Arctic Ice Melting Much Faster Than Thought: maybe they'll make amphibious SUVs

Jose G. Perez jgperez at netzero.net
Sat Nov 30 20:52:42 MST 2002


>>This is wrong. First, as any high school student will tell you, ice is
less
dense than water, which is why ice floats, so actually only a small
proportion of the frozen water's volume is displacing liquid water.<<

Where is Archimedes now that we really need him? At any rate, if a lesser
authority will do:

"Melting sea ice would not affect sea levels, but it could profoundly impact
summer shipping lanes, plankton blooms, ocean circulation systems, and
global climate." That's what NASA says. Notice they're talking about
"melting SEA ice."

As to why it must be that displaced liquid water is equal to the volume the
water that is now ice if it were melted, the reason is that the mass of the
water --or to oversimplify, its weight-- remains constant, whether in frozen
or liquid form. The ice floe displaces just enough water to equal its
weight. That gives it the bouyancy to float. It is, in a sense, being "held
up" by the water pushed aside. Because ice is less dense than water in
liquid form, there is a little bit of the ice that is "left over" after
enough water has been displaced to equal the mass/weight of the ice floe,
and that section is above the water line and is the proverbial "tip of the
iceberg."

In a common sense way, think of a light, plastic bowl floating on top of
your son's bathwater (can you tell I have an 8-year-old son?). The more
heavy stuff you put inside the bowl, the lower in the water it goes. If the
object, or collection of objects displacing the water is denser than water,
the object sinks to the bottom and the amount of water displaced is equal to
the volume of the object. If the object floats, then the amount of water
displaced is equal to the mass (weight) of the object.

>>The problem is that a) antarctic ice and much of the polar ice is actually
on  land, and b) even the arctic ice cap is under tremendous pressure, is
condensed under the weight of the ice above. Yes, sea-level increase is a
problem.<<

Agreed. However, this specific study did not address ice over land, as
opposed to ice floating in the ocean, at all. It also didn't look at ice
on/around Antartica (the South Pole). It only examined sea ice around the
North pole. The Globe and Mail reporter confused the findings by throwing
all sorts of extra stuff into the article that weren't in the study, without
clearly demarcating between the two, which was one of the points I was
trying to make.

José




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