Interannual Variability in the Extratropical Ocean Carbon System

1
Interannual Variability in the Extratropical
Ocean Carbon System
Scott Doney (WHOI)
-Ubiquitous!! -Climate modes -Climate
change? -Experimental design
Hawaii Ocean Time-Series
Dore et al. (2002)
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Global Carbon Cycle
-Ocean sequester 30 of fossil fuel CO2 -Human
perturbations overlay large natural background C
cycle -Climate responses and feedbacks of ocean C
sink not well known
Doney and Schimel (2001)
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Interannual Variability in Global Carbon Cycle
ATMOSPHERE
Francey
-Large year to year changes in atmospheric CO2
growth rate -Variability dominated by land sinks
but role for the oceans -Primary global signal
associated with ENSO events
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Equatorial Pacific
Large-Scale EqPac Results (1997-2002) El Niño
0.2-0.4 PgC/y Non El Niño 0.7-0.9 PgC/y La
Niña 0.8-1.0 PgC/y Average
0.60.2 PgC/y -Dense time/space
coverage -Thermocline depth variation
subsurface iron supply -Corresponding changes in
productivity, biomass, community structure
Feely et al. (2003)
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Equatorial Pacific
physics
-DIC supply (dominant) export out of
phase -General agreement among field data, ocean
models top-down atmospheric estimates -But
what about the extratropics?
air-sea flux
export
Obata et al. (2003)
ocean model
data
Obata et al. (2003)
atmosphere
Le Quere et al. (2000)
Bousquet et al. (2000)
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Natural Climate Modes
Surface Pressure Anomaly
NAO North Atlantic Oscillation PDO Pacific
Decadal Oscillation AAO Antarctic
Oscillation -Shift of mass from subpolar lows
and subtropical highs -Changes in winds, SST,
ocean convection, freshwater flux, -Intrinsic
atmospheric variability (ocean,
stratosphere) -Tropical-extratropical interactions
NAO
Wang and Schimel (2003)
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Regional Spatial Patterns
Wang and Schimel (2003)
Correlation
Correlation
-0.6
0.8
0.8
-0.6
-Modes expressed on regional (sub-basin) scales
with significant cancellation (dipole
pattern) -Historical and future climate change
appear to project onto natural modes -Spatial
patterns may evolve with time
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Physical Biological Controls
pCO2 f(Temp., Salinity, DIC, Alkalinity)
() -
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SubtropicalNorth Atlantic
Mixed Layer
Negative NAO gt WML -SST
entrainment production CO2
uptake Extrapolate to subtropical gyre gt 0.2
PgC/y whole basin gt 0.3 PgC/y
CO2 uptake
Entrainment
Transport
Production
Gruber et al. (2002)
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Pacific Decadal Oscillation
ML Anomaly

Wang Schimel (2003)

PDO
Depth Integrated Chlorophyll
Subtropical nutrient limited prod. ML gt
Chlorophyll Production Subpolar/Pol
ar light limited prod. -ML gt Production multiple
impacts on higher trophic levels (e.g.
zooplankton, fisheries, mammels)
Karl et al. (2001)
Hare Mantura (2000)
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Antarctic Circumpolar Wave
-Ocean response to annular mode in the
atmosphere -Different regional biological
responses to mixed layer depth changes -Air-sea
CO2 flux correlated with wind stress/speed
Le Quere et al. (2002)
Wind Stress CO2 flux Anomalies
0.1
Obata et al. (2003)
-0.1
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Global Extratropical Variability
LeQuere 0.4 (70 Eq. Pac.) Obata 0.23 (gt50
Eq. Pac. 30
Southern) -Only partial reconciliation with
atmosphere inversions -Poor data coverage outside
of equatorial Pacific
LeQuere et al. (2000)
Obata et al. (2003)
Bousquet et al. (2003)
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SeaWiFS Ocean Color Data (1997-2003)
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SeaWiFS Ocean Color Data (1997-2003)
standard deviation
std/mean
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Coherent Regional-Scale Patterns
SeaWiFS Monthly Anomaly
SeaWiFS Monthly Anomaly
April 2000
Oct. 1998
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Multi-Century Coupled Carbon/Climate Simulations
1.5
14.1
-1.5
13.6
Surface Temp.
Net CO2 Flux (Pg C/yr)
0
200
year
Fung, Doney, Lindsay John
-Fully prognostic land/ocn BGC and
carbon/radiation -Stable carbon cycle and
climate over 200y -Projection of climate change
on natural modes -Detection attribution
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Variability Mechanisms
Particle export
Fresh- water
mol C/m2
-Regions of high variability in North Atlantic
Pacific, tropics and Southern Ocean -Mechanisms
differ across regions
Fung, Doney, Lindsay John
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Atmospheric Dust Deposition
-Significant interannual variability,
particularly in the North Atlantic -Driven mostly
by atmospheric transport, not sources -Largest
fraction is synoptic, within month variability
(standard deviation/mean)
Mahowald et al. (2003)
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Iron flux
Zonal Anomalies
Air-sea CO2 flux
N2 Fixation
Doney, Dusenberry, Moore Mahowald
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Conclusions
-Common feature of almost all ocean
time-series -Regional time-space structured by
climate modes biology -Natural experiments for
studying climate change response -Require more
spatially extensive design for ocean observation
Acknowledgements J. Dusenberry S. McCue WHOI K.
Lindsay NCAR NSF and NSF/ONR NOPP CCSM the NCAR
CSL