Antarctic lake suddenly disappears

JUNE 25, 2021

by University of California – San Diego

https://phys.org/news/2021-06-antarctic-lake-suddenly.html?fbclid=IwAR1uyHwiwLFynLKtvVC-fLDUL2gUDcp6MHew7B9OHZ30oN0QnQpSN4oiu6Q

<img src="https://scx1.b-cdn.net/csz/news/800a/2021/antarctic-lake-suddenl.jpg&quot; alt="Antarctic lake suddenly disappears" title="Landsat 8 images over the Southern Amery Ice Shelf show the ice-covered lake before drainage and the resulting ice doline with summer meltwater. Credit: <i>Geophysical Research Letters
Landsat 8 images over the Southern Amery Ice Shelf show the ice-covered lake before drainage and the resulting ice doline with summer meltwater. Credit: Geophysical Research Letters

A global team of scientists including several from Scripps Institution of Oceanography at the University of California San Diego discovered the sudden demise of a large, deep, ice-covered lake on the surface of an Antarctic ice shelf.https://bce2d4334d30033b51e2fcf07a96fa6c.safeframe.googlesyndication.com/safeframe/1-0-38/html/container.html

This rare event, chronicled in a study published today in the journal Geophysical Research Letters, occurred during the 2019 Antarctic winter on Amery Ice Shelf in East Antarctica, and it is estimated that 600-750 million cubic meters (21-26 billion cubic feet) of water, about twice the volume of San Diego Bay, were lost to the ocean.

Study authors used images from a radar satellite which can “see” during the polar night to pin the event’s timing down to a week or less in June. After drainage, in place of the lake, there was a crater-like depression in the ice shelf surface, covering about eleven square kilometers (4.25 square miles). This surface depression, known as an ice “doline,” contained the fractured remains of the ice cover.

“We believe the weight of water accumulated in this deep lake opened a fissure in the ice shelf beneath the lake, a process known as hydrofracture, causing the water to drain away to the ocean below,” said study lead author Roland Warner, a glaciologist with the Australian Antarctic Program Partnership at the University of Tasmania.

The hydrofracture process has been implicated in the collapse of smaller ice shelves in the Antarctic Peninsula, where meltwater forms on the surface of ice shelves during austral summer, but it is not often seen driving through ice as thick as the 1400 meters (4,590 feet) at this location on Amery Ice Shelf.

The austral winter event was also captured by a green-light laser instrument on NASA’s ICESat-2. This satellite transmits pulses of photons and accurately locates the reflection point of each photon it receives back from Earth.

Repeat orbits of ICESat-2 on the exact ground tracks before and after the lake drainage revealed the vertical scale of the disruption. The ice surface fell as much as 80 meters (260 feet) in the doline cavity, even though the loss of the water load made the floating ice shelf lighter and ocean pressure caused it to flex upwards, with the lake’s immediate surroundings rising as much as 36 meters (118 feet).https://googleads.g.doubleclick.net/pagead/ads?client=ca-pub-0536483524803400&output=html&h=280&slotname=5350699939&adk=3784993980&adf=780081655&pi=t.ma~as.5350699939&w=753&fwrn=4&fwrnh=100&lmt=1624821292&rafmt=1&psa=1&format=753×280&url=https%3A%2F%2Fphys.org%2Fnews%2F2021-06-antarctic-lake-suddenly.html%3Ffbclid%3DIwAR1uyHwiwLFynLKtvVC-fLDUL2gUDcp6MHew7B9OHZ30oN0QnQpSN4oiu6Q&flash=0&fwr=0&rpe=1&resp_fmts=3&wgl=1&uach=WyJXaW5kb3dzIiwiMTAuMCIsIng4NiIsIiIsIjkxLjAuNDQ3Mi4xMTQiLFtdLG51bGwsbnVsbCxudWxsXQ..&dt=1624816846461&bpp=94&bdt=7987&idt=1979&shv=r20210623&cbv=%2Fr20190131&ptt=9&saldr=aa&abxe=1&cookie=ID%3D5d55f89f953c9743-22f732a8bfc8007c%3AT%3D1624744826%3ART%3D1624744826%3AS%3DALNI_MbLeyyxtkyTA01qMXFQQ0lXAOJb-A&prev_fmts=0x0&nras=1&correlator=6295969967862&frm=20&pv=1&ga_vid=185394846.1565457508&ga_sid=1624816849&ga_hid=1409389891&ga_fc=0&u_tz=-420&u_his=1&u_java=0&u_h=640&u_w=1139&u_ah=607&u_aw=1139&u_cd=24&u_nplug=3&u_nmime=4&adx=263&ady=1974&biw=1123&bih=537&scr_x=0&scr_y=0&eid=21066435%2C31060972&oid=3&pvsid=3095820333588077&pem=466&ref=https%3A%2F%2Fl.facebook.com%2F&eae=0&fc=896&brdim=0%2C0%2C0%2C0%2C1139%2C0%2C1139%2C607%2C1139%2C537&vis=1&rsz=%7C%7CpEebr%7C&abl=CS&pfx=0&fu=128&bc=31&ifi=1&uci=a!1&btvi=1&fsb=1&xpc=Gz3t6qfJWE&p=https%3A//phys.org&dtd=M

“It is exciting to see ICESat-2 show us details of processes that are occurring on the ice sheet at such fine spatial scale,” said co-author Helen Amanda Fricker, a glaciologist at Scripps Institution of Oceanography who has long studied active sub-glacial lakes, discovering them in 2007. “Since surface meltwater on ice shelves can cause their collapse which ultimately leads to sea-level rise when grounded ice is no longer held back, it’s important to understand the processes that weaken ice shelves.”

In recent decades with rising air temperatures, some ice shelves have experienced greater surface melting, and the most recent model projections for future warming show that trend continuing and creating more melt lakes. This increases the risk of widespread hydrofracturing, which could lead to ice shelves collapsing, permitting faster discharge of ice from grounded ice sheets and increases in sea level. Now, possible increased flows into deep, ice-covered lakes and hydrofracture of thick ice shelves should also be considered in projections for future warming, said researchers.

The team also used surface elevation maps generated by the Polar Geospatial Center (PGC) at the University of Minnesota to show that the disruption modified the regional landscape across 60 square kilometers (23 square miles).

The amount of water lost to the ocean was calculated using the volume of the cavity and the extent of uplift. While Amery Ice Shelf does have many melt-lakes and streams in austral summer, the amount of water lost when the lake drained was many times the annual meltwater input to it.

The uplift of the lake created a new lake out of a shallow arm of the original one. During the next melt season this lake filled within a few days at more than a million cubic meters per day and overflowed into the doline cavity. When ICESat-2 crossed the doline again a few days later, the team was able to measure a meltwater channel 20 meters (65 feet) wide, freshly cut into the doline, detecting the water surface at three meters depth, and photons scattered from the stream bed a further three meters below.

The authors say that it is too early to conclude that the drainage of this meltwater lake was related to broader trends like the warming of the climate around Antarctica. With this new observation capability, and as more ICESat-2 and PGC data are collected, Fricker says they will be able to further understand how common these deep lakes are and how they evolve over time.

“This abrupt event was apparently the culmination of decades of melt-water accumulation and storage beneath that insulating lid of ice,” said co-author Jonathan Kingslake, professor at Lamont Doherty Earth Observatory at Columbia University, who aided in the measuring of the surface meltwater.

The future of the newly formed doline is uncertain. It may accumulate meltwater again or drain to the ocean more frequently. It appears that the fissure reopened briefly in the 2020 melt season. It is certain that scientists will now be watching.


Explore furtherExtreme melt on Antarctica’s George VI ice shelf

Antarctic ice-sheet melting to lift sea level higher than thought, study says

https://phys.org/news/2021-04-antarctic-ice-sheet-sea-higher-thought.html

APRIL 30, 2021

by Harvard University

Antarctic ice-sheet melting to lift sea level higher than thought, Harvard study says
This was taken in the Scotia Sea during the coring campaign in 2007. Credit: Michael Weber

Global sea level rise associated with the possible collapse of the West Antarctic Ice Sheet has been significantly underestimated in previous studies, meaning sea level in a warming world will be greater than anticipated, according to a new study from Harvard researchers.

The report, published in Science Advances, features new calculations for what researchers refer to as a water expulsion mechanism. This occurs when the solid bedrock the West Antarctic Ice Sheet sits on rebounds upward as the ice melts and the total weight of the ice sheet decreases. The bedrock sits below sea level so when it lifts, it pushes water from the surrounding area into the ocean, adding to global sea level rise.

The new predictions show that in the case of a total collapse of the ice sheet, global sea level rise estimates would be amplified by an additional meter within 1,000 years.

“The magnitude of the effect shocked us,” said Linda Pan, a Ph.D. in earth and planetary science in GSAS who co-led the study with fellow graduate student Evelyn Powell. “Previous studies that had considered the mechanism dismissed it as inconsequential.”

“If the West Antarctic Ice Sheet collapsed, the most widely cited estimate of the resulting global mean sea level rise that would result is 3.2 meters,” said Powell. “What we’ve shown is that the water expulsion mechanism will add an additional meter, or 30 percent, to the total.”

But this is not just a story about impact that will be felt in hundreds of years. One of the simulations Pan and Powell performed indicated that by the end of this century global sea level rise caused by melting of the West Antarctic Ice Sheet would increase 20 percent by the water expulsion mechanism.

“Every published projection of sea level rise due to melting of the West Antarctic ice sheet that has been based on climate modeling, whether the projection extends to the end of this century or longer into the future, is going to have to be revised upward because of their work,” said Jerry X. Mitrovica, the Frank B. Baird Jr. Professor of Science in the Department of Earth and Planetary Sciences and a senior author on the paper. “Every single one.”

Pan and Powell, both researchers in Mitrovica’s lab, started this research while working on another sea level change project but switched to this one when they noticed more water expulsion from the West Antarctic ice sheet than they were expecting.

The researchers wanted to investigate how the expulsion mechanism affected sea level change when the low viscosity, or the easy flowing material of the Earth’s mantle beneath West Antarctica, is considered. When they incorporated this low viscosity into their calculations they realized water expulsion occurred much faster than previous models had predicted.

“No matter what scenario we used for the collapse of the West Antarctic Ice Sheet, we always found that this extra one meter of global sea level rise took place,” Pan said.

The researchers hope their calculations show that, in order to accurately estimate global sea level rise associated with melting ice sheets, scientists need to incorporate both the water expulsion effect and the mantle’s low viscosity beneath Antarctica.

“Sea level rise doesn’t stop when the ice stops melting,” Pan said. “The damage we are doing to our coastlines will continue for centuries.”

Over a third of Antarctic ice shelf could collapse as climate change warms the Earth

https://www.space.com/antarctic-ice-shelf-collapse-as-earth-warms

By Chelsea Gohd 8 hours ago

The Larsen C ice shelf.

The Larsen C ice shelf. (Image credit: NASA ICE)

Over a third of the Antarctic ice shelf is at risk of collapsing as Earth continues to warm. 

In a new study, scientists at the University of Reading have found that as climate change continues, if Earth’s global temperature rises to 7.2 degrees Fahrenheit (4 degrees Celsius) above pre-industrial levels, about 193,000 square miles (500,000 square kilometers) of the Antarctic ice shelves could collapse into the sea. Ice shelves are permanent floating slabs of ice attached to coastline, and the collapse of these shelves could significantly raise global sea levels, the researchers suggest. 

“Ice shelves are important buffers preventing glaciers on land from flowing freely into the ocean and contributing to sea level rise. When they collapse, it’s like a giant cork being removed from a bottle, allowing unimaginable amounts of water from glaciers to pour into the sea,” lead study author Ella Gilbert, a research scientist in the University of Reading’s Department of Meteorology, said in a statement

Related: 2020 ties record for hottest year ever, NASA analysis showsClick here for more Space.com videos…https://imasdk.googleapis.com/js/core/bridge3.450.0_en.html#goog_201308220300:04 of 03:42Volume 0% PLAY SOUND

Every summer in Antarctica, ice on the surface of the ice shelf melts and that water travels into the snow below where it refreezes. But in years with more melting ice than snowfall, that water ends up pooling on the ice shelf’s surface and falls into cracks in the ice, melting and growing those cracks until the ice shelf breaks off into the ocean. This exact thing happened with the Larsen B ice shelf in 2002 and in this study researchers identify ice shelf Larsen C as at particular risk for collapse in warmer temperatures. 

In this study, researchers used high-resolution regional climate modeling technology to predict how melting ice and water runoff will affect ice shelf stability over time and at different global temperatures. They modeled ice shelf vulnerability at global temperatures 2.7 degrees F (1.5 degreesC), 3.6 degrees F (2 degrees C) and 7.2 degrees F (4 degrees C) above pre-industrial levels, three scenarios that are all possible within this century, according to the statement. 

“We know that when melted ice accumulates on the surface of ice shelves, it can make them fracture and collapse spectacularly. Previous research has given us the bigger picture in terms of predicting Antarctic ice shelf decline, but our new study uses the latest modelling techniques to fill in the finer detail and provide more precise projections,” Gilbert said. 

They found that, at 7.2 degrees F (4 degrees C) above pre-industrial global temperatures, 34%of all Antarctic ice shelves (including 67%of the ice shelf area on the Antarctic Peninsula) 

“The findings highlight the importance of limiting global temperature increases as set out in the Paris Agreement if we are to avoid the worst consequences of climate change, including sea level rise,” Gilbert said. 

The Paris Agreement is an international treaty that was signed in 2016, made within the United Nations Framework Convention on Climate Change. Under the agreement, nations have pledged to work to limit global temperature increase to 3.6 degrees F (2 degrees C), or preferably 2.7 degrees F (1.5 degrees C), above pre-industrial levels.

Related: Earth is hotter than ever — So what happens next?Click here for more Space.com videos…2020 tied for hottest year! Space.com talks with NASAhttps://imasdk.googleapis.com/js/core/bridge3.450.0_en.html#goog_2013082206Volume 0% PLAY SOUND

Scientists have been worried about the continued effects of global warming on floating ice shelves for some time. 

“The floating ice shelves around the coast of Antarctica are of particular concern,” Paul Cutler, a program director for National Science Foundation’s Antarctic Sciences Division, said during a live webinar Thursday (April 8). “They interface with the ocean which is changing, and they hold back the flow of the inland ice as it moves towards the ocean. So if you lose the integrity of those ice shelves, you release more inland ice to the ocean, and you cause even more sea level rise.”

Rising sea levels can have many dangerous effects including extreme coastal flooding, destructive erosion and more. 

Additionally, “with the loss of the glaciers, you actually lose their gravitational pull,” Cutler said. “So when you lose West Antarctica, you lose its gravitational pull on the United States. And actually, part of the sea level rise we see in the U.S. is related to the loss of ices by that indirect gravity effect as well.” 

“Limiting warming will not just be good for Antarctica — preserving ice shelves means less global sea level rise, and that’s good for us all,” Gilbert said.

SCIENTISTS DISCOVER “DOOMSDAY GLACIER” MORE UNSTABLE THAN EVER

https://futurism.com/the-byte/scientists-discover-doomsday-glacier-more-unstable-than-ever

WARM WATERS PUT THE GLACIER AT RISK OF COMPLETELY COLLAPSING.

FILIP STEDT

Doomed Doomsday Glacier

Researchers studied the waters underneath the Thwaites Glacier (aka the “Doomsday Glacier”) and have discovered that the ice shelf is melting faster than they previously thought. 

Scientists utilized an uncrewed submersible known as “Ran” to explore the underside of the glacier in Western Antarctica, according to SciTechDaily. There they discovered that the warm waters flowing underneath is wearing away at the glacier at a faster rate than they anticipated, creating cracks and fissures in the ice.   

This poses a glacier-sized problem: If the ice shelf collapses, we could all see a massive rise in global sea levels (that’s why it’s called the Doomsday Glacier). 

The researchers published a study of their findings in Science Advances

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Warm Waters Run Deep

The Thwaites Glacier is roughly 119,300 square miles big, according to Gizmodo. Despite its immense size, the ice is melting faster than any other glacier in Antarctica.

The Ran submersible discovered that the water beneath can rise as high as 33.89 degrees Fahrenheit — which is warm enough to deteriorate the ice. 

“The worry is that this water is coming into direct contact with the underside of the ice shelf at the point where the ice tongue and shallow seafloor meet,” said Alastair Graham, associate professor of geological oceanography at the University of Southern Florida and co-author of the study, to Gizmodo. 

He continued saying, “This is the last stronghold for Thwaites and once it unpins from the sea bed at its very front, there is nothing else for the ice shelf to hold onto. That warm water is also likely mixing in and around the grounding line, deep into the cavity, and that means the glacier is also being attacked at its feet where it is resting on solid rock.”

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So it’s certainly a bittersweet moment for the researchers. On the brightside, they were able to study a previously unexplored part of the glacier — but they also learned that the Doomsday Glacier might live up to its name sooner than they thought. 

READ MORE: First Exploration of Ocean Currents Beneath the “Doomsday Glacier” Triggers Concerns [SciTechDaily]

More on ice melt: A Melting Antarctica Could Raise the Sea Level More Than Expected

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A third of Antarctic ice shelf risks collapse as our planet warms

https://www.cnn.com/2021/04/08/world/ice-melt-antarctic-intl-scli-scn-climate/index.html

By Amy Woodyatt, CNN

Updated 9:07 AM ET, Thu April 8, 2021

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London (CNN)More than a third of the Antarctic ice shelf risks collapsing into the sea if global temperatures reach 4 degrees Celsius (7.2 degrees Fahrenheit) above pre-industrial levels as climate change warms the world, a new study from the UK’s University of Reading has warned.In a forecasting study, scientists found that 34% of the area of all Antarctic ice shelves, measuring some half a million square kilometers, could destabilize if world temperatures were to rise by 4 degrees. Some 67% of the ice shelf area on the Antarctic Peninsula would be at risk of destabilization under this scenario, researchers said.Ice shelves are permanent floating platforms of ice attached to areas of the coastline, formed where glaciers flowing off the land meet the sea. They can help limit the rise in global sea levels by acting like a dam, slowing the flow of melting ice and water into the oceans.

Each summer, ice at the surface of ice shelves melts and runs into smaller gaps in the snow below, where it usually refreezes. But when there is a lot of melting and little snowfall, this water instead pools onto the ice’s surface or flows into crevasses. This deepens and widens the crevasses, causing the shelf to fracture and collapse into the sea.

This huge iceberg calved from the Larsen C ice shelf.This huge iceberg calved from the Larsen C ice shelf.”Ice shelves are important buffers preventing glaciers on land from flowing freely into the ocean and contributing to sea level rise. When they collapse, it’s like a giant cork being removed from a bottle, allowing unimaginable amounts of water from glaciers to pour into the sea,” study lead author Ella Gilbert, a climate scientist in the University of Reading’s Department of Meteorology, said in a statement.

Gilbert told CNN that low-lying coastal areas, particularly small island states such Vanuatu and Tuvalu, in the South Pacific Ocean, are most at risk from global sea level rise.close dialog

Receive Fareed Zakaria’s Global Analysisincluding insights and must-reads of world newsActivate Fareed’s BriefingBy subscribing you agree to ourprivacy policy.“However, coastal areas all over the world would be vulnerable, and countries with fewer resources available to mitigate and adapt to sea level rise will see worse consequences,” she said.

In the new study, which used high-resolution regional climate modeling to predict the impact of increased melting and water runoff on ice shelf stability, researchers say that limiting temperature rise to 2 degrees Celsius rather than 4 degrees Celsius would halve the area at risk and potentially avoid significant sea level rise.The Intergovernmental Panel on Climate Change concluded in a landmark report that we only have until 2030 to drastically reduce our dependence on fossil fuels and prevent the planet from reaching the crucial threshold of 1.5 degrees Celsius (2.7 degrees Fahrenheit) above pre-industrial levels.This image shows a large iceberg which has separated from Pine Island Glacier.This image shows a large iceberg which has separated from Pine Island Glacier.Global net emissions of carbon dioxide would need to fall by 45% from 2010 levels by 2030 and reach “net zero” around 2050 in order to keep the warming around 1.5 degrees Celsius.”The findings highlight the importance of limiting global temperature increases as set out in the Paris Agreement if we are to avoid the worst consequences of climate change, including sea level rise,” Gilbert added.In the Paris accord, 197 countries agreed to the goal of holding global temperatures “well below” 2 degrees Celsius above pre-industrial levels and to pursue efforts to limit it to 1.5 degrees Celsius.

Antarctic sponges discovered under the ice shelf perplex scientistsBut we are on track for a world that is 3.2 degrees Celsius warmer by the end of the century.Gilbert told CNN that increased temperatures means melting occurs more frequently, and more intensely.Researchers identified four ice shelves that would be threatened by a warmer climate: The Larsen C, Shackleton, Pine Island and Wilkins ice shelves, which are vulnerable due to their geography, and the runoff predicted in those areas.Larsen C is the largest remaining ice shelf on the Antarctic Peninsula, and the Pine Island glacier has received a lot of attention in recent years because it has been melting rapidly in response to climate change, Gilbert said.

If these ice shelves all collapsed, which is not guaranteed, the glaciers they currently restrain would flow into the ocean, contributing to sea level rise — potentially by tens of centimeters, she explained.The study was published Thursday in the journal Geophysical Research Letters.

Evidence of Antarctic glacier’s tipping point confirmed for first time

https://phys.org/news/2021-04-evidence-antarctic-glacier.html

APRIL 2, 2021

by Northumbria University

Evidence of Antarctic glacier's tipping point confirmed for first time
Dr Sebastian Rosier at Pine Island Glacier in 2015. Credit: Dr Sebastian Rosier

Researchers have confirmed for the first time that Pine Island Glacier in West Antarctica could cross tipping points, leading to a rapid and irreversible retreat which would have significant consequences for global sea level.

Pine Island Glacier is a region of fast-flowing ice draining an area of West Antarctica approximately two thirds the size of the UK. The glacier is a particular cause for concern as it is losing more ice than any other glacier in Antarctica.

Currently, Pine Island Glacier together with its neighbouring Thwaites glacier are responsible for about 10% of the ongoing increase in global sea level.

Scientists have argued for some time that this region of Antarctica could reach a tipping point and undergo an irreversible retreat from which it could not recover. Such a retreat, once started, could lead to the collapse of the entire West Antarctic Ice Sheet, which contains enough ice to raise global sea level by over three metres.

While the general possibility of such a tipping point within ice sheets has been raised before, showing that Pine Island Glacier has the potential to enter unstable retreat is a very different question.

Now, researchers from Northumbria University have shown, for the first time, that this is indeed the case.

Their findings are published in leading journal, The Cryosphere.

Using a state-of-the-art ice flow model developed by Northumbria’s glaciology research group, the team have developed methods that allow tipping points within ice sheets to be identified.

For Pine Island Glacier, their study shows that the glacier has at least three distinct tipping points. The third and final event, triggered by ocean temperatures increasing by 1.2C, leads to an irreversible retreat of the entire glacier.

Evidence of Antarctic glacier's tipping point confirmed for first time
Pine Island Glacier. Credit: Dr Sebastian Rosier

The researchers say that long-term warming and shoaling trends in Circumpolar Deep Water, in combination with changing wind patterns in the Amundsen Sea, could expose Pine Island Glacier’s ice shelf to warmer waters for longer periods of time, making temperature changes of this magnitude increasingly likely.

The lead author of the study, Dr. Sebastian Rosier, is a Vice-Chancellor’s Research Fellow in Northumbria’s Department of Geography and Environmental Sciences. He specialises in the modelling processes controlling ice flow in Antarctica with the goal of understanding how the continent will contribute to future sea level rise.https://googleads.g.doubleclick.net/pagead/ads?client=ca-pub-0536483524803400&output=html&h=280&slotname=5350699939&adk=3784993980&adf=1857921027&pi=t.ma~as.5350699939&w=753&fwrn=4&fwrnh=100&lmt=1617479433&rafmt=1&psa=1&format=753×280&url=https%3A%2F%2Fphys.org%2Fnews%2F2021-04-evidence-antarctic-glacier.html&flash=0&fwr=0&rpe=1&resp_fmts=3&wgl=1&uach=WyJXaW5kb3dzIiwiMTAuMCIsIng4NiIsIiIsIjg5LjAuNDM4OS4xMTQiLFtdXQ..&dt=1617478985584&bpp=151&bdt=1757&idt=525&shv=r20210331&cbv=r20190131&ptt=9&saldr=aa&abxe=1&cookie=ID%3D5d55f89f953c9743-22704f0a26c700c0%3AT%3D1617478983%3ART%3D1617478983%3AS%3DALNI_MZQaypbQfavevwL_CfGfsS8Zmx3oA&prev_fmts=0x0&nras=1&correlator=6857462741682&frm=20&pv=1&ga_vid=185394846.1565457508&ga_sid=1617478986&ga_hid=629789158&ga_fc=0&u_tz=-420&u_his=1&u_java=0&u_h=640&u_w=1139&u_ah=607&u_aw=1139&u_cd=24&u_nplug=3&u_nmime=4&adx=263&ady=2834&biw=1123&bih=538&scr_x=0&scr_y=700&eid=44735932%2C44736525%2C21066435%2C44740079%2C44739387&oid=3&pvsid=1247426490552319&pem=466&ref=https%3A%2F%2Fnews.google.com%2F&rx=0&eae=0&fc=896&brdim=0%2C0%2C0%2C0%2C1139%2C0%2C1139%2C607%2C1139%2C537&vis=1&rsz=%7C%7CpEebr%7C&abl=CS&pfx=0&fu=8320&bc=31&ifi=1&uci=a!1&btvi=1&fsb=1&xpc=KP30SGBJMK&p=https%3A//phys.org&dtd=M

Dr. Rosier is a member of the University’s glaciology research group, led by Professor Hilmar Gudmundsson, which is currently working on a major £4million study to investigate if climate change will drive the Antarctic Ice Sheet towards a tipping point.

Dr. Rosier explained: “The potential for this region to cross a tipping point has been raised in the past, but our study is the first to confirm that Pine Island Glacier does indeed cross these critical thresholds.

“Many different computer simulations around the world are attempting to quantify how a changing climate could affect the West Antarctic Ice Sheet but identifying whether a period of retreat in these models is a tipping point is challenging.

“However, it is a crucial question and the methodology we use in this new study makes it much easier to identify potential future tipping points.”

Hilmar Gudmundsson, Professor of Glaciology and Extreme Environments worked with Dr. Rosier on the study. He added: “The possibility of Pine Island Glacier entering an unstable retreat has been raised before but this is the first time that this possibility is rigorously established and quantified.

“This is a major forward step in our understanding of the dynamics of this area and I’m thrilled that we have now been able to finally provide firm answers to this important question.

“But the findings of this study also concern me. Should the glacier enter unstable irreversible retreat, the impact on sea level could be measured in metres, and as this study shows, once the retreat starts it might be impossible to halt it.”

The paper, The tipping points and early warning indicators for Pine island Glacier, West Antarctica, is now available to view in The Cryosphere.


Explore furtherNew study reveals when West Antarctica’s largest glacier started retreating

Scientists accidentally found life under 3,000 feet of ice in Antarctica. ‘Never in a million years’ would they have expected it, the lead scientist said.

Marianne Guenot 9 hours ago

https://www.businessinsider.com/scientist-discover-life-3000-ft-under-ice-in-antarctica-2021-2

Animals found under Ice
An image from a video in which scientists saw stationary animals under ice in Antarctica. The creatures appear similar to sponges. 
  • Scientists stumbled upon life under 3,000 feet of ice in Antarctica.
  • They found two types of unidentified animals, where they had thought nothing could live.
  • Their next step is finding a way to get close enough to identify the creatures.
  • Visit the Business section of Insider for more stories.

Scientist have found life under 3,000 feet under of ice in Antarctica, challenging their assumption that nothing could live in such conditions.

The previous theory was that life couldn’t exist in such extremity: no food, freezing temperatures, and complete darkness.

The creatures were found attached to a boulder in the frigid seas under the Filchner-Ronne ice shelf. Experts from the British Antarctic Survey drilled through 2,860 feet of ice and then another 1,549 feet of water before making the discovery.

“The area underneath these ice shelves is probably one of the least-known habitats on Earth,” said Huw Griffiths, one of the scientists who made the discovery, in a Twitter video.https://f33ab413356d2368bc962a909775bc69.safeframe.googlesyndication.com/safeframe/1-0-37/html/container.html

“We didn’t think that these kinds of animals, like sponges, would be found there.”https://platform.twitter.com/embed/Tweet.html?dnt=false&embedId=twitter-widget-0&frame=false&hideCard=false&hideThread=false&id=1361198202905636864&lang=en&origin=https%3A%2F%2Fwww.businessinsider.com%2Fscientist-discover-life-3000-ft-under-ice-in-antarctica-2021-2&siteScreenName=SciInsider&theme=light&widgetsVersion=889aa01%3A1612811843556&width=550px

The Filchner-Ronne ice shelf is a massive floating ice sheet that stretches out from Antarctica.

It spans more than 579,000 square miles, but little has been explored under the ice.

Enormous icebergs occasionally break off ice shelves and drift away. In December, one of these icebergs threatened to crash into a breeding ground for sealions and penguins.

Filchner Ronne Ice Shelf, Antartica
An annotated satellite image of the Filchner-Ronne ice shelf. 
ice sheets
The Filchner-Ronne ice shelf is the second-biggest ice shelf in Antarctica. 

The scientists didn’t set out looking for life.https://f33ab413356d2368bc962a909775bc69.safeframe.googlesyndication.com/safeframe/1-0-37/html/container.html

They were drilling through the ice sheet to collect samples from the sea floor. Instead, their camera hit a boulder. When they reviewed the camera’s footage, it revealed this discovery.https://platform.twitter.com/embed/Tweet.html?dnt=false&embedId=twitter-widget-1&frame=false&hideCard=false&hideThread=true&id=1361198202905636864&lang=en&origin=https%3A%2F%2Fwww.businessinsider.com%2Fscientist-discover-life-3000-ft-under-ice-in-antarctica-2021-2&siteScreenName=SciInsider&theme=light&widgetsVersion=889aa01%3A1612811843556&width=550px

“Never in a million years would we have thought about looking for this kind of life, because we didn’t think it would be there,” Griffiths told The Guardian.

The video reveals two types of unidentified animals, shown here in a video from the British Antarctic Survey. The animals in red seem to have long stalks, whereas another type of animal, highlighted in white, looks more like a round sponge-like animal.

annotated video footage, new discovery animals, Antarctica
An annotated image of the footage that captured animals under the ice in Antarctica. 

Other studies had looked at life under ice sheets. A few mobile animals, such as fish, worms, jellyfish, or krill, could be found in that habitat.https://f33ab413356d2368bc962a909775bc69.safeframe.googlesyndication.com/safeframe/1-0-37/html/container.html

But it was thought that the deeper and farther away from a light source the habitat stretched, the less likely that life could be found.

What’s Hiding Under Antarctica’s Ice Matters for Our Planet’s Future

Scientists are mapping the land beneath this frozen underworld, which is crucial to predicting future sea level rise and the potential mayhem to come. 

By Anamaria SilicJanuary 26, 2021 3:00 PM

https://www.discovermagazine.com/planet-earth/whats-hiding-under-antarcticas-ice-matters-for-our-planets-future

South Pole View From Above - shutterstock

(Credit: Artsiom Petrushenka/Shutterstock)

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The frozen kingdom of Antarctica may appear featureless from above, but beneath all that ice lies a mysterious and complex world that researchers say could be pivotal to understanding the effects of climate change. 

It’s well established that the Antarctic ice sheet has been rapidly losing mass. As ocean temperatures have risen, the glaciers that make up the ice sheet are melting at a rate six times faster than that of 40 years ago. NASA reports that Antarctica is now losing 252 gigatons of ice per year — about three and a half Olympic swimming pools per second. 

According to the National Snow and Ice Data Center, if all of Antarctica’s ice were to melt, global sea levels would rise by 200 feet, flooding every single coastal city, and wiping whole countries completely off the map. Even a more modest change in sea level would be disastrous. For example, just a 5-foot change in sea level would be enough to cover an area the size of Denmark. In the U.S., for cities such as New York City and Miami, with infrastructure very close to sea level, it would mean millions losing their homes.about:blankabout:blank

But scientists have begun uncovering the features of a key factor that influences how fast Antarctica melts: an ancient continent twice the size of Australia, deep below the ice sheet. 

Welcome to the Frozen Kingdom

The 1.3-mile-thick ice sheet that’s accumulated in Antarctica over the eons covers 98 percent of the southernmost continent. But for almost 100 million years, the continent lay over the South Pole without freezing. It had a much warmer climate and was covered in lush rainforests similar to those that exist in New Zealand today, with dinosaurs foraging in the abundant vegetation.

Then, about 34 million years ago, a dramatic shift in climate happened at the boundary between the Eocene and Oligocene epochs. The warm greenhouse climate became dramatically colder, creating an icehouse at the poles that has continued to the present day. 

Antarctica today is divided into three regions: East Antarctica, West Antarctica and the Antarctic Peninsula, with each section comprising a different topography beneath. The ice of the Antarctic Peninsula, for example, hides a spine of mountains projecting northwest from the inside of the continent. 

East Antarctica, the largest sector, includes some flatter plains as well as mountains. Here, the Gamburtsev Mountain Range — spanning 750 miles with peaks topping 11,200 feet — is about the same size as the European Alps, and completely covered by more than 2,000 feet of ice.about:blankabout:blank

West Antarctica’s ground is almost entirely below sea level. The ocean bowl under the region was created during the last ice age, when the weight of the ice, much thicker at the time, pressed down on the bedrock. 

The lack of landmass under West Antarctica makes the region more vulnerable to melting, as it lacks the mountain ridges that stabilize the glaciers in the east. Satellite data collected between 1996 and 2006 showed that the thinning of the ice shelves (floating sheets of ice that connect to a landmass) stagnated in East Antarctica, while in West Antarctica, the rate of the melting tripled. 

In 2019, NASA created the most detailed map of the continent yet. By combining ice movement measurements, seismic data and radar images, the map — dubbed BedMachine Antarctica — revealed previously unknown topographical features, such as the broad ridges that protect the glaciers flowing across the Transantarctic Mountains, which divide East and West Antarctica.

Image: 

Antarctic BedMachine 4k.3625 print (1)

BedMachine captured the bed topography under the Denman Glacier in Antarctica, colored by the elevation. Areas below sea level are colored in shades of blue while areas above sea level are colored in green, yellow, and brown. (Credit: NASA’s Scientific Visualization Studio)about:blankabout:blank

BedMachine also revealed the world’s deepest land canyon below Denman Glacier in East Antarctica, at 11,000 feet below sea level. That’s far deeper than the Dead Sea, the lowest exposed region of land, which sits 1,419 feet below sea level. 

The map is an important resource that will help scientists predict precisely which regions of ice are at greatest risk of sliding into the ocean in the coming decades and centuries, and which sections might be more stable than expected. 

Despite major progress in the mapping of subglacial geology, significant sections of Antarctica remain unresolved and important spatial details are missing. Understanding what’s underneath Antarctica remains crucial to foresee the ice shifts accelerated by a changing climate. 

Blue whales have ‘rediscovered’ South Georgia

By Jonathan Amos
BBC Science CorrespondentPublished4 hours ago

https://www.bbc.com/news/science-environment-54994814

An Antarctic blue whale surfaces off South Georgia
image captionAn Antarctic blue whale surfaces off South Georgia

The resurgence of blue whales around the island of South Georgia is real and has probably been under way for a little while now, say scientists.

When a survey was conducted at the British Overseas Territory earlier this year, 58 of the animals were seen.

That was described as “astonishing” at the time because there had been so few sightings previously.

But a reassessment of 30 years of observational data suggests this bumper crowd of blues was no anomaly.

King penguins (c) George Lemann
image captionSouth Georgia is home to millions of king penguins

It most likely signals they really are making a comeback in the waters around the sub-Antarctic island.

South Georgia is infamous, of course, for being the epicentre of commercial whaling in the early 20th Century.

https://emp.bbc.com/emp/SMPj/2.36.3/iframe.htmlmedia captionJennifer Jackson: “I don’t think this is a surprise phenomenon”

Its steam boats, with their grenade-tipped harpoons, decimated all the large whale populations – and at the peak of the carnage were removing 3,000 blues a year.

And while fur and elephant seals, which were also heavily exploited, managed to bounce back to historic levels relatively quickly – the whales, and the blues in particular, did not.

Grytviken whaling station on South Georgia (c) GSGSSI
image captionGrytviken: Remnants of the old whaling stations can still be seen today

Their absence long after commercial whaling ended even led some whale experts to wonder if these majestic creatures would ever be seen again in significant numbers at South Georgia.

“It was held up as an example of how you can exploit a population beyond the point where it can recover,” Susannah Calderan, who led the reassessment, told BBC News.

Susannah Calderan
image captionSusannah Calderan uses ex-military sonobuoys to pick up the sounds of whales

It’s possible that as the population crashed, the blues simply lost the cultural memory that had drawn them to South Georgia in the first place, the Scottish Association for Marine Science (SAMS) fellow said.

The British Overseas Territory is in the path of a food train coming up from the Antarctic on strong currents. This train carries abundant krill, the small crustaceans that whales love.

But because there were so few blues left after commercial whaling, it may be that the knowledge of the island’s productive feeding ground could not be passed on to future generations – so the theory goes.

“So, perhaps now they have re-discovered ‘the larder’,” Susannah Calderan speculated. “South Georgia remains an extremely productive feeding ground. Nothing ever happened to its productivity. It’s not as if the whales stopped coming because there was nothing left to eat.”https://emp.bbc.com/emp/SMPj/2.36.3/iframe.htmlmedia captionMale blues communicate over vast distances with their repetitive, low-frequency calls (B.Miller/AAD)

The SAMS scientist, with colleagues, has reviewed all the observational data on blue whales at South Georgia going back three decades.

This includes the systematic surveys that have been conducted by researchers and the opportunistic reporting that’s come in from mariners and from cruise ships, whose visits to South Georgia have increased in frequency.

The study also includes data from acoustics – the use of listening devices, such as sonobuoys, which are put in the water to detect the booming, low-frequency calls that are made by blue whales.https://emp.bbc.com/emp/SMPj/2.36.3/iframe.htmlmedia captionSo-called D-calls made by blue whales are probably associated with social behaviour and feeding (B.Miller/AAD)

All this information points to a gradual increase in the presence of blue whale numbers around the island in recent years.

Even before the remarkable observation of 58 blues in February, it’s now recognised that a total of 41 animals from the species were photo-identified off South Georgia between 2011 and 2020.

South Georgia's Rosita Harbour (c) Oliver Prince
image captionConservationists say South Georgia is an all-too-rare example of an ecosystem in recovery

“It should be said, the survey we carried out at the beginning of this year was not dedicated to blues. This was an accidental finding. We were actually looking for right whales, but the team saw blue whales when they were doing their transects,” explained co-researcher Jennifer Jackson from the British Antarctic Survey, which led the February expedition.

“I don’t think this is a surprise phenomenon. I think we’re going to continue seeing blue whales in the years to come. What we need to understand now is why they are using South Georgia waters again.”

Humpback whale (c) BAS
image captionA humpback whale in the waters around South Georgia

And it’s not just blues. Those other species that were also driven to the brink, like the humpbacks, are also on the rise.

Susannah Calderan would like to see a network of acoustic moorings placed around the island, in particular off its southwest coastline where little systematic survey work has been conducted.

This would help fill gaps in the data and smooth biases which mean the same locations tend to dominate sightings – such as the popular routes taken by cruise ships.

Blue whale
image captionAt the peak of harvesting, 3,000 blue whales were being taken each year

The whale scientists are also now watching closely what will happen with the world’s biggest iceberg – the 4,200 sq km tabular block known as A68a.

Drifting in the same currents that deliver krill to South Georgia, it risks being caught in the shallows surrounding the island. If that happens, the iceberg could disrupt the foraging behaviour of many animals that depend on the krill.

“South Georgia is a kind of home to dead icebergs. Generally, they tend to go there to die. But, yes, this one’s massive,” said Susannah Calderan.

“Will it affect productivity? Will it affect the krill? Will that affect the whales? It’s a really interesting question.”

The team’s analysis, which is published in the journal Endangered Species Research, was funded by South Georgia Heritage Trust and Friends of South Georgia Island.

Iceberg A68a
image captionThe giant iceberg A68a could become stuck in shallow water near the island

Invisible Air Rivers in The Sky Have Been Leaving Giant Holes in Antarctic Ice

main article image

The 2017 polynya. (NASA)ENVIRONMENT

https://www.sciencealert.com/invisible-rivers-of-air-flowing-in-the-sky-are-leaving-giant-holes-in-antarctic-ice

PETER DOCKRILL12 NOVEMBER 2020

It appeared in 1973, seemingly out of nowhere: a hole in the sea ice off the coast of Antarctica. But this was no ordinary hole. It was so big it could swallow California.

The mysterious opening remained in place for the following three winters. Then it seemed to largely disappear before emerging again in 2017, with a giant maw the size of Maine.

This giant hole with a sometimes state-sized appetite is what’s called a polynya – an area of open water surrounded by sea ice, kind of like the opposite of an iceberg.

But the mysterious Weddell Polynya – occurring above the oceanic plateau of Maud Rise, in the Weddell Sea waters of the Southern Ocean – is a rather extreme example of this environmental phenomenon. Why it opens up so dramatically and yet so infrequently has long puzzled scientists.

Last year, researchers suggested that it required the coincidence of a range of climate anomalies all coming together at the same time for the Weddell Polynya to open up with such abandon.

Another study from 2019, led by atmospheric scientist Diana Francis, proposed what one such anomaly was: scars from severe cyclones produced by atmospheric circulation, which can pull floating sea ice in opposite directions and away from the eye of the storm, creating the giant opening.

Francis, now a senior scientist at Khalifa University, UAE, has just led a new study that sheds light on another, related contributor to the phenomenon that’s been overlooked until now: atmospheric rivers of warm, moist air.

In the new research, Francis and her team analysed atmospheric data going back to the 1970s, and found that these ‘rivers in the sky’ likely played a “crucial role” in the formation of the Weddell Polynya events of 1973 and 2017, with strong, persistent flows evident in the days preceding both occurrences.

“I was surprised to see an almost immediate melt in the sea ice covered by the atmospheric rivers during the coldest months of the year in Antarctica,” Francis told Nature Middle East.

The researchers say that atmospheric circulation transported a belt of warm, moist air all the way from the coast of South America to the polar region, inducing melting through a combination of effects, including: the release of heat in the air mass; a localised greenhouse effect created by water vapour; and contributions to cyclone dynamics.

“The atmospheric rivers also make the storms more intense because they provide more water vapour. They are linked, not independent,” Francis explained to New Scientist.

It’s unlikely to be the last word on what gives rise to the Weddell Polynya’s monumental meltdowns, but the new insights do broaden our understanding of what’s making the giant hole appear.

Given both atmospheric rivers and cyclones are predicted to increase in severity with global warming, this strange opening off the coast of Antarctica is something we might observe more often, but we’ll have to wait and see.

The findings are reported in Science Advances.