Our friends at NASA have a page on their Earth Observatory site (which should be on your list of “check every day” sites, needless to say) about the Mertz iceberg, Collision Calves Iceberg from Mertz Glacier Tongue, Antarctica : Image of the Day:
At 94 kilometers (58 miles) by 39 kilometers (24 miles) in size, the B-09B iceberg is comparable to the state of Rhode Island, which is wider but not quite so long. After lingering near the Mertz Glacier in Eastern Antarctica for several years, the massive iceberg collided with the glacier tongue on February 12 or 13, breaking it away from the rest of the glacier. The former glacier tongue formed a new iceberg nearly as large as B-09B. These images, all from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on NASA’s Aqua satellite, show the iceberg and glacier tongue immediately before and after the collision.
The top image is from February 7, 2010, when B-09B was approaching the Mertz Glacier Tongue. Chunks of sea ice float in the water between the smooth iceberg and the coast. It is clear that the iceberg and the glacier tongue are trapping the ice in place. The water beyond the tongue and the iceberg is black in these images, and contains far less ice. The ice tongue itself is an extension of the Mertz Glacier, created as the ice flows down the mountain and onto the water. Glacier tongues grow longer year by year until they eventually break off, calving a new iceberg. The Mertz Glacier Tongue was beginning to break before the B-09B iceberg rammed it. Dark horizontal cracks were visible in the ice tongue on February 7.
Sometime on February 12 or 13, B-09B struck the ice tongue. Clouds hid the event in MODIS satellite images, but on the afternoon of February 13, the clouds had thinned just enough to reveal that the ice tongue had broken away in the collision. The next cloud-free view of the region on February 20 (center image) shows the two icebergs. The glacier tongue had clearly broken along the rifts that were visible in early February. Over the course of the next week, the former Mertz Glacier Tongue pivoted away from the glacier like a door hinged at the point where B-09B hit it (lower image).
The iceberg formed from the Mertz Glacier Tongue is 78 kilometers (48 miles) long by 39 kilometers (24 miles) wide and has a mass of 700-800 billion tons, reported BBC News. The glacier tongue had previously contributed to keeping a section of the ocean free of ice, a condition known as a polynya. The polynya provided a significant feeding site for wildlife like penguins. The shorter tongue may not protect the area from sea ice, reducing or even eliminating the polynya and the access to food it provided.
The B9 iceberg broke from the Ross Ice Shelf in West Antarctica some time in 1987. It took the massive iceberg more than two decades to drift slowly out of the Ross Sea and along the coast to the Mertz Glacier in East Antarctica. Along the way, it broke apart, one segment becoming the massive B-09B iceberg that collided with the glacier tongue in February 2010.
The large images are the highest resolution version of the image available. The February 26, February 20, February 13, and February 7 images are all available in additional resolutions from the MODIS Rapid Response Team.
See the page above for the stunning photos.
In the endless articles about this events, there’s been a lot of speculation about what this immense ice cube will do to the world’s ocean currents. This brings up another interesting question: If it seems in a few years that this iceberg and B9B are indeed problematic as seems likely, then what can we do about it? Is there a way to tow a Luxembourg-size piece of ice? Is there a way to break it up and then tow the pieces? Just how many Margaritas can one make with 700-800 billion tons of ice?
Even a cursory look at the photos of the two ice masses reveals that B-09B did not break off the tongue of the Mertz Glacier. Rather some other forces acting on the north-west side of the tongue detached it and forced the tongue into B-09B, forcing B-09B slightly to the east and the western end of B-09B to the south.
Any force on the tongue from the east would place the west side of the tongue in compression and the east side in tension. If B-09B had really impacted the tongue from the east, the rupture of the tongue from the body of the glacier would have propagated from east to west, rather than the reverse (the actual case).
Furthermore, if B-09B impact transferred momentum to the tongue, the rotation of the long axis of the tongue would be counter clockwise, rather than the clockwise rotation shown.
To be onest, I was going to say much the same thing, but stopped myself. It’s entirely possible that B9B rubbed up against Mertz for some time, helped develop a huge crack (which would not have been obvious in all photos, considering the scale), and then B9B slid away with the current and Mertz happened to follow it (possible pulled along via a drafting effect?).
Or maybe you’re right and I’m reading too much into it.
This is one of those areas where I don’t think an amateur, like me, can look at a few satellite photos and figure out what happened to a 24×48-mile chunk of ice.