For the first time, researchers have been able to obtain data from underneath Thwaites Glacier, also known as the “Doomsday Glacier”. They find that the supply of warm water to the glacier is larger than previously thought, triggering concerns of faster m
UNIVERSITY OF GOTHENBURG
For the first time, researchers have been able to obtain data from underneath Thwaites Glacier, also known as the “Doomsday Glacier”. They find that the supply of warm water to the glacier is larger than previously thought, triggering concerns of faster melting and accelerating ice flow.
With the help of the uncrewed submarine Ran that made its way under Thwaites glacier front, the researchers have made a number of new discoveries. Professor Karen Heywood of the University of East Anglia commented:
“This was Ran’s first venture to polar regions and her exploration of the waters under the ice shelf was much more successful than we had dared to hope. We plan to build on these exciting findings with further missions under the ice next year.”
The submersible has, among other things, measured the strength, temperature, salinity and oxygen content of the ocean currents that go under the glacier.
Global sea level is affected by how much ice there is on land, and the biggest uncertainty in the forecasts is the future evolution of the West Antarctic Ice Sheet, says Anna Wåhlin, professor of oceanography at the University of Gothenburg and lead author of the new study now published in Science Advances.
Impacts global sea level
The ice sheet in West Antarctica accounts for about ten percent of the current rate of sea level rise; but also the ice in West Antarctica holds the most potential for increasing that rate because the fastest changes worldwide are taking place in the Thwaites Glacier. Due to its location and shape, Thwaites is particularly sensitive to warm and salty ocean currents that are finding their way underneath it.
This process can lead to an accelerated melting taking place at the bottom of the glacier and inland movement of the so-called grounding zone, the area where the ice transitions from resting on the seabed to floating in the ocean.
Due to its inaccessible location, far from research stations, in an area that is usually blocked by thick sea ice and many icebergs, there has been a great shortage of in situ measurements from this area. This means that there are big knowledge gaps for the ice-ocean boundary processes in this region.
First measurements performed
In the study, the researchers present the results from the submersible that measured strength, temperature, salinity and oxygen content of the ocean currents that go under the glacier.
“These were the first measurements ever performed beneath Thwaites glacier”, says Anna Wåhlin.
The results have been used to map the ocean currents underneath the floating part of the glacier. The researchers discovered that there is a deep connection to the east through which deep water flows from Pine Island Bay, a connection that was previously thought to be blocked by an underwater ridge.
The research group has also measured the heat transport in one of the three channels that lead warm water towards Thwaites Glacier from the north. “The channels for warm water to access and attack Thwaites weren’t known to us before the research. Using sonars on the ship, nested with very high-resolution ocean mapping from Ran, we were able to find that there are distinct paths that water takes in and out of the ice shelf cavity, influenced by the geometry of the ocean floor” says Dr Alastair Graham, University of Southern Florida.
The value measured there, 0.8 TW, corresponds to a net melting of 75 km3 of ice per year, which is almost as large as the total basal melt in the entire ice shelf. Although the amount of ice that melts as a result of the hot water is not much compared to other global freshwater sources, the heat transport has a large effect locally and may indicate that the glacier is not stable over time.
Not sustainable over time
The researchers also noted that large amounts of meltwater flowed north away from the front of the glacier.
Variations in salinity, temperature and oxygen content indicate that the area under the glacier is a previously unknown active area where different water masses meet and mix with each other, which is important for understanding the melting processes at the base of the ice.
The observations show warm water approaching from all sides on pinning points, critical locations where the ice is connected to the seabed and give stability to the ice shelf. Melting around these pinning points may lead to instability and retreat of the ice shelf and, subsequently, the upstream glacier flowing off the land. Dr Rob Larter of the British Antarctic Survey commented:
“This work highlights that how and where warm water impacts Thwaites Glacier is influenced by the shape of the sea floor and the ice-shelf base as well as the properties of the water itself. The successful integration of new sea-floor survey data and observations of water properties from the Ran missions shows the benefits of the multidisciplinary ethos within the International Thwaites Glacier Collaboration.”
“The good news is that we are now, for the first time, collecting data that is necessary to model the dynamics of Thwaite’s glacier. This data will help us better calculate ice melting in the future. With the help of new technology, we can improve the models and reduce the great uncertainty that now prevails around global sea level variations.” says Anna Wåhlin.
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“Doomsday Glacier” would make a great title for a sci-fi movie. A small, intrepid team of scientists are busy studying the Thwaites Glacier, monitoring it for any changes, when one of them starts noticing things happening, then others. Then they try to alert the world, but nobody will listen. Then, there’s a chain reaction, setting off Thermageddon. Now to figure out who to cast for it, budgeting, etc.
Cha-chingggg!!!!!
”Satellite reveals surprising ebb and flow of subglacial lakes under Thwaites Glacier”.
”…an unexpected discovery about how lakes beneath Thwaites Glacier drain and recharge in quick succession.”
”A study published in the journal Geophysical Research Letters in December 2020 describes how a decade of radar altimetry observations have revealed a network of four subglacial lakes under Thwaites Glacier”
https://thwaitesglacier.org/news/satellite-insight-subglacial-lakes
Worse than we thought is obvious spin. Nothing these people say can be trusted.
The export of cold deep ocean currents from Antarctica is increasing, not decreasing. Talk of warming and melt in Antarctica is wishful thinking only.
https://ptolemy2.wordpress.com/2020/09/12/widespread-signals-of-southern-hemisphere-ocean-cooling-as-well-as-the-amoc/
I follow the temperature at the Doomsday Glacier or more precisely The West Antarctic Ice Sheet. Right now, the temperature there is balmy -41 C. I saw with amazement one year ago when a BBC reporter reported from there about global warming while he suffered from hypothermia in a snowstorm. The irony with this was not apparent for BBC. The researchers made a hole in the Shelf Ice down to the water beneath. One other thing I noticed were the expensive equipment they used. Climate scientists don’t suffer from lack of funds.
Would it be too much to hope that it snows in Cornwall in June for the G7 conference – that would be much harder to explain away. However as a Brit with the French seemingly hating us over Brexit and Macron spitting feathers at us – I cant say I feel much sympathy
They failed to mention that these upwelling currents come from a depth as much as 800 meters
For a glacier that is floating on the ocean, whether it melts or remains frozen has no effect on sea level, because floating ice already displaces its weight in water. People have known this since the time of Archimedes.
Ocean currents under sea ice will have no effect on land-based ice.
So what’s the problem?
If this study is looking at the W Antarctic area, and only that, this is nonsense. WAP is a tiny bit of the continent and it means little. But the US is stationed there, so American scientists sturdy there and then extrapolate their numbers to the rest of Antarctica without taking into much besides the ratio of WAP to the rest of Antarctica. The geography and ocean arrangement there is nothing like the vast expanse of East Antarctica, which has long, long straight coastlines of ice and large inland areas of ice cap. (It is very much apples and bananas.)