Historic Sea Level Rise Identified By Scientists

LONDON (Reuters) - The collapse of an ice sheet in Antarctica up to 14,650 years ago might have caused sea levels to rise between 14 and 18 meters (46-60 feet), a study showed on Wednesday, data which could help make more accurate climate change predictions.

The melting of polar ice could contribute to long-term sea level rise, threatening the lives of millions, scientists say.

Sea levels have increased on average about 18 centimeters (7 inches) since 1900 and rapid global warming will accelerate the pace of the increase, experts say, putting coastlines at risk and forcing low-lying cities to build costly sea defenses.

Scientists last month said that thinning glaciers and ice caps were pushing up sea levels by 1.5 millimeters a year, and experts forecast an increase of as much as two meters by 2100.

A very rapid sea level rise is thought to have occurred 14,650 years ago but details about the event have been unclear.

Some past sea level records have suggested glacier melt led to a 20 meter increase in less than 500 years.

But uncertainty lingered about the source of the melt, its force and its link to the changes in climate.

A team of scientists, including researchers from France's Aix-Marseille University and the University of Tokyo, claim to have solved the mystery which may shed light on climate change.

They reconstructed sea level changes by analyzing samples of coral collected from reefs in Tahiti and dated them to determine the extent and timing of the sea level rise.

"Our results ... reveal that the increase in sea level in Tahiti was between 12 and 22 meters, with a most probable value between 14 and 18 meters, establishing a significant meltwater contribution from the southern hemisphere," said the authors of the study published in the journal Nature.

This implies the rate of sea level rise was more than 40 millimeters a year, they said.

A U.N. climate panel on Wednesday said all nations will be vulnerable to the expected increase in heat waves, intense rains, floods and a probably rise in the intensity of droughts.

(Reporting by Nina Chestney; Editing by Louise Ireland)

Comments

[bruce1234]

04:17 PM on 04/09/2012

I GUESS THEY JUST CANT MAKE UP THEIR MINDS. WHICH IS IT?

[NewportMac]

11:03 AM on 04/03/2012

Comparisons to the distant past can be misleading.

The oceans were approximately 140m below current levels at the end of the last ice age due to glaciation. The bulk of the glaciation was in the Northern Hemisphere.

Yes, a collapsing ice shelf in Antarctica can raise sea level but Antarctica isn't losing annual sea ice.

"A U.N. climate panel on Wednesday said all nations will be vulnerable to the expected increase in heat waves, intense rains, floods and a probably rise in the intensity of droughts."

What are they basing this on? The MET Office is only capable of a 5-7 day forecast and hopes to be able to forecast out to 30 days in the future. The same models that are used for the forecasting are also used for their climate modeling.

The weather patterns mentioned in the US are largely ENSO driven -- La Nina and El Nino routinely cycle...

[Pharos]

01:06 AM on 04/07/2012

Predicting weather is like predicting a roll of the dice. Predicting climate is like predicting the outcome of millions of rolls of the dice. Casinos make a fortune of of doing exactly that. Just because it's hard to forecast weather doesn't mean we can't forecast the climate (a 30 year average of weather).

You also should research climate models (assuming you really care).

[LetsKeepitSimple]

09:30 AM on 03/30/2012

Most past records show CO2 increasing after the warming with approx 200 year lag, since current warming started in the late 1700's I think that the CO2 rise is based on warming over last 200-300 yrs and the ocean's releasing co2 as they warm

[alteredstory]

11:54 AM on 03/30/2012

Cite your sources if you're not making it up.

[LetsKeepitSimple]

12:48 PM on 03/30/2012

Not making it up, there are many sources, of course there are others that discount it.
Have read it numerous times over the years, a quick google search shows many links, here is one of many
http://www.skepticalscience.com/co2-lags-temperature.htm

[trumphent]

05:29 AM on 04/01/2012

It's not so simple. isotopes of carbon and their ratios prove otherwise. C14 has decreased in lockstep with the increase in C12. This is only accounted for by the burning of fossil fuels, especially coal. The oceans are still considered to be a sink, not a source of CO2. And, the Keeling Curve exactly accounts for increase of atmospheric CO2 being attributed to the burning of fossil fuels. Actually, it is simple once you stop and think about it.

[DeanWormer]

10:30 PM on 03/29/2012

They have have alot of SUV's back then.

[Aladdin Sane1]

08:53 PM on 03/29/2012

Gyah! Reuters, cite your sources! Man, I hate that.

Two google attempts. Found it:

"Ice-sheet collapse and sea-level rise at the Bølling warming 14,600 years ago"
Pierre Deschamps, Nicolas Durand, Edouard Bard, Bruno Hamelin, Gilbert Camoin, Alexander L. Thomas, Gideon M. Henderson, Jun'ichi Okuno & Yusuke Yokoyama
Nature 483, 559–564 (29 March 2012) doi:10.1038/nature10902
Received 09 July 2011 Accepted 26 January 2012 Published online 28 March 2012

http://www.nature.com/nature/journal/v483/n7391/full/nature10902.html

"Instant access to this article: US$32"

"Past sea-level records provide invaluable information about the response of ice sheets to climate forcing. Some such records suggest that the last deglaciation was punctuated by a dramatic period of sea-level rise, of about 20 metres, in less than 500 years. Controversy about the amplitude and timing of this meltwater pulse (MWP-1A) has, however, led to uncertainty about the source of the melt water and its temporal and causal relationships with the abrupt climate changes of the deglaciation. Here we show that MWP-1A started no earlier than 14,650 years ago and ended before 14,310 years ago, making it coeval with the Bølling warming. Our results, based on corals drilled offshore from Tahiti during Integrated Ocean Drilling Project Expedition 310, ... ."

Rather alarming to me as a non-scientist reading this stuff (because it is bound to confuse): In this article "MWP" does *not* mean "Medieval Warm Period," it means "meltwater pulse."

[robodawa]

11:27 PM on 03/28/2012

14,650 years ago - was the overall climate wetter or drier? Which species thrived?
Can we replant forests to somehow slow the advance?

[BlackbirdHighway]

07:23 AM on 03/29/2012

It was colder. The last Ice Age was ending, and ice was melting fast.

[Jim Milks]

10:12 AM on 03/29/2012

"Can we replant forests to somehow slow the advance?"

We could replant forests but all it would do at this point is slow the rate of CO2 increase a bit, make up for some of the loss of CO2 holding capacity in the oceans as temperatures rise. The bottom line is that if we have any hope of really slowing or reversing global warming, we're going to have to get off fossil fuels and do so fairly rapidly.

[grappler1987]

11:14 PM on 03/28/2012

"Levels now rising at more than 40 mm (1-1/2 inches) a year"

Isn't it closer to 4 mm/year? Seems like a decimal placement error.

http://climate.nasa.gov/keyIndicators/index.cfm#seaLevel

[Sunwyn Ravenwood]

11:21 PM on 03/28/2012

You are right. Reuters is wrong. Surprise! No one on the editorial staff fact checks anything around here. Thanks for doing their job. ;-)

[Dallas Dunlap]

07:26 AM on 03/29/2012

grappler - It looks like they have transposed the rate of rise at the end of the ice age as measured in Tahiti. Current sea level rise is on the order of 3.18 mm/yr.

[grappler1987]

09:02 AM on 03/29/2012

That makes sense. Thanks.

Maybe it should say "then" instead of "now".