The world’s largest iceberg has finally crashed into a massive tongue of ice floating in Antarctic waters.


The predicted “collision of the century”- between the B15-A iceberg and the Drygalski ice tongue – had been expected to happen on 15 January 2005 in McMurdo Sound in the Ross Sea. But the icy colossus instead became stranded on a shallow seamount a few kilometres away from the 70-km-long tongue – starving penguins and blocking shipping supply routes to Antarctic bases.



Now, after breaking free in early April, the ice giant has finally scraped the side of the long-lived Drygalski ice tongue, an extension of the David glacier into the ocean. An image snapped by the European Space Agency’s Envisat satellite on 15 April shows a 5-km-long section of the ice tongue breaking off at its seaward end as the bottle-shaped iceberg brushes past.



“It was more of a bump in the night [than the] collision of the century,” admits Mark Drinkwater, head of ESA’s oceans and ice unit in The Netherlands. But the renegade iceberg may yet prove problematic.



“Since it touched [Drygalski], it’s turned around quite dramatically from its original orientation,” explains Drinkwater. “The question now is whether the currents can get a hold of it and carry it out [to the open sea] without it getting lodged in the Terra Nova bay.”



If the 115-km-long iceberg gets trapped in the bay it may interfere with the local penguins’ feeding routes and could cause problems for an Italian research base. It might even affect the flow of water from the bay. This is one of the sources of cold, dense water that drives the global oceanic currents, which in turn exert a major climatic influence.



Winds sweeping through the bay keep the area clear of sea ice, which is less salty than the sea water in which it floats. If B15-A blocks the bay it may interfere with this, causing ice to become trapped. If this trapped ice were to melt, it would decrease the density of the water, making it less likely to sink and drive the global currents.



However, although a risk, Drinkwater thinks B15-A is fairly unlikely to get caught in the bay, considering the currents it will encounter and the shape and depth of the ocean floor in the bay.



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