Human-driven climate change significantly intensified the retreat of one the most important glaciers in the Antarctica during the twentieth century.
The Pine Island Glacier, which drains a large part of the West Antarctic Ice Sheet into the Amundsen Sea, is one of the single biggest contributors to global sea level rise.
This landmark research, led by scientists at King’s College London and the British Antarctic Survey and published in The Cryosphere, is the first study to directly attribute the changes of a major Antarctic outlet glacier to the activities of humans.
The authors of the study are also warning that the impact of human activity will continue to shape Antarctic ice loss for centuries.
The research finds that greenhouse gas emissions increased the retreat of Pine Island Glacier by around 18-20% since the 1940s. This has added several kilometres to its landward withdrawal.
Lead author Dr Alex Bradley, Department of Geography, says that the scale of retreat seen over the industrial era is very unlikely to have occurred without human influence.
“Our results show that climate change made the retreat of the Pine Island Glacier substantially worse,” said Dr Bradley, the study’s lead author. “Without sustained warming of the surrounding ocean since the mid twentieth century, the glacier would not have retreated as far as it has.”
While attribution studies have previously linked the retreat of mountain glaciers to human‑driven warming, applying similar techniques to Antarctic glaciers has proven far more challenging.
“This kind of work has become common for heatwaves and floods, and increasingly for mountain glaciers,” said Dr Bradley. “What’s new here is showing, quantitatively, how human influence has altered the course of a major Antarctic glacier.”
Mira Adhikari, an Ice Sheet Modeller at the British Antarctic Survey , said: “Our results add to growing evidence that human-driven climate change is likely 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."
Geological records indicate that Pine Island Glacier began retreating rapidly in the 1940s, which was likely due to stronger intrusions of warm ocean water beneath its ice shelf. This study showed that human-driven ocean warming, which is thought to have begun in the 1960s, enhanced the retreat after this.
Using a model that simulates glacier behaviour using observed changes in ice thickness and retreat to constrain its estimates, the researchers compared scenarios with and without human-driven global warming.
By 2015, simulations excluding human influence showed around 4 km less grounding‑line retreat. That difference accounts for just under one‑fifth of the glacier’s observed retreat.
Looking ahead, 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 in the twenty-second century.
“Ice sheets respond slowly,” Dr Bradley said. “The impacts of today’s emissions will continue to shape Antarctic ice loss for centuries.”
Journal
The Cryosphere