Antarctic ice melts as sea warms but cause unknown (I'm confused)

ABC News ^ | Oct 17, 2005 | Jeremy Lovell

[Ben Mugged]

Antarctica is melting, adding to the inexorable rise in global sea levels, endangering millions of lives and whole economies, leading scientists said on Monday.

But while the effect is well known after years of monitoring from land and space, the reasons for the sea warming are not.

"We know sea levels will rise. We need to know by how much and why," Anthony Payne of the University of Bristol and one of the organizers of a major scientific conference in London, told Reuters on the sidelines of the meeting at the Royal Society, Britain's national academy of science.

"This has implications for the whole world — most people and industries are in coastal areas," he added.

Payne said there was a net loss of mass in Antarctica as the snowfall in the center of the frigid landmass was more than offset by sea ice melting around the edges.

The key was to find out whether the process was accelerating, or whether it might stabilize or even reverse.

And the important factor was understanding the complex interaction between ocean and wind currents and how much — if any — of the warming of the seas was due to mankind's contribution to global warming.

"We know a lot more about the ice sheets than we did before," Payne said. "We know change is happening and that it is rapid. What we don't know is why or what is causing it — what proportion is anthropomorphic."

Scientists calculate that average world temperatures — which have already risen by 0.6 degrees Celsius (1.1 Fahrenheit) since 1900 — could rise by at least two more degrees this century, due in large part to greenhouse gases from burning fossil fuels.

[claudiustg]

Here's a little tidbit:

---Sea Level Over the past century, sea level is estimated to have risen about 4 to 8 inches (10-20 centimeters) worldwide. If global warming causes sea level to rise, scientists claim it will be from two main factors: the partial melting of the ice caps, snow fields, and small glaciers, and the thermal expansion of sea water; as it warms, it takes up more volume. Other more localized factors, besides atmospheric warming, may influence sea level rise including: human-caused subsidence by pumping out groundwater, oil, natural gas, or erosion by hurricanes of natural sand buffers. Predictions of future sea level rise are hard to make, but some scientists estimate that melting ice and warming ocean water could raise sea level by as much as one meter by 2100.

One of the least understood areas is the West Antarctic ice sheet and its potential for breaking up into giant icebergs. In one scenario, if global warming results in even a small rise in sea level, warmer water could flow under the West Antarctic ice sheet and break off ice chunks the size of New England. These ice chunks, which now sit on land, could raise sea level an estimated 18 feet worldwide, flooding coastal cities like Portland, Maine and Boston, Massachusetts. Most scientists now think this scenario is unlikely to occur, and if it did, it would take centuries to happen. Some scientists say that increased moisture from global warming could turn to snow in the Antarctic. This could actually contribute to a fall in sea level as the Antarctic locks up the moisture as ice. Most scientists caution that it is very hard to predict what will actually happen.

Why won't the floating ice caps melting in the North Pole/Arctic Ocean affect sea level? (Because this floating ice is already displacing its own volume in water.) Only the ice that breaks off or melts from land, i.e. the Greenland ice sheet, Antarctic ice sheet, and mountain glaciers can raise sea level.---

http://octopus.gma.org/surfing/antarctica/antarctica.html

So it could rise a meter or 18 feet or it might fall...

[gondramB]

Thanks for finding that... I was unaware of the thermal expansion issue.

[corkoman]

Sea level is rising. That is a fact.

The sky is falling and thats a fact.

So many folks running around with big red noses and large floppy shoes squirting water out of a flower on their lapel.

I live on the water. I see the turn of the tide every day. The barnacle line has not made any headway in the past 5 years, and thats a fact.

[corkoman]

Water shrinks as it freezes

Water expands as it freezes. Thats why roads up north get mondo cracks in the winter - liquid water fills cracks and the force of the expanding ice expands small cracks into big ones. Place a bottle of water, capped, in the freezer and check it out after a few hours. Use a plastic bottle.

[Fraxinus]

Figures don't lie, but liars can figure. - Mark Twain

All satellites actually follow a contracting spiral. How large are the differences between these measurements? If they border on the infinitesimal, they are probably statistical artifacts.

As for land based measurements, the mid-atlantic (MD, DE, NJ) coast is falling because the Labrador coast is rising (magmatic movements). Greece has rising sea levels, Turkey has dropping sea levels; there are faults in the area that are generally blamed for this state of affairs.

[gondramB]

"I live on the water. I see the turn of the tide every day. The barnacle line has not made any headway in the past 5 years, and thats a fact."


It is possible for local conditions to effect local tide level. I was referring to global sea level. I'm sorry if that wasn't clear. BTW, thats why they have hundreds of tidal measuring stations - to average local variations.

BTW that average closely matches the level recorded by sattelite.

[gondramB]

I am, to be honest, am not prepared to argue the scientific details.. I have read the NASA, NOAA and several other positions but that doesn't make me any kind of expert.

But I am convinced by the complete agreement of diverse groups of scientists measuring in several different way in may different countries that the sea level is rising.

I am similarly convinced that the average surface temperature of the earth is rising.

What I am not convinced of is that humans are causing either or these.

I am also not convinced we can stop it.

[Sioux-san]

Thank goodness for Polar-tec!

[maryz]

A lot of media, professorships and pundit jobs are on the line if this global warming stuff isn't true.

Takes too long before definitive proof comes in.

I haven't heard of anyone predicting that computers would bring about the "paperless office" losing his job. Nor those who were predicting that by the 80s, productivity gains would be such that no one would have to work full time, and the main demand for labor would be for psychotherapists to help the masses deal with all that free time. (Yes, I read that in a newspaper back in the 70s! I remember because it was so patently ridiculous it was hard to forget.)

Of course, maybe they didn't lose their jobs because no one can remember who they were. ;-)

[JustDoItAlways]

Anarctica has been frozen for at least 35 million years.

There have been lots of warm periods since then and yet the ice remains.

The bulk of scientific studies show there is no net loss of glacial ice across the continent. Some ice shelves are losing mass while others are growing. The actual temperature records show some areas warming, some areas getting colder. As you would expect.

Here is a link to the temperature record for the actual South Pole since 1957. The average temperature has fallen by about 5 deg. C to minus 50 C.

(might have to cut and paste into the address bar to get the link.)

http://data.giss.nasa.gov/cgi-bin/gistemp/gistemp_station.py?id=700890090008&data_set=1&num_neighbors=1

[kidd]

Sea level is rising. That is a fact.

Complete BS.

The satelite data is not able to distinguish between sea level changes and changes in land elevation due to tectonic activity or erosion. El Nino and shifting water temperatures (and densities) are additional complications in proving a clear answer on sea levels.

It has been estimated that another 25 years of data collection will be required to make a distinction between these factors.

[gondramB]

" It has been estimated that another 25 years of data collection will be required to make a distinction between these factors."

Who estimated that?

[F.J. Mitchell]

Oops! I guess I was using junk science to arrive at my conclusion. Considering that the human body is made up of mostly water and considering how certain bodily appendages, (which shall remain nameless since this is a family friendly site) swiftly shrink in direct proportion to the drop in temperature, it just seemed logical that water shrank as it froze.

[gondramB]

"Oops! I guess I was using junk science to arrive at my conclusion. Considering that the human body is made up of mostly water and considering how certain bodily appendages, (which shall remain nameless since this is a family friendly site) swiftly shrink in direct proportion to the drop in temperature, it just seemed logical that water shrank as it froze."

Most materials do shrink. But water has a phenomenum called hydrogen bonding that prevents this... on the other hand if it were not for hydrogen bonding there probably would be any liquid water on the earth so overall its a good thing.

[kidd]

I cannot find my exact source, but the following well-sourced article:

http://www.agu.org/revgeophys/dougla01/node3.html

provides a good discussion of the difficulties in determining sea level, and that many more years of data collection are required to determine the rate of sea level change.

[gondramB]

Thank you. i'll take a look at that. I used the NASA, NOAA and Intergovernmental Panel on Climate Change web sites but this is way outside my field.. I only had threee courses total in atmospheric and oceanographic dynamics and its been 15 years so there is a lot I don't understand.

[F.J. Mitchell]

"so overall it's a good thing"

I'll drink to that.