First 3-D map of under the East Antarctic sea ice

Mapping East Antarctic sea ice

Video transcript

Dr Guy Williams — Antarctic Climate and Ecosystems Cooperative Research Centre

Sea ice thickness represents one of these sort of holy grail at the moment. It’s something that we have difficulty in measuring with great accuracy and with any sort of great success on large scales. So thickness is important because we want to know how much there is. We’ve got a good idea of the area from the satellites, but the satellites can’t tell us the thickness and without the thickness we won’t know the total volume or the total amount of sea ice.

Dr Clay Kunz – Woods Hole Oceanographic Institution

So this is an Autonomous Underwater Vehicle, or AUV, and what it does is it’s a free swimming underwater robot. So it carries on board all of its power and intelligence and navigation equipment so that it is basically free swimming through the water and doing its own thing, as opposed to be being remotely controlled over a tether.

On this particular trip, since we are looking at the underside of the ice, we want to be pretty close to it. So we are driving around, so far we’ve been generally 20 metres underneath the water actually which is less distance under the ice because of course the ice sticks down into the water quite away.

The AUV has a lot of waypoints that it’s trying to get to as it is driving around underwater and the last waypoint that its set to get to is basically back where it started again, which is in open water off the stern of the ship.

Dr Guy Williams — Antarctic Climate and Ecosystems Cooperative Research Centre

It represents a leap forward in observational capability in terms of how we can measure thickness. The multi-beam sonar that we have on this AUV will provide us with a 3-D view of the underside of the sea ice. That will, together with the surface measurements that we are getting from other platforms, like the helicopter, we’ll have a full 3-D map of the entire sea ice flow.

Dr Jan Lieser — Antarctic Climate and Ecosystems Cooperative Research Centre

We are here in Antarctica to measure the thickness of the snow cover and the sea ice which is separating the atmosphere from the ocean. When we know how the thickness of the sea ice cover is changing over time we can estimate the influence of global changing climate on the overall environment down here, which includes not only the physical environment, in terms of sea ice, atmosphere and ocean, but also the biosphere.

We have this helicopter equipped with a whole heap of instruments which we call our flying toolbox. The flying toolbox consists of an aerial photography which is in this bucket down here, we have a radar, a snow thickness radar, which is mounted beneath the skids back there. We have a laser scanner and pyrometer on the front over here. And the whole thing will be combined together with an INS and GPS so that we know where we are and how we are orientated in a 3-D space. It is all driven with an electronics control unit which is in the centre here. This time around we also have a microwave radiometer from our Japanese colleagues which is installed in the boot there. So we fly about 60 nautical miles in one direction, then turn 120 degrees, fly 60 nautical miles in the next direction and then fly back to the ship.

What I like most about working in Antarctica is that so many people from so many different skills come together, work seamlessly, know what they are doing and we are all working towards one goal of gathering as much data as possible on sea ice environment down here.

[end transcript]

The AUV under the ice with the Aurora Australis propeller (Photo: AUV team/Australian Antarctic Division)
The AUV under the ice with the Aurora Australis propeller (Photo: AUV team/Australian Antarctic Division)
The AUV being lowered off the stern of the ship. The data from the robot will be used to make 3-D maps of the underside of the sea ice (Photo: Wendy Pyper)The AUV surfaces after a successful mission (Photo: Guy Williams)A preliminary 3-D map produced from multibeam sonar data collected by the AUV under an ice floe on 4 October 2012. The map shows a typical ‘lawnmower’ grid of about 150 x 150m and the depth bar on the left shows deeper ice in red (up to about 10m below the surface) and shallower ice in blue. Image © AUV team/Australian Antarctic DivisionThe AUV team from L-R: Peter Kimball (WHOI), Polly Alexander (Australian Maritime College, CSIRO), Rowan Frost (Australian Maritime College). Back (L-R): Clay Kunz (WHOI), Guy Williams (ACE CRC) (Photo: Wendy Pyper)An aerial photograph taken with the high resolution digital camera in the helicopter, showing part of a survey area or ‘transect’ to the left of the ship with scientists working on the ice. The roughness of the snow cover is discernible. (Photo: Jan Lieser)Dr Jan Lieser and pilot Leigh Hornsby in the instrumented helicopterThe instrumented helicopter carries a laser scanner, pyrometer and inertial navigation system within the housing to the right of the helicopter nose, a snow radar across the rear of the skids, a digital camera in the silver bucket underneath and a microwave radiometer in the ‘boot’ of the aircraft. GPS antennae are above the front windows

For the first time in East Antarctica, climate scientists have produced a three-dimensional (3-D) map of the surface beneath a sea ice floe, revealing an inverted complex topography evocative of lakes and mountain ranges.

Researchers, on a two-month voyage to the region on the Australian Antarctic Division’s icebreaker Aurora Australis, are using an Autonomous Underwater Vehicle (AUV).

This free-swimming robotic submarine is measuring the topography of the underside of the sea ice 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.

The AUV swims 20 metres below the ice, travelling at about 30cm per second in a “lawnmower” grid pattern. The data is stored in an onboard computer and converted into a 3-D map at the end of each survey.

AUV research engineer Dr Clay Kunz, from the Woods Hole Oceanographic Institution in the United States, said the robotic submarine 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 the underside of the sea ice with surface measurements of snow and ice, they will have a comprehensive 3-D map of the entire ice floe.

Aerial measurements of sea ice thickness and snow cover are being gathered by Antarctic Climate and Ecosystems Cooperative Research Centre Marine Glaciologist Dr Jan Lieser.

He is using a range of instruments mounted in a Squirrel helicopter, including a high resolution digital camera, a snow radar and a laser scanning system.

Dr Lieser said measuring sea ice thickness and snow cover is 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 says.

Any changes in sea ice thickness will affect the formation of cold, salty Antarctic Bottom Water that drives ocean currents around the world, and the organisms that depend on the ice for habitat and food, from phytoplankton and krill, to whales.”

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.

The seven-week Sea Ice Physics and Ecosystem eXperiment (SIPEX-2) voyage — is a continuation and extension of SIPEX-1, which took place in September-October 2007 and is jointly coordinated by the Australian Antarctic Division and the Antarctic Climate and Ecosystems Cooperative Research Centre.

SIPEX-2 brings together scientists from Australia, Belgium, Canada, France, Germany, Japan, New Zealand and the United States.