3-D map reveals underside of Antarctic ice

Wednesday 17th Oct 2012 by theWeather Club

Climate scientists from the Australian Antarctic Division have produced the first 3-D map of the surface beneath a sea ice floe in East Antarctica, revealing an inverted complex topography evocative of lakes and mountain ranges. During a two month voyage on the icebreaker Aurora Australis researchers used an Autonomous Underwater Vehicle (AUV) to gather the data. This free-swimming robotic submarine measured the topography of the underside of the sea ice in order to learn more about its thickness and volume.

The AUV project leader, Dr Guy Williams from the Antarctic Climate and Ecosystems Cooperative Research Centre, said this technology is a huge step forward in the way scientists measure sea ice thickness. "In the past we took drill line measurements or observed ice thickness as we moved through it on a ship, but with the AUV we can now use multi-beam sonar to measure an entire ice floe in unprecedented detail," Dr Williams said. For this project the AUV cruised in a grid pattern at a depth of 20m below the ice. The data was stored in an on-board computer during each dive and converted into the map once the data from a series of surveys had been combined.

AUV research engineer Dr Clay Kunz, from the Woods Hole Oceanographic Institution in the United States, explained that this project represented a radical change of use for the AUV which is normally used to map the sea floor. "For this Antarctic mission we mounted all the navigation and scientific instruments on top of the vehicle so they can measure upwards, rather than down," Dr Kunz says.

When the scientists combine measurements of the underside of the sea ice with surface measurements of snow and ice, they will have a comprehensive map of the entire ice floe.

Aerial measurements of sea ice thickness and snow cover are gathered by Antarctic Climate and Ecosystems Cooperative Research Centre Marine Glaciologist Dr Jan Lieser, who described measuring sea ice thickness and snow cover as the "holy grail" of climate science.

"The thickness of sea ice is regarded amongst climate scientists as one of the crucial indicators of change. When we know how the thickness of sea ice cover is changing over time, we can estimate the influence of global climate change on the Antarctic environment," Dr Lieser continued.

The information gathered on the ice this voyage will be compared with satellite measurements to provide a large-scale view of the amount of sea ice in East Antarctica. Giving scientists a much clearer picture of the situation and setting a benchmark against which similar measurements can be measured in the future.