Human Water Use Accounts For 42% of Recent Sea Level Rise

scibri writes "During the latter half of the twentieth century, global sea level rose by about 1.8 millimeters per year. The combined contribution from heating of the oceans, which makes the water expand, along with melting of ice caps and glaciers, is estimated to be 1.1 millimeters per year, which left some 0.7 millimeters per year unaccounted for. It seems that the effects of human water use on land could fill that gap. Researchers report in Nature Geoscience that land-based water storage could account for 0.77 millimeters per year, or 42%, of the observed sea-level rise between 1961 and 2003. The extraction of groundwater for irrigation and home and industrial use, with subsequent run-off to rivers and eventually to the oceans, represents the bulk of the contribution. It would be even worse if we weren't also locking up lots of water from rivers behind dams like the Hoover Dam."

Re:Worse?

[BMOC]

Coral Atolls cannot suffer from sea level rise, they are the result of life living near the surface creating a deposit that itself builds the atoll. The Maldives will never suffer from gradual sea level rise. Charles Darwin himself discovered how Atolls remain above water. If these islands were bedrock, you might be right, but they're not. Atolls are essentially floating islands.

http://www.pacificdisaster.net/pdnadmin/data/original/The_dynamic_response.pdf [pacificdisaster.net]

Results show that 86% of islands remained stable (43%) or increased in area (43%) over the timeframe of analysis. Largest decadal rates of increase in island area range between 0.1 to 5.6 hectares. Only 14% of study islands exhibited a net reduction in island area.

Despite small net changes in area, islands exhibited larger gross changes. This was expressed as changes in the planform configuration and position of islands on reef platforms. Modes of island change included: ocean shoreline displacement toward the lagoon; lagoon shoreline progradation; and, extension of the ends of elongate islands. Collectively these adjustments represent net lagoonward migration of islands in 65% of cases.

Results contradict existing paradigms of island response and have significant implications for the consideration of island stability under ongoing sea level rise in the central Pacific.

First, islands are geomorphologically persistent features on atoll reef platforms and can increase in island area despite sea level change....

Re:How?

[Sir Realist]

I wondered this too... so I went and read the linked original article, which quite clearly states:

"Artificial reservoirs, such as the Hoover Dam on the Colorado River and the Three Gorges Dam on the Yangtze River in China, have the opposite effect, locking up water that would otherwise flow into the seas."

So your (and my) suspicions were correct; reservoirs don't make this problem worse, as the /. summary implies, but instead partially counteract it. Bad /. summary; no biscuit.

Re:The relevant part

[skine]

The older method, still in use, is to use tide gauges. Basically, these are long cylinders placed below the water level, and thus are able to remain mostly unaffected by waves. Hundreds, if not thousands of measurements are taken electronically every day, and these measurements give a good measure of the water level at that location over the course of the year. According to Wikipedia, there are over 1700 tide gauges being used worldwide, so you wind up getting a good average of the worldwide sea level.

The newer method is to use satellite altimeters which use radar to give accurate measures of the altitude of the land or sea below them.

The two methods combined give millions of data points over the course of a year, and scientists have been taking measurements since the mid-1800's.

Despite what one may think, it's not quite like there are scientists on beaches around the world placing a new toothpick in the sand for each and every wave.

sea level rise has been a lie/scam anyway.

[argStyopa]

http://www.telegraph.co.uk/comment/columnists/christopherbooker/5067351/Rise-of-sea-levels-is-the-greatest-lie-ever-told.html [telegraph.co.uk]

But if there is one scientist who knows more about sea levels than anyone else in the world it is the Swedish geologist and physicist Nils-Axel MÃrner, formerly chairman of the INQUA International Commission on Sea Level Change. And the uncompromising verdict of Dr MÃrner, who for 35 years has been using every known scientific method to study sea levels all over the globe, is that all this talk about the sea rising is nothing but a colossal scare story.
Despite fluctuations down as well as up, "the sea is not rising," he says. "It hasn't risen in 50 years." If there is any rise this century it will "not be more than 10cm (four inches), with an uncertainty of plus or minus 10cm". And quite apart from examining the hard evidence, he says, the elementary laws of physics (latent heat needed to melt ice) tell us that the apocalypse conjured up by
Al Gore and Co could not possibly come about. ...
When running the International Commission on Sea Level Change, he launched a special project on the Maldives, whose leaders have for 20 years been calling for vast sums of international aid to stave off disaster. Six times he and his expert team visited the islands, to confirm that the sea has not risen for half a century. Before announcing his findings, he offered to show the inhabitants a film explaining why they had nothing to worry about. The government refused to let it be shown.

But hey, we all know that "there is 100% consensus among the serious scientists on AGW", right?

Re:Worse?

[Anonymous Coward]

They're not laughing in the Maldives

Actually, they are lauging. Sea level in the Maldives actually went down, but they really love the attention and money they can get from claiming that they're drowning.

Re:Worse?

[riverat1]

An acre-foot of water is one acre of area covered by a foot of water. It is a common unit in the United States for measuring large volumes of water. One acre-foot is equal to 1233.48184 cubic meters or 325851.4 US gallons. Hogsheads vary is size but if you take it to be 63 gallons then an acre-foot is about 5,172 hogsheads. Troy ounces is a measure of mass, not volume.

Re:sea level rise has been a lie/scam anyway.

[ath1901]

Mörner is not one of the serious scientists. I thought I recognized his name and looked him up at wikipedia. One of his previous achievements is winning the "Deceiver of the year" award for supporting dowsing.

http://en.wikipedia.org/wiki/Nils-Axel_M%C3%B6rner#Views_on_dowsing [wikipedia.org]

Oh, and his claims about the sea level is not supported by satellite measurements.

Re:Worse?

[Cramer]

Perfectly "clean" rainwater should have a pH close to 7.0 -- being pure water. 5.6 is bordering on "acid rain". (I'll check my rainwater sisterns, but they've had a long time to settle.)

Yes, sea water is highly buffered. However, that buffer is not instant. Look at the small scale in my (freshwater) aquariums... they have carbonate buffers in there (a lot of it, in fact -- aragonite and commerical buffers) and the pH can still dip below 6.6. If I draw a sample for testing, sealed in the tube, the pH will slowly recover to 8.4 as the disolved buffer does it's job. A great deal of the buffer capacity of the oceans are the coral in them.

But yes, I agree, CO2 is not what's going to destroy our oceans. We've been doing far, far worse things to them for a long time now.

Re:Really?

[rickb928]

Depends on your location and context...