Scientists know the West Antarctic ice sheet \u2013 which includes Thwaites and Pine Island \u2013 is retreating because of warm water eroding the ice sheet from below.\u00a0<\/p>\n
But the extent to which this process has been driven by human-caused greenhouse gas emissions, as opposed to natural variations to the Earth\u2019s climate, remains unknown.<\/p>\n
Our study, published in the Cryosphere<\/a>, looks at how human-caused warming has contributed to the retreat of the Pine Island glacier since pre-industrial times.\u00a0<\/p>\n The research, the first attribution study of glacier retreat on Antarctica, finds that climate change has been responsible for around 4km \u2013 roughly a fifth \u2013 of the glacier\u2019s retreat.<\/p>\n The West Antarctic ice sheet\u00a0<\/p>\n Glaciers are frozen rivers of ice and snow that move slowly over land. They are found at high elevations on mountains and on ice sheets.\u00a0<\/p>\n There are two ice sheets on Earth \u2013 covering Antarctica and Greenland. Both were formed over millennia, as layers of snow compressed into dense ice.<\/p>\n Ice sheets grow and shrink depending on temperature and snowfall conditions. In the past, when global temperatures were much colder than present day, vast ice sheets also covered large areas of North America, Scandinavia and Patagonia.\u00a0<\/p>\n Today, human-driven climate change is accelerating the retreat of ice sheets<\/a>. This is contributing to sea level rise<\/a> and altering the Earth\u2019s climate system<\/a> by pumping vast quantities of fresh melt water into the ocean.\u00a0<\/p>\n Our research looks at the Pine Island glacier, which is found on the western part of the Antarctic ice sheet.<\/p>\n It is one of the fastest-melting glaciers in the world. Research has shown it has been responsible for a fifth of net ice loss<\/a> from the West Antarctic ice sheet, which, in turn, has been responsible for almost all ice loss in Antarctica<\/a> over the past 40 years.<\/p>\n At the coldest point of the last ice age<\/a> \u2013 the \u201clast glacial maximum<\/a>\u201d period around 20,000 years ago \u2013 the West Antarctic ice sheet was much bigger than it is today. Since then, it has retreated by approximately 500km \u2013 roughly the distance from Paris to London.<\/p>\n Most of this retreat took place between 10,000 and 20,000 years ago. For the past 10,000 years or so, the ice sheet has been about as big as it is today.\u00a0<\/p>\n Sediment records<\/a> beneath the Pine Island glacier reveal that, for hundreds of years until the 1940s, the glacier rested on a seabed ridge that is about 30km ahead of where it sits today.\u00a0<\/p>\n The sediment records also tell us that the Pine Island glacier started to retreat in the 1940s.\u00a0 This coincided with a strong El Ni\u00f1o event<\/a>, a recurring climate pattern<\/a> in the tropical Pacific that drives up global temperatures, that brought a large pulse of warm water to the ice sheet.\u00a0<\/p>\n This is illustrated in the figures below, which shows how the grounding line \u2013 the boundary between grounded and floating ice \u2013 of the Pine Island glacier shifted between pre-industrial times (red line) and 2015 (bright blue line).\u00a0<\/p>\n The map on the left shows an aerial view of grounding line retreat from pre-industrial times (red) to 2015 (blue). The graphic on the right illustrates how the grounding line has shifted across a cross-section of the glacier.\u00a0<\/p>\n Both illustrate how the glacier has contracted.\u00a0<\/p>\n Climate reconstructions<\/a> suggest that human-caused climate change only started to increase the amount of warm water reaching the West Antarctic ice sheet in the 1960s.\u00a0<\/p>\n This indicates that climate change started to affect the melt rate in the region 20 years after the retreat had already been initiated.\u00a0<\/p>\n In our research, we wanted to find out how important climate change was to the overall retreat since the 1940s.<\/p>\n Attributing ice sheet retreat\u00a0<\/p>\n Currently, scientists do not know precisely how much of the retreat of the world\u2019s ice sheets \u2013 and the associated sea level rise \u2013 is due to human-caused global warming.\u00a0<\/p>\n Through the field of attribution science<\/a>, the links between climate change and extreme weather and climate events, including heatwaves, wildfires and droughts, are routinely quantified by scientists.<\/p>\n In attribution studies<\/a>, scientists typically use climate models<\/a> 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 \u201ccounterfactual\u201d world that has not been affected by human-caused warming.<\/p>\n By comparing the model runs, scientists can assess how much climate change influenced an event.<\/p>\n To create these two modelled worlds in an Antarctic context, scientists need to run historical models for at least 200 years into the past. This is because ice sheets respond very slowly to changes in the climate, with very small changes year-on-year.<\/p>\n This presents a challenge, given the limited information available about ice sheet change before satellite records began in the 1970s.\u00a0<\/p>\n To build a picture of the ice sheets prior to this, scientists have to rely on a few, sparse, palaeoclimate records<\/a> \u2013 including sediment records<\/a> and seafloor imprints<\/a> \u2013 which tell us where ice was present in the past.<\/p>\n Reconstructing Pine Island\u2019s past\u00a0<\/p>\n![\"Graphic:](\"https:\/\/www.europesays.com\/ie\/wp-content\/uploads\/2026\/07\/anarctica1-01-scaled.webp\")
<\/p>\n![\"Map](\"https:\/\/www.europesays.com\/ie\/wp-content\/uploads\/2026\/07\/Screenshot-2026-06-25-at-4.39.30-PM-1024x381.png\")
Left: Map of the grounding line \u2013 where the ice transitions from grounding to floating \u2013 of Pine Island glacier in 2015 (bright blue) and in pre-industrial times (red). The background colour shows the bed depth. Right: The shape of the ice measured along the white line in (a) in 2015 (blue) and prior to the 1940s (red). The brown area shows the bed. Credit: Bradley, A et al. (2026<\/a>)<\/p>\n
![\"Grounding](\"https:\/\/www.europesays.com\/ie\/wp-content\/uploads\/2026\/07\/Screenshot-2026-06-25-at-4.41.42-PM.png\")
Grounding line retreat in reconstruction (blue) and counterfactual (green) of Pine Island glacier, with shading indicating uncertainty in these. Red dots with errors bars indicate observations of grounding line position in 1930 and 2015. Adapted from Bradley et al. (2026). <\/p>\n