atlantic meridional overturning circulation effects on the carbon cycle and atmospheric co2
TRANSCRIPT
AMOC Effects on the Carbon Cycle and Atmospheric CO2
Andreas SchmittnerOregon State University
Paleo AMOC Workshop, Boulder, May 24, 2016
Ahn and Brook (2014) Nature Communications
The Ice Core RecordMulti-Millennial Scale Changes
Marcott et al. (2014) Nature Ahn et al. (2012) GRL
The Ice Core RecordMulti-Millennial Scale Changes
Circulatio
n
CO2
Soil
CO2
Land Carbon Cycle
Circulation
CO2
Plankton
DICPO4
DICPO4
Ocean Carbon Cycle
The Carbon CycleΔCA+ΔCO+ΔCL=0
CA=600 Gt CL=2,000 Gt
CO=40,000 Gt
DIC
Marchal et al. (1998) Paleoceanography
AMOC
(Sv)
Scholze et al. (2003) Holocene
ΔT
ΔP
ΔNPP
Early modeling studies showed that changes in AMOC affect• Ocean Carbon Storage
• Land Carbon Storage
• Atmospheric CO2
SummaryIce core data suggest CO2 increases if AMOC is shutdown.
Ocean Carbon Cycle
• Solubility Pump
• Biological Pump
• Soft Tissue (organic carbon)
• Hard Tissue (CaCO3)
It contributes ~1/3 to the total globalsurface-to-deep DIC gradient
It contributes ~2/3 to the total globalsurface-to-deep DIC gradient
The Ocean’s Carbon Pumps
Solubility SoftTissue
Preformed
HardTissue
Circulati
o
n
Circulation
Plankton
DICPO4
DICPO4
DICPO4
CO2
Schmittner et al. (2013) Biogeosc.
Plankton
DICPO4
DICPO4
remineralized
PO4
PO4preforme
d
Soft-Tissue Pump and Preformed (Unused) Nutrient Inventory
PtotPpref
Ptot=Ppre+Prem
Prem
Marinov et al. 2008 GBCIto & Follows
2005 J. Mar. Res
NADW injects relatively low preformed nutrients
into deep ocean.
This makes biologicalpump efficient.
AABW & AAIW inject highpreformed nutrients
into deep ocean.
This makes biological pump
inefficient.
Preformed Nutrients Change model year 2500
Pacific Atlantic
Schmittner & Galbraith 2008 Nature
Dept
h (m
)
Schmittner & Galbraith 2008 Nature
HypothesisAMOC shutdown decreases
input of low pre-formed nutrientsthus increases the pre-formed nutrient inventory of the ocean
Schmittner & Galbraith 2008 Nature
Simulated changesin CO2 are similarto observations.
Schmittner and Lund (2015) Climate of the Past
Simulated changes
are highly correlated
with sedimentreconstructions
(r=0.85)
(2014) Paleoceanogr.
FW fluxes in SO and EEqP
required to simulate observed CO2 increase
Köhler et al. (2005)
Land carbon responseis sensitive to initial
conditions
Bauska et al. (2015) Nat. Geo.
Observedcentennial CO2 variability
remains unexplained.
Is there an AMOC connection?
Nye et al. (2014) JMS
AMO Impacts on Ecosystems Correlation SST-AMO
dryer
wetter
dryer
wetter
Conclusions• Multi-millennial CO2 changes due to AMOC
effects on biological pump efficiency
• Rapid CO2 changes remain unexplained (Land ?)
• Multi-centennial CO2 changes in Holocene remain unexplained