Antarctic: ‘No role’ for climate in Halley iceberg splitting

By Paul Homewood

 

h/t Philip Bratby

 

 

The BBC report through gritted teeth!

 

image

When a giant iceberg breaks away from near Britain’s Halley research base, it won’t be because of climate change.

Scientists Jan De Rydt and Hilmar Gudmundsson have spent years studying the area and say the calving will be the result of natural processes only.

The Antarctic station, which sits on a floating platform of ice, was moved in 2017 to get it away from a large chasm.

That crack is now expected to dump a berg the size of Greater London into the Weddell Sea.

It’s not clear precisely when this will happen, but the breakaway looks imminent, prompting the British Antarctic Survey (BAS) to withdraw its staff from Halley as a precaution.

As soon as the calving does occur, though, it can be guaranteed that one of the first questions everyone will ask is: what was the influence of climate change?

And the Northumbria University team believes it will be able to answer with high confidence: "There was none."

Jan De Rydt and Hilmar Gudmundsson have built a model to describe the behaviour of the floating ice platform, which is known as the Brunt Ice Shelf.

Image copyright Jan De Rydt Image caption The model explains why Chasm One opened up where it did, and the direction it took

The Brunt is essentially an amalgam of glacier ice that’s flowed off land and pushed out to sea at a rate of about 400m per year.

Incorporating satellite and surface-gathered data, the team’s model reveals how stress is distributed across the 150-250m-thick structure. And it predicts accurately where cracks are likely to develop and the path they will take.

"It all fits together; it’s a very compelling piece of work," says Prof Gudmundsson.

"It shows that the chasm started to grow because of the stresses building up, and they built up because of the natural growth of the ice shelf. The ice shelf itself created this chasm."

The Brunt has never been in quite so advanced a position. The famous explorer Sir Ernest Shackleton mapped its ice front in 1915 and the modern cliff edge is well beyond what he saw. A calving seems overdue.

Graphic of Brunt

The chasm is not the only major split in the Brunt, however. To the east of Halley is a crack dubbed Halloween, after its discovery on 31 October 2016. This fissure is likely to produce its own berg at some point, but, again, this behaviour can be described simply by the developing stresses in the shelf.

"There is no indication from oceanographic or atmospheric data that the climate is changing in the Brunt area," Dr De Rydt told BBC News.

"Our ocean observations are limited but whatever we have doesn’t indicate anything unusual; and our model shows that what we are seeing can be perfectly explained by natural changes in the geometry of the ice shelf."

https://www.bbc.co.uk/news/science-environment-47817510

 

The comparison with Shackleton’s mapping in 1915 is an interesting one, worth remembering when we get nagged about “melting ice caps”.

But there should really be little surprise about any of this. It is the way icebergs have always formed.

The idea that glaciers flow down to the sea, but somehow never break off is infantile.

via NOT A LOT OF PEOPLE KNOW THAT

http://bit.ly/2UpF89R

April 5, 2019 at 04:31AM

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