NASA Study Shows Antarctic Ice Sheet Shrinking 407
deman1985 writes "A recently released NASA study has shown that the Antarctic ice shelf is shrinking at an alarming rate of 36 cubic miles per year. The study, run from April 2002 to August 2005, indicates that the melting accounted for 1.2 millimeters of global sea level rise for the period. From the article: 'That is about how much water the United States consumes in three months and represents a change of about 0.4 millimeter (0.01575 inch) per year to global sea level rise, the study concluded. The study claims the majority of the melting to have occurred in the West Antarctic ice sheet."
Re:0.4mm a year.... (Score:4, Informative)
0.4mm per year just from the Antarctic ice sheet, and 2500 years for a meter presuming a constant rate. On the other hand there are other factors at play such as the Greenland glaciers, which are accelerating their slide into the sea [realclimate.org], which means it might be worth considering the possibility of acceleration of the loss of Antarctic ice. There's also thermal expansion as another factor causing sea levels to rise.
It's also worth noting that, in the grand scheme of things, 0.4mm per year is quite a lot: sea level change over the last 3000 years averages to about 0.1mm to 0.2mm per year.
Is this a clear indication of catastrophic distaster? Far from it. Nor is it the least bit implicit of any sort of bizarre Waterworld scenario. However, even a 1 meter change in sea will have signficant impact given the large numbers of cities very close to sea level - even a small rise makes them far more susceptible to flooding from, say, storm swell or similar. In practice even a small change is going to displace an awful lot of people, costing an awful lot of money, and having a significant economic impact. It may not be a disaster of biblical proportions, but it is most definitely something to be concerned about and to keep an eye on.
Jedidiah.
Re:Effect of Antarctic melting exaggerated (Score:3, Informative)
H2O is a greenhouse gas. It does reduce heating from the sun if it forms into daytime clouds. The same clouds also hold heat in at night. Then just to complicate things further, the more ice melts, the less reflection there is from the polar regions, and solar heating goes up.
Re:Which way is west? (Score:3, Informative)
Re:Greenhouse gasses (Score:1, Informative)
Re:just to remind that (Score:1, Informative)
See here: http://www.newsandevents.utoronto.ca/bin2/020328c
Re:just to remind that (Score:5, Informative)
Errr... WHAT?
Time to do the math again, I guess. Every now and then this bit of ugly science rears its ugly head.
Useful numbers:
Density of Seawater: 1025kg/m^3 [hypertextbook.com].
Density of Freshwater: 1000kg/m^3 [hypertextbook.com] (rounded up from 999.98 at freezing point)
Density of Ice: 916kg/m^3 [same source].
Things to know:
The vast majority of icebergs are not frozen seawater, they break off from land glaciers and float out to sea.
Buoyancy tells us that X will float in Y if X displaces a volume of Y where the mass of the displaced volume equals the mass of X.
Hollowed out shapes can contain more volume than a solid block of mass (this is why metal boats float).
So, lets say we have a solid, convex iceberg floating in an ocean ever so slightly above freezing, consisting of exactly 1025kg of ice right about to melt. To float, this iceberg must displace 1025kg of saltwater, which by sheer coincidence is exactly one cubic meter. Thus, when this iceberg broke off the glacier and fell into the water, the sea level increased by the height of one cubic meter spread out really thin across the entire surface. If you lifted the iceberg out without letting it melt, that one cubic meter would come back and fill the hole where it was.
Naturally, the sea being ever so slightly above freezing and the ice being ever so slightly below, the ice absorbs heat from the ocean and melts. Thanks to wonderful conservation of mass, we know we now have 1025kg of fresh water at ever so slightly above freezing, with a density of 1000kg/m^3. Thus, we have 1.025 cubic meters of fresh water to fill that 1 cubic meter hole where the iceberg used to be.
So because the iceberg fell into the ocean and melted, the sea level is now 1.025 cubic meters (spread out real thin over the entire ocean) higher than it used to be. Even if the ice started in the ocean (as in the Arctic), it's still 0.025 cubic meters high! It gets worse if the ice is sitting on the bottom of the ocean (then there is more ice than displaced water)! Even if you assume that the seawater is less dense in the Arctic (a fallacy, as the freezing action actually increases the saline content of the water around the ice), as long as the density of the seawater is greater than the density of the water you get from melting the ice (almost always freshwater), you will get an increase in sea level from melting the ice.
Incidentially, arctic ice is not all frozen seawater, much of it is from precipitation falling on top of the frozen seawater, so you can't even claim that the water in the ice came directly from the ocean in the first place (not that that claim would really help any, because that water has been locked up for thousands and thousands of years, returning it to water would definitely raise the ocean level beyond anything in written history). Plus, once the water is liquid and continues to heat, it will continue to expand: at 30C freshwater is only 995.65kg/m^3.
Since I whipped out the math anyway, 1025kg of ice is 1025kg*(1m^3/916kg)=1.119 m^3. Since it's solid and convex we know that there must be 0.119 m^3 of ice above sea level. This shows that roughly 10% of the 1.119 m^3 of ice is above sea level, thereby supporting the old adage that 9/10 of the iceberg is below the waterline.
A bit O.T. - Misleading tagline (Score:3, Informative)
Actually, Polar bears are Arctic critters -
http://en.wikipedia.org/wiki/Polar_bears [wikipedia.org]
Re:Stop Whining (Score:3, Informative)
Everything else in your post is just a bunch of name-calling - not exactly the argumentative tactic preferred by those who actually have a point.
knock yourself out (Score:2, Informative)
here you go, i thought this was a nerds site not one for lazy fskers, you overweight by any chance ?
http://en.wikipedia.org/wiki/Sea_level_change [wikipedia.org]
or perhaps a middle school project would explain it better
http://pumas.jpl.nasa.gov/PDF_Examples/02_10_97_1
Re:Stop Whining (Score:5, Informative)
We have a number of temperature reconstructions going back about 2000 years. They do vary because they use http://en.wikipedia.org/wiki/Image:2000_Year_Temp
Change is the natural way of things. I think it's pretty presumptious of us to think we're causing it.
Well there are the remarkable correlations between atmospheric carbon dioxide and temperature, even over the 650,000 years spanned by Antarctic ice cores. Combine that with the present spike in carbon dioxide, which is verifiably anthropogenic [realclimate.org], and the absorption spectra of carbon dioxide which makes it an effective greenhouse gas, together with the close correlation between the recent spike in atmospheric carbon dioxide and temperature, and you have some good reasons to start thinking we may be causing it. Is that conclusive? No. But then there's plenty more evidence than what I can pack into a quick paragraph.
Volcanoes put out far more greenhouse gasses than anything humans do.
This one is just a bizarre bit of disinformation that keeps getting circulated. It is quite false. Volcanoes put out around 130 to 230 teragrams [wikipedia.org] of carbon dioxide a year. The US alone puts out around
5844 teragrams [wikipedia.org]. Atmospheric carbon dioxide from volcanoes is less than 1% of the amount from human activities. Please, put this particular myth to bed.
Jedidiah.
Wrong. Consensus exists. (Score:5, Informative)
Wrong. There is widespread scientific consensus on the existence of global warming, and that human activity is contributing to it. A 2004 Survey [sciencemag.org] of 928 peer-reviewed research articles related to climate change from 1993-2003 concluded that:
"Many details about climate interactions are not well understood, and there are ample grounds for continued research to provide a better basis for understanding climate dynamics. The question of what to do about climate change is also still open. But there is a scientific consensus on the reality of anthropogenic climate change. Climate scientists have repeatedly tried to make this clear. It is time for the rest of us to listen."
Noteworthy is that none of the articles dissented with the consensus opinion. None of them. Not much of a controversy, at least among people who know what they are talking about.
Re:A Whitehouse spokesperson was quoted as saying. (Score:4, Informative)
From http://www.washingtonpost.com/wp-dyn/content/arti
"In Katrina's wake, Louisiana politicians and other critics have complained about paltry funding for the Army Corps in general and Louisiana projects in particular. But over the five years of President Bush's administration, Louisiana has received far more money for Corps civil works projects than any other state, about $1.9 billion; California was a distant second with less than $1.4 billion, even though its population is more than seven times as large."
"..overall, the Bush administration's funding requests for the key New Orleans flood-control projects for the past five years were slightly higher than the Clinton administration's for its past five years. Lt. Gen. Carl Strock, the chief of the Corps, has said that in any event, more money would not have prevented the drowning of the city, since its levees were designed to protect against a Category 3 storm, and the levees that failed were already completed projects."
So WTF have they been doing with the money?
"By 1998, Louisiana's state government had a $2 billion construction budget, but less than one tenth of one percent of that -- $1.98 million -- was dedicated to levee improvements in the New Orleans area. State appropriators were able to find $22 million that year to renovate a new home for the Louisiana Supreme Court and $35 million for one phase of an expansion to the New Orleans convention center."
I've wasted enough time on this, you can google the rest yourself.
The liberal leadership in New Orleans reaped exactly what it sowed for so many years.
Re:Stop Whining (Score:1, Informative)
Cause now we can have vineyards in England again, right?
Or there is a massive food surplus out of an unfrozen North?
Yes it is warmer than we are used to but it's not unreasonably hot in comparison with human history. We've had warmer.
Now what I want is a series of concrete measures to solve it. If you are going to complain don't just do fear. Come up with a way to solve it with out asking for us to live in communes.
Oh and our Sun is a G2 sequence that over time will heat up and have small spectral shifts in it's output. We don't have that many years of data of good spectra data for it. Nor has an exhaustive study been done on effects of nonlinear optics in the low UV region with common earth elements.
http://science.nasa.gov/ssl/pad/solar/sunspots.ht
The sun spot number has have a recorded correlation with temperatures. UV and X-ray emissions are affected and another possible effect as they may be absorbed far more readily than normal.
Which would explain why mars is warming too. http://www.space.com/scienceastronomy/mars_ice-ag
Re:0.4mm a year.... (Score:2, Informative)
Essentially, the study used gravity variation measurements from space to do their estimates. The Western part showed some melting in the 3 year time period they studied, but the 3x as large Eastern part didn't. Of course, if you look at a larger time period (a similar study was done for 82-03), the 3 years worth of data these guys chose just happens to start at a high period for the ice thickness and actually, the Eastern part has been getting thicker over the longer time period.
So the study just used a cool application of observations of gravitational variations, rather than bearing any relevance to the issue of global climate change and its implications.
So don't let your misunderstanding of the study blow up into some sort of big global warming scare. It's unscientific conclusions like that which give non-climatologists a bad name when it comes to these kinds of FUD political tactics.
Not Relevant??? (Score:3, Informative)
Nature has the headline "Antarctica is shrinking" with the sub-heading "Gravity survey shows overall loss in ice". Your link does not give reference to the fact that the paper was published in "Science", rather it takes issue with an article about the paper in "ScienceExpress". Off course they have no trouble picking out and twisting a different "Science" paper to suit their agenda.
"It's unscientific conclusions like that which give non-climatologists a bad name when it comes to these kinds of FUD political tactics."
So why assist them by proffering links to their FUD?
Re:0.4mm a year.... (Score:3, Informative)
"The 1841 sea level benchmark (centre) on the `Isle of the Dead', Tasmania. According to Antarctic explorer, Capt. Sir James Clark Ross, it marked mean sea level in 1841. Photo taken at low tide 20 Jan 2004. Mark is 50 cm across; tidal range is less than a metre."
See photos [john-daly.com] to go with caption.