If I understand correctly, if the Thwaite Glacier retreats a couple of
km behing a sub-sea-level ridge it is currently resting upon, there's
a scenario which can't be eliminated whereby about a quarter of the
WAIS turns into a huge relatively fast flowing glacier leading to as
much as 2 meters sea level rise on a time scale on the order of a
century. It would be like popping a cork on a bottle; the ice sheet
would just spill out the opening.
This is summarized in Hansen's "rising sea level helps unhinge the ice
from pinning points".
I'm not sure this is regarded as likely, but it at least it's not very unlikely.
The quaternary record does indeed show abrupt warmings and sea level
rises, and recent observations have revealed new mechanisms of abrupt
ice failure.
Why should we be immune to abrupt failures of ice sheets. They have
happened in the past.
In what way is the analogy to the paleo record unsupportable?
I think Hansen carefully avoided quantitative predictions. Informally
speaking, over a meter of sea level rise in excess of thermal
expansion, in this century, is not at all off the table from what I am
hearing from people whose business it is to think about this problem.
I am sure you hear from others, but I don't know why they or you feel
confident in discounting this.
mt
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