Greenland Ice Swells Ocean Rise

BBC ^ | 2-16-2006 | Paul Ricon

[muawiyah]

Parts of California's "Central Valley" are already BELOW SEA LEVEL.

[Sawdring]

You might like this book:

After the Ice : A Global Human History 20,000-5000 Bc

[blam]

Thanks, I'll check it out.

[GOP_1900AD]

Please post your figures and the URL for their source.

[Robert A Cook PE]

From the article: "The Greenland ice sheet covers 1.7 million sq km and is up to 3km thick."

Apparently the ice sheet is up to about 2 miles thick, so if scientists have an accurate estimate of ice thickness then I'm sure their calculation is correct. That would be a massive amount of water, but that ice thickness estimate could be easily estimated too high to make this problem seem bigger than it really is.

...

Couple of reality points here:

First: NOT ALL of the Greenland ice cap is that thick: It is basically a bowl made by mountains surrounding a deeper center. The center may be that thick, but even the majority of the center of Greenland is NOT covered by ice that thick. You CANNOT multiply "ice 2 miles thick" x Area of Greenland = Amount of water released by melting the ice!

Second: The "bowl" is an deep hollow: example: TWO MILES of ice = 10,000 FEET (plus) in elevation IF (bit IF) all of the ice were actually above sea level. Now, what is the maximum elevation of the top of the ICE PACK in Greenland? (Don't know offhand, and will try to look it up later.)

NASA reports (in the following) that little of the icepack is actually above 2000 meters (7000 feet), so obviously, ANY assumption that the top of entire ice mass is above 10,000 feet is foolish.

...
Science 21 July 2000:
Vol. 289. no. 5478, pp. 428 - 430
DOI: 10.1126/science.289.5478.428

Prev | Table of Contents | Next
Reports

Greenland Ice Sheet: High-Elevation Balance and Peripheral Thinning

W. Krabill,1* W. Abdalati,2 E. Frederick,3 S. Manizade,3 C. Martin,3 J. Sonntag,3 R. Swift,3 R. Thomas,3 W. Wright,1 J. Yungel3

Aircraft laser-altimeter surveys over northern Greenland in 1994 and 1999 have been coupled with previously reported data from southern Greenland to analyze the recent mass-balance of the Greenland Ice Sheet. Above 2000 meters elevation, the ice sheet is in balance on average but has some regions of local thickening or thinning. Thinning predominates at lower elevations, with rates exceeding 1 meter per year close to the coast. Interpolation of our results between flight lines indicates a net loss of about 51 cubic kilometers of ice per year from the entire ice sheet, sufficient to raise sea level by 0.13 millimeter per year--approximately 7% of the observed rise.

1 Laboratory for Hydrospheric Processes, NASA Goddard Space Flight Center and
3 EG&G Services, Wallops Flight Facility, Building N-159, Wallops Island, VA 23337, USA.
2 Laboratory for Hydrospheric Processes, NASA Goddard Space Flight Center, Building 33, Room A225, Greenbelt, MD 20771, USA.
* To whom correspondence should be addressed. E-mail: krabill@osb1.wff.nasa.gov

[Robert A Cook PE]

#
3. The total surface of the Greenland ice sheet is approximately 1.7 million square km;
4. The average depth of the Greenland ice sheet is approximately 1.5 km.

Justify those two assumptions please. The ice pack doesn't cover all of Greenland, and most of its depth is much shallower than 1.7 km.

[snarks_when_bored]

3. The total surface of the Greenland ice sheet is approximately 1.7 million square km;
4. The average depth of the Greenland ice sheet is approximately 1.5 km.

Justify those two assumptions please. The ice pack doesn't cover all of Greenland, and most of its depth is much shallower than 1.7 km.

Reasonable requests...I posted hurriedly, without providing references.

Justification of #3, from an Encyclopædia Britannica page (my underline):

The Greenland Ice Sheet, though subcontinental in size, is huge compared with other glaciers in the world except that of Antarctica. Greenland is mostly covered by this single large ice sheet (1,730,000 square kilometres)...

Justification of #4, from another Encyclopædia Britannica page (my underline):

[The Greenland Ice Sheet] extends 1,570 miles (2,530 km) north-south, has a maximum width of 680 miles (1,094 km) near its northern margin, and has an average thickness of about 5,000 feet (1,500 m).

[Robert A Cook PE]

http://www.awi-bremerhaven.de/ATM/asood/route.html

But the outer rim of the mountains surrounding the ice cap is 700 meters to 900 meters. The ice cap within this area has a very small region at ELEVATION 3200 meters, (not thickness of 3200 meters!). Then the ice slopes down towards the mountains, with only a few valleys as an outlet to the sea.

Thus, the ICE is NOT 1.7 km thick. Nor 1.5 km, despite the Encyclopædia Britannica. They are not allowing for the "bowl" effect of the rock under under ice.

[Robert A Cook PE]

Slightly different info: A little larger area than your Encyclopedia Brit. data, but includes volume data.

http://www.nat.is/greenlandeng/greenlandglacier.htm

The Greenland Icecap has an area of 1.833.900 km². The average yearly temperature up there is about –30°C, in July about –10°C. Its volume is estimated to be 2.600.000 km³, or about 8% of the ice supplies of the earth.

The reigning wind direction is westerly, but is deflected to the southwest on the East Coast by the Coriolis force. The Piterak-wind in the Angmagssalik Area reaches speeds of 250 km/hour. The southernmost elevation of the glacier reaches 2760 m above sea level and the northernmost about 3200 m.

Every year, about 630 cubic kilometres of ice are created. The movement of the ice 100 km from the coast has reached the speed of 160 km a year. The advance of the glacier snouts is very different, sometimes up to 40 m per day, which is the greatest speed of any glacier tongues in the world

[snarks_when_bored]

Hmmm, I notice the following sentence in the passage you included in your last post:

Its volume is estimated to be 2.600.000 km³, or about 8% of the ice supplies of the earth.

That's pretty close to the 2.55 million cubic kilometers that I used, basing it on a surface area of about 1.7 million square kilometers and an average depth of 1.5 kilometers. Interesting. I guess the sheet does have a volume somewhere in that vicinity.