Warm ocean water melts largest glacier in East Antarctica
Dr Steve Rintoul – Voyage Science Leader
The Totten glacier has remained a secret, has remained unobserved for so long because its so difficult to get to.
We were extremely lucky on this voyage. When we left Casey and started heading to the Totten I thought it was very unlikely that we were going to be able to reach the Totten itself because we had about 100 km of heavy sea ice to traverse to get to the front of the Totten. And we were very lucky we got just the right weather conditions, just the right wind conditions that allowed us to take advantage of a crack in the ice that opened up that extended all the way to the front of the Totten.
The Totten glacier flows off Antarctica and starts to float and the floating part of the glacier is about 120 km long. Out at the front of the glacier where we made our measurements the ice is about 200 metres thick. It then gets thicker as it goes back towards the Antarctica continent and the grounding line, the place where the glacier leaves the bedrock and starts to float is 2 km below sea level.
The surface of the glacier is sinking, it’s thinning. The question is why? It could be related to the dynamics of the ice itself or it could be because the ocean is melting the glacier from below. The Aurora Australis voyage that we just completed was aimed at testing that second idea – is there any evidence that warm ocean water reaches the glacier capable of driving melt of the floating glacier?
What we found is evidence that exactly that is happening. That warm water does reach the Totten glacier. The temperatures that we measured at the front of the Totten are about 3 degrees warmer than the freezing point at the grounding line and so that’s a measure of how much heat is available to melt the ice.
We can detect melting of glacial ice a few different ways. One is just from the temperature. If we see temperatures that are minus two degrees, we know that must have happened at great depth below the floating ice shelf. That’s the only way you can produce temperatures that cold. As the glacial ice melts, it also leaves a signature in the water, that we can detect using different chemical elements and isotopes.
One of the spectacular successes of the voyage were recovery of oceanographic moorings. One year ago the US ship Nathaniel B Palmer deployed Australian and US moorings near the Totten. So we were able to recover all six of those. Those are important because it will provide a year round record of what’s happening near the Totten.
I’ve been going down south for almost 30 years now. I’ve done 15 trips, 12 of them to Antarctica and I’d have to say that this is probably the most successful trip that I’ve been part of that entire time.
Jobs in Antarctica 2015
Davis station decorates the living quarters for Christmas
Happy New Year from Casey station
New Year’s Eve in Antarctica, Casey station – a combination of Australian, Italian and French expeditioners celebrating New Year’s Eve near the south pole.
Happy New Year to Australia and all our loved-ones.
Action stations: Australian activity in Antarctica
Robb Clifton, Operations Manager
It’s a little bit like a game of chess and playing with a Rubiks cube at the same time, and at the end we come up with an answer that is a plan for the season.
So in an average year, we probably run 80 to 90 projects in Antarctica or the subantarctic and around about 500 to 600 people will travel south over that summer period.
So there’s a whole range of factors that come into play about when we actually need to schedule various activities, and then we need to deconflict those activities if they’re trying to pull on the same resources.
So for example some resupply operations we need good and thick sea ice to undertake the operation, and some science projects might need animals at a certain phase of their biological cycle, so they need to be somewhere at a certain time.
It can be very hard in the Antarctic to link things up. Often you are travelling vast distances that are beyond the range of an aircraft for example, and so you need to have intermediate fuel stops. Now they may or may not exist, you may need to place them yourself, then there’s a long process to do that safely and then do the actual flight that you want to do.
I think the other factor that really comes into play in Antarctica are environmental factors. So it’s pretty unusual in Australia for a sea port or an airport to get closed for some reason, yet our sea port and airports get closed all the time in Antarctica, mainly because of weather, strong winds, the sea states too high, there’s too much sea ice, there’s not enough sea ice, or the visibility’s poor, and so we’re often trying to link up a range of activities, for example a ship arriving at a station with scientists to meet an aircraft to fly them to their science location, and to get all of that to actually happen and those weather windows over distance to link up is very difficult.
For us it’s about having a bit of a bag of tricks I suppose that you can roll out as things change or don’t work out quite how you would like them to.
Mapping East Antarctic sea ice
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.