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Author Topic: CO2 spikes during deglaciation  (Read 3684 times)

Pmt111500

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CO2 spikes during deglaciation
« on: January 06, 2015, 10:51:24 AM »
I guess this report of this detailed record has already been noted here somewhere, too tired to catch up on all threads.
Scripps institute has obtained and initally resolved a detailed core from West Antarctic Ice Sheet that shows fast increases in ghg levels during deglaciation period in northern hemisphere. The source of the ghgs is still unclear but these spikes of increased natural emissions took place 16,100 years ago, 14,700 years ago, and 11,700 years ago making a very large part (c.35-55%) of the total CO2 rise during the deglaciation.

https://scripps.ucsd.edu/programs/keelingcurve/2014/10/29/new-study-shows-three-abrupt-pulses-of-co2-during-last-deglaciation/

Lennart van der Linde

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Re: CO2 spikes during deglaciation
« Reply #1 on: January 06, 2015, 07:28:49 PM »
The pulse at 14.700 years ago is about a century before the start of Meltwater Pulse 1A, or maybe in tandem with it? Coincidence, or are they connected to some extent?

AbruptSLR

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Re: CO2 spikes during deglaciation
« Reply #2 on: January 06, 2015, 08:00:45 PM »
The linked reference (with free pdf, images and supplemental data) provides paleo-evidence that CO2 ventilation from the Southern Ocean can contribute significantly to global warming, as there are many parallels between the condition of the Southern Ocean at present and those conditions during past warming spells:

Skinner, Luke C. and Waelbroeck, Claire and Scrivner, Adam E. and Fallon, Stewart J. (2014) "Radiocarbon evidence for alternating northern and southern sources of ventilation of the deep Atlantic carbon pool during the last deglaciation," Proceedings of the National Academy of Sciences, 111 (15). pp. 5480-5484. ISSN 0027-8424, 1091-6490, doi: 10.1073/pnas.1400668111

http://eprints.esc.cam.ac.uk/3046/

Abstract: "Recent theories for glacial–interglacial climate transitions call on millennial climate perturbations that purged the deep sea of sequestered carbon dioxide via a “bipolar ventilation seesaw.” However, the viability of this hypothesis has been contested, and robust evidence in its support is lacking. Here we present a record of North Atlantic deep-water radiocarbon ventilation, which we compare with similar data from the Southern Ocean. A striking coherence in ventilation changes is found, with extremely high ventilation ages prevailing across the deep Atlantic during the last glacial period. The data also reveal two reversals in the ventilation gradient between the deep North Atlantic and Southern Ocean during Heinrich Stadial 1 and the Younger Dryas. These coincided with periods of sustained atmospheric CO2 rise and appear to have been driven by enhanced ocean–atmosphere exchange, primarily in the Southern Ocean. These results confirm the operation of a bipolar ventilation seesaw during deglaciation and underline the contribution of abrupt regional climate anomalies to longer-term global climate transitions."

Edit:  See the attached image with the following caption:

Caption for attached image: "Figure illustrating the ‘smoking gun’ of apparently ‘old’ CO2 being injected into the atmosphere at the end of the last glacial period, presumably from the ocean. Marine radiocarbon records would confirm this if they showed an opposing trend to that seen in the atmosphere; emerging data suggest they do."

« Last Edit: January 06, 2015, 08:07:33 PM by AbruptSLR »
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AbruptSLR

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Re: CO2 spikes during deglaciation
« Reply #3 on: January 06, 2015, 08:24:37 PM »
The linked article discusses Antarctic contribution to sea-level rise during Meltwater Pulse 1A, due to reduced Southern Ocean overturning:

N. R. Golledge, L. Menviel, L. Carter, C. J. Fogwill, M. H. England, G. Cortese & R. H. Levy, (2014), "Antarctic contribution to meltwater pulse 1A from reduced Southern Ocean overturning", Nature Communications 5, Article number: 5107 doi:10.1038/ncomms6107
http://www.nature.com/ncomms/2014/140929/ncomms6107/full/ncomms6107.html

Abstract: "During the last glacial termination, the upwelling strength of the southern polar limb of the Atlantic Meridional Overturning Circulation varied, changing the ventilation and stratification of the high-latitude Southern Ocean. During the same period, at least two phases of abrupt global sea-level rise—meltwater pulses—took place. Although the timing and magnitude of these events have become better constrained, a causal link between ocean stratification, the meltwater pulses and accelerated ice loss from Antarctica has not been proven. Here we simulate Antarctic ice sheet evolution over the last 25 kyr using a data-constrained ice-sheet model forced by changes in Southern Ocean temperature from an Earth system model. Results reveal several episodes of accelerated ice-sheet recession, the largest being coincident with meltwater pulse 1A. This resulted from reduced Southern Ocean overturning following Heinrich Event 1, when warmer subsurface water thermally eroded grounded marine-based ice and instigated a positive feedback that further accelerated ice-sheet retreat."

See also discuss in the following linked article (and attached image) about how this applies to current conditions:

http://www.climatecentral.org/news/antarctica-ice-melt-sea-level-18155

Caption from image: "Antarctic melting during Meltwater Pulse 1A was accelerated by ocean circulation changes, modeling suggests"
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Lennart van der Linde

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Re: CO2 spikes during deglaciation
« Reply #4 on: January 06, 2015, 08:52:01 PM »
Thanks, ASLR.

I've been wondering for a while how much of the 100 ppm or so CO2-rise during the last deglaciation came from the oceans, and how much from melting permafrost. I've not seen any clear conclusions on that yet, but haven't had time too look for them much either. Maybe you or anyone else knows?

AbruptSLR

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Re: CO2 spikes during deglaciation
« Reply #5 on: January 06, 2015, 09:47:38 PM »
Lennart,

I do not know that answer to your question, but I am re-posting the following information from the Paleo thread in the Antarctic folder because as we now have evidence that the WAIS is already in the process of collapsing, the linked reference (with an open access pdf) shows that a collapse (or partial collapse as was the case for MWP 1A) of the WAIS can drive Arctic amplification (and associated permafrost degradation) by pushing warm ocean water through the Bering Strait into the Arctic Ocean:

Martin Melles, Julie Brigham-Grette, Pavel S. Minyuk, Norbert R. Nowaczyk, Volker Wennrich, Robert M. DeConto,  Patricia M. Anderson, Andrei A. Andreev, Anthony Coletti, Timothy L. Cook, Eeva Haltia-Hovi, Maaret Kukkonen, Anatoli V. Lozhkin, Peter Rosén, Pavel Tarasov, Hendrik Vogel, & Bernd Wagner, (2012), "2.8 Million Years of Arctic Climate Change from Lake El’gygytgyn, NE Russia", Science, Vol. 337 no. 6092 pp. 315-320, DOI: 10.1126/science.1222135


http://bhap.artsrn.ualberta.ca/images/uploads/BHAP_Papers_2012/Melles_et_al._Science_2012.pdf



ABSTRACT
"The reliability of Arctic climate predictions is currently hampered by insufficient knowledge of natural climate variability in the past. A sediment core from Lake El’gygytgyn in northeastern (NE) Russia provides a continuous, high-resolution record from the Arctic, spanning the past 2.8 million years. This core reveals numerous “super interglacials” during the Quaternary; for marine benthic isotope stages (MIS) 11c and 31, maximum summer temperatures and annual precipitation values are ~4° to 5°C and ~300 millimeters higher than those of MIS 1 and 5e. Climate simulations show that these extreme warm conditions are difficult to explain with greenhouse gas and astronomical forcing alone, implying the importance of amplifying feedbacks and far field influences. The timing of Arctic warming relative to West Antarctic Ice Sheet retreats implies strong interhemispheric climate connectivity."

See also:
http://www.newscientist.com/article/dn21959-loss-of-antarctic-ice-could-trigger-superinterglacial.html#.VKxIOqPTnIU

Extract: " At least eight times in the last 2.8 million years, the Arctic experienced super-interglacials – periods in which summers there were 5 °C warmer than they are today.
Climate models cannot explain these unusually warm spells, but there could be an unexpected cause: the collapse of the West Antarctic ice sheet (WAIS), on the other side of the planet. The sheet could collapse again as the world warms, perhaps heralding super-interglacial number nine.
The evidence for the super-interglacials comes from a sediment core drilled from the bed of Lake El'gygytgyn in north-east Russia by Martin Melles of the University of Köln in Germany, and his colleagues.

Toasty warm

The Arctic ice sheets have been advancing and retreating for the last 2.6 million years, as temperatures fell and rose. Warmer periods – including the one we now live in – are known as interglacials. The Lake El'gygytgyn core confirms that Arctic temperatures during eight of these periods were on average 4 to 5 °C warmer than in the region today. "That's really a lot," says Melles.
What triggered these super-interglacials? Earlier studies hinting that they occurred encouraged Paul Valdes at the University of Bristol, UK, to try to find out. Last year he discovered that standard climate models couldn't simulate them (Journal of Quaternary Science, DOI: 10.1002/jqs.1525).
Melles ran into the same problem. He used a state-of-the-art climate model that included key positive feedbacks, such as vegetation moving north and thus absorbing more heat. But he could not trigger a super-interglacial in his simulations.
He turned to sediment records from Antarctica for further clues. These records suggest that the WAIS disintegrated during each of the super-interglacials.
All around the world
Despite being half a world away, the collapse of the ice sheet might be the trigger for an Arctic super-interglacial, says Melles. As the WAIS disintegrates, it would raise global sea levels by about 5 metres. This would push more warm water from the Pacific Ocean through the Bering Strait into the Arctic Ocean, warming the Arctic region.
Valdes agrees such a process could well be important, particularly as it was not included in the models he studied last year. So a collapsing WAIS would not just drive up sea levels, it might also heat up the Arctic. The $64,000 question is, will it collapse again in the near future?
"What we see today is a dramatic decrease of the WAIS," Melles says. Some scientists think it will start to break up this century. But Melles says it could be centuries before the whole thing goes, and the effects would then take time to reach the Arctic.
"I don't think we know what it will take to lose the WAIS," says Valdes, "but if it goes, it would have climate consequences for the whole globe."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson