Coral links ice to ancient 'mega flood'

Mar 30, 2012
Scientists drilled down to the sea floor to collect coral samples. Photo: IODP

(PhysOrg.com) -- Coral off Tahiti has linked the collapse of massive ice sheets 14,600 years ago to a dramatic and rapid rise in global sea-levels of around 14 metres.

Previous research could not accurately date the but now an Aix-Marseille University-led team, including Oxford University scientists Alex Thomas and Gideon Henderson, has confirmed that the event occurred 14,650-14,310 years ago at the same time as a period of known as the Bølling warming.

The finding will help scientists currently modelling future climate change scenarios to factor in the dynamic behaviour of major ice sheets.

A report of the research is published in this week’s Nature.

"It is vital that we look into Earth’s geological past to understand rare but high impact events, such as the collapse of giant ice sheets that occurred 14,600 years ago," said Dr Alex Thomas of Oxford University’s Department of Earth Sciences, an author of the paper. "Our work gives a window onto an extreme event in which deglaciation coincided with a dramatic and rapid rise in – an ancient ‘mega flood’. Sea level rose more than ten times more quickly than it is rising now! This is an excellent test bed for climate models: if they can reproduce this extraordinary event, it will improve confidence that they can also predict future change accurately."

During the Bølling warming high latitudes of the Northern hemisphere warmed as much as 15 degrees Celsius in a few tens of decades. The team has used dating evidence from Tahitian corals to constrain the sea level rise to within a period of 350 years, although the actual rise may well have occurred much more quickly and would have been distributed unevenly around the world’s shorelines.

Dr Thomas said: "The Tahitian coral is important because samples, thousands of years old, can be dated to within plus or minus 30 years. Because Tahiti is an ocean island, far away from major ice sheets, sea-level evidence from its coral reefs gives us close to the ‘magic’ average of sea levels across the globe, it is also subsiding into the ocean at a steady pace that we can easily adjust for."

The research is part of a large international consortium, the Integrated Ocean Drilling Program (IODP), and the samples were obtained by drilling down to the sea floor from a ship positioned off the coast of Tahiti.

What exactly caused the Bølling warming is a matter of intense debate: a leading theory is that the ocean’s circulation changed so that more heat was transported into Northern latitudes.

The new sea-level evidence suggests that a considerable portion of the water causing the sea-level rise at this time must have come from melting of the ice sheets in Antarctica, which sent a ‘pulse’ of freshwater around the globe. However, whether the freshwater pulse helped to warm the climate or was a result of an already warming world remains unclear.

The UK’s contribution to this research, and involvement in the IODP programme, was funded through the Natural and Environmental Research Council (NERC), and was supported by the Oxford Martin School.

A report of the research, ‘ collapse and sea-level rise at the Bølling warming 14,600 years ago’, is published in the journal Nature.

The team comprised researchers from Aix-Marseille University (France), Oxford University’s Department of Earth Sciences (UK), University of Tokyo (Japan), National Institute of Polar Research, Tokyo (Japan) and Institute of Biogeosciences, JAMSTEC, Yokosuka (Japan). 

Explore further: Antarctic ice sheet is result of CO2 decrease, not continental breakup

More information: Nature paper - www.nature.com/nature/journal/… ull/nature10902.html

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RitchieGuy
1.9 / 5 (13) Mar 30, 2012
"""It is vital that we look into Earths geological past to understand rare but high impact events, such as the collapse of giant ice sheets that occurred 14,600 years ago," said Dr Alex Thomas of Oxford Universitys Department of Earth Sciences, an author of the paper. "Our work gives a window onto an extreme event in which deglaciation coincided with a dramatic and rapid rise in global sea levels an ancient mega flood. Sea level rose more than ten times more quickly than it is rising now! ""

Mindboggling!! All that and WITHOUT the aid of anthropogenic global warming CO2 emanating from cars, trucks, buses, and planes. AGWites will want to know: how was that possible without mankind's use of fossil fuels and the internal combustion engine?

Could it have been the volcanism under the Antarctica ice sheet that melted the ice over 14,000 ya? Is it happening now?
Mayday
2.5 / 5 (11) Mar 30, 2012
Yeah, anyone considering jumping on the AGW bandwagon should first spend just a little time studying the natural climate and sea-level oscillations of the last 15-30 thousand years. Climate continuously changes. IMO, seeking to stop climate change is the bizarrest notion that mankind has ever cooked up. And the most unfortunate distraction from other more meaningful issues.
ComputerWiz
2.3 / 5 (6) Mar 30, 2012
Right on, RitchieGuy and Mayday. Antarctic water would need to be warmed by some geological event to get to the proper temperature to warm northern climes.

I thought I read an article elsewhere about evidence of an asteroid strike along the southern ocean sea floor not too far from Antarctica around this time. It would seem plausible to hypothesize that volcanism occurred under or near the ice sheet not too long afterward.

Imagine living in such a world. Even in North America, the catastrophic levels of flooding would likely wipe out any human settlements for hundreds of miles.
Musashi
4.3 / 5 (6) Mar 30, 2012
Yeah, anyone considering jumping on the AGW bandwagon should first spend just a little time studying the natural climate and sea-level oscillations of the last 15-30 thousand years.


That's not an argument as to whether or not humans make it much worse than it has to be.

Climate continuously changes. IMO, seeking to stop climate change is the bizarrest notion that mankind has ever cooked up.


How detrimental to Humanity must the change be before you consider doing something about it?
drel
1.3 / 5 (4) Mar 30, 2012
Because Tahiti is an ocean island... it is also subsiding into the ocean at a steady pace that we can easily adjust for."

I would like to know how they know it is subsiding "at a steady pace". I would assume from looking at coral samples.
sea-level evidence from its coral reefs gives us close to the magic average of sea levels across the globe,
I know I would wait for data from other locations to back this up before I would draw global conditions from one set of data. It is all based upon the "steady pace" assumption and I really would like to know more about how that was determined (does this new data from drilling require rethinking that assumption? I don't know I'm just saying...)
RitchieGuy
1.7 / 5 (6) Mar 30, 2012
The major point is that nothing can be done about the climate change that is caused by natural changes in the Earth. Volcanism is a fact and the center of the Earth is a molten mass that goes up through the layers of mantle until it reaches a weak spot and. . .voila. . .you've got volcanoes erupting and earthquakes happening. Also island building.
Bottom line is that it's prudent for humans to not pollute the air, land, and waters. It's simple enough with education of people to be good stewards of their environment. But it's ridiculous to blame humans for the CO2 and give natural processes a pass as though volcanoes never erupt and CO2 doesn't come up out of the Earth.
ormondotvos
5 / 5 (3) Mar 31, 2012
Uh, the calculations on human generated co2 versus volcanism have been done and are available to anyone who wants to do more than squirt opinions out their anal orifice.
Vendicar_Decarian
1 / 5 (1) Mar 31, 2012
RyggTard gave the answer from the Libertarian/Randite ideological camp.

"Evolve or die." - RyggTard

"How detrimental to Humanity must the change be before you consider doing something about it?" - Musashi

Identify the enemy. Know the enemy.

barakn
5 / 5 (1) Mar 31, 2012
Because Tahiti is an ocean island... it is also subsiding into the ocean at a steady pace that we can easily adjust for."

I would like to know how they know it is subsiding "at a steady pace". I would assume from looking at coral samples.

Oceanic crust sinks as it cools, because it gets denser. That's why there's a ridge in the mid-Atlantic where the newest, hottest seafloor is. Since there's so much seafloor and it is so thick, its cooling and sinking is slow and steady. Additionally a seamount or island with actively growing coral can gain enough mass that it sinks, causing a dimple in the local seafloor.