On Feb 10, 10:37 pm, "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>
wrote:
> > > Doing it in 50y would be very fast. OTOH since that would have to involve
> > > essentially unknown mechanisms, why not invoke other unknowns to make it
> > > faster?
>
> Let me give you an example of a potential good reason why it cannot
> happen, say a large fraction of the Greenland ice sheet sits between
> mountains, then that fraction cannot slide into the sea, as it would
> have to overcome a hill first so to say. Very straightforward, absent
> the green men James mentions it's pretty hard to see much movement.
You are correct, if you are talking about two north-south ridges on
the east and west sides of Greenland, and if the ice cannot escape
northward nor southward. It seems doubtful that the latter is true.
Moreover, the containment of the ice requires that Greenland is one
island, but that is now disputed and may be proved untrue as the ice
melts and the true shape of continetal Greenland is revealed.
> But given a lubricated surface and an incline towards the sea, what's
> the obvious limiting factor keeping speed down? Is this merely argued
> based on analogy with observed glacier movement (which mightn't be all
> that analogous, cubic kilometers of water below 2 km of ice might
> quite considerably lead to very different speeds than what's observed
> with alpine or antarctic glaciers)?
The point is that if the ice on the surface of the ice sheet starts to
melt quickly, it can drill moulins into the ice which will allow the
water to reach the base of the glacier and release the potential
energy of a fall of two miles! This allows teh glaciers to flow
faster into the ocean and so raise sea level. This floats the ice
shelves in the Antarctic, sending the grounding line proximally. The
ice sheets then flow faster into the ocean and the ice shelves break
off due to the upwards torque.
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