An underwater robot has enabled researchers to produce the first detailed, high-resolution 3-D maps of Antarctic sea ice. Scientists from the UK, USA and Australia say the new technology provides accurate ice thickness measurements from areas that were previously too difficult to access.
Scientists use a range of technologies and techniques to measure sea ice thickness. Satellite observations can measure large-scale thickness from space, but interpreting the data accurately can be difficult due to snow cover on the ice. Measurements made on the sea ice by drilling holes, together with visual observations from ships are critical for building a more complete picture, but difficulties in getting access to thicker areas of sea ice leaves gaps in the data. Now, with the Autonomous Underwater Vehicle (AUV) known as SeaBED, scientists have a new tool to fill this gap.
SeaBED was fitted with an upward-looking sonar in order to measure and map the underside of sea ice floes. The AUV operated at a depth of 20 to 30 meters and was driven in back and forth. These lines of data were merged to form high-resolution 3D bathymetric surveys of the underside of the ice.
The data from SeaBED, combined with airborne measurements of sea-ice surface elevation, ice coring surveys, and satellite observations, vastly improves scientists’ estimates of ice thickness and total sea ice volume.
“The AUV missions have given us a real insight into the nature of Antarctic sea ice – like looking through a microscope. We can now measure ice in far greater detail and were excited to measure ice up to 17 meters thick,” says co-author Jeremy Wilkinson from British Antarctic Survey.
The research was carried out by scientists at the Institute of Antarctic and Marine Science (Australia), Antarctic Climate and Ecosystem Cooperative Research Centre (Australia), Woods Hole Oceanographic Institution (USA) and British Antarctic Survey (UK).
Thick and deformed Antarctic sea ice mapped with autonomous underwater vehicles by G. Williams, T. Maksym, J. Wilkinson, C. Kunz, C. Murphy, P. Kimball, H. Singh is published in Nature Geoscience on 24 November 2014.
The AUV captured extensive deformation, with the underside revealing large ‘rubble fields’ of sea ice, suggesting repeated, multi-directional collisions between ice floes through the winter period. This is in contrast to what scientists previously understood from the Arctic, where larger sections of sea ice, under constant pressure, produce longer linear ‘ridge’ features.