The crumbling Thwaites Glacier
I shared a news article that gradually spread across a lot of the media last week. I said:
TIL (Today I Learned) that the state of Florida is bigger than England + Wales, and only a bit smaller than all of the island of Britain.
How did I learn that? Oh, because so is the Thwaites Glacier. It's the one that holds back the West Antarctic Ice Sheet.
Well, held. It's crumbling.
Scientists watch giant ‘doomsday’ glacier in Antarctica with concern
Cracks and fissures stoke fears of breakup that could lead to half-metre rise in global sea levels - or more
This got some reactions, as it should, but of course, it also aroused (as ever, ill-informed) scepticism. It seems inevitable. So I tried to answer some queries.
> Their maths isn't very good. First they say it's the size of England, then they say it's 50 miles wide.
Hint: it's not square.
Here's a fairly explanatory pic.
(Source: Why scientists are so worried about this glacier)
If that narrow bottleneck goes, then the rest slides into the sea rapidly. It doesn't need to melt, any more than ice cubes dropped into a glass need to melt to make the glass overflow. It doesn't matter if they take decades to melt; the sea-level rise due to displacement will take only about 12 days to spread out and equalise worldwide.
The key point here is that the fairly narrow point where the glacier flows into the sea is a bottleneck, and once the bung is removed, the flow speeds up.
Another said:
> TIL that the estimated time it could take for the doomsday glacier to melt has reduced from 40
> years to just five years in the space of seven months.
It doesn't need to melt. It doesn't really matter when it melts.
The West Antarctic Ice Sheet is sitting on rock that is below sea level. Ice is very slightly less dense than water. That means it floats. If water gets underneath the ice, it slides into the sea and floats off. It displaces vast amounts of water and the sea-levels rise.
It is not about melting. Melting could take decades to centuries but it's irrelevant. It's when it floats away that is important.
And the Thwaites glacier is one of the 2 main points that the WAIS pours out into the sea.
I added some other articles:
BBC News: Thwaites: Antarctic glacier heading for dramatic change
NBC News:
Antarctic ice shelf could crack, raise seas by feet within decade, scientists warn
Thwaites, the widest glacier in the world, has doubled its rate of melt in the last 30 years, a researcher said.
Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder:
The Threat from Thwaites: The Retreat of Antarctica’s Riskiest Glacier
Ice sheet’s demise poses the biggest threat for sea-level rise this century
> The article refers throughout to Antarctic ice "thinning and melting"
I specifically already addressed this.
If you are lying in a bath tub & the water is within millimetres of the rim, which will cause it to overflow quicker?
[a] Turning on the taps and adding 10 litres of water. That takes 1 minute using typical bath taps.
[b] Dropping 10kg of ice cubes into the water, in one motion. 1kg of ice is 1 litre, in case you don't know your SI units. I'm a sprightly 54 but I don't speak fluid ounces and all that stuff I'm afraid. It doesn't matter in this context.
If I tip a 10kg bag of ice cubes into a full bath, it will overflow immediately. If I pour water in at 10l/min it will take tens of seconds.
No, it is not about melting. It is about adding ice to the oceans, which adds mass. Archimedes' principle etc. Crystalline solids are a state of matter, a phase. It is irrelevant what phase the water is in; it's how much you add.
> Since 1950, the waters south of the Antarctic Circumpolar Current have warmed at a rate of only 0.02º/decade.
The poster didn't say degrees F or C.
But I submit that the numbers are irrelevant. The poles are warming much faster than the rest of the globe, but because most of Antarctica is a big raised continent with the icecap on top, it's much less in there. *Except* the Antartic peninsular - the long spur that points towards South America - which is the fastest-warming land on the planet:
Climate explained: why is the Arctic warming faster than other parts of the world?
The southern polar ocean is warming faster than the oceans as a whole:
Antarctica has experienced air temperature increases of 3°C in the Antarctic Peninsula. Although that might not seem very much, it is 5 times the mean rate of global warming as reported by the Intergovernmental Panel on Climate Change (IPCC).
The numbers may look small but the changes are vast. As a comparison, the Gulf Stream transports about 0.8 of a petaWatt of energy from the equator to the north pole. A fraction of a unit doesn't sound impressive. But the total energy output of humanity is about 23 teraWatts (2018 figures, latest I can find.)
1 PW = 1000 TW.
So humanity produces 0.023 PW. The very slightly warmer water flowing up the east coast of North America transports about 35 times the total energy output of humanity.
I have seen other estimates it's more like 60 times.
Which means that any human attempt to change the Gulf Stream is pretty futile. A mosquito pushing on the prow of a supertanker.
But the increase in CO₂ levels humanity has accomplished, from 280 parts per million before the Industrial Revolution to 410 now, is more than enough to trap enough heat to melt Greenland faster than it's collecting snow in winter, dumping over 500 thousand million tonnes of freshwater into the Arctic ocean and slowing the Gulf Stream, which is powered by warm, saltier water cooling and sinking to the bottom in the Arctic ocean.
The numbers look small but the real effects are vast and impossible to imagine on human scales. 0.2ºF (my guess as to what they meant) sounds like nothing, it seems trivial, but it's huge.
TIL (Today I Learned) that the state of Florida is bigger than England + Wales, and only a bit smaller than all of the island of Britain.
How did I learn that? Oh, because so is the Thwaites Glacier. It's the one that holds back the West Antarctic Ice Sheet.
Well, held. It's crumbling.
Scientists watch giant ‘doomsday’ glacier in Antarctica with concern
Cracks and fissures stoke fears of breakup that could lead to half-metre rise in global sea levels - or more
This got some reactions, as it should, but of course, it also aroused (as ever, ill-informed) scepticism. It seems inevitable. So I tried to answer some queries.
> Their maths isn't very good. First they say it's the size of England, then they say it's 50 miles wide.
Hint: it's not square.
Here's a fairly explanatory pic.
(Source: Why scientists are so worried about this glacier)
If that narrow bottleneck goes, then the rest slides into the sea rapidly. It doesn't need to melt, any more than ice cubes dropped into a glass need to melt to make the glass overflow. It doesn't matter if they take decades to melt; the sea-level rise due to displacement will take only about 12 days to spread out and equalise worldwide.
The key point here is that the fairly narrow point where the glacier flows into the sea is a bottleneck, and once the bung is removed, the flow speeds up.
Another said:
> TIL that the estimated time it could take for the doomsday glacier to melt has reduced from 40
> years to just five years in the space of seven months.
It doesn't need to melt. It doesn't really matter when it melts.
The West Antarctic Ice Sheet is sitting on rock that is below sea level. Ice is very slightly less dense than water. That means it floats. If water gets underneath the ice, it slides into the sea and floats off. It displaces vast amounts of water and the sea-levels rise.
It is not about melting. Melting could take decades to centuries but it's irrelevant. It's when it floats away that is important.
And the Thwaites glacier is one of the 2 main points that the WAIS pours out into the sea.
I added some other articles:
BBC News: Thwaites: Antarctic glacier heading for dramatic change
NBC News:
Antarctic ice shelf could crack, raise seas by feet within decade, scientists warn
Thwaites, the widest glacier in the world, has doubled its rate of melt in the last 30 years, a researcher said.
Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder:
The Threat from Thwaites: The Retreat of Antarctica’s Riskiest Glacier
Ice sheet’s demise poses the biggest threat for sea-level rise this century
> The article refers throughout to Antarctic ice "thinning and melting"
I specifically already addressed this.
If you are lying in a bath tub & the water is within millimetres of the rim, which will cause it to overflow quicker?
[a] Turning on the taps and adding 10 litres of water. That takes 1 minute using typical bath taps.
[b] Dropping 10kg of ice cubes into the water, in one motion. 1kg of ice is 1 litre, in case you don't know your SI units. I'm a sprightly 54 but I don't speak fluid ounces and all that stuff I'm afraid. It doesn't matter in this context.
If I tip a 10kg bag of ice cubes into a full bath, it will overflow immediately. If I pour water in at 10l/min it will take tens of seconds.
No, it is not about melting. It is about adding ice to the oceans, which adds mass. Archimedes' principle etc. Crystalline solids are a state of matter, a phase. It is irrelevant what phase the water is in; it's how much you add.
> Since 1950, the waters south of the Antarctic Circumpolar Current have warmed at a rate of only 0.02º/decade.
The poster didn't say degrees F or C.
But I submit that the numbers are irrelevant. The poles are warming much faster than the rest of the globe, but because most of Antarctica is a big raised continent with the icecap on top, it's much less in there. *Except* the Antartic peninsular - the long spur that points towards South America - which is the fastest-warming land on the planet:
Climate explained: why is the Arctic warming faster than other parts of the world?
The southern polar ocean is warming faster than the oceans as a whole:
Antarctica has experienced air temperature increases of 3°C in the Antarctic Peninsula. Although that might not seem very much, it is 5 times the mean rate of global warming as reported by the Intergovernmental Panel on Climate Change (IPCC).
The numbers may look small but the changes are vast. As a comparison, the Gulf Stream transports about 0.8 of a petaWatt of energy from the equator to the north pole. A fraction of a unit doesn't sound impressive. But the total energy output of humanity is about 23 teraWatts (2018 figures, latest I can find.)
1 PW = 1000 TW.
So humanity produces 0.023 PW. The very slightly warmer water flowing up the east coast of North America transports about 35 times the total energy output of humanity.
I have seen other estimates it's more like 60 times.
Which means that any human attempt to change the Gulf Stream is pretty futile. A mosquito pushing on the prow of a supertanker.
But the increase in CO₂ levels humanity has accomplished, from 280 parts per million before the Industrial Revolution to 410 now, is more than enough to trap enough heat to melt Greenland faster than it's collecting snow in winter, dumping over 500 thousand million tonnes of freshwater into the Arctic ocean and slowing the Gulf Stream, which is powered by warm, saltier water cooling and sinking to the bottom in the Arctic ocean.
The numbers look small but the real effects are vast and impossible to imagine on human scales. 0.2ºF (my guess as to what they meant) sounds like nothing, it seems trivial, but it's huge.