A new study led by the University of Cambridge has unveiled a surprising truth about Antarctica: its ice shelves hold far more meltwater than previously estimated. Thanks to artificial intelligence (AI) technology, researchers were able to map the continent’s surface and discovered that slush, a water-saturated snow mix, makes up a staggering 57 per cent of all meltwater.
The rest of the meltwater can be found in surface ponds and lakes. The findings have significant implications for the ongoing rise in sea levels worldwide. The study was published in the journal Nature Geoscience.
Slush, which forms when snow falls onto a water surface, generates 2.8 times more meltwater than standard climate models predict because it absorbs more solar heat compared to ice or snow alone.
Each summer, as Antarctica warms, water accumulates on the surfaces of its floating ice shelves. Research has shown that surface meltwater lakes can induce fractures and potentially cause these ice shelves to collapse, as the weight of the water can bend or break the ice.
However, assessing the influence of slush on ice shelf stability presents more complex challenges.
While satellite imagery can map meltwater lakes across much of Antarctica, mapping slush has been challenging due to its similarity to other features like cloud shadows, lead author Rebecca Dell from Cambridge’s Scott Polar Research Institute said in statement.
The Cambridge team, in collaboration with researchers from the University of Colorado Boulder and the Delft University of Technology, trained a machine learning model to generate monthly records of slush and meltwater lakes across 57 Antarctic ice shelves from 2013 to 2021.
Using their machine learning model, the researchers discovered that at the height of the Antarctic summer in January, more than half (57 per cent) of all meltwater on Antarctica’s ice shelves is held in slush. The remaining 43 per cent was in meltwater lakes.
Previous research focused solely on ponded water, ignoring this significant portion of the meltwater. Mapping both slush and ponded water is essential because slush helps reduce the air content in ice shelves, leads to the formation of ponded water, which can cause the ice shelf to flex and potentially break, and affects the surface energy balance of the ice shelves.
Dell explained that more information from the satellite can be used by analysing more wavelengths of light than the human eye can see, enabled by machine learning. This allows slush to be accurately identified and quickly mapped across the entire continent.
Slush across all of Antarctica's large ice shelves has never been comprehensively mapped on a large scale, leading to the neglect of over half of all surface meltwater until now, according to Dell,. This oversight could be significant for the hydrofracture process, wherein fractures in the ice can be created or enlarged by the weight of meltwater.
Co-author Professor Ian Willis from SPRI also stated that the research aim is to understand the amount of slush present during the Antarctic summer and its changes over time. Although slush is more solid than meltwater and won't cause hydrofracture like lake water, it is still a crucial factor to consider when predicting the potential collapse of ice shelves.