For the arithmetically inclined: Do The
Math--Proof that Greenland's Melting Ice is a LONG-term problem - Let me
take an engineer's view of melting Greenland's Ice Sheets. You can look these
numbers up on the internet and wade through the math yourself to check the
calculations:
- Area of Greenland Ice: 1,710,000 square kilometers
- Thickness of Ice: 1.666 kilometers (average)
- Volume of Ice: 2,848,000 cubic kilometers
If it all melted, worlds oceans
would rise by:
- Area of world's oceans: 361,000,000 square kilometers (Wikipedia)
- Calculated sea level rise from melt: 7.26 meters (2.848 million cu-km of ice
spread across 361 million sq-km of ocean, including the loss of volume from
melting---ice shrinks when melted.)
Oh-oh, that looks like a real
problem--it's nearly 24 feet of rise!!! But, hold on a minute: How long would it
take to melt that much ice? That depends on how much ice there is and the
physical properties of water, particularly the latent heat of fusion:
- Volume of Ice: 2,848,000 cubic kilometers
- Mass of Ice: 2,848,000,000,000,000,000 kilograms
- Heat of Fusion: 334 kiloJoules/kilogram (a physical property of water; this
must be added to ice at 0 deg-C to cause the phase change to liquid water)
- Heat of Fusion Required for Melting:
- 951,519,000,000,000,000,000 kiloJoules = 15,849,000,000,000,000,000 kwh
(One kiloJoule is 1 kilowatt applied for 1 second, or a
kilowatt-second or 0.0166 kilowatt-hours--the same unit as on your electric
bill.)
That's a lot of energy and it must all come from somewhere. The
sun is really the only source available. Barrow, Alaska, is at about the same
latitude as the middle of Greenland. Solar radiation falling on Barrow averages
about 2 kwh/square-meter/day (Funny; no one seems to know the insolation for
Thule, Greenland.)
(Source:
http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/serve.cgi)
- Area of Greenland Ice: 1,710,000 square kilometers= 1,710,000,000,000
square meters
- Greenland Solar Radiation: 3,420,000,000,000 kwh/day
So if all the
solar radiation that hits Greenland is totally devoted to melting ice (no
reflection, no heating of air) , the time required is 4,637,000 days, (Heat of
fusion required divided by the available average solar radiation).
That
is a little over
12,700 years. And this is just to melt the ice that has
already reached 0 deg-C; it takes more to raise the temperature from ambient to
the melting point. (What's the average temperature of the ice today? I
dunno...)
It's just an opinion, but this tells me that my distant
great-great's will have plenty of time to move from their beach-front
property---if a melt really does occur...
(If you were good with
thermodamics and heat transfer, you could probably take the IPCC temperature
foreguesses and figure how long it would take for the "warmer" air temperatures
to melt the ice, too.) -- Correspondence from Bill Brown