Space: Icebreaker event

Mar 05, 2010
Credit: ESA (Click "Enlarge" for animation)

(PhysOrg.com) -- This animation, made up of eight Envisat radar images, shows the 97-km long B-9B iceberg (right) ramming into the Mertz Glacier Tongue in Eastern Antarctica in early February. The collision caused a chunk of the glacier?s tongue to snap off, giving birth to another iceberg nearly as large as B-9B.

The new iceberg, named C-28, is roughly 78-km long and 39-km wide, with a surface area of 2500 sq km (the size of Luxembourg).
Since the collision, the two icebergs have drifted together into a polynya, which is an area of open water surrounded by . Polynyas produce dense, cold, and salty water - known as 'bottom water' - that sinks to the sea bottom and drives .

There is concern that if the icebergs stay in the polynyas area, they could block the formation of the bottom water. This would mean less oxygen going into the deep currents that feed the oceans and would have implications for marine life in the region.

The Mertz Glacier, 72-km long and about 32-km wide, flows into the off East along the George V Coast. It forms a 160-km floating tongue that extends northward into the ocean in the general direction of Australia. The tongue had large cracks (visible) that developed years before the collision.

B-9B broke off the B9 iceberg that calved from the Ross Ice Shelf in West Antarctica in 1987. It drifted westwards and in 1992 ran aground less than 100 km to the east of the Mertz Glacier Tongue, where it has remained until last month. The image to the right shows the positions of the Mertz Glacier Tongue and the B-9B iceberg in December 2007.

The National Ice Center, located in Maryland, U.S., names icebergs that are at least 10 nautical miles (or 19 km) long and are located within a set distance from the . The names are assigned according to where and when they first broke off from a glacier or ice shelf. The first letter represents one of the four longitudinal quadrants of Antarctica ranging from A to D; quadrant A faces the southern tip of South America, while quadrant C faces Australia.

A sequential number is then assigned to the iceberg, corresponding to how many named icebergs have emerged from a particular quadrant since 1976. So, C-28 was given its name because it is the 28th to form in the C quadrant.

’s Advanced Synthetic Aperture Radar (ASAR) acquired these images from 10 February to 4 March in Wide Swath Mode, providing spatial resolution of 150 m. ASAR can pierce through clouds and local darkness and is capable of differentiating between different types of ice.

Explore further: NASA sees developing Tropical Storm Halong causing warning

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User comments : 6

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croghan27
not rated yet Mar 05, 2010
I see from the animation that B-9B hits at the 'top' of the ice tongue - but it breaks off at the bottom.

Is there and explaination for that?
thermodynamics
not rated yet Mar 05, 2010
croghan27: I do not have a definite answer for you, but it appears that the crack where the iceberg broke was there already. They mention in the text: "The tongue had large cracks (visible) that developed years before the collision." Looking at the first frame of the sequence the crack is visible and then opens up. I suspect that the B-9B iceberg acted as a force on the tongue "lever" that opened the crack forming the new iceberg C-28. Once open the new iceberg was free from the tongue it was able to float away with B-9B.
Caliban
1 / 5 (1) Mar 05, 2010
That sounds like a reasonable mechanism.
I wonder if there is any data relating to the numbers, persistence, and perambulations of these named icebergs over the past few decades? Numbers increasing? Decreasing? Steady?
Pretty awe-inspiring that you could be out boating and encounter a piece of ice the size of Rhode Island. You could camp out on it. Invite your friends and have a party!
PPihkala
not rated yet Mar 06, 2010
I wonder what pros and cons there would be if one would tow smaller icebergs for example to cost of Africa to provide non-salty water to locals? Has anybody done feasibility study about that? Normal desalination is energy hungry and leaves the accuisition site with higher salinity. Iceberg mining would provide less salty local spot because of solar induced melting. That effect could be used to melt the ice at the top of iceberg just by cowering suitable area with dark 'cloth' and then letting the melt water to flow downwards to shore by gravity through suitable piping. First of course one would need to tow/push the iceberg to suitable shore by some big tugboats.
PPihkala
not rated yet Mar 06, 2010
Alternatively one could put a big 'plastic bag' underside and around an iceberg and let it melt into that. Then water tankers could be used to transfer the resulting bagged melt water to shore where it could be desalinated if not done already at the iceberg by solar power.
rwinners
not rated yet Mar 06, 2010
Towing has been though of long before this. Go here:
http://news.googl...,6025604

for an instance. Don't know if there was any follow up or what the French investigation concluded.