(The Conversation) – The Arctic has warmed nearly four times faster than the global average since 1979. Svalbard, an archipelago near the northeast coast of Greenland, is at the frontline of this climate change, warming up to seven times faster than the rest of the world.

More than half of Svalbard is covered by glaciers. If they were to completely melt tomorrow, the global sea level would rise by 1.7cm. Although this won’t happen overnight, glaciers in the Arctic are highly sensitive to even slight temperature increases.

To better understand glaciers in Svalbard and beyond, we used an AI model to analyse millions of satellite images from Svalbard over the past four decades. Our research is now published in Nature Communications, and shows these glaciers are shrinking faster than ever, in line with global warming.

Specifically, we looked at glaciers that drain directly into the ocean, what are known as “marine-terminating glaciers”. Most of Svalbard’s glaciers fit this category. They act as an ecological pump in the fjords they flow into by transferring nutrient-rich seawater to the ocean surface and can even change patterns of ocean circulation.

Where these glaciers meet the sea, they mainly lose mass through iceberg calving, a process in which large chunks of ice detach from the glacier and fall into the ocean. Understanding this process is key to accurately predicting future glacier mass loss, because calving can result in faster ice flow within the glacier and ultimately into the sea.

Despite its importance, understanding the glacier calving process has been a longstanding challenge in glaciology, as this process is difficult to observe, let alone accurately model. However, we can use the past to help us understand the future.

AI replaces painstaking human labour

When mapping the glacier calving front – the boundary between ice and ocean – traditionally human researchers painstakingly look through satellite imagery and make digital records. This process is highly labour-intensive, inefficient and particularly unreproducible as different people can spot different things even in the same satellite image. Given the number of satellite images available nowadays, we may not have the human resources to map every region for every year.

Photo by Chris-Håvard Berge on Unsplash

A novel way to tackle this problem is by using automated methods like artificial intelligence (AI), which can quickly identify glacier patterns across large areas. This is what we did in our new study, using AI to analyse millions of satellite images of 149 marine-terminating glaciers taken between 1985 and 2023. This meant we could examine the glacier retreats at unprecedented scale and scope.

Insights from 1985 to today

We found that the vast majority (91%) of marine-terminating glaciers across Svalbard have been shrinking significantly. We discovered a loss of more than 800km² of glacier since 1985, larger than the area of New York City, and equivalent to an annual loss of 24km² a year, almost twice the size of Heathrow airport in London.

The biggest spike was detected in 2016, when the calving rates doubled in response to periods of extreme warming. That year, Svalbard also had its wettest summer and autumn since 1955, including a record 42mm of rain in a single day in October. This was accompanied by unusually warm and ice-free seas.

How ocean warming triggers glacier calving

In addition to the long-term retreat, these glaciers also retreat in the summer and advance again in winter, often by several hundred metres. This can be greater than the changes from year to year.

We found that 62% of the glaciers in Svalbard experience these seasonal cycles. While this phenomenon is well documented across Greenland, it had previously only been observed for a handful of glaciers in Svalbard, primarily through manual digitisation.

We then compared these seasonal changes with seasonal variations in air and ocean temperature. We found that as the ocean warmed up in spring, the glacier retreated almost immediately. This was a nice demonstration of something scientists had long suspected: the seasonal ebbs and flows of these glaciers are caused by changes in ocean temperatures.

A global threat

Svalbard experiences frequent climate extremes due to its unique location in the Arctic yet close to the warm Atlantic water. Our findings indicate that marine-terminating glaciers are highly sensitive to climate extremes and the biggest retreat rates have occurred in recent years.

This same type of glaciers can be found across the Arctic and, in particular, around Greenland, the largest ice mass in the northern hemisphere. What happens to glaciers in Svalbard is likely to be repeated elsewhere.

If the current climate warming trend continues, these glaciers will retreat more rapidly, the sea level will rise, and millions of people in coastal areas worldwide will be endangered.

Tian Li, Senior Research Associate, Bristol Glaciology Centre, University of Bristol; Jonathan Bamber, Professor of Glaciology and Earth Observation, University of Bristol, and Konrad Heidler, Chair of Data Science in Earth Observation, Technical University of Munich

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

At the most northerly tip of the UK, looking north from the island of Muckle Flugga, Shetland, the cold wind whips up the sea and gannets dive.

While biodiversity loss in the Arctic Ocean may seem like a distant issue, the Shetland Islands lie further north than the Arctic Ocean’s southernmost waters.
The Arctic Circle is only 380 miles (610km) north of British waters – the same distance as London to Edinburgh by road.

Arctic wildlife is changing in ways that scientists like us don’t yet fully understand. Better protection for these species is urgently needed.

Establishing a new North Pole marine reserve where industrial activities such as shipping, oil and gas exploration and fishing are banned could provide an ocean sanctuary for wildlife.

Explorer-turned-conservationist Pen Hadow wants to create an internationally agreed marine reserve in the Central Arctic Ocean by 2037. He was the first person to trek solo from Canada to the geographic North Pole 21 years ago. The route he took in 2003 is no longer possible due to climate change.

In 2021, Hadow founded the 90 North Foundation, an environmental charity that is campaigning for a North Pole marine reserve to protect the Arctic’s peoples, its wildlife and its natural landscape.

Our team of marine researchers at the University of Exeter is collaborating with Hadow to explore how climate change will affect the ice and oceans in the Arctic and beyond.

Projected climate change poses great peril for wildlife such as polar bears and narwhals which are highly adapted to Arctic waters, relying on multi-year ice for foraging and breeding habitat.

So far, we have completed two ten-day surveys for whales and dolphins using both visual sightings and acoustic or sound monitoring underwater. We have also collected water samples to test for “environmental DNA” or eDNA. By filtering water and collecting small fragments of biological material, we can identity the presence of species by sequencing the trail they leave behind in the water in the form of fish scales, poo, skin or mucus, for example.

Once we have built a picture of where wildlife lives and how it moves about, changes in the Arctic ecosystem can be more easily monitored.

Arctic animals are also regularly spotted in British waters.

Ringed seals have been seen as far south as Cornwall. Beluga whales have been spotted off the coast of Shetland, and Atlantic white-sided and white-beaked dolphins frequently move between UK waters and the low Arctic. Bearded seals have been spotted in UK coastal waters, as have walrus and harp seals.

Brent geese, barnacle geese and pink-footed geese plus eider ducks, red knot, ringed plover and bar-tailed godwits all migrate between the Arctic and the UK. These birds breed in the Arctic and sub-Arctic, then overwinter in the UK and Ireland. These birds are particularly vulnerable because climate change is leading to wetter springs that can reduce their breeding success.

The wildlife living along UK’s shores is already changing as a result of climate change. Some species might expand their range northwards and this could further disrupt the Arctic ecosystem.

As well as monitoring wildlife, we are tracking the changing volume and routes of ships travelling through the Arctic Ocean. While our research is at an early stage, it’s already clear that industrial vessel activity in the Arctic Ocean is increasing as fishing vessels and cargo ships take advantage of the receding ice to make swifter routes across the globe.

The Arctic albedo

As the Arctic changes, the ramifications will be felt globally. The Earth’s northernmost white cap acts as a reflective shield against solar radiation. As the ice recedes, and the surface of the Earth darkens, so too does the planet’s in-built ability to reflect the sun’s warming rays.

Standing on a boat at the edge of the Arctic ice, we can see the powerful glow of sunlight reflecting from the icy surfaces. Any loss of this albedo (the ability of white ice to reflect sunlight and heat from the sun) triggers further warming, catalysing a negative feedback loop with profound implications. Rising temperatures can only be tackled by reducing greenhouse gas emissions.

Alongside this, we must protect the unique wildlife that have made the Arctic their home. A broad and encompassing approach to conservation of northern ecosystems could help limit the effects of human activities and the changing climate across the Arctic region and beyond. A well-connected global network of marine reserves that includes the Arctic Ocean is urgently needed.

Kirsten Freja Young, Senior Lecturer, Ecology, University of Exeter and Brendan Godley, Professor of Conservation Science, University of Exeter

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

Featured image: Kirsten Young has been monitoring wildlife in the Arctic Ocean. Danielle Zalcman, CC BY-NC-ND.

(The Conversation) – The melting of one of North America’s largest icefields has accelerated and could soon reach an irreversible tipping point. That’s the conclusion of new research colleagues and I have published on the Juneau Icefield, which straddles the Alaska-Canada border near the Alaskan capital of Juneau.

In the summer of 2022, I skied across the flat, smooth and white plateau of the icefield, accompanied by other researchers, sliding in the tracks of the person in front of me under a hot sun. From that plateau, around 40 huge, interconnected glaciers descend towards the sea, with hundreds of smaller glaciers on the mountain peaks all around.

Our work, now published in Nature Communications, has shown that Juneau is an example of a climate “feedback” in action: as temperatures are rising, less and less snow is remaining through the summer (technically: the “end-of-summer snowline” is rising). This in turn leads to ice being exposed to sunshine and higher temperatures, which means more melt, less snow, and so on.

Like many Alaskan glaciers, Juneau’s are top-heavy, with lots of ice and snow at high altitudes above the end-of-summer snowline. This previously sustained the glacier tongues lower down. But when the end-of-summer snowline does creep up to the top plateau, then suddenly a large amount of a top-heavy glacier will be newly exposed to melting.

That’s what’s happening now, each summer, and the glaciers are melting much faster than before, causing the icefield to get thinner and thinner and the plateau to get lower and lower. Once a threshold is passed, these feedbacks can accelerate melt and drive a self-perpetuating loss of snow and ice which would continue even if the world were to stop warming.

Ice is melting faster than ever

Using satellites, photos and old piles of rocks, we were able to measure the ice loss across Juneau Icefield from the end of the last “Little Ice Age” (about 250 years ago) to the present day. We saw that the glaciers began shrinking after that cold period ended in about 1770. This ice loss remained constant until about 1979, when it accelerated. It accelerated again in 2010, doubling the previous rate. Glaciers there shrank five times faster between 2015 and 2019 than from 1979 to 1990.

Associated Press Video: “Melting of Alaska’s Juneau icefield accelerates, losing snow nearly 5 times faster than in the 1980s”

Our data shows that as the snow decreases and the summer melt season lengthens, the icefield is darkening. Fresh, white snow is very reflective, and much of that strong solar energy that we experienced in the summer of 2022 is reflected back into space. But the end of summer snowline is rising and is now often occurring right on the plateau of the Juneau Icefield, which means that older snow and glacier ice is being exposed to the sun. These slightly darker surfaces absorb more energy, increasing snow and ice melt.

As the plateau of the icefield thins, ice and snow reserves at higher altitudes are lost, and the surface of the plateau lowers. This will make it increasingly hard for the icefield to ever stabilise or even recover. That’s because warmer air at low elevations drives further melt, leading to an irreversible tipping point.

Longer-term data like these are critical to understand how glaciers behave, and the processes and tipping points that exist within individual glaciers. These complex processes make it difficult to predict how a glacier will behave in future.

The world’s hardest jigsaw

We used satellite records to reconstruct how big the glacier was and how it behaved, but this really limits us to the past 50 years. To go back further, we need different methods. To go back 250 years, we mapped the ridges of moraines, which are large piles of debris deposited at the glacier snout, and places where glaciers have scoured and polished the bedrock.

To check and build on our mapping, we spent two weeks on the icefield itself and two weeks in the rainforest below. We camped among the moraine ridges, suspending our food high in the air to keep it safe from bears, shouting to warn off the moose and bears as we bushwhacked through the rainforest, and battling mosquitoes thirsty for our blood.

We used aerial photographs to reconstruct the icefield in the 1940s and 1970s, in the era before readily available satellite imagery. These are high quality photos, but were taken before global positioning systems made it easy to locate exactly where they were taken.

A number also had some minor damage in the intervening years – some Sellotape, a tear, a thumb print. As a result, the individual images had to be stitched together to make a 3D picture of the whole icefield. It was all rather like doing the world’s hardest jigsaw puzzle.

Work like this is crucial as the world’s glaciers are melting fast – all together they are currently losing more mass than the Greenland or Antarctic ice sheets, and thinning rates of these glaciers worldwide has doubled over the past two decades.

Our longer time series shows just how stark this acceleration is. Understanding how and where “feedbacks” are making glaciers melt even faster is essential to make better predictions of future change in this important region

Bethan Davies, Senior Lecturer in Physical Geography, Newcastle University

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

Superstorms, abrupt climate shifts and New York City frozen in ice. That’s how the blockbuster Hollywood movie “The Day After Tomorrow” depicted an abrupt shutdown of the Atlantic Ocean’s circulation and the catastrophic consequences.

While Hollywood’s vision was over the top, the 2004 movie raised a serious question: If global warming shuts down the Atlantic Meridional Overturning Circulation, which is crucial for carrying heat from the tropics to the northern latitudes, how abrupt and severe would the climate changes be?

Twenty years after the movie’s release, we know a lot more about the Atlantic Ocean’s circulation. Instruments deployed in the ocean starting in 2004 show that the Atlantic Ocean circulation has observably slowed over the past two decades, possibly to its weakest state in almost a millennium. Studies also suggest that the circulation has reached a dangerous tipping point in the past that sent it into a precipitous, unstoppable decline, and that it could hit that tipping point again as the planet warms and glaciers and ice sheets melt.

In a new study using the latest generation of Earth’s climate models, we simulated the flow of fresh water until the ocean circulation reached that tipping point.

The results showed that the circulation could fully shut down within a century of hitting the tipping point, and that it’s headed in that direction. If that happened, average temperatures would drop by several degrees in North America, parts of Asia and Europe, and people would see severe and cascading consequences around the world.

We also discovered a physics-based early warning signal that can alert the world when the Atlantic Ocean circulation is nearing its tipping point.

The ocean’s conveyor belt

Ocean currents are driven by winds, tides and water density differences.

In the Atlantic Ocean circulation, the relatively warm and salty surface water near the equator flows toward Greenland. During its journey it crosses the Caribbean Sea, loops up into the Gulf of Mexico, and then flows along the U.S. East Coast before crossing the Atlantic.

This current, also known as the Gulf Stream, brings heat to Europe. As it flows northward and cools, the water mass becomes heavier. By the time it reaches Greenland, it starts to sink and flow southward. The sinking of water near Greenland pulls water from elsewhere in the Atlantic Ocean and the cycle repeats, like a conveyor belt.

Too much fresh water from melting glaciers and the Greenland ice sheet can dilute the saltiness of the water, preventing it from sinking, and weaken this ocean conveyor belt. A weaker conveyor belt transports less heat northward and also enables less heavy water to reach Greenland, which further weakens the conveyor belt’s strength. Once it reaches the tipping point, it shuts down quickly.

What happens to the climate at the tipping point?

The existence of a tipping point was first noticed in an overly simplified model of the Atlantic Ocean circulation in the early 1960s. Today’s more detailed climate models indicate a continued slowing of the conveyor belt’s strength under climate change. However, an abrupt shutdown of the Atlantic Ocean circulation appeared to be absent in these climate models.

Ted-Ed Video: “How do ocean currents work? – Jennifer Verduin”

This is where our study comes in. We performed an experiment with a detailed climate model to find the tipping point for an abrupt shutdown by slowly increasing the input of fresh water.

We found that once it reaches the tipping point, the conveyor belt shuts down within 100 years. The heat transport toward the north is strongly reduced, leading to abrupt climate shifts.

The result: Dangerous cold in the North

Regions that are influenced by the Gulf Stream receive substantially less heat when the circulation stops. This cools the North American and European continents by a few degrees.

The European climate is much more influenced by the Gulf Stream than other regions. In our experiment, that meant parts of the continent changed at more than 5 degrees Fahrenheit (3 degrees Celsius) per decade – far faster than today’s global warming of about 0.36 F (0.2 C) per decade. We found that parts of Norway would experience temperature drops of more than 36 F (20 C). On the other hand, regions in the Southern Hemisphere would warm by a few degrees.

These temperature changes develop over about 100 years. That might seem like a long time, but on typical climate time scales, it is abrupt.

The conveyor belt shutting down would also affect sea level and precipitation patterns, which can push other ecosystems closer to their tipping points. For example, the Amazon rainforest is vulnerable to declining precipitation. If its forest ecosystem turned to grassland, the transition would release carbon to the atmosphere and result in the loss of a valuable carbon sink, further accelerating climate change.

The Atlantic circulation has slowed significantly in the distant past. During glacial periods when ice sheets that covered large parts of the planet were melting, the influx of fresh water slowed the Atlantic circulation, triggering huge climate fluctuations.

So, when will we see this tipping point?

The big question – when will the Atlantic circulation reach a tipping point – remains unanswered. Observations don’t go back far enough to provide a clear result. While a recent study suggested that the conveyor belt is rapidly approaching its tipping point, possibly within a few years, these statistical analyses made several assumptions that give rise to uncertainty.

Instead, we were able to develop a physics-based and observable early warning signal involving the salinity transport at the southern boundary of the Atlantic Ocean. Once a threshold is reached, the tipping point is likely to follow in one to four decades.

The climate impacts from our study underline the severity of such an abrupt conveyor belt collapse. The temperature, sea level and precipitation changes will severely affect society, and the climate shifts are unstoppable on human time scales.

It might seem counterintuitive to worry about extreme cold as the planet warms, but if the main Atlantic Ocean circulation shuts down from too much meltwater pouring in, that’s the risk ahead.

This article was updated on Feb. 11, 2024, to fix a typo: The experiment found temperatures in parts of Europe changed by more than 5 F per decade.

René van Westen, Postdoctoral Researcher in Climate Physics, Utrecht University; Henk A. Dijkstra, Professor of Physics, Utrecht University, and Michael Kliphuis, Climate Model Specialist, Utrecht University

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

The global climate is changing and the Arctic is warming rapidly. These are objectively true statements that most people have come to accept.

But it is also true that Earth’s climate has never been stagnant and climate anomalies have been frequent throughout the past.

How then, do we understand our current situation relative to past climate shifts? Are the impacts of modern climate change comparable to those of the medieval warm period (MWP) or the little ice age (LIA)?

Our recently published study in Anthropocene demonstrates a much more substantial impact to polar bears resulting from recent climate change compared to observations over the last 4,000 years. This suggests that current climatic changes are, indeed, unprecedented in human history.

Ecosystem background

Predators at the top of the food chain, like polar bears, reflect changes across the entire ecosystem, all the way down to microscopic algae.

In the Arctic, the base of the food web is sourced from two categories: sea ice-associated algae and open-water phytoplankton, which are distinguishable through their carbon isotopes.

In our study area — centred on Lancaster Sound in the Canadian Arctic Archipelago — the food web is fed by a combination of both sea ice algae and phytoplankton. We can assess the relative importance of these two sources through the stable isotopes incorporated into the tissues of animals.

The relative abundance of carbon isotopes does not change as they are transferred through the food web, so these isotopes tell us about the carbon sources at the base of the food web. Nitrogen isotopes do change as they are passed up the food chain, which tells us who is eating whom.

Results from our study

In our study we examined stable carbon and nitrogen isotopes in polar bear bone collagen.

The polar bears were all from the Lancaster Sound sub-population and spanned the last 4,000 years. We acquired samples of modern polar bear (1998-2007) obtained through hunting and we were able to compare them to samples from archaeological excavations conducted in the region.

The span of time captured by the archaeological samples was vast, but by dividing them into time bins associated with the cultural traditions in the region we were able to compare the samples across time before present (BP): pre-Dorset (4000-2800 years BP), Dorset (1500-700 BP) and Thule (700-500 BP).

The Dorset/Thule cultural transition occurred at the onset of the medieval warm period, so a comparison of these time bins allows us to look at the state of the food web before and during a known climate shift. The Thule time bin also extends into the beginning of the little ice age giving us a glimpse into that period as well.

What it all means

First, the good news. The results of the nitrogen isotopes showed that throughout time, 4,000 years BP to the present, the structure of the Lancaster Sound food web was relatively unchanged. Polar bears eat seals, seals eat cod, cod eat zooplankton, et cetera. There were no surprising shifts in the diets of polar bears despite past and present climate change. This is comforting.

The results of the carbon isotopes tell a less encouraging story, however. Throughout the four millennia encapsulated by the ancient time bins, we saw stability in the mixture of sea ice algae and open water phytoplankton. We did not detect a difference in the origin of carbon at the base of the food web resulting from the medieval warm period or the little ice age.

The modern samples, however, showed a significant difference in the source of carbon, resulting from a greater proportion of open water phytoplankton and less reliance on sea ice algae.

Evidence of a warming climate

Sea ice is an important habitat in the high Arctic. For polar bears it is a platform for hunting. For ringed seals, the primary prey of polar bears, it is a platform for denning and raising young.

The algae that grows in association with sea ice is also very important for jumpstarting biological productivity before the open water season. Our study shows that the loss of biological productivity associated with sea ice is unprecedented on a very long timescale.

Archaeological materials can provide valuable context to the ongoing climate discussion. Much of the valuable work being undertaken is tracking ecosystem changes on a short timescale, seasons to decades. But as we have demonstrated, the Arctic has already changed, so we should not always assume that we are looking at a pristine or undisturbed state.

Image by Peter Fischer from Pixabay

Adding a lens that looks back into the distant past gives resolution and context to our collective understanding of our situation.

In this case, we have illustrated the magnitude of difference occurring in the modern Arctic, relative to past climate anomalies. The medieval warm period and onset of the little ice age were not visible in the isotopes of the Lancaster Sound food web but modern warming is very apparent. We can, therefore, not dismiss calls to action on climate change on the basis that the climate has always fluctuated.

Jennifer Routledge, PhD Candidate, Environmental and Life Sciences, Trent University

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

About 400,000 years ago, large parts of Greenland were ice-free. Scrubby tundra basked in the Sun’s rays on the island’s northwest highlands. Evidence suggests that a forest of spruce trees, buzzing with insects, covered the southern part of Greenland. Global sea level was much higher then, between 20 and 40 feet above today’s levels. Around the world, land that today is home to hundreds of millions of people was under water.

Scientists have known for awhile that the Greenland ice sheet had mostly disappeared at some point in the past million years, but not precisely when.

In a new study in the journal Science,
we determined the date, using frozen soil extracted during the Cold War from beneath a nearly mile-thick section of the Greenland ice sheet.

NSF UVM Community “Greenland’s ice is vulnerable: a mile of ice vanished from northwest Greenland 400,000 years ago”

The timing – about 416,000 years ago, with largely ice-free conditions lasting for as much as 14,000 years – is important. At that time, Earth and its early humans were going through one of the longest interglacial periods since ice sheets first covered the high latitudes 2.5 million years ago.

The length, magnitude and effects of that natural warming can help us understand the Earth that modern humans are now creating for the future.

A world preserved under the ice

In July 1966, American scientists and U.S. Army engineers completed a six-year effort to drill through the Greenland ice sheet. The drilling took place at Camp Century, one of the military’s most unusual bases – it was nuclear powered and made up of a series of tunnels dug into the Greenland ice sheet.

The drill site in northwest Greenland was 138 miles from the coast and underlain by 4,560 feet of ice. Once they reached the bottom of the ice, the team kept drilling 12 more feet into the frozen, rocky soil below.

In 1969, geophysicist Willi Dansgaard’s analysis of the ice core from Camp Century revealed for the first time the details of how Earth’s climate had changed dramatically over the last 125,000 years. Extended cold glacial periods when the ice expanded quickly gave way to warm interglacial periods when the ice melted and sea level rose, flooding coastal areas around the world.

For nearly 30 years, scientists paid little attention to the 12 feet of frozen soil from Camp Century. One study analyzed the pebbles to understand the bedrock beneath the ice sheet. Another suggested intriguingly that the frozen soil preserved evidence of a time warmer than today. But with no way to date the material, few people paid attention to these studies. By the 1990s, the frozen soil core had vanished.

Several years ago, our Danish colleagues found the lost soil buried deep in a Copenhagen freezer, and we formed an international team to analyze this unique frozen climate archive.

In the uppermost sample, we found perfectly preserved fossil plants – proof positive that the land far below Camp Century had been ice-free some time in the past – but when?

Dating ancient rock, twigs and dirt

Using samples cut from the center of the sediment core and prepared and analyzed in the dark so that the material retained an accurate memory of its last exposure to sunlight, we now know that the ice sheet covering northwest Greenland – nearly a mile thick today – vanished during the extended natural warm period known to climate scientists as MIS 11, between 424,000 and 374,000 years ago.

To determine more precisely when the ice sheet melted away, one of us, Tammy Rittenour, used a technique known as luminescence dating.

Over time, minerals accumulate energy as radioactive elements like uranium, thorium, and potassium decay and release radiation. The longer the sediment is buried, the more radiation accumulates as trapped electrons.

In the lab, specialized instruments measure tiny bits of energy, released as light from those minerals. That signal can be used to calculate how long the grains were buried, since the last exposure to sunlight would have released the trapped energy.

Paul Bierman’s laboratory at the University of Vermont dated the sample’s last time near the surface in a different way, using rare radioactive isotopes of aluminum and beryllium.

These isotopes form when cosmic rays, originating far from our solar system, slam into the rocks on Earth. Each isotope has a different half-life, meaning it decays at a different rate when buried.

By measuring both isotopes in the same sample, glacial geologist Drew Christ was able to determine that melting ice had exposed the sediment at the land surface for less than 14,000 years.

Ice sheet models run by Benjamin Keisling, now incorporating our new knowledge that Camp Century was ice-free 416,000 years ago, show that Greenland’s ice sheet must have shrunk significantly then.

At minimum, the edge of the ice retreated tens to hundreds of miles around much of the island during that period. Water from that melting ice raised global sea level at least 5 feet and perhaps as much as 20 feet compared to today.

Warnings for the future

The ancient frozen soil from beneath Greenland’s ice sheet warns of trouble ahead.

During the MIS 11 interglacial, Earth was warm and ice sheets were restricted to the high latitudes, a lot like today. Carbon dioxide levels in the atmosphere remained between 265 and 280 parts per million for about 30,000 years. MIS 11 lasted longer than most interglacials because of the impact of the shape of Earth’s orbit around the sun on solar radiation reaching the Arctic. Over these 30 millennia, that level of carbon dioxide triggered enough warming to melt much of the Greenland’s ice.

Today, our atmosphere contains 1.5 times more carbon dioxide than it did at MIS 11, around 420 parts per million, a concentration that has risen each year. Carbon dioxide traps heat, warming the planet. Too much of it in the atmosphere raises the global temperature, as the world is seeing now.

Over the past decade, as greenhouse gas emissions continued to rise, humans experienced the eight warmest years on record. July 2023 saw the hottest week on record, based on preliminary data. Such heat melts ice sheets, and the loss of ice further warms the planet as dark rock soaks up sunlight that bright white ice and snow once reflected.

Even if everyone stopped burning fossil fuels tomorrow, carbon dioxide levels in the atmosphere would remain elevated for thousands to tens of thousands of years. That’s because it takes a long time for carbon dioxide to move into soils, plants, the ocean and rocks. We are creating conditions conducive to a very long period of warmth, just like MIS 11.

Unless people dramatically lower the concentration of carbon dioxide in the atmosphere, evidence we found of Greenland’s past suggests a largely ice-free future for the island.

Everything we can do to reduce carbon emissions and sequester carbon that is already in the atmosphere will increase the chances that more of Greenland’s ice survives.

The alternative is a world that could look a lot like MIS 11 – or even more extreme: a warm Earth, shrinking ice sheets, rising sea level, and waves rolling over Miami, Mumbai, India and Venice, Italy.

Paul Bierman, Fellow of the Gund Institute for Environment, Professor of Natural Resources and Environmental Science, University of Vermont and Tammy Rittenour, Professor of Geosciences and Director of Luminescence Lab, Utah State University

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

I’m striding along the steep bank of a raging white-water torrent, and even though the canyon is only about the width of a highway, the river’s flow is greater than that of London’s Thames. The deafening roar and rumble of the cascading water is incredible – a humbling reminder of the raw power of nature.

As I round a corner, I am awestruck at a completely surreal sight: A gaping fissure has opened in the riverbed, and it is swallowing the water in a massive whirlpool, sending up huge spumes of spray. This might sound like a computer-generated scene from a blockbuster action movie – but it’s real.

A moulin is forming right in front of me on the Greenland ice sheet. Only this really shouldn’t be happening here – current scientific understanding doesn’t accommodate this reality.

As a glaciologist, I’ve spent 35 years investigating how meltwater affects the flow and stability of glaciers and ice sheets.

This gaping hole that’s opening up at the surface is merely the beginning of the meltwater’s journey through the guts of the ice sheet. As it funnels into moulins, it bores a complex network of tunnels through the ice sheet that extend many hundreds of meters down, all the way to the ice sheet bed.

When it reaches the bed, the meltwater decants into the ice sheet’s subglacial drainage system – much like an urban stormwater network, though one that is constantly evolving and backing up. It carries the meltwater to the ice margins and ultimately ends up in the ocean, with major consequences for the thermodynamics and flow of the overlying ice sheet.

Scenes like this and new research into the ice sheet’s mechanics are challenging traditional thinking about what happens inside and under ice sheets, where observations are extremely challenging yet have stark implications. They suggest that Earth’s remaining ice sheets in Greenland and Antarctica are far more vulnerable to climate warming than models predict, and that the ice sheets may be destabilizing from inside.

This is a tragedy in the making for the half a billion people who populate vulnerable coastal regions, since the Greenland and Antarctic ice sheets are effectively giant frozen freshwater reservoirs locking up in excess of 65 meters (over 200 feet) of equivalent global sea level rise. Since the 1990s their mass loss has been accelerating, becoming both the primary contributor to and the wild card in future sea level rise.

How narrow cracks become gaping maws in ice

Moulins are near-vertical conduits that capture and funnel the meltwater runoff from the ice surface each summer. There are many thousands across Greenland, and they can grow to impressive sizes because of the thickness of the ice coupled with the exceptionally high surface melt rates experienced. These gaping chasms can be as large as tennis courts at the surface, with chambers hidden in the ice beneath that could swallow cathedrals.

But this new moulin I’ve witnessed is really far from any crevasse fields and melt lakes, where current scientific understanding dictates that they should form.

In a new paper, Dave Chandler and I demonstrate that ice sheets are littered with millions of tiny hairline cracks that are forced open by the meltwater from the rivers and streams that intercept them.

Because glacier ice is so brittle at the surface, such cracks are ubiquitous across the melt zones of all glaciers, ice sheets and ice shelves. Yet because they are so tiny, they can’t be detected by satellite remote sensing.

Under most conditions, we find that stream-fed hydrofracture like this allows water to penetrate hundreds of meters down before freezing closed, without the crack’s necessarily penetrating to the bed to form a full-fledged moulin. But, even these partial-depth hydrofractures have considerable impact on ice sheet stability.

As the water pours in, it damages the ice sheet structure and releases its latent heat. The ice fabric warms and softens and, hence, flows and melts faster, just like warmed-up candle wax.

The stream-driven hydrofractures mechanically damage the ice and transfer heat into the guts of the ice sheet, destabilizing it from the inside. Ultimately, the internal fabric and structural integrity of ice sheets is becoming more vulnerable to climate warming.

Emerging processes that speed up ice loss

Over the past two decades that scientists have tracked ice sheet melt and flow in earnest, melt events have become more common and more intense as global temperatures rise – further exacerbated by Arctic warming of almost four times the global mean.

The ice sheet is also flowing and calving icebergs much faster. It has lost about 270 billion metric tons of ice per year since 2002: over a centimeter and a half (half an inch) of global sea-level rise. Greenland is now, on average, contributing around 1 millimeter (0.04 inches) to the sea level budget annually.

A 2022 study found that even if atmospheric warming stopped now, at least 27 centimeters – nearly 1 foot – of sea level rise is inevitable because of Greenland’s imbalance with its past two decades of climate.

Understanding the risks ahead is crucial. However, the current generation of ice sheet models used to assess how Greenland and Antarctica will respond to warming in the future don’t account for amplification processes that are being discovered. That means the models’ sea-level rise estimates, used to inform Intergovernmental Panel on Climate Change (IPCC) reports and policymakers worldwide, are conservative and lowballing the rates of global sea rise in a warming world.

Our new finding is just the latest. Recent studies have shown that:

• Warming ocean currents are intruding into the Antarctic and Greenland coastlines, flowing under the ice shelves to undercut outlet glaciers and destabilize their calving fronts.

• Increasing rainfall across the Greenland ice sheet not only depletes snow accumulation, it also accelerates surface melting and ice flow.

• Algae and microbes, along with surface snowpack melt, darken the ice sheet surface, absorbing more solar radiation, which also accelerates ice melt.

• Superimposed ice slabs within the snowpack are forming across the accumulation zone, forming an impermeable barrier that depletes meltwater retention and drives extraordinary runoff.

• Water at the base of the ice sheet thaws and softens the frozen bed, thereby triggering basal sliding and accelerating interior ice sheet flow to the margins.

In the last months, other papers also described previously unknown feedback processes underway beneath ice sheets that computer models currently can’t include. Often these processes happen at too fine a scale for models to pick up, or the model’s simplistic physics means the processes themselves can’t be captured.

Two such studies independently identify enhanced submarine melting at the grounding line in Greenland and Antarctica, where large outlet glaciers and ice streams drain into the sea and start to lift off their beds as floating ice shelves. These processes greatly accelerate ice sheet response to climate change and, in the case of Greenland, could potentially double future mass loss and its contribution to rising sea level.

Current climate models lowball the risks

Along with other applied glaciologists, “structured expert judgment” and a few candid modelers, I contend that the current generation of ice sheet models used to inform the IPCC are not capturing the abrupt changes being observed in Greenland and Antarctica, or the risks that lie ahead.

Ice sheet models don’t include these emerging feedbacks and respond over millennia to strong-warming perturbations, leading to sluggish sea level forecasts that are lulling policymakers into a false sense of security. We’ve come a long way since the first IPCC reports in the early 1990s, which treated polar ice sheets as completely static entities, but we’re still short of capturing reality.

As a committed field scientist, I am keenly aware of how privileged I am to work in these sublime environments, where what I observe inspires and humbles. But it also fills me with foreboding for our low-lying coastal regions and what’s ahead for the 10% or so of the world’s population that lives in them.

Alun Hubbard, Professor of Glaciology, Arctic Five Chair, University of Tromsø

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

Featured Image: Richard Bates and Alun Hubbard kayak a meltwater stream on Greenland’s Petermann Glacier, towing an ice radar that reveals it’s riddled with fractures.
Nick Cobbing.

(The Conversation) – The Arctic Ocean could be ice-free in summer by the 2030s, even if we do a good job of reducing emissions between now and then. That’s the worrying conclusion of a new study in Nature Communications.

Predictions of an ice-free Arctic Ocean have a long and complicated history, and the 2030s is sooner than most scientists had thought possible (though it is later than some had wrongly forecast). What we know for sure is the disappearance of sea ice at the top of the world would not only be an emblematic sign of climate breakdown, but it would have global, damaging and dangerous consequences.

The Arctic has been experiencing climate heating faster than any other part of the planet. As it is at the frontline of climate change, the eyes of many scientists and local indigenous people have been on the sea ice that covers much of the Arctic Ocean in winter. This thin film of frozen seawater expands and contracts with the seasons, reaching a minimum area in September each year.

The ice which remains at the end of summer is called multiyear sea ice and is considerably thicker than its seasonal counterpart. It acts as barrier to the transfer of both moisture and heat between the ocean and atmosphere. Over the past 40 years this multiyear sea ice has shrunk from around 7 million sq km to 4 million. That is a loss equivalent to roughly the size of India or 12 UKs. In other words, it’s a big signal, one of the most stark and dramatic signs of fundamental change to the climate system anywhere in the world.

As a consequence, there has been considerable effort invested in determining when the Arctic Ocean might first become ice-free in summer, sometimes called a “blue ocean event” and defined as when the sea ice area drops below 1 million sq kms. This threshold is used mainly because older, thicker ice along parts of Canada and northern Greenland is expected to remain long after the rest of the Arctic Ocean is ice-free. We can’t put an exact date on the last blue ocean event, but one in the near future would likely mean open water at the North Pole for the first time in thousands of years.

One problem with predicting when this might occur is that sea ice is notoriously difficult to model because it is influenced by both atmospheric and oceanic circulation as well as the flow of heat between these two parts of the climate system. That means that the climate models – powerful computer programs used to simulate the environment – need to get all of these components right to be able to accurately predict changes in sea ice extent.

Melting faster than models predicted

Back in the 2000s, an assessment of early generations of climate models found they generally underpredicted the loss of sea ice when compared to satellite data showing what actually happened. The models predicted a loss of about 2.5% per decade, while the observations were closer to 8%.

The next generation of models did better but were still not matching observations which, at that time were suggesting a blue ocean event would happen by mid-century. Indeed, the latest IPCC climate science report, published in 2021, reaches a similar conclusion about the timing of an ice-free Arctic Ocean.

Photo by NOAA on Unsplash

As a consequence of the problems with the climate models, some scientists have attempted to extrapolate the observational record resulting in the controversial and, ultimately, incorrect assertion that this would happen during the mid 2010s. This did not help the credibility of the scientific community and its ability to make reliable projections.

Ice-free by 2030?

The scientists behind the latest study have taken a different approach by, in effect, calibrating the models with the observations and then using this calibrated solution to project sea ice decline. This makes a lot of sense, because it reduces the effect of small biases in the climate models that can in turn bias the sea ice projections. They call these “observationally constrained” projections and find that the Arctic could become ice-free in summer as early as 2030, even if we do a good job of reducing emissions between now and then.

There is still plenty of uncertainty around the exact date – about 20 years or so – because of natural chaotic fluctuations in the climate system. But compared to previous research, the new study still brings forward the most likely timing of a blue ocean event by about a decade.

Why this matters

You might be asking the question: so what? Other than some polar bears not being able to hunt in the same way, why does it matter? Perhaps there are even benefits as the previous US secretary of state, Mike Pompeo, once declared – it means ships from Asia can potentially save around 3,000 miles of journey to European ports in summer at least.

But Arctic sea ice is an important component of the climate system. As it dramatically reduces the amount of sunlight absorbed by the ocean, removing this ice is predicted to further accelerate warming, through a process known as a positive feedback. This, in turn, will make the Greenland ice sheet melt faster, which is already a major contributor to sea level rise.

The loss of sea ice in summer would also mean changes in atmospheric circulation and storm tracks, and fundamental shifts in ocean biological activity. These are just some of the highly undesirable consequences and it is fair to say that the disadvantages will far outweigh the slender benefits.

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Jonathan Bamber, Professor of Physical Geography, University of Bristol

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

Coastal erosion in Gleneden Beach in March 2021 caused houses to sit on the edge of the cliff. (Courtesy of Hailey Bond)

Wildfires have a big impact on health. Poor air quality affects early childhood health and can cause lower birth weights, Fleishman said. Smoke also aggravates cardiac and respiratory conditions, which in turn, can overload the health care system as COVID did during the pandemic.

But leaders – in Oregon and elsewhere – can help stem some of the impact of climate change, Fleishman said.

“It depends in part on what people around the country and around the world want to do and are able to do in terms of both adapting to climate change and mitigating the causes of climate change,” Fleishman said.

This session the Legislature is considering an array of bills aimed at improving the state’s wildfire strategy and forest management. At the same time, the State Fire Marshal’s office is educating the public about protecting their homes from wildfires while officials redo the wildfire risk map. The Oregon Department of Forestry will notify homeowners in high and extreme risk and they may be subject to future changes to hardscape their homes from wildfires.

And last year new rules from Oregon Occupational Safety and Health went into effect, mandating breaks for workers exposed to high heat with designated rest areas and water. Employers also have to provide respirator masks in smoky conditions.

“Oregon is a leader in climate response strategies and worker protections,” Fleishman said. “We hope this assessment will support the state’s ongoing efforts to advance climate equity and evidence-based investments in adaptation and mitigation.”

 

Lynne Terry

Lynne Terry has more than 30 years of journalism experience, including a recent stint as editor of The Lund Report, a highly regarded health news site. She reported on health and food safety in her 18 years at The Oregonian, was a senior producer at Oregon Public Broadcasting and Paris correspondent for National Public Radio for nine years.

 

Oregon Capital Chronicle

Published  under Creative Commons license CC BY-NC-ND 4.0.