Australian scientists have discovered a "mind boggling" 2.2km-deep canyon underneath an Antarctic glacier.
It is hoped water samples from the depths will help paint a picture of how warming oceans contribute to glacial melt from below.
Data from Vanderford Glacier in the frozen continent's east was collected by researchers aboard Australia's new icebreaker RSV Nuyina on her maiden voyage south.
"Although we've been visiting this region for decades on (previous icebreaker) the Aurora Australis, we haven't had the capability to do this sort of detailed mapping before," acoustician Floyd Howard said.
"As a result, current navigational charts of this area are based on fairly limited surveys.
"Our work has shown that the seafloor is deeper and more complex than we thought."
The Nuyina was navigating Vincennes Bay after a refuelling operation at Casey Station when its multi-beam echosounder, which sends out pings of sound in a fan shape, was switched on.
It mapped out a previously unknown canyon measuring more than 2200m deep, 2000m wide and at least 55km long.
"It is truly mind boggling to look northward to the nearby Browning Peninsula and know that there is 2200m of water underneath the keel," voyage leader Lloyd Symons said.
"It will be really interesting to see how we can use Nuyina's acoustic capabilities to improve our understanding of the seafloor bathymetry around our other stations in the future."
Water from the canyon was sampled using a conductivity, temperature, depth instrument used to measure changes in water properties, including ocean temperature and salinity near glaciers.
It will help researchers understand how warming water contributes to glacial melt from below.
Echosounder information will add to global efforts to map the world's oceans by 2030.
The Nuyina is expected to return to Hobart by January 30 to prepare for a second voyage this Antarctic season, to Davis and Macquarie Island research stations.
After several delays, the $529 million vessel departed the Tasmanian capital in mid-December and is working towards full operational capacity.
Australian Associated Press