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Переписка с Майклом Бевисом о льдах Гренландии
davidarans
On Dec 22, 2011, at 7:40 PM, David Arans wrote:

Dear Mr. Bevis, 100 billions tons of ice is 100 cubic kilometers. The
volume of the ice shield of Greenland is over 3.5 millions of cubic kilometers.
Are you sure that the loss of less then 1/35000th of weight really does any
difference?

From: Michael Bevis

Difference for or to what?

Difference to the amount of pressure of Greenland's ice shield on the
island’s bedrock.
http://researchnews.osu.edu/archive/greenlift.htm Spreading 100 cubic
kilometers of ice all over the surface of Greenland creates a layer of ice
about 2.25 inches thick. Are you sure that the removal of 2.25 inches of
ice from the top of 1.3 miles high ice layer results in rose of island’s
bedrock an additional quarter of an inch?

Yes, I am sure. However, not all of Greenland lifts up this much. All
our GPS stations are in the coastal zone (embedded in rock) - between
the ice and the ocean. But the great majority of the ice loss occur at
the edge of the ice sheet, near the GPS stations. So the GPS feels
pretty large vertical motions in response to cycles, trends or 'jumps'
in ice loss.

Well, if ice melts at the edge of the ice sheet and doesn't in the middle
(probably more ice freezes there) there is nothing unusual about it, it goes
on for eons. That is how icebergs form. It must be some other reason for the
vertical motions and it worries me that we can miss some geological
catastrophe in that region.

Ice does accumulate in the middle, and melt at the edges. But this
flux (flow) of ice mass can happen in steady-state meaning there is
not net change in total ice mass. The amount of melting keeps up with
the amount of new ice forming from snow. But net uplift of the rock
implies a net loss of ice mass. That is, melting is now outstripping
snow accumulation.