melt – Cabot Institute for the Environment blog

We built an AI model that analysed millions of images of retreating glaciers – what it found is alarming

Posted on January 20, 2025 by amanda.woodman-hardy

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.

Map of Arctic — Svalbard (in red) belongs to Norway and is one of the northernmost places int he world.
Peter Hermes Furian / shutterstock

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.

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.

Glacier flows into sea — Svalbard is slightly smaller than Scotland yet has more than 2,000 glaciers.
RUBEN M RAMOS / shutterstock

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.

Aerial view of island of mountains and glaciers — Svalbard’s many glaciers grow and shrink with the seasons.
Wildnerdpix / shutterstock

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.

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This blog is written by 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.

How glacier algae are challenging the way we think about evolution

Posted on June 19, 2024 by amanda.woodman-hardy

People often underestimate tiny beings. But microscopic algal cells not only evolved to thrive in one of the most extreme habitats on Earth – glaciers – but are also shaping them.

With a team of scientists from the UK and Canada, we traced the evolution of purple algae back hundreds of millions of years and our findings challenge a key idea about how evolution works. Though small, these algae are having a dramatic effect on the glaciers they live on.

Glaciers are among the planet’s fastest changing ecosystems. During the summer melt season as liquid water forms on glaciers, blooms of purple algae darken the surface of the ice, accelerating the rate of melt. This fascinating adaptation to glaciers requires microscopic algae to control their growth and photosynthesis. This must be balanced with tolerance of extreme ice melt, temperature and light exposure.

Our study, published in New Phytologist, reveals how and when their adaptations to live in these extreme environments first evolved. We sequenced and analysed genome data of the glacier algae Ancylonema nordenskiöldii. Our results show that the purple colour of glacier algae, which acts like a sunscreen, was generated by new genes involved in pigment production.

This pigment, purpurogallin, protects algal cells from damage of ultraviolet (UV) and visible light. It is also linked with tolerance of low temperatures and desiccation, characteristic features of glacial environments. Our genetic analysis suggests that the evolution of this purple pigment was probably vital for several adaptations in glacier algae.

We also identified new genes that helped increase the algae’s tolerance to UV and visible light, important adaptations for living in a bright, exposed environment. Interestingly these were linked to increased light perception as well as improved mechanisms of repair to sun damage. This work reveals how algae are adapted to live on glaciers in the present day.

Next, we wanted to understand when this adaptation evolved in Earth’s deep history.

The evolution of glacier algae

Earth has experienced many fluctuations of colder and warmer climates. Across thousands and sometimes millions of years, global climates have changed slowly between glacial (cold) to interglacial (warm) periods.

One of the most dramatic cold periods was the Cryogenian, dating back to 720-635 million years ago, when Earth was almost entirely covered in snow and ice. So widespread were these glaciations, they are sometimes referred to by scientists as “Snowball Earth”.

Scientists think that these conditions would have been similar to the glaciers and ice sheets we see on Earth today. So we wondered could this period be the force driving the evolution of glacier algae?

After analysing genetic data and fossilised algae, we estimated that glacier algae evolved around 520-455 million years ago. This suggests that the evolution of glacier algae was not linked to the Snowball Earth environments of the Cryogenian.

As the origin of glacier algae is later than the Cryogenian, a more recent glacial period must have been the driver of glacial adaptations in algae. Scientists think there has continuously been glacial environments on Earth up to 60 million years ago.

We did, however, identify that the common ancestor of glacier algae and land plants evolved around the Cryogenian.

In February 2024, our previous analysis demonstrated that this ancient algae was multicellular. The group containing glacier algae lost the ability to create complex multicellular forms, possibly in response to the extreme environmental pressures of the Cryogenian.

Rather than becoming more complex, we have demonstrated that these algae became simple and persevered to the present day. This is an example of evolution by reducing complexity. It also contradicts the well-established “march of progress” hypothesis, the idea that organisms evolve into increasingly complex versions of their ancestors.

Our work showed that this loss of multicellularity was accompanied by a huge loss of genetic diversity. These lost genes were mainly linked to multicellular development. This is a signature of the evolution of their simple morphology from a more complex ancestor.

Over the last 700 million years, these algae have survived by being tiny, insulated from cold and protected from the Sun. These adaptations prepared them for life on glaciers in the present day.

So specialised is this adaptation, that only a handful of algae have evolved to live on glaciers. This is in contrast to the hundreds of algal species living on snow. Despite this, glacier algae have dramatic effects across vast ice fields when liquid water forms on glacier surfaces. In 2016, on the Greenland ice sheet, algal growth led to an additional 4,400–6,000 million tonnes of runoff.

Understanding these algae helps us appreciate their role in shaping fragile ecosystems.

Our study gives insight into the evolutionary journey of glacier algae from the deep past to the present. As we face a changing climate, understanding these microscopic organisms is key to predicting the future of Earth’s icy environments.

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This blog is written by Dr Alexander Bowles, Postdoctoral research associate, University of Bristol

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

Siberia heatwave: why the Arctic is warming so much faster than the rest of the world

Posted on June 29, 2020March 31, 2023 by janet.crompton

Smoke from wildfires cloaks the skies over Siberia, June 23 2020.
EPA-EFE/NASA

On the eve of the summer solstice, something very worrying happened in the Arctic Circle. For the first time in recorded history, temperatures reached 38°C (101°F) in a remote Siberian town – 18°C warmer than the maximum daily average for June in this part of the world, and the all-time temperature record for the region.

New records are being set every year, and not just for maximum temperatures, but for melting ice and wildfires too. That’s because air temperatures across the Arctic have been increasing at a rate that is about twice the global average.

All that heat has consequences. Siberia’s recent heatwave, and high summer temperatures in previous years, have been accelerating the melting of Arctic permafrost. This is the permanently frozen ground which has a thin surface layer that melts and refreezes each year. As temperatures rise, the surface layer gets deeper and structures embedded in it start to fail as the ground beneath them expands and contracts. This is what is partly to blame for the catastrophic oil spill that occurred in Siberia in June 2020, when a fuel reservoir collapsed and released more than 21,000 tonnes of fuel – the largest ever spill in the Arctic.

So what is wrong with the Arctic, and why does climate change here seem so much more severe compared to the rest of the world?

The warming models predicted

Scientists have developed models of the global climate system, called general circulation models, or GCMs for short, that reproduce the major patterns seen in weather observations. This helps us track and predict the behaviour of climate phenomena such as the Indian monsoon, El Niño, Southern Oscillations and ocean circulation such as the gulf stream.

GCMs have been used to project changes to the climate in a world with more atmospheric CO₂ since the 1990s. A common feature of these models is an effect called polar amplification. This is where warming is intensified in the polar regions and especially in the Arctic. The amplification can be between two and two and a half, meaning that for every degree of global warming, the Arctic will see double or more. This is a robust feature of our climate models, but why does it happen?

Fresh snow is the brightest natural surface on the planet. It has an albedo of about 0.85, which means that 85% of solar radiation falling on it is reflected back out to space. The ocean is the opposite – it’s the darkest natural surface on the planet and reflects just 10% of radiation (it has an albedo of 0.1). In winter, the Arctic Ocean, which covers the North Pole, is covered in sea ice and that sea ice has an insulating layer of snow on it. It’s like a huge, bright thermal blanket protecting the dark ocean underneath. As temperatures rise in spring, sea ice melts, exposing the dark ocean underneath, which absorbs even more solar radiation, increasing warming of the region, which melts even more ice. This is a positive feedback loop which is often referred to as the ice-albedo feedback mechanism.

Melting Arctic sea ice is increasing warming in the region.
Jonathan Bamber, Author provided

This ice-albedo (really snow-albedo) feedback is particular potent in the Arctic because the Arctic Ocean is almost landlocked by Eurasia and North America, and it’s less easy (compared to the Antarctic) for ocean currents to move the sea ice around and out of the region. As a result, sea ice that stays in the Arctic for longer than a year has been declining at a rate of about 13% per decade since satellite records began in the late 1970s.

In fact, there is evidence to indicate that sea ice extent has not been this low for at least the last 1,500 years. Extreme melt events over the Greenland Ice Sheet, that used to occur once in every 150 years, have been seen in 2012 and now 2019. Ice core data shows that the enhanced surface melting on the ice sheet over the past decade is unprecedented over the past three and a half centuries and potentially over the past 7,000 years.

In other words, the record-breaking temperatures seen this summer in the Arctic are not a “one-off”. They are part of a long-term trend that was predicted by climate models decades ago. Today, we’re seeing the results, with permafrost thaw and sea ice and ice sheet melting. The Arctic has sometimes been described as the canary in the coal mine for climate breakdown. Well it’s singing pretty loudly right now and it will get louder and louder in years to come.

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This blog is written by Cabot Institute member 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.

Professor Jonathan Bamber