“What’s driving the changes we’re seeing?”: Research voyage heads to Denman glacier

28 February 2025 — republished from Australian Antarctic Division

It’s RSV Nuyina‘s first dedicated marine science voyage and the first time scientists working with the Australian Antarctic Program have had the opportunity to study the Denman Glacier, in East Antarctica, from the sea.

The Denman has retreated 5km in just over two decades and scientists want to know what that accelerated melt rate could mean for global sea levels and regional biodiversity in future.

The Denman Terrestrial Campaign based glaciologists, geologists, marine ecologists and other experts inland for two seasons.

Now Denman Marine scientists on RSV Nuyina will investigate the factors influencing the glacier’s retreat, and the likely impacts, from the sea. A key aim is quantifying just how much the glacier might contribute to rising sea levels in a warming climate in the centuries to come.

The Denman Glacier sits on a trench that’s believed to be the deepest point on continental earth, at 3.5km. Scientists suspect that warmer waters coming up underneath the glacier may have something to do with why it’s melting at such an astounding rate. One study projects the Denman alone will contribute 22mm to sea-level rise by 2300. 

The high rate of uncertainty in the models is a key reason for studying the Denman Glacier system. 

Icebreaker’s labs to work at full capacity

Physical oceanographer Dr Laura Herraiz Borreguero, from the CSIRO, is working with the Australian Antarctic Program Partnership on the Denman Marine Voyage. 

“The key question for the Denman is what is driving the changes we’ve observed through the satellite record,” Dr Borreguero said.

“The grounding line, where the ice meets the ocean, is retreating inland really rapidly and that’s telling us there are processes that are taking ice away from the Antarctic ice sheet.

“We’ve never been there. We have very little information about what the ocean conditions are like so we really trying to pinpoint what’s driving the changes we are seeing, how likely they are to be sustained in the future and what the impacts of those changes are on our sea levels.”

One of the instruments Dr Borreguero and her colleagues will deploy is a remotely-operated sea glider, which dives to 1000m and monitors water temperature, salinity, and the creatures living in the water column.

“We can launch it and tell it where we want it to go,” Dr Borreguero said.

“It’s very independent of the ship, so we can collect a lot more information about ocean physics. We’ll get a better understanding of the changes happening in ocean circulation and salinity and how the environment is changing in response to that.”

When people on RSV Nuyina are sleeping, the sea glider can be controlled remotely by colleagues working in the United States. 

Change drivers, biodiversity and DNA under the microscope

The Denman Marine is the most ambitious ship-based science campaign run by the Australian Antarctic Program in decades, involving more than 60 scientists from four funding bodies, working staggered 24-hour shifts from late February to early May, around the Shackleton Ice Shelf.

The voyage from Hobart is about 60 days long, with a week’s transit each way, and will see the icebreaker’s science labs working at full capacity for the first time. 

The largest science cohort is from the Australian Centre for Excellence in Antarctic Science (ACEAS), followed by the Australian Antarctic Program Partnership (AAPP), Securing Antarctica’s Environmental Future (SAEF) and the Australian Antarctic Division, with projects focussing on physical and chemical oceanography, atmospheric processes, eDNA and biodiversity.

Marine biodiversity will be assessed by analysing environmental DNA (eDNA) samples collected by AAD voyage science lead, Dr Leonie Suter and her molecular team, using traditional sampling methods and cutting edge autonomous eDNA samplers.

“eDNA is genetic material shed by all organisms into the environment,” Dr Suter said.

“By taking just a small water sample, we can determine what animals live in the environment from the genetic traces they left behind, without the need of directly observing or collecting the animals.”

The data will contribute to long-term monitoring of Southern Ocean biodiversity through the AAD’s East Antarctic Monitoring Program and the Southern Ocean Ecosystem Program.

Data crucial to understanding diversity, distribution, connectivity

The Denman Marine Voyage has a large number of early career researchers and Professor Delphine Lannuzel from the University of Tasmania, working with ACEAS, said she was particularly excited by the “breadth of expertise and career stages brought together on this voyage”. 

“The Denman Glacier is one of the most dynamic and vulnerable parts of the East Antarctic Ice Sheet,” she said.

“This is a unique opportunity for ACEAS scientists and collaborators to study this remote area and contribute our piece of the puzzle to understand the drivers and consequences of changes.”

Scientists from SAEF will investigate the region’s biodiversity. One major project will seek to reveal life on the seafloor, including octopus, sea spiders, starfish and urchins.

“The ocean off the Denman Glacier terminus is a freezing, remote and almost unexplored habitat, yet if it is anything like other parts of the Southern Ocean, it could be home to a surprising diversity of life, potentially rivalling that found in tropical seas,” SAEF science coordinator Professor Jan Strugnell, from James Cook University, said.

“The data gathered on this trip will be crucial to understanding the diversity, distribution and connectivity of life in this habitat, which is key to its conservation.

“In addition, harnessing some of the information encoded in their DNA will enable us to look into the future and improve projections of the behaviour of the East Antarctic Ice Sheet and its contributions to sea level rise.”

The voyage is scheduled to leave Hobart on March 1 and return in early May. 

The Denman Marine Voyage is a collaboration between the Australian Antarctic Division, Securing Antarctica’s Environmental Future (SAEF), the Australian Centre for Excellence in Antarctic Science (ACEAS) and the Australian Antarctic Program Partnership (AAPP).

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