Introduction
The Pine Island glacier in West Antarctica is one of the fastest-changing glaciers in the world. Alongside its neighbor, the Thwaites glacier, it is responsible for almost half the sea level rise caused by melting ice sheets in Antarctica.
Scientists know that the West Antarctic ice sheet – which includes Thwaites and Pine Island – is retreating because of warm water eroding the ice sheet from below.
However, the extent to which this process has been driven by human-caused greenhouse gas emissions, as opposed to natural variations to the Earth’s climate, remains unknown.
The Study
Our study, published in the Cryosphere, looks at how human-caused warming has contributed to the retreat of the Pine Island glacier since pre-industrial times.
The research, the first attribution study of glacier retreat on Antarctica, finds that climate change has been responsible for around 4 km – roughly a fifth – of the glacier’s retreat.
Attributing Ice Sheet Retreat
Currently, scientists do not know precisely how much of the retreat of the world’s ice sheets – and the associated sea level rise – is due to human-caused global warming.
Through the field of attribution science, the links between climate change and extreme weather and climate events, including heatwaves, wildfires, and droughts, are routinely quantified by scientists.
In attribution studies, scientists typically use climate models to simulate the severity or frequency of an event in two worlds. The first is our existing, climate-changed world and the second is a “counterfactual” world that has not been affected by human-caused warming.
Reconstructing Pine Island’s Past
To reconstruct the retreat of the Pine Island glacier – and, therefore, determine the role of climate change – we used a combination of physical climate models and machine learning.
First, we ran many simulations of our model under a range of different settings.
Then, we compared the results of these simulations to modern satellite observations and older sediment records, allowing us to narrow down the settings that were most realistic.
Interpreting the Numbers
Our work quantifies, for the first time, the role of climate change in the retreat of a glacier in the world’s ice sheets – directly linking greenhouse gas emissions with glacier decline.
We also find that the Pine Island glacier may have retreated even without climate change, just not as far.
One of the key challenges in our research arises from not knowing exactly how large the ice sheet was prior to satellite records.
Source / Reference: https://www.carbonbrief.org/guest-post-climate-change-has-caused-one-fifth-of-pine-island-glacier-retreat/