Heat from El Niño can warm oceans off West Antarctica – and melt floating ice shelves from below

AndreAnita/Shutterstock Maurice Huguenin, UNSW Sydney; Matthew England, UNSW Sydney, and Paul Spence, University of Tasmania

As snow falls on Antarctica, layers build up and turn to ice. Over time, this compressed snow has become a continent-sized glacier, or ice sheet. It’s enormous – almost double the size of Australia and far larger than the continental United States.

As the weight of ice builds up, the ice sheet begins to move towards the oceans. When it reaches the sea, the ice floats. These floating extensions are known as ice shelves. The largest is over 800 kilometres wide.

When the ocean water has a temperature close to 0°C, these ice shelves can persist for a long time. But when temperatures rise, even a little, the ice melts from below. Antarctic ice shelves are now losing an alarming 150 billion tons of ice per year, adding more water to the ocean and accelerating global sea level rise by 0.6 mm per year. Ice shelves in West Antarctica are particularly prone to melting from the ocean, as many are close to water masses above 0°C.

While the melting trend is clear and concerning, the amount can vary substantially from year-to-year due to the impact of both natural climate fluctuations and human-made climate change. To figure out what is going on and to prepare for the future, we need to tease apart the different drivers – especially El Niño-Southern Oscillation, the world’s largest year-to-year natural climate driver.

Our new research explores how heat brought by El Niño can warm the ocean around West Antarctica and increase melting of the ice shelves from below.

Antarctic Ice Mass Loss 2002-2023. Credit: NASA Climate Change.

How can El Niño-Southern Oscillation affect Antarctica?

Australians are very familiar with the two phases of this climate driver, El Niño and La Niña, as they tend to bring us hotter, dryer weather and cooler, wetter weather, respectively. But the influence of this cycle is much larger, affecting weather and climate all around the Pacific.

Can it reach through Antarctica’s cold, fast currents of air and water? Yes.

Giant convective thunderstorms in the Pacific’s equatorial regions move east during El Niño and intensify in the West during La Niña. As these storm systems change, they excite ripples in the atmosphere that are able to travel large distances, just as waves can cross oceans. Within two months, these atmospheric waves reach the Antarctic continent, where their energy can affect the coastal atmosphere and ocean circulation. During El Niño, the energy from these waves weakens the easterly winds off West Antarctica (and vice versa for La Niña).

Using satellite data, researchers recently found that West Antarctic ice shelves actually gain height but lose mass during El Niño. That’s because more low-density snow falls at the top of the ice shelves, while at the same time more warm water flows under the ice shelves where it melts compressed high-density ice from underneath.

What we don’t yet know is how this warmer water (above zero) comes up from below. Similarly, we don’t know what happens during La Niña.

Answering these questions with the few observations we have from Antarctica is challenging because this climate driver doesn’t happen in isolation. Storms, tides, large eddy currents and other climate drivers such as the Southern Annual Mode can change the temperatures of the water under ice shelves too, and they can occur at the same time as El Niño.

Finding a needle in the ice stack

So how did we do it? Modelling.

We take a high-resolution global ocean circulation model and added El Niño and La Niña events to the baseline simulation. By doing so, we can examine what these anomalies do to the currents and temperatures around Antarctica.

The energy brought by El Niño’s atmospheric waves to West Antarctica weakens the prevailing easterly winds along the coasts.

Normally, most of the warm water reservoir is located off the continental shelf rather than on the continental shelf. As the winds weaken, more of this warmer water – known as Circumpolar Deep Water – is able to flow onto the continental shelf and near the base of the floating ice shelves.

During El Niño, weaker winds along the coasts push less cold Antarctic surface waters towards the continent, allowing warmer Circumpolar Deep Water to flow to the base of the ice shelves. During La Niña, stronger winds drive a wedge of cold water up towards the continent, reducing the inflow of warm water. Maurice Huguenin, CC BY-SA

We call this water mass “warm”, but that’s relative – it’s only 1–2°C above freezing, and the heat only warms the water on the continental shelf by about 0.5°C. But that’s enough to begin melting ice shelves, which are at or below freezing point.

As you’d expect, the longer the warm water stays on the shelf and the hotter it is, the more melting occurs.

During La Niña, the opposite occurs and the ice rebounds. Winds along the coast strengthen, pushing more cold surface water onto the continental shelf and preventing warm water from flowing under the ice shelves.

What does this mean for the near future?

Researchers have found El Niño and La Niña have already become more frequent and more extreme.

If this trend continues, as climate projections suggest, we can expect warming around West Antarctica to get even stronger during El Niño events, accelerating ice shelf melting and speeding up sea level rise.

More frequent and stronger El Niño events could also push us closer to a tipping point in the West Antarctic ice sheet, after which accelerated melting and mass loss could become self-perpetuating. That means the ice wouldn’t melt and reform but begin to steadily melt.

More bad news? Unfortunately, yes. The only way to stop the worst from happening is to get to net zero carbon emissions as quickly as humanly possible.

Maurice Huguenin, Postdoctoral research associate in Physical Oceanography, UNSW Sydney; Matthew England, Scientia Professor and Deputy Director of the ARC Australian Centre for Excellence in Antarctic Science (ACEAS), UNSW Sydney, and Paul Spence, Associate professor of oceanography, University of Tasmania

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Read More........→April 09, 2024

The first pig kidney has been transplanted into a living person. But we’re still a long way from solving organ shortages

Massachusetts General Hospital Christopher Rudge, University of Sydney

In a world first, we heard last week that US surgeons had transplanted a kidney from a gene-edited pig into a living human. News reports said the procedure was a breakthrough in xenotransplantation – when an organ, cells or tissues are transplanted from one species to another.

The world’s first transplant of a gene-edited pig kidney into a live human was announced last week.

Champions of xenotransplantation regard it as the solution to organ shortages across the world. In December 2023, 1,445 people in Australia were on the waiting list for donor kidneys. In the United States, more than 89,000 are waiting for kidneys.

One biotech CEO says gene-edited pigs promise “an unlimited supply of transplantable organs”.

Not, everyone, though, is convinced transplanting animal organs into humans is really the answer to organ shortages, or even if it’s right to use organs from other animals this way.

There are two critical barriers to the procedure’s success: organ rejection and the transmission of animal viruses to recipients.

But in the past decade, a new platform and technique known as CRISPR/Cas9 – often shortened to CRISPR – has promised to mitigate these issues.

What is CRISPR?

CRISPR gene editing takes advantage of a system already found in nature. CRISPR’s “genetic scissors” evolved in bacteria and other microbes to help them fend off viruses. Their cellular machinery allows them to integrate and ultimately destroy viral DNA by cutting it.

In 2012, two teams of scientists discovered how to harness this bacterial immune system. This is made up of repeating arrays of DNA and associated proteins, known as “Cas” (CRISPR-associated) proteins.

When they used a particular Cas protein (Cas9) with a “guide RNA” made up of a singular molecule, they found they could program the CRISPR/Cas9 complex to break and repair DNA at precise locations as they desired. The system could even “knock in” new genes at the repair site.

In 2020, the two scientists leading these teams were awarded a Nobel prize for their work.

In the case of the latest xenotransplantation, CRISPR technology was used to edit 69 genes in the donor pig to inactivate viral genes, “humanise” the pig with human genes, and knock out harmful pig genes.

How does CRISPR work?

A busy time for gene-edited xenotransplantation

While CRISPR editing has brought new hope to the possibility of xenotransplantation, even recent trials show great caution is still warranted.

In 2022 and 2023, two patients with terminal heart diseases, who were ineligible for traditional heart transplants, were granted regulatory permission to receive a gene-edited pig heart. These pig hearts had ten genome edits to make them more suitable for transplanting into humans. However, both patients died within several weeks of the procedures.

Earlier this month, we heard a team of surgeons in China transplanted a gene-edited pig liver into a clinically dead man (with family consent). The liver functioned well up until the ten-day limit of the trial.

How is this latest example different?

The gene-edited pig kidney was transplanted into a relatively young, living, legally competent and consenting adult.

The total number of gene edits edits made to the donor pig is very high. The researchers report making 69 edits to inactivate viral genes, “humanise” the pig with human genes, and to knockout harmful pig genes.

Clearly, the race to transform these organs into viable products for transplantation is ramping up.

From biotech dream to clinical reality

Only a few months ago, CRISPR gene editing made its debut in mainstream medicine.

In November, drug regulators in the United Kingdom and US approved the world’s first CRISPR-based genome-editing therapy for human use – a treatment for life-threatening forms of sickle-cell disease.

The treatment, known as Casgevy, uses CRISPR/Cas-9 to edit the patient’s own blood (bone-marrow) stem cells. By disrupting the unhealthy gene that gives red blood cells their “sickle” shape, the aim is to produce red blood cells with a healthy spherical shape.

Although the treatment uses the patient’s own cells, the same underlying principle applies to recent clinical xenotransplants: unsuitable cellular materials may be edited to make them therapeutically beneficial in the patient.

CRISPR technology is aiming to restore diseased red blood cells to their healthy round shape. Sebastian Kaulitzki/Shutterstock

We’ll be talking more about gene-editing

Medicine and gene technology regulators are increasingly asked to approve new experimental trials using gene editing and CRISPR.

However, neither xenotransplantation nor the therapeutic applications of this technology lead to changes to the genome that can be inherited.

For this to occur, CRISPR edits would need to be applied to the cells at the earliest stages of their life, such as to early-stage embryonic cells in vitro (in the lab).

In Australia, intentionally creating heritable alterations to the human genome is a criminal offence carrying 15 years’ imprisonment.

No jurisdiction in the world has laws that expressly permits heritable human genome editing. However, some countries lack specific regulations about the procedure.

Is this the future?

Even without creating inheritable gene changes, however, xenotransplantation using CRISPR is in its infancy.

For all the promise of the headlines, there is not yet one example of a stable xenotransplantation in a living human lasting beyond seven months.

While authorisation for this recent US transplant has been granted under the so-called “compassionate use” exemption, conventional clinical trials of pig-human xenotransplantation have yet to commence.

But the prospect of such trials would likely require significant improvements in current outcomes to gain regulatory approval in the US or elsewhere.

By the same token, regulatory approval of any “off-the-shelf” xenotransplantation organs, including gene-edited kidneys, would seem some way off.

Christopher Rudge, Law lecturer, University of Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Read More........→March 29, 2024

How global warming is reshaping winter life in Canada

H. Damon Matthews, Concordia University and Mitchell Dickau, Concordia University As we begin to emerge out of yet another mild winter, Canadians are once again being reminded of just how acutely global warming has changed Canada’s winter climate.

The impacts of this mild winter were felt across the country and touched all aspects of winter culture. From melting ice castles at Québec’s winter carnival, to a dismal lack of snow at many Western Canada ski resorts, seemingly no part of Canada was unaffected. But the change that will likely be felt most keenly by many Canadians is the loss of a reliable outdoor skating season.

For the second year running, Ottawa’s Rideau Canal Skateway was closed for what should be the peak of the skating season. In 2022-2023, the Skateway did not open at all for the first time ever. This winter, a portion of the Skateway opened briefly in January, but continuing mild temperatures forced a closure again after only four days of skating. In Montréal, fewer than 40 per cent of the city’s outdoor rinks were open in the middle of February.

There is no obvious upside to this story. Outdoor skating in Canada is fast becoming the latest casualty of our failure to confront the reality of the climate crisis.

On thin ice

More than a decade ago, our research group published our first analysis of how outdoor skating was being affected by warming winter temperatures in Canada. We showed that even as of 2005, there was already evidence of later start dates, and shorter skating seasons across most of the country.

A report on the management of the Rideau Canal Skateway in 2023, produced by the CBC.

These conclusions were echoed by subsequent publications from the RinkWatch project, which has reported consistent declines in skating season length and quality in many Canadian cities.

Meanwhile in Ottawa, skating days on the Rideau Canal Skateway have been trending downwards over the last 20 years. In this time, the typical skating season has decreased by almost 40 per cent, a trend that is clearly correlated with increasing winter temperatures over the same period.

Moving in the wrong direction

Climate mitigation progress continues to be far too slow.

Global CO2 emissions reached their highest level ever recorded in 2023, and average global temperatures have now reached 1.3 C above pre-industrial temperatures. If these trends continue, we are on track to reach 1.5 C — the lower threshold of the Paris Agreement temperature target — in less than seven years.

In our 2012 paper, we estimated that suitable rink flooding days could disappear across most of southern Canada by mid-century. In a more recent analysis of Montréal’s outdoor rinks, we estimated that the number of viable skating days in Montréal could decrease to zero by as early as 2070.

In hindsight, these and other similar projections may have been far too optimistic. In a study of Rideau canal skating days published in 2015, the authors projected declining but sustained skating conditions throughout this century, even in a high future emissions scenario. The reality of the past two seasons shows that skating conditions have deteriorated far more quickly than predicted.

Global temperatures in 2023 were the highest ever recorded, as were winter temperatures in December 2023 and January 2024. Since 1950, winter temperatures in Canada have increased by more than 3 C, which is about three times the rate of global warming over this same period.

Outdoor rinks require at least three consecutive very cold days to establish a foundation of ice, followed by enough cold days to maintain a good ice surface. Temperatures above freezing are poorly tolerated by outdoor rinks, and rain is often disastrous.

A few degrees of warming in January and February temperatures can be the difference between a rink that is skatable and one that is not. As winters continue to warm, the case for building and maintaining outdoor municipal rinks will become harder to justify.

A stark and still changing new reality

As years go by without any real progress on climate mitigation, it is becoming increasingly difficult to imagine a future in which outdoor rinks will be widely available without artificial refrigeration. Other winter activities will also be affected by changing snow conditions, but outdoor skating will likely be hit first in direct response to warming winter temperatures.

Wayne Gretzky famously learned to skate and play hockey in Branford, Ont. in the 1960s on an outdoor rink built by his father. Reliable winter skating conditions in southern Ontario are already mostly a thing of the past, and are becoming more and more scarce as global warming progresses. It is increasingly unlikely that current and future generations will be able to follow Gretzky’s path.

This reality is both a tragic injustice for many young Canadians and an existential threat to a core aspect of the Canadian winter identity.

Preserving what remains of Canada’s winter skating culture will require that we rapidly step up our efforts to drive down CO2 emissions and stabilize global temperatures. Otherwise, Joni Mitchell’s “river I could skate away on” will become an increasingly wishful dream that soon will exist only in the lyrics of old songs.

H. Damon Matthews, Professor and Climate Scientist, Department of Geography, Planning and Environment, Concordia University and Mitchell Dickau, PhD Candidate, Geography, Planning, and Environment Department, Concordia University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Read More........→March 28, 2024

Man Ignores Naysayers to Revive Tiny Sparrow with CPR – Watch the Moment his Patience is Rewarded

Submitted by Costakis Constantinou: In a heartwarming video, a 67-year-old actor from Cyprus became determined to use his CPR expertise to save a tiny, helpless sparrow. The avian creature was found unconsciousness following an “unfortunate pool mishap”. In the background of the video, you can hear a chorus of teasing and snickering, with voices urging him to dispose of the seemingly lifeless bird—but Costakis Constantinou remained undeterred. “Nobody thought this was possible or even worth trying,he  however, stayed focus and patiently continued,” his son Rolandos told GNN. With unwavering determination, he persistently, applied his life-saving skills until, against all odds, the sparrow gradually regained consciousness, fluttering back to life. “I can say with confidence that he was very, very happy, relieved, and satisfied when the little sparrow open its eyes and flied away.” When Rolandos rewatched the video again (see below), he got emotional and telephoned his dad to tell him how proud he was. “In the past he saved two people from heart attack by applying CPR. For some reason my father is at the right place the right time.” “I wanted to surprise him by sending over his video,” said Rolandos in an email. “I’m so proud of him.”Watch the moment his patience was rewarded…Man Ignores Naysayers to Revive Tiny Sparrow with CPR – Watch the Moment his Patience is Rewarded:

Read More........→March 20, 2024

Our brains take rhythmic snapshots of the world as we walk – and we never knew

Blazej Lyjak/Shutterstock Matthew Davidson, University of Sydney

For decades, psychology departments around the world have studied human behaviour in darkened laboratories that restrict natural movement.

Our new study, published today in Nature Communications, challenges the wisdom of this approach. With the help of virtual reality (VR), we have revealed previously hidden aspects of perception that happen during a simple everyday action – walking.

We found the rhythmic movement of walking changes how sensitive we are to the surrounding environment. With every step we take, our perception cycles through “good” and “bad” phases.

This means your smooth, continuous experience of an afternoon stroll is deceptive. Instead, it’s as if your brain takes rhythmic snapshots of the world – and they are synchronised with the rhythm of your footfall.

The next step in studies of human perception

In psychology, the study of visual perception refers to how our brains use information from our eyes to create our experience of the world.

Typical psychology experiments that investigate visual perception involve darkened laboratory rooms where participants are asked to sit motionless in front of a computer screen.

Often, their heads will be fixed in position with a chin rest, and they will be asked to respond to any changes they might see on the screen.

This approach has been invaluable in building our knowledge of human perception, and the foundations of how our brains make sense of the world. But these scenarios are a far cry from how we experience the world every day.

This means we might not be able to generalise the results we discover in these highly restricted settings to the real world. It would be a bit like trying to understand fish behaviour, but only by studying fish in an aquarium.

Instead, we went out on a limb. Motivated by the fact our brains have evolved to support action, we set out to test vision during walking – one of our most frequent and everyday behaviours.

Doing tests in a lab isn’t quite the same as seeing and interacting with things in the real world. sirtravelalot/Shutterstock

A walk in a (virtual) forest

Our key innovation was to use a wireless VR environment to test vision continuously while walking.

Several previous studies have examined the effects of light exercise on perception, but used treadmills or exercise bikes. While these methods are better than sitting still, they don’t match the ways we naturally move through the world.

Instead, we simulated an open forest. Our participants were free to roam, yet unknown to them, we were carefully tracking their head movement with every step they took.

Participants walked in a virtual forest while trying to detect brief visual ‘flashes’ in the moving white circle.

We tracked head movement because as you walk, your head bobs up and down. Your head is lowest when both feet are on the ground and highest when swinging your leg in-between steps. We used these changes in head height to mark the phases of each participant’s “step-cycle”.

Participants also completed our visual task while they walked, which required looking for brief visual “flashes” they needed to detect as quickly as possible.

By aligning performance on our visual task to the phases of the step-cycle, we found visual perception was not consistent.

Instead, it oscillated like the ripples of a pond, cycling through good and bad periods with every step. We found that depending on the phases of their step-cycle, participants were more likely to sense changes in their environment, had faster reaction times, and were more likely to make decisions.

Oscillations in nature, oscillations in vision

Oscillations in vision have been shown before, but this is the first time they have been linked to walking.

Our key new finding is these oscillations slowed or increased to match the rhythm of a person’s step-cycle. On average, perception was best when swinging between steps, but the timing of these rhythms varied between participants. This new link between the body and mind offers clues as to how our brains coordinate perception and action during everyday behaviour.

Next, we want to investigate how these rhythms impact different populations. For example, certain psychiatric disorders can lead to people having abnormalities in their gait.

There are further questions we want to answer: are slips and falls more common for those with stronger oscillations in vision? Do similar oscillations occur for our perception of sound? What is the optimal timing for presenting information and responding to it when a person is moving?

Our findings also hint at broader questions about the nature of perception itself. How does the brain stitch together these rhythms in perception to give us our seamless experience of an evening stroll?

These questions were once the domain of philosophers, but we may be able to answer them, as we combine technology with action to better understand natural behaviour.

Matthew Davidson, Postdoctoral research fellow, lecturer, University of Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Read More........→March 19, 2024