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.
