Glaciologists and geomorphologists have speculated for a long time about the manner in which meltwater moves beneath an ice sheet or ice stream in a polar situation. In some parts of Antarctica there are spectacular 'labyrynths' of meltwater channels, suggesting that catastrophic meltwater flows have occurred in the past, with erosion on a massive scale being the result. when my colleague David Sugden and I found big meltwater systems on two of the ice-free peninsulas of the South Shetlands (Byers Peninsula on Livingstone Island and Fildes Peninsula on King George Island) we wondered where all the water had come from, and also wondered whether these channels had been cut during a rapid and catastrophic melting phase at the end of the last glacial episode.
The Labyrynth, in the Taylor Dry Valleys system of East Antarctica, is the most famous example of a chaotic system of connected valleys -- suggested to have been formed during the Miocene by subglacial floods. As long ago as 1965 CA Cotton was speculating as to the origin of the "scablands" in the Wright Valley.
There is also a considerable amount of speculation in the glaciology literature about how water moves beneath great thicknesses of ice -- and how meltwater actually assists in lubricating the glacier bed and thus encourages ice movement and glacial erosion.
But naturally enough, it is virtually impossible to OBSERVE meltwater activity in real ice sheet situations where ice may be kilometres thick and where ice surface conditions may be very hostile indeed for field parties undertaking research. Drilling projects in many parts of Antartica have revealed the presence of meltwater lakes -- some of them very large indeed -- but little has been known about where the water comes from, how it is maintained, and where it goes to.
Now a new advance in radar technology has allowed researchers to identify two different types of meltwater flow beneath very thick ice, associated with rapid ice movement. Beneath the Thwaites Glacier in West Antarctica, Schroeder and his colleagues have used radar signals to differentiate two types of meltwater flow -- one essentially like a swamp, with no deep channels but with sheets of water interconnected and flowing extensively across the land-ice interface; and the other involving concentrated meltwater flow in distinct channels:
There are strong implications in all of this work for the processes that might have operated in North Pembrokeshire during the Anglian and Devensian glacial episodes, when the Irish Sea Glacier cvovered much of the landscape. For example, what does this work tell us about the cutting of the Gwaun Valley meltwater channel system, or even about the cutting of the gorge at Rhosyfelin? Watch this space.....
Scientists Image Vast Subglacial Water System Underpinning West Antarctica’s Thwaites Glacier
Evidence for a water system transition beneath Thwaites Glacier, West Antarctica
Dustin M. Schroeder,
Donald D. Blankenship, and
Duncan A. Young