Larsen C calves trillion ton iceberg
A one trillion tonne iceberg – one of the biggest ever recorded – has calved away from the Larsen C Ice Shelf in Antarctica. The calving occurred sometime between Monday 10th July and Wednesday 12th July 2017, when a 5,800 square km section of Larsen C finally broke away. The iceberg, which is likely to be named A68, weighs more than a trillion tonnes. Its volume is twice that of Lake Erie, one of the Great Lakes.
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A crack in the Larsen C ice shelf, which grew 17 kilometres in DecemberA crack in the Larsen C ice shelf, which grew 17 kilometres in December | Geology |
The impending separation of what’s expected to be one of the largest icebergs ever recorded just got a dramatic step closer, after an epic 180-km-long (111.8-mile) rift in Antarctica suddenly split in two.
Scientists have been watching this massive crack in the Larsen C ice shelf develop slowly for decades, but a series of rapid developments in the past year has now seen the rift divide into two separate paths, with a new secondary branch advancing 15 km (9.3 miles) in a matter of days.
“While the previous rift tip has not advanced, a new branch of the rift has been initiated,” says glaciologist Adrian Luckman from Swansea University in the UK.
“This is approximately 10 km (6.2 miles) behind the previous tip, heading towards the ice-front.”
With this new branch of the rift making a beeline for the Weddell Sea, there’s only 20 km (12.4 miles) of ice keeping a 5,000 sq km (1,930.5 sq mile) chunk of the shelf from floating adrift.
If – or, more likely, when – that happens, it would amount to the third largest loss of Antarctic ice in recorded history.
For context, depending on your local geography, that’s an iceberg about the size of Delaware – or roughly one-quarter the size of Wales.
The TV said that if this iceberg melts (don’t they all?) that the world sea level will rise 200 feet. I doubt that. Maybe 200 centimeters. Or do you have a reliable source, Oui?
○ Melting icebergs in polar oceans causing sea level rise globally, new assessment finds
Different story with landbound glacier melt …
○ The great Greenland meltdown
It’s urgent to figure out why, and how the melting might evolve in the future, because Greenland holds the equivalent of more than 7 m of sea level rise in its thick mantle of ice. Glaciologists were already fully occupied trying to track and forecast the surge in glacial calving. Now, they are striving to understand the complex feedbacks that are speeding up surface melting.
This particular iceberg is mostly sea water, so it won’t raise ocean water level significaantly (see https://www.nytimes.com/interactive/2017/06/09/climate/antarctica-rift-update.html). The danger is if the land ice that it held back also breaks free in the future, though that wouldn’t be anywhere close to 200′.
Which TV station said that?
Not sure. WGN or ABC or FOX. I don’t watch FOX much, but they are on when others aren’t or have crapola like “Good Morning America”. Any “news” show that starts with female squealing, I switch off immediately. George S. makes it doubly bad.
The ice in an ice shelf is not saline. During the freezing process, solutes are “rejected” and become concentrated in pockets or expelled entirely.
Oops yes of course. What I meant to say was that the iceberg was floating on the sea, not that it was actually composed of salt water.
Further reading:
○ Ice Ages and Sea Level
○ Sea Level Rise, After the Ice Melted and Today | NASA |
Global sea level has fluctuated widely in the recent geologic past. It stood 4-6 meters above the present during the last interglacial period, 125,000 years ago, but was 120 m lower at the peak of the last ice age, around 20,000 years ago. A study of past sea level fluctuations provides a longer-term geologic context, which can help us better anticipate future trends.
Massive ice sheets covered parts of North America, northern Europe, and several other regions during the last ice age. This huge volume of ice lowered global sea level by around 120 meters as compared to today. After the ice sheets began to melt and retreat, sea level rose rapidly, with several periods of even faster spurts. The first such spurt may have started about 19,000 years ago, at which time ocean levels rose 10-15 m in less than 500 years.
First, a link to an item in the American Geophysical Union newsletter.
Second, the issue about sea level rise has almost nothing to do with ice shelves, which are afloat. Sea level rise is driven in a minor way by thermal expansion of warming water, but the lion’s share of potential sea level rise is associated with the loss of “grounded” ice (such as, potentially, the West Antarctic ice sheet).
Yes, a few seconds reflection reminded me that once an iceberg is actually afloat, it has already displaced its weight and so the sea level rise has already occurred. melting affects salinity and temperature but not level. Flogging myself for overlooking freshman physics.
However, salinity and temperature affect currents which have major effects on climate.
Here are some headlines of the last week that make the the Trump-Russia matters trivial:
The Uninhabitable Earth: Famine, economic collapse, a sun that cooks us: What climate change could wreak — sooner than you think.
Era of `Biological Annihilation’ Is Underway, Scientists Warn
Burning Fossil Fuels Almost Ended All Life on Earth: A road trip through the geological ruins of our planet’s worst mass extinction.
We’ve got to fix the belligerence of Russia’s Putin first, planet Earth comes later!
○ Trump appears to keep door open to a change of position on the 2015 Paris climate change agreement