Greg & Andrew,
In the short term, anoxic conditions should reduce available organic nitrogen because anoxic bacteria convert nitrate to N2 (denitrification). Less oxygen dissolves in warmer water. Low oxygen favors anoxic bacteria who obtain oxygen from nitrate.
The following may answer some of your questions about denitrification in general if not the specific event.
The acceleration of oceanic denitrification during deglacial warming
- Journal name:
- Nature Geoscience 02 June 2013
---------- Original Message --------
Subject: Re: [geo] Rock weathering: Effective, planetary scale CO2
management
From: Andrew Lockley <[email protected]>
Date: Sat, July 27, 2013 2:49 pm
To: [email protected], geoengineering
<[email protected]>
Poster's note: Original paper abstract/link below. I find it
interesting how similar this purported event is to AGW. This change
seemingly resulted in partially 'dead oceans' and it would be
interesting to ascertain whether Chicken McNuggets could have survived
in such an environment (if that sounds like nonsense, please refer to
group archives for the relevant threads). I'm keen to hear from
paleo-experts on this lists whether this warming occurred in an ice
age or hothouse world, and if an ice age, whether a glacial or
interglacial. The relevance of the preceding period to cryogenically
stored methane (or vanilla carbon in permafrost) is obvious, although
potentially very different from modern times, due to continental
configurations, vegetation, etc.
http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo1875.html
Lithium isotope evidence for enhanced weathering during Oceanic Anoxic Event 2
Philip A. E. Pogge von Strandmann, Hugh C. Jenkyns & Richard G. Woodfine
Nature Geoscience (2013) doi:10.1038/ngeo1875
Published online 07 July 2013
Abstract
The Ocean Anoxic Event 2 (OAE2) about 93.5 million years ago was
marked by high atmospheric CO2 concentration, rapid global warming and
marine anoxia and euxinia. The event lasted for about 440,000 years
and led to habitat loss and mass extinction. The marine anoxia is
thought to be linked to enhanced biological productivity, but it is
unclear what triggered the increased production and what allowed the
subsequent rapid climate recovery. Here we use lithium isotope
measurements from carbonates spanning the interval including OAE2 to
assess the role of silicate weathering. We find the lightest values of
the Li isotope ratio (δ7Li) during OAE2, indicating high levels of
weathering—and therefore atmospheric CO2 removal—which we attribute to
an enhanced hydrological cycle. We use a geochemical model to simulate
the evolution of δ7Li and the Ca, Sr and Os isotope tracers. Our
simulations suggest a scenario in which the eruption of a large
igneous province led to high atmospheric CO2 concentrations and rapid
global warming, which initiated OAE2. The simulated warming was
accompanied by a roughly 200,000 year pulse of accelerated weathering
of mafic silicate rocks, which removed CO2 from the atmosphere. The
weathering also delivered nutrients to the oceans that stimulated
primary productivity. We suggest that this process, together with the
burial of organic carbon, allowed the rapid recovery and stabilization
from the greenhouse state.
On 27 July 2013 22:30, Greg Rau <[email protected]> wrote:
> Further evidence that rock weathering is the major player in removing CO2
> from 10GT/yr x 10kyr events. In managing our present "event", how about
> building on and accelerating this proven, global-scale process?
> -Greg
>
> http://www.sciencedaily.com/releases/2013/07/130726074939.htm?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+sciencedaily%2Fearth_climate%2Fglobal_warming+%28ScienceDaily%3A+Earth+%26+Climate+News+--+Global+Warming%29
>
>
> Rocks Can Restore Our Climate ... After 300,000 Years
> July 26, 2013 — A study of a global warming event that happened 93 million
> years ago suggests that the Earth can recover from high carbon dioxide
> emissions faster than thought, but that this process takes around 300,000
> years after emissions decline.Scientists from Oxford University studied
> rocks from locations including Beachy Head, near Eastbourne, and South
> Ferriby, North Lincolnshire, to investigate how chemical weathering of rocks
> 'rebalanced' the climate after vast amounts of carbon dioxide (CO2) were
> emitted during more than 10,000 years of volcanic eruptions.
>
> In chemical weathering CO2 from the atmosphere dissolved in rainwater reacts
> with rocks such as basalt or granite, dissolving them so that this
> atmospheric carbon then flows into the oceans, where a large proportion is
> 'trapped' in the bodies of marine organisms.
> The team tested the idea that, as CO2 warms the planet, the reactions
> involved in chemical weathering speed up, causing more CO2 to be 'locked
> away', until, if CO2 emissions decline, the climate begins to cool again.
> The Oxford team looked at evidence from the 'Ocean Anoxic Event 2' in the
> Late Cretaceous when volcanic activity spewed around 10 gigatonnes of CO2
> into the atmosphere every year for over 10,000 years. The researchers found
> that during this period chemical weathering increased, locking away more CO2
> as the world warmed and enabling the Earth to stabilise to a cooler climate
> within 300,000 years, up to four times faster than previously thought.
> A report of the research is published in Nature Geoscience.
> 'Looking at this event is rather like imagining what the Earth would be like
> if humans disappeared tomorrow,' said Dr Philip Pogge von Strandmann of
> Oxford University's Department of Earth Sciences, who led the research.
> 'Volcanic CO2 emissions in this period are similar to, if slightly slower
> than, current manmade emissions so that we can imagine a scenario in which,
> after human CO2 emissions ceased, the planet's climate would start to
> recover and cool down. The bad news is that it's likely this would take
> around 300,000 years.'
> Reconstructing a record of past chemical weathering is challenging because
> of how plants and animals take carbon out of the environment. To get around
> this the team used a recently-developed technique involving studying lithium
> isotopes in marine limestone (this lithium could only come from weathering
> and is not changed by biological organisms).
> The Ocean Anoxic Event 2 is believed to have been caused by a massive
> increase in volcanic activity in one of three regions: the Caribbean,
> Madagascar, or the Solomon Islands. The event saw the temperature of
> seawater around the equator warm by about 3 degrees Celsius. It is thought
> that this warming caused around 53% of marine species to go extinct. Animals
> like turtles, fish, and ammonites were amongst those severely affected.
> 'Everyone remembers the mass extinction of land animals caused by the K-T
> meteorite impact 30 million years later, thought to be responsible for the
> demise of the dinosaurs, but in many ways this was just as devastating for
> marine life,' said Dr Pogge von Strandmann. 'Whilst nutrients from
> weathering caused a population boom of some species near the surface of the
> oceans, it also led to a loss of oxygen to the deeper ocean, killing off
> over half of all marine species and creating a 'dead zone' of decaying
> animals and plants. It's a scenario we wouldn't want to see repeated today.
> 'Our research is good news, showing that the Earth can recover up to four
> times faster than we thought from CO2 emissions, but even if we stopped all
> emissions today this recovery would still take hundreds of thousands of
> years. We have to start doing something soon to remove CO2 from the
> atmosphere if we don't want to see a repeat of the kind of mass extinctions
> that global warming has triggered in the past.'
> The research was supported by the UK's Natural Environment Research Council.
>
> --
> You received this message because you are subscribed to the Google Groups
> "geoengineering" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to [email protected].
> To post to this group, send email to [email protected].
> Visit this group at http://groups.google.com/group/geoengineering.
> For more options, visit https://groups.google.com/groups/opt_out.
>
>
--
You received this message because you are subscribed to the Google Groups "geoengineering" group.
To unsubscribe from this group and stop receiving emails from it, send an email to [email protected].
To post to this group, send email to [email protected].
Visit this group at http://groups.google.com/group/geoengineering.
For more options, visit https://groups.google.com/groups/opt_out.
You received this message because you are subscribed to the Google Groups "geoengineering" group.
To unsubscribe from this group and stop receiving emails from it, send an email to [email protected].
To post to this group, send email to [email protected].
Visit this group at http://groups.google.com/group/geoengineering.
For more options, visit https://groups.google.com/groups/opt_out.
