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Q: Earth's weight distribution ( Answered,   5 Comments )
Subject: Earth's weight distribution
Category: Science > Astronomy
Asked by: flashtivo-ga
List Price: $2.00
Posted: 31 Jul 2006 21:03 PDT
Expires: 30 Aug 2006 21:03 PDT
Question ID: 751323
will the earth?s axis be changed by the distribution of weight caused
by ice melting?
Subject: Re: Earth's weight distribution
Answered By: keystroke-ga on 01 Aug 2006 06:34 PDT
The only reference I can find to answer your question is as follows

"Melting ice in Antarctica produced global sea level rises of 0.4
mm/year between 2002 and 2005, according to a new study published
March 2, 2006 in the on-line journal Science Express. The study,
titled "Measurements of Time-Variable Gravity Show Mass Loss in
Antarctica", by University of Colorado researchers Isabella Velicogna
and John Wahr, used satellite data from two NASA satellites called the
Gravity Recovery and Climate Experiment (GRACE). The satellites
measured the changing pull of gravity from the two large ice sheets
covering Antarctica to determine how much ice was on the continent,
and how fast the ice was changing. Most of the melting discovered was
from the West Antarctic Ice Sheet. This is the smaller of the two ice
sheets covering Antarctica, and holds enough ice to raise global sea
levels 20 feet should it completely melt. The rock on which the West
Antarctic ice rests is below sea level, and the sheet could be melting
on its underside due to warming ocean waters penetrating there and
melting it from both below and along the edges. The study found little
melting of the huge East Antarctic Ice Sheet (which would raise global
sea levels 200 feet if it were to melt). This ice sheet is on rock
high above sea level, so warmer ocean waters cannot affect it.
Additionally, the East Antarctic Ice Sheet has average temperatures so
cold that even a 5-10C increase in temperatures is not expected to
seriously threaten it.

The net Antarctic melting reported comes as a surprise, since the
"official" prediction from the latest 2001 report from the
Intergovernmental Panel on Climate Change is that global warming
should cause increased precipitation over Antarctica this century.
This increased precipitation is expected to exceed Antarctica's
melting enough to decrease global sea level. This decrease in sea
level by 2100 is predicted to be about 3 inches (8 cm), ± 4 inches (10
cm), but would be offset by increases in sea level due to thermal
expansion of the seas due to warmer water temperatures, plus melting
of Greenland and glaciers on other continents.

As I reported in my blog on Greenland's greenhouse, total global sea
level rise in recent years has been between 1.5 and 2.9 mm/year. Thus,
the .4 mm/year contribution from Antarctica found by the new study
represents a significant portion of this rise. However, another study
published in December 2005 in the Journal of Glaciology titled, "Mass
changes of the Greenland and Antarctic ice sheets and shelves and
contributions to sea-level rise: 1992-2002" found a rate of melting
for Antarctica five times smaller, for the earlier period 1992-2002.
This research, performed by a team led by NASA scientist H. Jay
Zwally, used satellite radar altimetry data from the European
Remote-sensing Satellites ERS-1 and -2, and found a net melting of
only .08 mm/year from Antarctica. Did Antarctica's melting really
increase 5-fold in past three years? If so, is this a short term
fluctuation, or indication of a long term trend? I'm of the opinion
that's it's too soon to tell. It is extremely difficult to do mass
balance studies of these huge ice sheets, since it requires finding a
small change in a very large number. The same problem affects the
recent estimates of Greenland's mass balance. The new study from the
Journal of Glaciology also reported that between 1992 and 2002, the
total mass of the Greenland Ice Sheet increased and thus Greenland
caused a .03 mm/year decrease in sea level. This result is in
contradiction to the two studies I quoted in my Greenland blog, by Box
et al. (2004), who found that Greenland contributed to a net increase
in global sea level of 1.5 mm/year, and Rignot et al. (2006), who
found a .23 mm/year rise for the year 1996, increasing to .57 mm/year
by 2005. I'd like to see at least three to five more years of
satellite measurements before concluding that Antarctica or Greenland
are undergoing significant melting. The European Space Agency is
launching a satellite called CryoSat in March 2009 that should help
answer these questions. If you want a more technical discussion of the
issues, published a nice analysis last week.

Coverage in the press
It was interesting to watch the reaction of the press to the release
of the new study. The New York Times titled their article, "Loss of
Antarctic Ice Increases", and did a reasonable job covering some of
the uncertainties. The USA Today was a bit more alarmist, headlining
their article, "Study: Antarctic ice sheet in 'significant decline'".
The Washington Post had a very alarmist title to their article,
"Antarctic Ice Sheet Is Melting Rapidly". The facts and uncertainties
involved in the making ice sheet balance measurements do not support
this claim, as of now. Although any news of an increase in melting
from Antarctica or Greenland is worthy of concern, I thought that in
general, the media's headlines on the matter were too alarmist, given
the uncertainties involved.

My next blog will be Thursday, when perhaps I'll be able to talk about
Phoenix's first rain in 142 days. They've got a 20% chance of rain on

Jeff Masters

Box, J.E., D.H. Bromwich, and L-S Bai, 2004. Greenland ice sheet
surface mass balance 1991-2000: Application of Polar MM5 mesoscale
model and in situ data. J. Geophys. Res., 109, D16105,

Rignot, E., and P. Kanagaratnam, "Changes in the Velocity Structure of
the Greenland Ice Sheet" Science 311, 986-990, 17 February 2006, DOI:
10.1126/science.1121381 "

This is from the following website.

Subject: Re: Earth's weight distribution
From: qed100-ga on 01 Aug 2006 06:45 PDT
Melting polar ice: No.

   Being situated primarily in the vicinity of the poles, the ice has
minimal impact on the planet's moment of inertia. If the ice melts, it
then blends homogenously with the ocean water, which gets distributed
approximately uniformly throughout the ocean basin. So even if polar
ice melts, the relative distribution of liquid mass won't change.*

*Won't change significantly. It's possible to speculate that
polar-region glacial ice, currently resting upon land, could melt and
therefore raise sea level by some amount (North polar pack ice floats
on liquid water, and is already contributing as much to sea level as
is possible.), delivering water to inland river systems, which could
in theory constitute a change in the relative distribution of liquid
mass. In reality there's not enough glacial ice to raise sea level by
all that much. Over 99.9% of all the water on Earth is already in the
form of liquid ocean water.
Subject: Re: Earth's weight distribution
From: pugwashjw65-ga on 01 Aug 2006 22:12 PDT
Whatever happens to the balance of the earth because of ice melting
will not change it as a place for us to live. A Bible scripture
guarantees it. And this is a promise direct from God. Psalm 37;29 The
righteous themselves will possess the earth,
And they will reside forever upon it.
Ecclesiastes 1;? 4 A generation is going, and a generation is coming;
but the earth is standing even to time indefinite.
Subject: Re: Earth's weight distribution
From: qed100-ga on 02 Aug 2006 04:08 PDT
A guarantee is a promise of compensation in the event that the
original terms of a bargain fail to be met, e.g., "Satisfaction
guaranteed or double your money back."

   So, if the Bible guarantees the habitability of Earth infinitely
far into the future, then what does it offer in the event of the
failure of habitablity?
Subject: Re: Earth's weight distribution
From: eestudent-ga on 07 Aug 2006 21:29 PDT
What about the promise that the Earth and everything on it will be destroyed?
Subject: Re: Earth's weight distribution
From: qed100-ga on 08 Aug 2006 06:04 PDT
"What about the promise that the Earth and everything on it will be destroyed?"

   That too carries a guarantee. If God fails to obliterate Earth and
all its stuff, we'll get double the damnation in return.

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