Sunday, 2 July 2017

Larsen C: Going, going.... at 33 feet per day

Larsen C Ice Shelf Rift Approaching Its End, Outer Edge Moving Away From Ice Shelf At Speed Of 33 Feet Per Day


 by James Ayre 
30 June, 2017
The Larsen C ice shelf crack that we’ve reported on numerous times in recent months appears to be nearing the point of calving. This will become the second-largest iceberg ever recorded, according to the researchers at Project MIDAS.
What’s happening is that the ice near where the rift began is now moving away from the rest of the ice shelf at a rate of around 33 feet per day, which is apparently unprecedented. There is still a tether of about 8 miles keeping the soon-to-be iceberg from breaking loose, but given how fast the far edge from this tether is now moving away from the ice shelf, this tether likely won’t last too long.
To put that all in plainer language, the future iceberg is now “wiggling like a loose tooth.”


As worded by the Project MIDAS researchers on their site: “In another sign that the iceberg calving is imminent, the soon-to-be-iceberg part of Larsen C ice shelf has tripled in speed to more than 10 meters per day between 24th and 27th June 2017. The iceberg remains attached to the ice shelf, but its outer end is moving at the highest speed ever recorded on this ice shelf.”
Climate Central provides more: “The speed-up is the latest sign that an iceberg is truly on the brink of forming. Project MIDAS researchers have been monitoring the state of the ice shelf since October 2015. During that time, they’ve observed periods of massive growth in the length of the crack across the ice shelf, widening to the point where you could lay the Empire State Building on its side to form a bridge across the chasm. More recently, a new branch sprouted, further warping the ice.
The latest change brings the break-off date that much closer to happening, though researchers cautioned it could still be weeks before the crack breaks through completely. When it does, though, it will drastically alter one of the largest ice shelves on the Antarctic Peninsula.”
What’s meant by “drastically alter” is that as much as 10% of the Larsen C ice shelf may end up breaking off with the new iceberg — an area around the size of the US state of Delaware — but that’s only the initially result. The event may well destabilize the whole ice shelf and prepare it for collapse — as occurred with the Larsen B ice shelf a while back. For another more common example, think of how an ice cube takes a while to form a hole, but then melts quickly once that hole is formed.
Regardless of the coming iceberg calving, the overall situation in Antarctica has been changing rapidly in recent years. West Antarctica seems to be fast approaching the point at which ice sheet collapse is inevitable — something that will lead to a large rise in sea levels over the coming century or two.
Images via Project MIDAS


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