West Antarctic laser lead: Seabed sand grains reveal ancient ice sheets

Sea level rise depends on the stability of the West Antarctic Ice Sheet, which we still know little about. Reconstructing past changes in the size of the ice sheet can help constrain our models and better predict sea level rise. To do this, we can use material eroded by the ice and deposited as marine sediment. We’ve developed a new way of tracing the source of this sediment, which allows us to infer where the ice was in the past and how it has changed through previous climate states. Fitting a Gaussian Mixture Model to cluster the lead isotopic data from individual sand grains in modern shelf sediments, we show a distinctive signature of Thwaites Glacier, known as “The weak underbelly of the West Antarctic ice sheet”. We then use the model to classify new data from the last 3 million years from an offshore core and assess the variability of the inputs from the different ice streams.