The headline:
Antarctica's Denman Glacier is sinking into the world's deepest canyon
Is objectively wrong.
Presumeably some
space.com staffer who didn't comprehend the article wrote that sensationalist headline.
The "world's deepest (terrestrial) canyon" is already full of Denman Glacier ice hence the glacier cannot "sink" into it.
Seems odd to measure a "terrestrial" canyon based on sea-level rather than by the difference in elevation of the rock structure.
Perhaps measuring it as a true terrestrial canyon would be, it's depth might not be TheDeepest ?
Seems to me it is a (non-deepest) marine canyon which happens to be full of ice - frozen seawater - which is not technically part of the glacier.
I expect the glacier, the freshwater ice which precipitated and compressed, possibly flows over the marine-ice-filled trench en-route to the sea.
The essential bit here is the trench holds back and slows down the rate of advancement of the "inland" glacier.
Once the grounding point is breached - which is unlikely to occur as a cataclysmic event but as an incremental diminshing-rate advance down the trench slope, the undermining of the ice by seawater both melts it from below, and reduces the resistance to ice-advancement by "unmooring" it.
My guess is that the further the grounding point advances inward or rather retreats, the less thermal energy would be carried in to melt the ice further.
I was speculating whether the lower-density meltwater could cause a convection current sufficient to draw (low density) warm ocean water down to the grounding point.
Come to think of it, at the time of the freezing of the poles, sea level would have been much higher than it is now. I was apprised that I was conceiving of the old pole-centric glaciation model which is now succeeded by the distributed high-altitude glaciation model.
no matter how much sea level were drawn down by global mid latitude glaciation, that trench would be flooded at least 3000m deep when polar glaciation commenced.
It is hard to imagine that trench freezing from the top down...
The ice has an insulating effect slowing down further freezing.
At some point that marine trench would have been ice-capped with the depths still seawater.
I'm also curious if there is an elevation above which the glacier ice is freshwater and below which it is seawater.
Anyway, a more accurate but boring headline would be:
Denman Glacier threatened with melting by undermining seawater.