The warmer Southern Ocean is melting the glacier from underneath and they want to measure exactly what is happening. When the base of the glacier melts further, it will fall, slide, crack and create floating icebergs
The Southern Ocean forms a uniform band around the entire Antarctic Continent, relatively unobstructed by land masses as in the Northern Hemisphere.
So if the "warm", GHE-heated waters of the Southern Ocean are melting the Antarctic coast. Would not the melting occur uniformly around the continent? Yet it seems concentrated in "hot spots", such as Pine Island and the Thwaites Glacier.
And how is this warm water able to "sink" below the colder water above it? The usual pattern of ocean temperatures is a monotonic decline from the surface to the bottom, usually with a rapid drop in the thermocline.
A more believable theory to explain how the glacier seems to be melting from underneath surface would be exposure to enhanced geothermal flux from local volcanic "hot spots". This would create subglacial outflows from rock-ice interface and would also explain the apparent speedup of ice sliding out to the ocean over warmer rock.
In fact, such volcanic activity was discovered recently (2018) around Pine Island. Indeed many dozens of volcanoes are known lie under the West Antarctic Ice Sheet (WAIS):
Previously unsuspected volcanic activity confirmed under West Antarctic Ice Sheet at Pine Island Glacier
Potential effects of volcanic warming on ice-sheet melting and sea level rise still to be determined
https://www.nsf.gov/news/news_...
So, it may have nothing to do with Global Warming, which is primarily observed in the Northern Hemisphere, where the people live. (But CO2 is well mixed gas, so any CO2-induced warming should be uniformly observed in both hemispheres)