The
Breaking of the Ice Bridge Holding the "Wilkins
Ice Shelf" to Land
"Ice
Bridge Collapses"
As
someone who is very
interested in the climate, I have been watching
reports of the steady
thinning of the connection of the "Wilkins
Ice
Shelf" to land,
specifically, the narrow ice bridge connecting the
Wilkins Ice Shelf
to Charcot and Latady Islands. We heard the news that
this ice bridge has now shattered.
While
the melting of floating
ice has no immediate effect on sea levels, it
is one more major loss
of long term ice from round Antarctica.
Although
there will be a temporary increase in the ice area during
the Southern
Winter, this will be thin ice that will disappear
relatively quickly in
the southern summer.
A smaller area of ice means a smaller area to
reflect the summer
sun. Liquid water absorbs much
more heat than ice.
As
the floating ice shelves of
Antarctica retreat there is less to hold
back the glaciers of
Antarctica; the melting of this land ice will
raise the sea level.
In the past it has often been considered
that the ice of
the northern hemisphere is in much more danger of
melting than the
Antarctic ice. There are good
reasons to think this.
For
one thing the temperature in the Arctic is increasing much faster
than
the temperature in the Antarctic.
But how
stable is the
Antarctic ice? The problem with this question is
that we do not know
the answer. Some would say that the Eastern part
of Antarctica is
totally stable and not in any danger, but the
western part which is an
ice shelf over an archipelago rather than a
continental mass is not
stable.
Although the melting of floating ice
does not raise sea
levels, grounded ice shelves as exist in western
Antarctica are a
completely different thing; if they collapse and
melt sea levels will
increase.
An important corollary to the
statement that the
melting of floating ice will not raise the water
level which is
sometimes ignored is that adding ice to water
immediately increases the
water level.
You can easily see this on a small scale when you add ice
to a
drink. Of course it increases
the level of liquid in the drink.
Similarly,
if ice slides from land into the sea it will immediately
increase
the sea level. It does not have
to melt to do this.
There
is the potential for sea levels to increase very rapidly.
Steve Challis
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