Satellite images have helped scientists shed light on melting from the underside of Antarctica’s ice shelves.
Their findings help to explain the formation of huge inverted canyons in the underbelly of ice shelves. Ice shelves extend from the ice sheet to reach out onto coastal waters. Understanding how these shelves change is important, as they help to buttress ice sheets, slowing their flow as they creep seaward.
The recently discovered canyons are hidden from view but can be mapped from satellite data. They potentially make the ice shelves more fragile and may cause speed-up of the ice sheet, adding to sea level rise. Researchers have studied the Dotson ice shelf in West Antarctica, by analysing data from European Space Agency satellites. They found that warm ocean waters flows to the underside of the ice shelf and is stirred by the Earth’s rotation, causing canyons to form under the ice.
Scientists used ESA’s CryoSat-2 to study changes in the surface of the ice sheet and the Copernicus Sentinel-1 mission to study how ice shelves flow. Scientists suggest that the pattern of melting that they have uncovered has been taking place for at least 25 years – the entire time that satellites have been recording changes in Antarctica. Their study of the Dotson ice shelf shows that a channel up to 200 metres deep and 15 km across has been calved over time. This runs the entire length of the underside of the ice shelf. The canyon is deepening by about 7 metres a year and the ice above is heavily crevassed. Researchers estimate that 4 billion tonnes of freshwater from this canyon alone is poured into the Southern Ocean every year, and that the entire Dotson shelf releases about 40 billion tonnes each year.
"Ice shelves are already suffering from thinning. These deepening canyons mean that fractures are more likely to develop and the grounded ice upstream more likely to flow faster than would be the case otherwise. This is the first time that we’ve been able to see this process in the making and we will now expand our area of interest to the shelves all around Antarctica to see how they are responding. We couldn’t do this without CryoSat-2 and the European Commission’s Copernicus Sentinel missions.”
- Noel Gourmelen, School of GeoSciences
"This study reveals the complexity with which the ocean interacts with Antarctic ice shelves, and will be of value in assessing the future of the ice-ocean-biology system of the Antarctic coastline, and its sensitivity to changes in climate."
- Dan Goldberg, School of GeoSciences
N Gourmelen, D N Goldberg, K Snow, S F Henley, R G Bingham, S Kimura, A E Hogg, A Shepherd, J Mouginot, J T M Lenaerts, S R M Ligtenberg, W J van de Berg. Geophysical Research Letters, October 2017. Channelised Melting Drives Thinning Under a Rapidly Melting Antarctic Ice Shelf
European Space Agency: CryoSat Programme