̽��ֱ�� of Cambridge - Antarctic Ice Sheet

Thriving Antarctic ecosystems found following iceberg calving

Anonymous — Tue, 25 Mar 2025 10:22:45 +0000

An international team of scientists have uncovered a thriving underwater ecosystem off the coast of Antarctica that had never before been accessible to humans.

̽��ֱ��team, including researchers from the ̽��ֱ�� of Cambridge, were working in the Bellingshausen Sea off the coast of Antarctica when a massive iceberg broke away from the George VI Ice Shelf in January of this year.

̽��ֱ��team, on board Schmidt Ocean Institute’s R/V Falkor (too), changed their plans and reached the newly exposed seafloor 12 days later, becoming the first to investigate the area.

Their expedition was the first detailed study of the geology, physical oceanography, and biology beneath such a large area once covered by a floating ice shelf. ̽��ֱ��A-84 iceberg was approximately 510 square kilometres (209 square miles) in size, and revealed an equivalent area of seafloor when it broke away from the ice shelf.

"We seized upon the moment, changed our expedition plan, and went for it so we could look at what was happening in the depths below," said expedition co-chief scientist Dr Patricia Esquete from the ̽��ֱ�� of Aveiro, Portugal. "We didn't expect to find such a beautiful, thriving ecosystem. Based on the size of the animals, the communities we observed have been there for decades, maybe even hundreds of years.”

Using Schmidt Ocean Institute’s remotely operated vehicle, ROV SuBastian, the team observed the deep seafloor for eight days and found flourishing ecosystems at depths as great as 1300 meters.

Their observations include large corals and sponges supporting an array of animal life, including icefish, giant sea spiders, and octopus. ̽��ֱ��discovery offers new insights into how ecosystems function beneath floating sections of the Antarctic ice sheet.

Little is known about what lies beneath Antarctica’s floating ice shelves. In 2021, British Antarctic Survey researchers first reported signs of bottom-dwelling life beneath the Filchner-Ronne ice shelf in the Southern Weddell Sea. ̽��ֱ��current expedition was the first to use an ROV to explore this remote environment.

̽��ֱ��team was surprised by the significant biomass and biodiversity of the ecosystems and suspect they have discovered several new species.

Deep-sea ecosystems typically rely on nutrients from the surface slowly raining down to the seafloor. For centuries, the ecosystems under the ice shelf have been covered by ice almost 150 metres thick, completely cutting them off from surface nutrients. " ̽��ֱ��fact that we found long-living species suggests that the lateral transport, which mostly consists of glacial meltwater from the ice shelf, could be the source of the nutrients to sustain the life we found," said team member Dr Laura Cimoli, from Cambridge’s Department of Applied Mathematics and Theoretical Physics.

̽��ֱ��newly exposed Antarctic seafloor also allowed the team, with scientists from Portugal, the United Kingdom, Chile, Germany, Norway, New Zealand, and the United States, to gather critical data on the past behaviour of the larger Antarctic ice sheet. ̽��ֱ��ice sheet has been shrinking and losing mass over the last few decades due to climate change.

“ ̽��ֱ��ice loss from the Antarctic Ice Sheet is a major contributor to sea level rise worldwide,” said expedition co-chief scientist Sasha Montelli of ̽��ֱ�� College London (UCL). “Our work is critical for providing longer-term context of these recent changes, improving our ability to make projections of future change — projections that can inform actionable policies. We will undoubtedly make new discoveries as we continue to analyse this data.”

“We were thrilled by the opportunity to explore the newly exposed seafloor,” said team member Dr Svetlana Radionovskaya from Cambridge’s Department of Earth Sciences. “ ̽��ֱ��research will provide key insights into ice sheet dynamics, oceanography and sub-ice shelf ecosystems. At a time when the West Antarctic Ice Sheet is melting at an alarming rate, understanding these dynamics and their impacts is crucial.”

photo1_fkt250110-20250117-gliderdeploymentzodiac-ingle-2717.jpg

̽��ֱ��oceanography team, led by Cimoli in collaboration with the ̽��ֱ�� of East Anglia and the British Antarctic Survey, used autonomous underwater vehicles to characterise the ocean circulation of the region and study the impacts of glacial meltwater on the physical and chemical seawater properties. "Antarctica and the Southern Ocean are a nexus point for ocean circulation, so changes that happen around Antarctica can affect global ocean circulation and global climate," said Cimoli.

̽��ֱ��researchers are also investigating how the iceberg calving event has contributed to mix the upper ocean, not just in the recently exposed area, but also further downstream as the iceberg floats away. As the giant iceberg drifts, it can generate turbulence that mixes water properties and could potentially mix the deep nutrient-rich water with the surface waters, fuelling biological productivity.

̽��ֱ��expedition was part of Challenger 150, a global cooperative focused on deep-sea biological research and endorsed by the Intergovernmental Oceanographic Commission of UNESCO (IOC/UNESCO) as an Ocean Decade Action.

“ ̽��ֱ��science team was originally in this remote region to study the seafloor and ecosystem at the interface between ice and sea,” said Schmidt Ocean Institute Executive Director, Dr Jyotika Virmani. “Being right there when this iceberg calved from the ice shelf presented a rare scientific opportunity. Serendipitous moments are part of the excitement of research at sea – they offer the chance to be the first to witness the untouched beauty of our world.”

Svetlana Radionovskaya is a Junior Research Fellow at Queens’ College, Cambridge. Laura Cimoli is a Research Fellow at the Institute of Computing for Climate Science, Department of Applied Mathematics and Theoretical Physics at the ̽��ֱ�� of Cambridge.

Adapted from a media release by the Schmidt Ocean Institute.

Inset image: Dr Cimoli (right) and Dr Meyer (UEA, left) prepare an underwater glider for deployment. Credit: Alex Ingle/Schmidt Ocean Institute.

Scientists explore a seafloor area newly exposed by iceberg A-84; discover vibrant communities of ancient sponges and corals.

ROV SuBastian / Schmidt Ocean Institute

Deep-sea coral at a depth of 1200 metres

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

Yes

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Attribution-Noncommercial-ShareAlike

Ice shelves fracture under weight of meltwater lakes

sc604 — Fri, 03 May 2024 14:31:26 +0000

When air temperatures in Antarctica rise and glacier ice melts, water can pool on the surface of floating ice shelves, weighing them down and causing the ice to bend. Now, for the first time in the field, researchers have shown that ice shelves don’t just buckle under the weight of meltwater lakes — they fracture.

As the climate warms and melt rates in Antarctica increase, this fracturing could cause vulnerable ice shelves to collapse, allowing inland glacier ice to spill into the ocean and contribute to sea level rise.

Ice shelves are important for the Antarctic Ice Sheet’s overall health as they act to buttress or hold back the glacier ice on land. Scientists have predicted and modelled that surface meltwater loading could cause ice shelves to fracture, but no one had observed the process in the field, until now.

̽��ֱ��new study, published in the Journal of Glaciology, may help explain how the Larsen B Ice Shelf abruptly collapsed in 2002. In the months before its catastrophic breakup, thousands of meltwater lakes littered the ice shelf’s surface, which then drained over just a few weeks.

To investigate the impacts of surface meltwater on ice shelf stability, a research team led by the ̽��ֱ�� of Colorado Boulder, and including researchers from the ̽��ֱ�� of Cambridge, travelled to the George VI Ice Shelf on the Antarctic Peninsula in November 2019.

First, the team identified a depression or ‘doline’ in the ice surface that had formed by a previous lake drainage event where they thought meltwater was likely to pool again on the ice. Then, they ventured out on snowmobiles, pulling all their science equipment and safety gear behind on sleds.

Around the doline, the team installed high-precision GPS stations to measure small changes in elevation at the ice’s surface, water-pressure sensors to measure lake depth, and a timelapse camera system to capture images of the ice surface and meltwater lakes every 30 minutes.

In 2020, the COVID-19 pandemic brought their fieldwork to a screeching halt. When the team finally made it back to their field site in November 2021, only two GPS sensors and one timelapse camera remained; two other GPS and all water pressure sensors had been flooded and buried in solid ice. Fortunately, the surviving instruments captured the vertical and horizontal movement of the ice’s surface and images of the meltwater lake that formed and drained during the record-high 2019/2020 melt season.

GPS data indicated that the ice in the centre of the lake basin flexed downward about a foot in response to the increased weight from meltwater. That finding builds upon previous work that produced the first direct field measurements of ice shelf buckling caused by meltwater ponding and drainage.

̽��ֱ��team also found that the horizontal distance between the edge and centre of the meltwater lake basin increased by over a foot. This was most likely due to the formation and/or widening of circular fractures around the meltwater lake, which the timelapse imagery captured. Their results provide the first field-based evidence of ice shelf fracturing in response to a surface meltwater lake weighing down the ice.

“This is an exciting discovery,” said lead author Alison Banwell, from the Cooperative Institute for Research in Environmental Sciences (CIRES) at the ̽��ֱ�� of Colorado Boulder. “We believe these types of circular fractures were key in the chain reaction style lake drainage process that helped to break up the Larsen B Ice Shelf.”

“While these measurements were made over a small area, they demonstrate that bending and breaking of floating ice due to surface water may be more widespread than previously thought,” said co-author Dr Rebecca Dell from Cambridge’s Scott Polar Research Institute. “As melting increases in response to predicted warming, ice shelves may become more prone to break up and collapse than they are currently.”

“This has implications for sea level as the buttressing of inland ice is reduced or removed, allowing the glaciers and ice streams to flow more rapidly into the ocean,” said co-author Professor Ian Willis, also from SPRI.

̽��ֱ��work supports modelling results that show the immense weight of thousands of meltwater lakes and subsequent draining caused the Larsen B Ice Shelf to bend and break, contributing to its collapse.

“These observations are important because they can be used to improve models to better predict which Antarctic ice shelves are more vulnerable and most susceptible to collapse in the future,” Banwell said.

̽��ֱ��research was funded by the U.S. National Science Foundation (NSF) and the Natural Environment Research Council (NERC), part of UK Research and Innovation (UKRI). ̽��ֱ��team also included researchers from the ̽��ֱ�� of Oxford and the ̽��ֱ�� of Chicago. Rebecca Dell is a Fellow of Trinity Hall, Cambridge.

Reference:
Alison F Banwell et al. ‘Observed meltwater-induced flexure and fracture at a doline on George VI Ice Shelf, Antarctica.’ Journal of Glaciology (2024). DOI: 10.1017/jog.2024.31

Adapted from a CIRES press release.

Heavy pooling meltwater can fracture ice, potentially leading to ice shelf collapse

Ian Willis

Ali Banwell and Laura Stevens installing the time-lapse camera used in this study on the George VI Ice Shelf in Antarctica.

Yes

Ice cores provide first documentation of rapid Antarctic ice loss in the past

cmm201 — Thu, 08 Feb 2024 10:00:00 +0000

̽��ֱ��evidence, contained within an ice core, shows that in one location the ice sheet thinned by 450 metres — that’s more than the height of the Empire State Building — in just under 200 years.

This is the first evidence anywhere in Antarctica for such a fast loss of ice. Scientists are worried that today’s rising temperatures might destabilize parts of the West Antarctic Ice Sheet in the future, potentially passing a tipping point and inducing a runaway collapse. ̽��ֱ��study, published in Nature Geoscience, sheds light on how quickly Antarctic ice could melt if temperatures continue to soar.

“We now have direct evidence that this ice sheet suffered rapid ice loss in the past,” said Professor Eric Wolff, senior author of the new study from Cambridge’s Department of Earth Sciences. “This scenario isn’t something that exists only in our model predictions and it could happen again if parts of this ice sheet become unstable.”

From west to east, the Antarctic ice sheets contain enough freshwater to raise global sea levels by around 57 metres. ̽��ֱ��West Antarctic Ice Sheet is considered particularly vulnerable because much of it sits on bedrock below sea level.

Model predictions suggest that a large part of the West Antarctic Ice Sheet could disappear in the next few centuries, causing sea levels to rise. Exactly when and how quickly the ice could be lost is, however, uncertain.

One way to train ice sheet models to make better predictions is to feed them with data on ice loss from periods of warming in Earth’s history. At the peak of the Last Ice Age 20,000 years ago, Antarctic ice covered a larger area than today. As our planet thawed and temperatures slowly climbed, the West Antarctic Ice Sheet contracted to more or less its current extent.

“We wanted to know what happened to the West Antarctic Ice Sheet at the end of the Last Ice Age, when temperatures on Earth were rising, albeit at a slower rate than current anthropogenic warming,” said Dr Isobel Rowell, study co-author from the British Antarctic Survey. “Using ice cores we can go back to that time and estimate the ice sheet’s thickness and extent.”

Ice cores are made up of layers of ice that formed as snow fell and was then buried and compacted into ice crystals over thousands of years. Trapped within each ice layer are bubbles of ancient air and contaminants that mixed with each year’s snowfall — providing clues as to the changing climate and ice extent.

̽��ֱ��researchers drilled a 651-metre-long ice core from Skytrain Ice Rise in 2019. This mound of ice sits at the edge of the ice sheet, near the point where grounded ice flows into the floating Ronne Ice Shelf.

After transporting the ice cores to Cambridge at -20C, the researchers analysed them to reconstruct the ice thickness. First, they measured stable water isotopes, which indicate the temperature at the time the snow fell. Temperature decreases at higher altitudes (think of cold mountain air), so they could equate warmer temperatures with lower-lying, thinner ice.

They also measured the pressure of air bubbles trapped in the ice. Like temperature, air pressure also varies systematically with elevation. Lower-lying, thinner ice contains higher-pressure air bubbles.

These measurements told them that ice thinned rapidly 8,000 years ago. “Once the ice thinned, it shrunk really fast,” said Wolff, “this was clearly a tipping point — a runaway process.”

They think this thinning was probably triggered by warm water getting underneath the edge of the West Antarctic Ice Sheet, which normally sits on bedrock. This likely untethered a section of the ice from bedrock, allowing it to float suddenly and forming what is now the Ronne Ice Shelf. This allowed neighbouring Skytrain Ice Rise, no longer restrained by grounded ice, to thin rapidly.

̽��ֱ��researchers also found that the sodium content of the ice (originating from salt in sea spray) increased about 300 years after the ice thinned. This told them that, after the ice thinned, the ice shelf shrunk back so that the sea was hundreds of kilometres nearer to their site.

“We already knew from models that the ice thinned around this time, but the date of this was uncertain,” said Rowell. Ice sheet models placed the retreat anywhere between 12,000 and 5,000 years ago and couldn’t say how quickly it happened. “We now have a very precisely dated observation of that retreat that can be built into improved models,” said Rowell.

Although the West Antarctic Ice Sheet retreated quickly 8,000 years ago, it stabilised when it reached roughly its current extent. “It’s now crucial to find out whether extra warmth could destabilise the ice and cause it to start retreating again,” said Wolff.

Reference

Grieman et al. (2024) Abrupt Holocene ice loss due to thinning and ungrounding in the Weddell Sea Embayment. Nature Geoscience. DOI: 10.1038/s41561-024-01375-8

Researchers from the ̽��ֱ�� of Cambridge and the British Antarctic Survey have uncovered the first direct evidence that the West Antarctic Ice Sheet shrunk suddenly and dramatically at the end of the Last Ice Age, around 8,000 years ago.

̽��ֱ�� of Cambridge / British Antarctic Survey

Tents at Skytrain Ice Rise

Yes

Ice sheets can collapse faster than previously thought possible

sc604 — Wed, 05 Apr 2023 14:59:35 +0000

An international team of researchers used high-resolution imagery of the seafloor to reveal just how quickly a former ice sheet that extended from Norway retreated at the end of the last Ice Age, about 20,000 years ago.

̽��ֱ��team, including researchers from the ̽��ֱ�� of Cambridge, mapped more than 7,600 small-scale landforms called corrugation ridges across the seafloor. ̽��ֱ��ridges are less than 2.5 metres high and are spaced between about 25 and 300 metres apart.

These landforms are understood to have formed when the ice sheet’s retreating margin moved up and down with the tides, pushing seafloor sediments into a ridge every low tide. Given that two ridges would have been produced each day, the researchers were able to calculate how quickly the ice sheet retreated.

Their results, reported in the journal Nature, show the former ice sheet underwent pulses of rapid retreat at a speed of 50 to 600 metres per day. This is much faster than any ice sheet retreat rate that has been observed from satellites or inferred from similar landforms in Antarctica.

“Our research provides a warning from the past about the speeds that ice sheets are physically capable of retreating at,” said Dr Christine Batchelor from Newcastle ̽��ֱ��, who led the research. “Our results show that pulses of rapid retreat can be far quicker than anything we’ve seen so far.”

Information about how ice sheets behaved during past periods of climate warming is important to inform computer simulations that predict future ice sheet and sea-level change.

“This study shows the value of acquiring high-resolution imagery about the glaciated landscapes that are preserved on the seafloor,” said co-author Dr Dag Ottesen from the Geological Survey of Norway, who is involved in the MAREANO seafloor mapping programme that collected the data.

̽��ֱ��new research suggests that periods of such rapid ice-sheet retreat may only last for short periods of time: from days to months.

“This shows how rates of ice-sheet retreat averaged over several years or longer can conceal shorter episodes of more rapid retreat,” said co-author Professor Julian Dowdeswell from Cambridge’s Scott Polar Research Institute. “It is important that computer simulations are able to reproduce this ‘pulsed’ ice-sheet behaviour.”

̽��ֱ��seafloor landforms also shed light into the mechanism by which such rapid retreat can occur. ̽��ֱ��researchers found that the former ice sheet had retreated fastest across the flattest parts of its bed.

“An ice margin can unground from the seafloor and retreat near-instantly when it becomes buoyant,” said co-author Dr Frazer Christie, also from the Scott Polar Research Institute. “This style of retreat only occurs across relatively flat beds, where less melting is required to thin the overlying ice to the point where it starts to float.”

̽��ֱ��researchers conclude that pulses of similarly rapid retreat could soon be observed in parts of Antarctica. This includes at West Antarctica’s vast Thwaites Glacier, which is the subject of considerable international research due to its potential susceptibility to unstable retreat. ̽��ֱ��authors of this new study suggest that Thwaites Glacier could undergo a pulse of rapid retreat because it has recently retreated close to a flat area of its bed.

“Our findings suggest that present-day rates of melting are sufficient to cause short pulses of rapid retreat across flat-bedded areas of the Antarctic Ice Sheet, including at Thwaites”, said Batchelor. “Satellites may well detect this style of ice-sheet retreat in the near future, especially if we continue our current trend of climate warming.”

Other co-authors are Dr Aleksandr Montelli and Evelyn Dowdeswell at the Scott Polar Research Institute, Dr Jeffrey Evans at Loughborough ̽��ֱ��, and Dr Lilja Bjarnadóttir at the Geological Survey of Norway. ̽��ֱ��study was supported by Peterhouse, Cambridge, the Faculty of Humanities and Social Sciences at Newcastle ̽��ֱ��, the Prince Albert II of Monaco Foundation, and the Geological Survey of Norway.

Reference:
Christine L Batchelor et al. ‘Rapid, buoyancy-driven ice-sheet retreat of hundreds of metres per day’. Nature (2023), DOI: 10.1038/s41586-023-05876-1

Adapted from a press release by Newcastle ̽��ֱ��.

Ice sheets can retreat up to 600 metres a day during periods of climate warming, 20 times faster than the highest rate of retreat previously measured.

Copernicus EU/ESA, processed by Dr Frazer Christie

Sentinel-1 image composite depicting the highly fractured and fast-flowing frontal margin of the Thwaites and Crosson ice shelves

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

Yes

Runaway West Antarctic ice retreat can be slowed by climate-driven changes in ocean temperature

sc604 — Mon, 16 Jan 2023 09:45:30 +0000

New research finds that ice-sheet-wide collapse in West Antarctica isn’t inevitable: the pace of ice loss varies according to regional differences in atmosphere and ocean circulation.

Sea ice can control Antarctic ice sheet stability, new research finds

sc604 — Fri, 13 May 2022 09:00:50 +0000

Despite the rapid melting of ice in many parts of Antarctica during the second half of the 20th century, researchers have found that the floating ice shelves which skirt the eastern Antarctic Peninsula have undergone sustained advance over the past 20 years.

Antarctic ice sheets capable of retreating up to 50 metres per day

sc604 — Thu, 28 May 2020 18:00:00 +0000

̽��ֱ��study, led by the Scott Polar Research Institute at the ̽��ֱ�� of Cambridge, used patterns of delicate wave-like ridges on the Antarctic seafloor to calculate how quickly the ice retreated roughly 12,000 years ago during regional deglaciation.

̽��ֱ��ridges were produced where the ice sheet began to float, and were caused by the ice squeezing the sediment on the seafloor as it moved up and down with the movement of the tides. ̽��ֱ��images of these landforms are at unprecedented sub-metre resolution and were acquired from an autonomous underwater vehicle (AUV) operating about 60 metres above the seabed. ̽��ֱ��results are reported in the journal Science.

While modern satellites are able to gather detailed information about the retreat and thinning rates of the ice around Antarctica, the data only goes back a few decades. Calculating the maximum speed at which an ice sheet can retreat, using sets of these seafloor ridges, reveals historic retreat rates that are almost ten times faster than the maximum observed rates of retreat today.

“By examining the past footprint of the ice sheet and looking at sets of ridges on the seafloor, we were able to obtain new evidence on maximum past ice retreat rates, which are very much faster than those observed in even the most sensitive parts of Antarctica today,” said lead author Professor Julian Dowdeswell, Director of the Scott Polar Research Institute.

̽��ֱ��study was carried out as part of the Weddell Sea Expedition, which set out in early 2019 to undertake a science programme and to find Sir Ernest Shackleton’s doomed ship Endurance. Although sea ice conditions at the time prevented the team from acquiring imagery of the legendary wreck, they were able to continue with their scientific work, including mapping of the seafloor close to the Larsen Ice Shelf, east of the Antarctic Peninsula.

Using drones, satellites and AUVs, the researchers were able to study ice conditions in the Weddell Sea in unprecedented detail.

Their goals were to investigate the present and past form and flow of the ice shelves, the massive floating sections of ice that skirt about 75% of the Antarctic coastline, where they act as a buttress against ice flow from inland.

Like much of the rest of the ice in the polar regions, these buttresses are weakening in some parts of Antarctica, as witnessed most dramatically at the Larsen A and B ice shelves, which collapsed rapidly in 1998 and 2002, when roughly 1250 square miles of ice fragmented and collapsed in little over a month.

̽��ֱ��ice shelves are thinning because relatively warm water currents are eating away at them from below, but they’re also melting from the top as summer air temperatures rise. Both these effects thin and weaken the ice shelves and, as they do, the glaciers they are holding back flow faster to the sea and their margins retreat.

Using AUVs, the team were able to gather data on historic ice shelf fluctuations from the geological record on the Antarctic continental shelf.

“By examining landforms on the seafloor, we were able to make determinations about how the ice behaved in the past,” said Dowdeswell, who was chief scientist on the Weddell Sea Expedition. “We knew these features were there, but we’ve never been able to examine them in such great detail before.”

̽��ֱ��team identified a series of delicate wave-like ridges on the seafloor, each only about one metre high and spaced 20 to 25 metres apart, dating to the end of the last great deglaciation of the Antarctic continental shelf, roughly 12,000 years ago. ̽��ֱ��researchers have interpreted these ridges as formed at what was formerly the grounding line – the zone where grounded ice sheet begins to float as an ice shelf.

̽��ֱ��researchers inferred that these small ridges were caused by the ice moving up and down with the tides, squeezing the sediment into well-preserved geological patterns, looking a little like the rungs of a ladder, as the ice retreated. Assuming a standard 12-hour cycle between high and low tide, and measuring the distance between the ridges, the researchers were then able to determine how fast the ice was retreating at the end of the last Ice Age.

They calculated that the ice was retreating as much as 40 to 50 metres per day during this period, a rate that equates to more than 10 kilometres per year. In comparison, modern satellite images show that even the fastest-retreating grounding lines in Antarctica today, for example in Pine Island Bay, are much slower than these geological observations, at only about 1.6 kilometres per year.

“ ̽��ֱ��deep marine environment is actually quite quiet offshore of Antarctica, allowing features such as these to be well-preserved through time on the seafloor,” said Dowdeswell. “We now know that the ice is capable of retreating at speeds far higher than what we see today. Should climate change continue to weaken the ice shelves in the coming decades, we could see similar rates of retreat, with profound implications for global sea-level rise.”

̽��ֱ��research was funded in part by the Flotilla Foundation and Marine Archaeology Consultants Switzerland.

Reference:
J. A. Dowdeswell et al. ‘Delicate seafloor landforms reveal past Antarctic grounding-line retreat of kilometers per year.’ Science (2020). DOI: 10.1126/science.aaz3059

̽��ֱ��ice shelves surrounding the Antarctic coastline retreated at speeds of up to 50 metres per day at the end of the last Ice Age, far more rapid than the satellite-derived retreat rates observed today, new research has found.

Should climate change continue to weaken the ice shelves in the coming decades, we could see similar rates of retreat, with profound implications for global sea-level rise

Julian Dowdeswell

View from Agulhas II

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

Yes

Vintage film reveals Antarctic glacier melting

sc604 — Tue, 03 Sep 2019 09:20:55 +0000

Newly digitized vintage film has doubled how far back scientists can peer into the history of underground ice in Antarctica, and revealed that an ice shelf on Thwaites Glacier in West Antarctica is being thawed by a warming ocean more quickly than previously thought. This finding contributes to predictions for sea-level rise that would impact coastal communities around the world.

̽��ֱ��researchers made their findings by comparing ice-penetrating radar records of Thwaites Glacier with modern data. Their results are reported in the Proceedings of the National Academy of Sciences.

“By having this record, we can now see these areas where the ice shelf is getting thinnest and could break through,” said lead author Dustin Schroeder from Stanford ̽��ֱ��, who led efforts to digitize the historical data from airborne surveys conducted in the 1970s. “This is a pretty hard-to-get-to area and we’re really lucky that they happened to fly across this ice shelf.”

Researchers digitized about 250,000 flight miles of Antarctic radar data originally captured on 35mm optical film between 1971 and 1979 as part of a collaboration between Stanford and the Scott Polar Research Institute (SPRI) at the ̽��ֱ�� of Cambridge. ̽��ֱ��data has been released to an online public archive through Stanford Libraries, enabling other scientists to compare it with modern radar data in order to understand long-term changes in ice thickness, features within glaciers and baseline conditions over 40 years.

Professor Julian Dowdeswell, Director of the Scott Polar Research Institute, a co-author of the paper, commented: “These early records of ice thickness provide an important baseline against which we can measure the rate of change of the Antarctic Ice Sheet over the past 40 or so years. ̽��ֱ��high-resolution digitization of these records crucially makes them available for a series of important investigations on aspects of Antarctic environmental change.”

̽��ֱ��information provided by historic records will help efforts like the Intergovernmental Panel on Climate Change (IPCC) in its goal of projecting climate and sea-level rise for the next 100 years. By being able to look back 40 to 50 years at subsurface conditions rather than just the 10 to 20 years provided by modern data, scientists can better understand what has happened in the past and make more accurate projections about the future, Schroeder said.

“You can really see the geometry over this long period of time, how these ocean currents have melted the ice shelf – not just in general, but exactly where and how,” said Schroeder. “When we model ice sheet behaviour and sea-level projections into the future, we need to understand the processes at the base of the ice sheet that made the changes we’re seeing.”

̽��ֱ��film was originally recorded in an exploratory survey using ice-penetrating radar, a technique still used today to capture information from the surface through the bottom of the ice sheet. ̽��ֱ��radar shows mountains, volcanoes and lakes beneath the surface of Antarctica, as well as layers inside the ice sheet that reveal the history of climate and flow.

̽��ֱ��researchers identified several features beneath the ice sheet that had previously only been observed in modern data, including ash layers from past volcanic eruptions captured inside the ice and channels where water from beneath the ice sheet is eroding the bottom of ice shelves. They also found that one of these channels had a stable geometry for over 40 years, information that contrasts their findings about the Thwaites Glacier ice shelf, which has thinned from 10 to 33 percent between 1978 and 2009.

“ ̽��ֱ��fact that we were able to have one ice shelf where we can say, ‘Look, it’s pretty much stable. And here, there’s significant change’ – that gives us more confidence in the results about Thwaites,” Schroeder said.

̽��ֱ��scientists hope their findings demonstrate the value of comparing this historical information to modern data to analyse different aspects of Antarctica at a finer scale. In addition to the radar data, the Stanford Digital Repository includes photographs of the notebooks from the flight operators, an international consortium of American, British and Danish geoscientists.

“It was surprising how good the old data is,” Schroeder said. “They were very careful and thoughtful engineers and it’s much richer, more modern looking, than you would think.”

Reference:
Dustin M. Schroeder et al. ‘Multidecadal observations of the Antarctic ice sheet from restored analog radar records.’ Proceedings of the National Academy of Sciences (2019). DOI: 10.1073/pnas.1821646116

Adapted from a Stanford press release.

A bold response to the world’s greatest challenge
̽��ֱ�� ̽��ֱ�� of Cambridge is building on its existing research and launching an ambitious new environment and climate change initiative. Cambridge Zero is not just about developing greener technologies. It will harness the full power of the ̽��ֱ��’s research and policy expertise, developing solutions that work for our lives, our society and our biosphere.

Newly available archival film has revealed the eastern ice shelf of Thwaites Glacier in Antarctica is melting faster than previous estimates, suggesting the shelf may collapse sooner than expected.

̽��ֱ��high-resolution digitization of these records crucially makes them available for a series of important investigations on aspects of Antarctic environmental change

Julian Dowdeswell

NASA

Thwaites Glacier

Yes