A map of American Antarctic bases – yellow dot on lower left is the centre of the Western Antarctic Ice Sheet (WAIS), where researchers often run field camps during the southern summer.
Credit: U.S. National Science Foundation
CHICAGO: A collapse of the West Antarctic ice sheet will have devastating impacts on sea levels and even weaken the Earth's gravity field, affecting the planet's rotation – but global seas will not rise as much as first thought, a new study suggests.
Using new measures of the ice sheet's geometry, British and Dutch researchers predict its collapse would cause sea levels to rise by 3.2 metres rather than previous estimates of five to seven metres.
However, the study published in the journal Science earlier today found that even a one meter rise in sea levels would be significant enough to weaken the Earth's gravity field in the southern hemisphere and affect the Earth's rotation.
Water will move north
That rotational shift would cause water to pile up in the northern oceans and could result in dramatic regional differences in sea levels, with the largest rise on the east and west coast of the United States.
"The pattern of sea level rise is independent of how fast or how much of the WAIS [Western Antarctic Ice Sheet] collapses," said lead author Jonathan Bamber of the University of Bristol in England.
"Even if the WAIS contributed only a meter of sea level rise over many years, sea levels along North America's shorelines would still increase 25% more than the global average." Antarctica holds about nine times the volume of ice as Greenland and is considered a sleeping giant when it comes to sea levels.
The western ice sheet is of particular concern because enormous sections sit in inland basins on bedrock that is entirely below sea level.
Science fear ice sheet collapse
Vast floating ice shelves currently limit ice loss to the ocean but scientists fear the sheet could collapse if the floating ice shelves break free.
The study authors based their predictions on the assumption that only ice on the downward sloping and inland-facing side of the basins would be lost while ice grounded on bedrock that is above sea level or slopes upward would survive.
Researchers do not know how quickly the shelf would collapse. But if such a large amount of ice melted steadily over 500 years it would raise sea levels by about 6.5 millimetres per year. That's about twice the current rate due to all sources.
"Though smaller than past predictions, the scale of the fully manifested instability is enormous," cautioned Erik Ivins of the California Institute of Technology in an accompanying article.
"The total mass gained by the oceans ... would be roughly equal to the mass showered to Earth by the impact of about 2,000 Halley-sized comets."
Further complicating the situation is the fact that Greenland seems to be losing as much or more ice than Antarctica, even though it doesn't have the same unstable configuration.
"Greenland needs only half the mass loss rate of Antarctica to have an equivalent effect on polar motion due to its less polar position," he wrote.
Even "more ominous" are the current accelerations of ice flow into the Amundsen Sea Embayment in Antarctica, he wrote.
"Should the ice sheet grounding line migrate farther inland, ice resting on bedrock well below sea level could become unstable."
whaaaat?
"raise sea levels by enough to weaken the Earth's gravity field"
What can this ridiculous statement possibly mean?
Sysadmin Guess
Well i suspect as the locations of mass on the planet change there would be an effect on the planet due to centrifugal motion, which is why the sea level rise is related to the latitude of the coastline.
As the earths Magnetic field is created by the molten iron core of the planet, the change in ocean level would change pressure on tectonic plates which would then pass this change onto the molten core of the planet.
(similar to how the 3 gorges dam may have contributed to the recent earthquake, but on a much larger scale)
now i am in no way a scientist, so this is just guesswork, but i figured it would throw it out there so someone who knows what they are talking about can correct me and answer the above posters question.
whaaaat? Yes what, The Earth is spinning, wobbling.
Raising sea levels will amplify the wobble at the equator as the earth wobbles like jello on a child's plate. The change will eventually be absorbed by the earths crust changing to absorb the pressure changes,
and large changes change the magnetic field, slow the rotation to lessen the power of the field, and any event could occur during this next decade of earth change from the suns increase in heat radiation and now reduction
in solar radiation. The plant growth will slow, human burning fuels will diagrammatically increase then slow with dramatic population losses as nuclear bomb activity slows. Then in 20 years the winter snow deposits will change to add dramatic weight back to the poles, it means unexpected earthquakes, and if the field fluctuates radically from the suns burst every 10-11 years or 2012 is the next burst or burp up, if it is a bad kill shot, it will at the least do like one of the last decade burst: flood delicate electronics like computers and interact with the earths
own electric or magnetic field and further increase the "big one" flip.
rotational change
Get a bucket of water, add a short rope. Swing it around in a circle and see what happens. NOW... Take the same bucket, one pint less water, and add a one pound weight to one side of the bucket. (a pint equals a pound) Swing it around as before. Get the picture?
gravity field more help
I do get it and the above comment explained it very simply, thank you. I immediately grabbed my old physical geography text book and although still useful it is too old to help me here. I know we have the dear old internet for up to date information, but it lumbers a bit too slowly nowadays, even if you know what you are looking for. There is so much rubbish posted, now everyone uses it, and finding what you want just takes too long for my ultra-busy lifestyle - and brain. (Perhaps a new search engine for the more seriously minded might be a good idea). I may be old-fashioned (friends and family are throwing away their text books) but can any of you Geography teachers tell me a title to update my (yes! still useful) 1966 A level book where I can find what I want in seconds not minutes.....
No laughter allowed please, and thanks Cosmos for all this seriously, serious stuff in one quick place, I don't know what I did without you.
Seriously exaggerated
The figures quoted in the article seem to be seriously exaggerated at first sight.
Let's say the whole west antarctic shelf goes.
How large is it (square kilometers) and how thick?
What is its relation to total ocean surface?
If that shelf has already been "sitting on" the water, how could it increase sea levels once melted?
Ice that is sitting on the sea or swimming in the sea like an iceberg is already displacing as much water as the melted water from the ice will eventually become. So what is the basis for the claim that the ice shelf will increase sea levels by even one meter?
no exaggeration
1- What you describe as "sitting on" the water is part of the same ice shield that is on bedrock and in some cases above sea level. Therefore, it hasn't displaced anywhere near the amount of water that it will displaced when it breaks off.
2- The reason such an increase in levels in the northern hemisphere is because the earth's rotation is on a tilt, remember? It'll basically "sling" the extra water towards the north. Get it?
PS- The water frozen in the shelves is FRESH water as opposed to salt water. Completely different density, etc. Adding so much fresh water will completely change the buoyancy of the entire global oceans as well as currents, water temp's... EVERYTHING.