Complementary Constraints from Carbon and Nitrogen Isotopes on the LGM Ocean’s Biological Pump Andreas Schmittner and Christopher Somes College of Earth, Ocean, and Atmospheric Sciences Oregon State University δ 13 C I’ll tell you about circulation δ 15 N I’ll tell you about iron fertilization Δ 14 C I’ll tell you about ventilation Funded by NSF’s Marine Geology and Geophysics Program IPODS Workshop Aug. 27, 2016, Utrecht
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Complementary Constraints from Carbon and Nitrogen Isotopes on the LGM Ocean’s Biological Pump
Andreas Schmittner and Christopher Somes College of Earth, Ocean, and Atmospheric Sciences
Oregon State University
δ13C
I’ll tell you about
circulation δ15N
I’ll tell you about iron
fertilization Δ14C
I’ll tell you about
ventilation
Funded by NSF’s Marine Geology and Geophysics Program
IPODS Workshop Aug. 27, 2016, Utrecht
Goals• Explore effects of changes in physics (e.g.
circulation, sea ice) and biology (e.g. iron fertilization) on LGM distributions of δ13C, δ15N
• Compare model solutions to reconstructions
• Was the LGM biological pump stronger?
Schmittner and Somes (2016) Paleoceanography, doi:10.1002/2015PA002905.
Detritus
DIC
PO4
NO3
O2
Photosynthesis
Fast Recycling
13C
Water ColumnDenitrification
Sinking
15N15N13C
Grazing
Mortality
Remineralization
Excretion
CO2O2
13C
N-Fixation
N2δ15NN2=0
BenthicDenitrification
(Fe)
εBD ! −4‰
εWCD ! −25‰
εP ! −5‰
εP
εP
εE = −6‰
εAS
CaCO3
δ13C ! 2‰13C
δ13CDIC ! 2‰
Phytoplankton
15N13C δ
13C ! −20‰
Diazotrophs
15N13C δ 13C ! −12‰
δ13C ! −20‰
Zooplankton
15N13C δ
13C ! −20‰
14CDecay
δ 13CCO2 ! −6.5‰
δ 13CDIC ! 0.5‰
DOM
15N13C δ
13C ! −20‰
εP ! −20‰
εNF ! −1‰δ 15NNO3 ! 9‰
δ 15NNO3 ! 5.5‰
δ 15N ! −1‰
δ 15N ! 4‰
δ 15N ! 7‰
δ 15N ! 5‰
δ 15N ! 6‰
MOBI Model of Ocean Biogeochemistry and Isotopes Somes et al. (2013, 2015) Schmittner et al. (2015)
Numerical Experiments• Pre-industrial Control (piCtrl) μmax = 0.6 d-1