Successful mooring deployment to unlock deep secrets of glacier stability
The successful deployment of a deep-water mooring line in between the Scott and Denman Glaciers will feed back critical long-term data on the area’s warming waters, giving researchers new insights into the drivers of potential ice melt.
In a breakthrough moment of the Denman Terrestrial Campaign (DTC), a remote field and research team managed to position the mooring through a small protected ‘window’ of sea ice near the remote Cape Hoadley, and into the ocean below – with instant results.
Remarkably, it revealed 1200m of water just 500 metres from the coast – that’s roughly the height of kunanyi / Mt Wellington, which towers over Tasmania’s capital, Hobart.
The mooring holds a series of long-term sensors on a cable from the sea floor to the surface, measuring the ocean properties in real time.
Grainy vision taken from a camera attached to the mooring shows its descent through the ice, while imagery captured by the team at the deployment site shows its remoteness, the drill and reeling work required to break through.
Dr Maria (Coti) Manassero (ACEAS/University of Tasmania) has been assisting glaciologist and team leader Dr Sarah Thompson (AAPP/University of Tasmania) in the field this season, along with the AAD’s polar field guide Nick Morgan.
She says the team is “super happy with the deployment and surprised to have found 1200 metres of water so close to the shore.”
Geomorphologist and Associate Professor Duanne White (ACEAS/University of Canberra) was in the field last year and scoped out the site, after satellite imagery showed its unique geography.
“The site was chosen because it gives us access to the southernmost part of the ocean cavity beneath the ice shelf without having to drill through 600+ metres of glacial ice,” he says.
“This ‘window’ is tucked in behind a piece of protruding bedrock where the ice shelf isn’t able to flow into… this enabled us to safely and relatively easily access the ocean cavity beneath the ice shelf, using only tools designed for ice fishing on lakes in North America.”
Oceanographer Dr Madi Rosevear (formerly ACEAS, now at the University of Tasmania) says the discovery is “very significant.” She’s excited to see the data come in.
“Every day at 11:00am I’m now getting four emails from Antarctica, with hourly measurements of ocean temperature, salinity and current speed,” she says.
“Hopefully this continues for the next two to three years. This data will tell us how much heat is available to melt the Scott Glacier Ice Tongue and will give us important insights into the ocean circulation, including how it changes over time. The discovery of a 1200-metre deep seafloor at this location, close to the ice shelf, is very significant.”
Dr Rosevear says deep troughs and canyons around Antarctica provide pathways for warm, salty circumpolar deep water (CDW) to access ice shelves, where it can drive rapid melting.
The trough below the Denman Glacier has been mapped as the deepest on Earth, and the glacier holds so much ice, it alone could raise the world’s sea levels by 1.5 metres if it were to melt entirely.
It is already known to be one of the fastest-thinning glaciers of the East Antarctic ice sheet.
Assoc. Professor White says the mooring will allow the team to determine if the area’s warming waters are reaching right to the back of the ice shelf.
“Here we can measure the speed and characteristics of meltwater flowing out from the base of the ice shelf, right up near the grounding line, where ice from the Scott Glacier lifts off the bed and starts to form the ice shelf,” he says.
“This is where ice shelf melt rates are generally considered to be highest and much of the dynamic interaction between ice and seawater occurs.”
Speaking recently to media, Dr Thompson said the system was big and complex, and it was essential more was found about it “to allow us to better predict the changes and the impacts of those changes that we might see.”
The discovery follows an attempt on last year’s DTC field trip to access the ocean through a hole in the 200m thick Shackleton Ice Shelf, west of the Denman, using a hot water drilling technique.
This current 2024/25 Denman field trip is the last of a three-year land campaign to study the Denman Glacier, ahead of the upcoming Denman Marine Voyage on icebreaker RSV Nuyina, which will examine the glacier and its ice/ocean interactions from the water.
The Denman Terrestrial Campaign (DTC) and the Denman Marine Voyage (DMV) are a scientific collaboration between the Australian Centre of Excellence in Antarctic Science (ACEAS), the Australian Antarctic Program Partnership (AAPP), Securing Antarctica’s Environmental Future (SAEF) and the Australian Antarctic Division (AAD).
