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Health24.com | Nasal swab could help gauge smokers’ odds for lung cancer
Could a person’s risk for lung cancer someday be determined with a quick swab of the nose?
If the preliminary findings of a new study are any indication, it’s a distinct possibility.
Not a screening tool
The experimental nasal swab relies on the fact that most lung cancer patients are current and former smokers. It’s meant to be a non-invasive means of separating high-risk patients from low-risk patients, by spotting signs of gene damage produced by long-term exposure to cigarette smoke.
“[But] this is not a screening tool,” stressed study author Dr. Carla Lamb, director of interventional pulmonology at Lahey Hospital and Medical Center in Burlington, Massachusetts.
Instead the swab’s purpose is “to help us determine which [suspicious] lung nodules require more invasive evaluations”. The overriding goal, she said, is “to help guide that decision-making”.
And that’s a useful goal, said Dr Norman Edelman, senior medical adviser for the American Lung Association.
“The [standard] method used for early detection is the low-radiation-dose CT scan,” noted Edelman, who was not part of the study. “A major problem with this method is that it’s often difficult to decide whether an abnormality it picks up is or is not cancer.”
The study team made the same point, noting that the vast majority of the roughly two million lung nodules identified every year in the United States turn out to be benign.
Rigorous genetic testing
But in the absence of foolproof non-invasive tools, doctors are often left to make initial best guesses based on “clues and clinical judgment”, explained Edelman.
Lamb noted, “This uncertainty can lead to either unnecessary invasive diagnostic procedures or delay in diagnosis and treatment.”
So, with funding from the swab test’s manufacturer (Veracyte, a genomic diagnostics company based in San Francisco), the team set out to assess the test’s effectiveness among a pool of 261 patients.
All had previously undergone CT scans, and those scans had unearthed potentially problematic lung nodules. Further testing later confirmed which patients truly had lung cancer and which didn’t. But while the swab investigation was underway, no one on the study team knew the definitive results.
After using the swab to brush across each patient’s nasal passage, the collected contents were subjected to rigorous genetic testing.
If the test unearthed signs of smoke-induced damage, the patient would be classified as “high-risk”. That did not necessarily mean that he or she had lung cancer. But it meant that more invasive testing was warranted, along the lines of tissue excision and analysis (biopsy). Only invasive follow-up testing – not the swab test alone – could confirm lung cancer.
Test performed ‘consistently’
On the other hand, if the test found no signs of damage, then a patient could be deemed “low-risk”. He or she would then be spared the ordeal of more invasive exams, in favour of routine CT scans and monitoring.
In the end, the swab test correctly classified as low-risk more than 40% of the cancer-free patients. Similarly, the swab test also accurately classified as high-risk 40% of those patients who actually had cancer.
The team said that the test performed “consistently” across all lung nodule sizes, nodule locations and cancer types and stages.
And the results “had a very high specificity”, said Lamb, meaning that patients deemed high-risk and sent for further tests were very likely to have lung cancer.
The study findings suggest that “the test developed by these investigators should reduce the uncertainty as to whether an abnormality is benign or malignant in about 40% of people scanned,” Edelman said.
“And this may well be useful in the decision-making process,” he agreed. But he cautioned that as it stands, “the test is not specific enough to replace all of the other tools doctors now use to determine whether an abnormality is malignant or not.”
Preliminary findings
For the time being, Edelman said, “the best advice to former and current smokers is to check with your doctor to see if you are eligible for CT scan screening. It could save your life.”
The findings – which are considered preliminary and have not yet undergone peer review – were presented this week at the American College of Chest Physicians (CHEST) annual meeting, in New Orleans.
Image credit: iStock
Formation of ducts connecting digestive organs in zebrafish
A specialised system of ducts transports bile and enzymes from the liver and pancreas to the intestine. In a new study, researchers from the University of Copenhagen have shown how this ductal system is formed. The new knowledge can help understanding how congenital diseases in that part of the body arise.
The body’s liver, gallbladder and pancreas are connected by a specialised system of ducts, the so-called hepatopancreatic ductal system, that are leading to the intestine. Bile, digestive enzymes and other secretions flow through the ducts, which are therefore essential for enabling the digestion of food and the absorption of nutrients.
Now, researchers from the University of Copenhagen have investigated how this ductal system forms. The results have been published in the scientific journal Nature Communications.
The new findings may help to better understand rare diseases in the ductal system, such as biliary atresia. This is a disease in children where the ductal network is not properly developed, which can in some cases lead to severe liver damage.
‘We know very little about diseases such as biliary atresia, where the ducts are blocked or completely absent. In order to understand how and why these diseases occur, it is important to find out how the entire ductal system forms during development,’ says Associate Professor and co-author of the study Elke Ober, Novo Nordisk Foundation Center for Stem Cell Biology (DanStem).
‘In the study, we show that the ductal system is formed in a multi-step process, with different cell rearrangement and remodelling phases taking place until the ducts are open and fully developed. We have also found an important group of genes that control part of this process,’ says co-author and postdoc Ilcim Thestrup, who performed her PhD thesis at DanStem.
The researchers have characterised the formation of the ductal system in zebrafish. The system is formed during embryonic stages. In humans, this takes several weeks, while in zebrafish the ductal system develops in about 48 hours.
Zebrafish resemble humans in many ways: Organ systems, functional cell types and signals controlling developmental processes are highly similar. This together with the fast embryonic development, are the reason why Elke Ober’s research group chose to use zebrafish for this study.
In addition to experiments with zebrafish, the researchers examined human tissue samples to investigate if the group of genes, which they found in zebrafish, is also expressed in humans.
‘We found a group of genes called EphB and EphrinB in the zebrafish, which instruct part of the development of the ductal system. We have shown that this group is also expressed in humans. This indicates that these genes may play the same or a similar role in the formation of these ducts in humans and if misregulated, they may potentially cause ductal diseases,’ says Elke Ober.
How does language emerge?
How the languages of the world emerged is largely a mystery. Considering that it might have taken millennia, it is intriguing to see how deaf people can create novel sign languages spontaneously. Observations have shown that when deaf strangers are brought together in a community, they come up with their own sign language in a considerably short amount of time. The most famous example of this is Nicaraguan Sign Language, which emerged in the 1980s. Interestingly, children played an important role in the development of these novel languages. However, how exactly this happened has not been documented, as Manuel Bohn describes: “We know relatively little about how social interaction becomes language. This is where our new study comes in.”
In a series of studies, researchers at the Leipzig Research Centre for Early Childhood Development and the Max Planck Institute for Evolutionary Anthropology attempted to recreate exactly this process. The idea had been around for quite some time, says Gregor Kachel. But there was a problem: how to make children communicate with each other without them reverting to talking to each other? The solution came up in Skype conversations between the two researchers from Germany and their colleague Michael Tomasello in the US. In the study, children were invited to stay in two different rooms and a Skype connection was established between them. After a brief familiarization with the set-up, the researchers sneakily turned off the sound and watched as the children found new ways of communicating that go beyond spoken language.
The children’s task was to describe an image with different motifs in a coordination game. With concrete things — like a hammer or a fork — children quickly found a solution by imitating the corresponding action (e.g. eating) in a gesture. But the researchers repeatedly challenged the children with new, more abstract pictures. For example, they introduced a white sheet of paper as a picture. The depicted “nothing” is difficult to imitate. Kachel describes how two children nevertheless mastered this task: “The sender first tried all sorts of different gestures, but her partner let her know that she did not know what was meant. Suddenly our sender pulled her T-shirt to the side and pointed to a white dot on her coloured T-shirt. The two had a real breakthrough: of course! White! Like the white paper! Later, when the roles were switched, the recipient didn’t have a white spot on her T-shirt, but she nevertheless took the same approach: she pulled her T-shirt to the side and pointed to it. Immediately her partner knew what to do.” Within a very short time, the two had established a sign for an abstract concept. In the course of the study, the images to be depicted became more and more complex, which was also reflected in the gestures that the children produced. In order to communicate, for example, an interaction between two animals, children invented separate gestures for actors and actions and began to combine them — thus creating a kind of small local grammar.
How does a language emerge? Based on the present study, the following steps appear plausible: first, people create reference to actions and objects via signs that resemble things. The prerequisite for this is a common ground of experience between interaction partners. Partners also coordinate by imitating each other such that they use the same signs for the same things. The signs thus gain interpersonal and eventually conventional meaning. Over time, the relationships between the signs and things become more abstract and the meaning of the individual signs more specific. Grammatical structures are gradually introduced when there is a need to communicate more complex facts. However, the most remarkable aspect of the current studies is that these processes can be observed under controlled circumstances and within 30 minutes.
The studies demonstrate that communication cannot be reduced to words alone. When there is no way to use conventional spoken language, people find other ways to get their message across. This phenomenon forms the basis for the development of new languages. The study by Manuel Bohn, Gregor Kachel and Michael Tomasello shows what the first steps in the development of a new language could look like. According to Bohn, however, numerous new questions arise at this point: “It would be very interesting to see how the newly invented communication systems change over time, for example when they are passed on to new ‘generations’ of users. There is evidence that language becomes more systematic when passed on.”
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Materials provided by Max Planck Institute for Evolutionary Anthropology. Note: Content may be edited for style and length.
Finnish rivers transport carbon to Baltic Sea at an increasing rate
The amount of carbon transported via Finnish rivers to the Baltic Sea has risen substantially in the past few decades. This was found in a collaborative study by the University of Helsinki, Aarhus University and the Finnish Environment Institute. The researchers don’t know the exact effects yet.
The researchers investigated changes in the amount of organic carbon by exploring water-quality monitoring data for 30 rivers and a period of 25 years. The data demonstrated that Finnish rivers now transport 280,000 tonnes more carbon to the Baltic Sea each year than they did in the early 1990s.
Previous studies have shown that the riverine total organic carbon (TOC) load to the Baltic Sea is closely connected to precipitation: the load in a dry year may be less than half of that in a rainy year. Considerable year-on-year variation has hindered the observation of long-term trends, but the dataset collected in recent decades with modern measuring techniques is now sufficiently extensive for reliable assessments.
“We found that TOC concentrations have increased in almost every river since the early 1990s. When combined with discharges that have remained unchanged or increased, TOC discharge to the Baltic Sea has increased considerably: by almost 50% from 1993,” explains Eero Asmala, a postdoctoral researcher at the Faculty of Biological and Environmental Sciences, University of Helsinki.
The phenomenon can be attributed, in particular, to climate change and the associated increases in precipitation and temperature. The researchers discovered that the rise in TOC concentrations can be explained in half of the cases by changes in discharge, which has been caused, in turn, by changes in precipitation. In addition, increasing temperatures and decreasing acidity contributed to an increase in TOC concentrations observed in some areas. Land use also affected the growth of TOC concentrations.
“The larger the share of a catchment drained, the more TOC concentrations had increased. The rise in concentrations was approximately 20% in the least drained catchments, whereas it was twice as large in the most drained catchments,” notes Antti Räike, senior researcher at the Finnish Environment Institute.
The rising TOC concentrations and discharges of Finnish rivers have coincided with the decreasing TOC contents in Finnish soil. It is possible that at least some of the carbon that has disappeared from the soil has been transported by rivers to the Baltic Sea.
The increasing TOC concentration makes waters turbid and decreases water transparency. In addition, the increased organic load increases the risk of hypoxia in bottom waters.
“On balance, we still do not know much about how the carbon that ends up in the Baltic Sea affects the coastal ecosystem,” Asmala says.
However, several research projects at the University of Helsinki are currently exploring the climate effects of, in particular, carbon transported to coastal waters.
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Materials provided by University of Helsinki. Note: Content may be edited for style and length.
Health24.com | Winning the fight against TB
Dr Laura Trivino-Duran of Médecins sans Frontières (MSF), commonly known as Doctors Without Borders, says the mortality rate related to the injectables regimen treating TB was high and alarming. “It became so obvious that we couldn’t continue with the injectables, then the South African government decided to move ahead and get rid of the injectables fully and implement the World Health Organisation (WHO) recommendation in terms of SHORRT course regime without injectables.”
SHORRT stands for shorter highly-effective oral regimens for rifampicin-resistant tuberculosis therapy. It is now offered to all rifampicin resistant-tuberculosis (RR-TB) patients as a first option, and as of January this year, more than 95% of people living with RR-TB have been offered this regimen.
Global guidelines to treat TB
The WHO estimates that 480 000 people developed multi-drug-resistant tuberculosis (MDR-TB) in 2015 and 190 000 people died as a result of it. “MDR-TB cannot be treated with the standard six month course of first-line medication which is effective in most TB patients. Patients with rifampicin-resistant or MDR-TB are treated with a different combination of second-line drugs, usually for 18 months or more,” the organisation says. The WHO updated its treatment guidelines for drug-resistant TB in May 2016 and included a recommendation on the use of the shorter MDR-TB regimen under specific conditions.
“South Africa is contributing, regionally and globally, to the biggest number of patients in the SHORRT regimen,” says Trivino-Duran. She says the great thing about SHORRT therapy is that “you don’t have to go to the clinic every day because you don’t need to have an injectable every day”.
Southern African countries unite
At a recently held two-day workshop in Johannesburg hosted by South Africa’s health department and MSF, professionals from Southern Africa came together to see how they can support each other for the enrolment of the SHORRT course regimen to be successful.
“As a region we need to have a conversation whereby we’re all asking for the same things; somehow we’re all struggling with the same problems such as funding for drugs, training, transport and many more. But funding is not the only issue, there is also other issues that are important to overcome,” says Trivino-Duran.
Eswatini is set to introduce the SHORRT therapy early next year, without having done a clinical trial or implementation research due to lack of funding. “As Eswatini we introduced the SHORRT injectable base regimens in 2014 and we’ve observed that it improved the treatment outcomes but we still noted that about 60% pf patients were experiencing problems such as hearing loss. And we also noted the high mortality rate which was above 10%, which is why moving forward. We want to introduce the short oral regimens beginning next year February,” says Nonhlanhla Dlamini, Programmatic Management of Drug Resistant TB (PMDT) coordinator in Eswatini.
She adds: “The challenge we faced was mainly funding to implement the operation research, but moving forward, I don’t think we will have any problems because the drugs which we will be using are the ones we are already using in the long regimens like the 18-20 months’ programme. Currently we have already developed the protocol, and starting with the ethics committee and we are waiting for the approval.”
Reduction in mortality rate
Dlamini says that they will only start rolling out the therapy at a few health facilities, while hoping to have the treatment available throughout the country at the end of 2020. “We are starting with a pilot of about five facilities that are two of the richest in Eswatini, and after that we will roll out to the entire country, but we have not yet implemented a clinical trial or any other operational research. The regimens that we are planning to implement are bed aquiline and linezolid for a period of nine to twelve months.”
In Lesotho they have begun with the clinical trial for SHORRT-therapy but they are still faced with a challenge of patients who cross the border to seek better medical services in South Africa. MDR-TB programme manager at Partners in Health in Lesotho, Lawrence Oyewusi says that they have seen a reduction in mortality rate since they have put the SHORRT-Therapy on clinical trial in their health facilities.
“Lesotho has not really adopted the use of SHORRT regimens but we are doing it under clinical trial. But the clinical trial is completely different from operational research… When you do things under clinical trial there are so many things you need to look at, such as monitoring the patients very well. So far we have enrolled a lot of patients and I think they are doing so well because, if you look at the programme in Lesotho the mortality rate used to be very high at the range 30–33%, but ever since we started using the new drugs, the mortality rate has been reduced to about 17%. With the clinical trial we have seen a lesser mortality rate,” says Oyewusi.
He says the clinical trial will take about five years because it is also occurring in other countries. “The enrolments will be for about two and a half years and the follow up will be for two years as we do not want to give a SHORRT regimens without being sure if patients will relapse or not [so] we have to do follow ups, but after the trial it is something which everyone is looking forward to. The longer regimens which we used to use are very toxic as it has a lot of toxic drugs in there, but now things are changing as instead of treating patients for 18 months you can actually reduce it to nine months and save a lot of money.”
Progress in South Africa too
According to Dr Norbert Ndjeka, director of National TB and Management Cluster in South Africa, “When the country started using bedaquiline, we observed that the death rate was coming down slowly. We also noticed that we didn’t have any option for patients who developed ototoxicity, so we felt that maybe [it] is better than not to give an injectable to individuals who were [reacting] on toxicity.” Before that, Ndjeka says, patients had to choose to either to remain deaf or die. “We don’t like those options.”
He says this is why South Africa started using bedaquiline and there was an improvement in treatment success rate and hearing loss also decreased. He tells Health-e News that they carried on with the same logic in the shorter regimen. “In our shorter regimen we achieved a treatment success rate of 67%, it has never happened before in South Africa, everything used to be below 50%.” Ndjeka says if everyone could be on this regimen, the country will achieve 75% treatment success rate.
Jennifer Furin of Harvard Medical School says 500 000 people become sick with RR-TB each year, while only 156 071 (31%) are diagnosed and put on treatment. Only 51% of those diagnosed with TB have their strains tested for rifampicin resistance, and only 59% of those individuals received testing for second-line medications.
“New and repurposed drugs such as bedaquiline and linezolid are saving lives with shorter regimens leading to potentially more tolerable treatment as injectable-free regimens reduces exposure to toxic medications,” says Furin.
– Health-e News
Image credit: iStock
Health24.com | ‘Cannabis use disorder’ up in states that legalised recreational dagga
States that legalised recreational marijuana have seen an increase in problematic pot use among teens and adults aged 26 and older, a new study finds.
The researchers compared dagga use in Colorado, Washington, Alaska and Oregon – the first four states to legalise recreational marijuana – before and after legalisation. The investigators also compared trends in those states with states that did not legalise recreational marijuana.
Preventing unintended harms
“There are, indeed, important social benefits that legalizing marijuana can provide, particularly around issues of equity in criminal justice,” said lead author Magdalena Cerda. She’s director of the Center for Opioid Epidemiology and Policy at NYU Langone Health, in New York City.
However, “our findings suggest that as more states move toward legalising marijuana for recreational use, we also need to think about investing in substance use prevention and treatment to prevent unintended harms – particularly among adolescents,” Cerda added in an NYU news release.
The study authors examined marijuana use and frequent use (more than 20 days) in the past month, and problematic marijuana use (also called “cannabis use disorder”) over the past year. Signs of problematic use include increased tolerance, repeated attempts to control use or quit, spending a lot of time using, social problems due to use, and ignoring other activities in order to use.
The rate of problematic use among teens aged 12 to 17 rose from 2.18% to 2.72% after legalisation, and was 25% higher than in non-recreational states. But there was no change in rates of past-month or frequent use.
Among adults 26 or older, past-month marijuana use after legalisation was 26% higher than in non-recreational states. Past-month frequent use rose by 23% and past-year problematic use rose by 37%.
Benefits and potential harms
Among young adults aged 18 to 25, there was no increase in past-month, frequent or problematic marijuana use after legalisation, according to the study. The findings were published online in JAMA Psychiatry.
According to study senior author Dr Silvia Martins, “Cannabis use disorder in adolescence is associated with long-term adverse health, economic and social consequences.” She is an associate professor of epidemiology at Columbia University Mailman School of Public Health, in New York City.
“Given our findings on problematic use across age groups, legalisation efforts should coincide with prevention and treatment,” Martins said in the news release.
“The general public should be informed about both benefits and potential harms of marijuana products to make informed decisions,” Martins added.
Recreational marijuana use is legal in 11 states and Washington, D.C. Medical marijuana use is legal in 33 states, the study authors noted.
Image credit: iStock
‘Sugar overload’ warning for festive hot drinks
Seasonal lattes and hot chocolates sold by coffee chains can contain up to 23 spoonfuls, a study finds.
Antarctic ice sheets could be at greater risk of melting than previously thought
Antarctica is the largest reservoir of ice on Earth — but new research by the University of South Australia suggests it could be at greater risk of melting than previously thought.
Heat from the landmass beneath the Antarctic ice sheet is a major contributor to the way that glaciers melt and flow — and their impact on potential sea level rise. Hotter conditions allow meltwater to lubricate the base of the glacier, accelerating its movement and the rate of ice loss.
However, because of the environmental, logistical and financial challenges of accessing bedrock through ice up to several kilometres thick, drillcore samples have never been taken to directly measure the temperature conditions at the base of the ice sheet. Scientists therefore assume a fixed value for the amount of heat generated by the Earth’s crust in Antarctica — as if the bedrock was uniform when in fact it’s highly variable.
Research by UniSA is challenging these assumptions and suggests scientists may have underestimated the heat generated by the bedrock in East Antarctica.
UniSA PhD student Alicia Pollett, under the supervision of UniSA Associate Professor of Geology and Geochemistry Tom Raimondo, has used samples from a Geoscience Australia / SA Department of Energy & Mining drilling program in South Australia’s far west, in an area called The Coompana Province, to estimate heat flow in East Antarctica. Australia and East Antarctica were conjoined 160 million years ago.
“The findings show that there is significant variability in the heat generated by the bedrock in southern Australia that was previously joined to Antarctica,” Assoc Prof Raimondo says.
“Because East Antarctica and southern Australia were once part of the same landmass, almost like two pieces of the same jigsaw puzzle, we can extrapolate the data from the coastline of Australia to its matching coastline in Antarctica with a high level of confidence.
“Our research provides a more robust model for heat flow in East Antarctica.
“The results suggest scientists have underestimated the amount of heat generated from naturally occurring radiation in the rocks beneath East Antarctica — meaning that large areas are potentially more vulnerable to ice sheet movement and accelerated melting than we previously thought.”
The rocks beneath the ice sheets generate heat because they contain small amounts of the elements uranium, thorium and potassium, which undergo natural radioactive decay to release heat.
UniSA PhD student Alicia Pollett says the research findings will allow scientists to more accurately estimate the effect of geothermal heat flow from the Antarctic crust on the ice above.
“This is the first step towards a more representative heat flow map of the Antarctic crust, which will assist the scientific community to more accurately predict sea level rise caused by melting ice,” she says.
Although it hasn’t yet been possible to obtain core samples of bedrock in Antarctica, the glaciers themselves have served a useful purpose in exposing the rocks at their base. The glaciers pick up rocks as they move across the landscape and eventually deposit them as debris at their edges and ends.
Assoc Prof Raimondo says these samples, including some collected on the expedition led by Sir Douglas Mawson between 1911 and 1914, allow them to develop a “virtual drillcore” which can be used to help calculate heat flow maps.
“Our next ambition is to produce a web-based map containing a compilation of all published and legacy geological data from decades of research in Antarctica and to make it available to all researchers,” he says.
The research paper, Heat flow in southern Australia and connections with East Antarctica, is published in the journal of Geochemistry, Geophysics, Geosystems.
Key facts
- Of the basic parameters that shape and control ice flow, the most poorly understood is geothermal heat flow
- Antarctic-wide heat flow maps have been previously based on satellite magnetic or seismological data (geophysical models rather than direct sampling)
- UniSA researchers have produced the first regional heat flow map of an area that was formerly conjoined to East Antarctica — the Coompana Province, which straddles the South Australian-Western Australian border. It is located between the western Gawler Craton to the east, the Musgrave Province to the north and the Madura Province (Western Australia) to the west. Because the Coompana Province was formerly part of the same landmass as Antarctica (the supercontinent Gondwana) it can be used to more accurately model heat flow maps for that part of Antarctica
- The research by UniSA suggests traditional geophysical models underestimate the heat flow that contributes to subglacial melting.
- The new measurements in the Coompana Province correspond to the Totten Glacier catchment, which has previously been shown to be thinning at an accelerated rate compared to other glacial regions of Antarctica.
- 99 per cent of Antarctica is covered by ice, much of which is on average up to 2km thick. While there are drill holes in Antarctica, they are all relatively shallow — none have intersected the bedrock beneath.
- East Antarctica, also called Greater Antarctica, constitutes about two-thirds of the Antarctic continent, lying on the Indian Ocean side of the continent, separated from West Antarctica by the Transantarctic Mountains.
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Materials provided by University of South Australia. Note: Content may be edited for style and length.
Antarctica’s thinning ice shelves causing more ice to move from land into sea
Researchers have produced the first physics-based quantifiable evidence that thinning ice shelves in Antarctica are causing more ice to flow from the land into the ocean.
Their findings have been published in Geophysical Research Letters.
Satellite measurements taken between 1994 and 2017 have detected significant changes in the thickness of the floating ice shelves that surround the Antarctic Ice Sheet. These shelves buttress against the land-based ice, holding them in place like a safety band.
While it has been suggested that the thinning ice shelves were responsible for a direct loss of ice from the land-based ice sheet into the ocean, there was no actual evidence linking data and physics that could demonstrate this, until now.
Researchers in the UK and US have now undertaken the first continent-wide assessment of the impact the thinning ice shelves are having on the flow of ice in Antarctica.
They were particularly interested in seeing how much ice flowed across the ‘grounding line’. This is the point where the land-based ice sheet meets the sea-based ice shelves.
They used a state-of-the-art ice-flow model developed at Northumbria University, UK, and newly available measurements of changes in the geometry of ice shelves to calculate the changes in grounded ice flow.
When the modelled results were compared with those obtained by satellites over the last 25 years, the researchers found what they described as ‘striking and robust’ similarities in the pattern of ice flowing from the ice sheet into the ocean.
The largest impact was found in West Antarctica, which already makes a significant contribution to sea level change. The largest changes are taking place around the Pine Island and Thwaites glaciers. On Pine Island Glacier, evidence of these changes could be seen almost 100 miles (150km) inland, upstream of the grounding line.
Hilmar Gudmundsson, Professor of Glaciology and Extreme Environments at Northumbria University led the study. He said there has been a long-standing question as to what was causing the changes we have observed in land-based ice over the last 25 years, and that while the thinning of the floating ice-shelves had been suggested as a reason, the idea had never been put to the test before now.
“I found it striking how well our modelled changes agree with the pattern of observed mass loss,” he said.
“There are other processes in play as well, but we can now state firmly that the observed changes in ice-shelves do cause significant changes over the grounded ice, speeding up its flow into the ocean.”
A critical element of the findings was the speed at which the ice flowed from the sheet into the ocean as a result of the thinning ice shelves.
“One of the most important lessons from this study is that the impact is felt without any delay,” said Professor Gudmundsson.
“Generally, we distinguish between an instantaneous response or a delayed, transient response. Our study shows the thinning of the ice shelves results in a significant instantaneous response to ice flow and ongoing mass loss. This means that we are not protected against the impact of the Antarctic Ice Sheet on global sea levels by a long response time.”
He added: “This study closes an important hole in our understanding. Lack of data and limitations in modelling previously made it challenging to quantify the importance of ocean-induced changes as a driver for ongoing mass loss, but we have now shown that the observed ice shelf changes do indeed impact on upstream flow significantly.”
The research was led by Northumbria University, Newcastle in the UK, with the NASA Jet Propulsion Laboratory and the Scripps Institution of Oceanography at the University of California San Diego.
Helen Amanda Fricker, Professor at Scripps Institution of Oceanography, said: “Ice shelves are the most vulnerable parts of Antarctica’s ice sheet system and we know that they are shrinking, but what we didn’t know before this work was how that was impacting the grounded ice behind them.”
Fernando Paolo, postdoctoral scholar at Jet Propulsion Laboratory/California Institute of Technology, added: “It is striking how far inland the changes in ice shelves can impact the ice sheet flow. Since we now know that shrinking ice shelves are directly responsible for increases in ice discharge to the ocean, it is important that we keep monitoring them to watch how they evolve.”
It is believed that the ice shelves may be thinning due to changes in ocean heat content, either by ocean warming or from changes in how the ocean circulates around and below the shelves, but further research is needed to establish the specific reasons.
It was partially funded through both the International Thwaites Glacier Collaboration’s PROPHET project and through the recently announced TiPACCs study, which are respectively funded by the Natural Environment Research Council/National Science Foundation and European Union’s Horizon 2020 research and innovation programme.
