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| Titel |
Enhanced volcanic CO2 degassing at oceanic hotspots and mid-ocean ridges in response to falling sea level |
| VerfasserIn |
Jörg Hasenclever, Gregor Knorr, Lars Rüpke, Peter Köhler, Jason Morgan, Kristin Garofalo, Stephen Barker, Gerrit Lohmann, Ian Hall |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250133598
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| Publikation (Nr.) |
 EGU/EGU2016-14228.pdf |
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| Zusammenfassung |
| Evidence from paleo-climate proxy data as well as results from geodynamical and
biogeochemical modelling point to complex interactions between sea level variations,
pressure-release melting of oceanic mantle, associated volcanic degassing, and atmospheric
CO2 concentrations. Ice core data shows that the orbital component in global temperature
records gradually declined between ∼85,000-70,000 yr BP, while atmospheric CO2—instead
of continuing its long-term correlation with Antarctic temperatures—remained relatively
stable for several thousand years. Based on 2-D and 3-D geodynamical models we show that
the massive (60-100 m) sea level drop during this period of Earth history led to a significant
increase in magma and possibly CO2 fluxes along mid-ocean ridges (MOR) and especially
oceanic hotspot volcanoes.
We assess the MOR magma and CO2 fluxes using 2-D thermo-mechanical models that
solve for wet melting of the mantle and the partitioning of highly incompatible carbon
dioxide into the melt. These models have been run at various MOR opening rates, and we
integrate these results with the global distribution of spreading rates to compute baseline
fluxes as well as enhanced fluxes during the sea level fall. Furthermore we conducted
more than 120 3-D simulations of rising and melting mantle plumes to construct a
four-dimensional parameter space that covers a wide range of plume buoyancy fluxes, plume
excess temperatures, lithosphere thicknesses and plate speeds. Using published data on
43 oceanic hotspots and locating them in the parameter space we derive a global
hotspot-melting model that predicts magma and CO2 fluxes before and during the sea level
drop.
We find that, during a 80 m sea level drop over 10 kyr, global degassing at MOR and
oceanic hotspots increases by 26 % and 36 %, respectively. Biogeochemical carbon
cycle modelling further shows that the combined predicted increase in volcanic
emissions along the global mid-ocean ridge system and at oceanic hotspots is likely
to have raised atmospheric CO2 concentrations by up to 17 ppmv—sufficient to
explain the different trends of temperature and atmospheric CO2 over this period. |
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