In one of the most remote locations in the world, a glacier that is two thirds of the size of the UK is slowly retreating. If it disappears completely, the impact will be felt round the world.
Some 9,000 miles away in London, Dr Alex Bradley, a mathematician and climate scientist, has used computer modelling to try and understand what’s causing it, and how much humans are to blame.
He is the lead author on a piece of research with the British Antarctic Survey, which has – for the first time – attributed retreat of one of the world’s largest glaciers to human-driven climate warming.
Our results show that climate change made the retreat of the Pine Island Glacier substantially worse. Without sustained warming of the surrounding ocean since the mid twentieth century, the glacier would not have retreated as far as it has.– Dr Alex Bradley
The Pine Island Glacier
The Pine Island Glacier is in Western Antarctica, far south of South America. The size of the glacier is difficult to comprehend and goes far deeper than the “floating tongue” on the surface. The entire system that feeds it is around 170,000km2.
It’s one of the most remote places on Earth, over 1,000km from the nearest research base. While being difficult to access, it’s remained highly dynamic and has changed significantly over the last century.
Since the 1950s, clear signs of “retreat” have been observed, meaning that it’s losing more ice than it’s gaining. Now, it’s one of the fastest melting glaciers in Antarctica and responsible for about 13% of the continent’s total ice loss.
Aerial images showing calving from Pine Island Glacier from 2000-2019 (gif via NASA).
Retreat can be caused by multiple ways: by melting into the sea or slower snowfall on land. But Pine Island Glacier is notable for its “calving” meaning the loss of ice through parts of the glacier breaking into the sea. What once happened around every six years is now an annual event, and in 2018 its largest iceberg calved at 225km2, about twice the size of Paris.
The Pine Island Glacier and the neighbouring Thwaites Glacier are two of the largest ice streams in the Antarctic. If they were to both collapse completely, it’s estimated that sea levels would rise by 1.5 meters globally, which would permanently redraw our coastlines, threaten wildlife and displace human settlements across the world.
Alex’s research journey
After completing a DPhil in Mathematics from the University of Oxford, Alex has turned his expertise to climate science. Now a lecturer in Climate and Environmental Science in our Department of Geography, Alex is interested in using mathematical and computational modelling to better understand our changing frozen landscapes. In his research, he’s helped to attribute sea level rise from ice sheets to climate change and has projected future sea level rises.
To do this, Alex has used computer modelling. Modelling in glaciology involves entering inputs like what we know about the effects of the industrial era (1850 to now) on our Earth’s atmosphere or geological data to recreate model conditions.
The model is then run thousands of times using different scenarios and assumptions. By comparing the results with real-world observations, researchers like Alex can identify which simulations best match reality and estimate how glaciers are likely to respond to future climate change. So, while satellite images can show us how glaciers look today, computer modelling can help simulate the past and help to predict the future.
British Antarctic Survey field camp on Pine Island Glacier.
Computer modelling has been part of several important insights into the behaviour of ice sheets. It has shown that some parts of West Antarctica are already near thresholds of significant change, and that in some cases retreat of sheets may be hard to stop when triggered even if temperatures stabilised.
The input data to inform these models can be taken from various sources, like satellite imaging, dating rocks left behind by retreating ice, testing sediments from oceans and drilling into the ice itself.
Some of this data has been gathered by organisations like the British Antarctic Survey, who have made a handful of trips to Pine Island Glacier. But the remoteness of the glacier means that field missions are incredibly difficult, making computational methods of research so important.
What’s new about this research?
This is the first ever study to directly attribute Antarctic glacier retreat to man-made climate change.
Alex and the research team, which also included fellow King’s academic Professor Tamsin Edwards and several colleagues from the British Antarctic Survey, concluded that it’s unlikely that the glacier would have melted as much as it has without human-driven warming.
Our results add to growing evidence that human-driven climate change is affecting even the most remote regions of the planet. Changes in Antarctica have global consequences, particularly for sea level rise, highlighting the far-reaching impacts of a warming world.– Dr Alex Bradley
Using what is known about the impacts of human-driven warming, the team could ascertain that it has accelerated the retreat of the glacier by 18% in the industrial era. Although, mapping the glaciers loss has led them to think that it’s been losing mass from 1750 due to multiple factors, including the 1940s event and human-driven warming.
So, where does this leave us? Using the same modelling system, the team projected 174 years into the future to the end of the twenty-second century. The models suggest Pine Island Glacier may briefly stabilise later this century as it encounters a ridge in the bedrock beneath it. However, that pause is likely to be temporary if warming continues, with human influence becoming the dominant driver of retreat again before 2200.
Scientists generally believe that damage already done can’t simply be reversed. However, significant measures could lessen the magnitude of the future loss, and the ice sheets are thought to be responsive to climate action: burning less fossil fuels means less sea level rise.
However, action will need to happen quick. “Ice sheets respond slowly,” Dr Bradley said. “The impacts of today’s emissions will continue to shape Antarctic ice loss for centuries.”