The Ocean Inorganic Carbon System or what did we learn from the WOCEJGOFS era and where do we go fro

1
The Ocean Inorganic Carbon System or what did we
learn from the WOCE/JGOFS era and where do we go
from here?
Scott C. Doney, WHOI

• Ocean/atmosphere/ land integration
• Interannual variability
• New technology
• Model-data assimilation
• Monitoring, prediction mitigation
• Global carbon cycle, observing system major
  uncertainties

2
Global Carbon Cycle
Human perturbations due to fossil fuel combustion
and land-use change occur on top of a large
natural background cycle coupling the land,
atmosphere, and ocean
Doney and Schimel (2001)
3
CO2, Climate, and Radiative Forcing
CO2 contributes roughly ½ of anthropogenic
warming at present and its contribution will
almost certainly grow in the future.
4
Future Climate Projections
Major uncertainties -emissions (social,
political, economic) -atmospheric inventories
(climate-carbon feedbacks) -climate sensitivities
(clouds, water vapor)
5
Sarmiento and Gruber (2002)
6
Other stuff
Sarmiento and Gruber (2002)
7
Climate-Carbon System Feedbacks
Climate
CO2
Climate
CO2
LeQuere (2002)
8

• Major emphasis on processes that decouple carbon
  and macronutrients
• surface nutrient utilization
• differential remineralization
• nitrogen fixation
• Present conceptual understanding and models are
  insufficient to assess climate responses to
  stratification, pH, iron fertilization, etc.

9
Boyd and Doney (2002)
10
Glacial Interglacial CO2 Variability
100,000
0
200,000
300,000
400,000 years
280
Atmospheric pCO2 (Vostok)
ppm
200
2
Dust (Vostok)
ppm
Petit et al. (1999)
0

• The DCO2 explains about ½ glacial cooling
• Tantalizing hypotheses (dust, sea-ice etc.) but
  holy grail of chemical oceanography still
  unresolved

11
Major Science Questions

• Ocean anthropogenic CO2 inventory
• Magnitude and variability of air-sea CO2 flux
• Feedback mechanisms and climate sensitivities for
  ocean carbon storage
• Marine ecosystem responses to climate and global
  change
• Scientific basis for mitigation strategies
• role of ocean in regulating atmospheric CO2 levels

12
Basin-Scale Ocean Carbon Experiments

• Integrated Program of
• CLIVAR/CO2 repeat survey
• VOS/SOP surface pCO2
• Time-series/moorings/floats
• Coastal observing networks
• Process studies
• Remote Sensing
• New technology
• Modeling assimilation
• Atmospheric constraints
• Data management

Doney et al. (2000)
13
CO2 Observational Platforms and Sensors
time
centuries
Repeat Trans-basin Sections
decadal
Shipboard Time-Series
Inter-annual
Moored Time-Series
VOS surface pCO2
Remote sensing
seasonal
daily
Process Studies
Sweeney
hourly
space
Ocean Basin
1 m2
1 km2
Globe
Regional (106 km2)
different space and time scales, data coverage,
analysis methods ? consistent synthesis
14
New Technology Observational Paradigms
Chavez et al. (1999)
Bishop
15
(No Transcript)
16
Anthropogenic uptake estimates
Pre-JGOFS - 2.0/-0.8 Pg C/yr (1980s) -ocean
model based -regional DIC data sets
Present 1.7/-0.5 Pg C/yr (1990s) -ocean data
based (empirical Canthro, d13C, transient
tracer-CO2) -atmospheric estimates (d13C,
O2/N2) -Southern ocean sink -temporal evolution
of DIC
17
JGOFS/WOCE global survey
-Global baseline (hydrography, transient tracers,
nutrients, carbonate system) -Improved analytical
techniques (DIC 1-2 mmol/kg Alkalinity 2-3
mmol/kg) -Certified Reference Materials -Data
management, quality control, public data access
18
Empirical Anthropogenic CO2
Sarmiento and Gruber (2002)
Removal of large metabolic DIC and pre-industrial
solubility signals -steady state assumption -O2
surface saturation -uniform Redfield
ratios -seasonal sampling bias -air-water
disequilibrium -analogies of CFC and Canthro
19
Direct Measures of DIC Temporal Evolution
North Pacific
Multiple-linear regression techniques account for
shifts in natural background due to local changes
in physics biology
(1991)
(1999)
(1973)
DIC a? bS cAOU dSi(OH)4 ePO4
Feely et al. (2002)
20
Transient Tracer-CO2 Correlations
CFC-11 Age
Total Canthro
CFC-Canthro analog
Canthro (age lt 30y)
Year
Canthro
McNeil et al (2002)
Wanninkhof et al. (1999)
21
Decadal Time-Scale Variability of Biogeochemical
Fields
Changes in AOU (red 20 µmol/kg, blue -20
µmol/kg)
HOT Time-series
11/97-3/91
11/97-5/84
Karl (2002)

• Decadal-scale trend with higher NO3 and AOU in
  North Pacific thermocline
• Slowed ventilation or 30-40 increase in
  biological pump
• Resolvable in atmospheric O2?
• Possibly due to enhanced subtropical N2 fixation

24
11/97-8/80
Density
27
40
25
Latitude
Emerson et al. (2002)
22
Carbon Transport and Divergence
Northward Atlantic DIC Transport
Modern (1990-94)
Global ocean transport
Preindustrial
-derivable from hydrographic section data using
inverse methods -provides for basin-scale
closure -seperation of Canthro inputs from
accumulation -net preindustrial southward
transport across equator (global 0.2-0.4 Pg C/yr)
leading to atmospheric gradients
Preindustrial atmospheric gradient
Orr et al.
23
Air-Sea CO2 Flux Estimates
Pre-JGOFS -limited air-sea DpCO2 data set (N.
Hemisphere, summer bias) -empirical wind-speed
gas exchange parameterizations -regional mean
seasonal cycle
Present -greatly enhanced global data coverage
(VOS, moorings) 250K (Takahashi 97) 940K
(Takahashi 02) -biological/physical factors
affecting seasonal pCO2 -interannual flux
variability (ENSO-equatorial Pacific) -new gas
exchange techniques (direct eddy-covariance
fluxes, satellite scatterometers, atmospheric
constraints)
Takahashi et al. (2002)
24
Gas Exchange Kinetics
GasEx-2001

• Eddy covariance measurements suggest more
  non-linear relationship to wind-speed (cubic?)
• Mechanistic studies need to move beyond wind
  speed to underlying physio-chemical factors (near
  surface turbulence, microscale breaking,
  surfactants, bubbles)

25
Time/Space Sampling Issues

• Even with increased VOS and research vessel
  coverage and instrumenting of Antarctic resupply
  vessels, the Southern ocean will likely remain
  undersampled
• Remote sensing (SST, ocean color, wind speed/gas
  exchange velocity) data assimilation may play
  key roles

Glover and Frew
26
Top-down Atmospheric Constraints
Transcom3 Gurney et al. (2002)

• Using atmospheric transport models and inverse
  techniques, one can estimate regional net air-sea
  carbon fluxes from spatial CO2 field
• Carbon isotopes and O2/N2 provide more global
  constraints

27
Reconcile ocean and atmosphere estimates of
Southern Ocean uptake?
28

• Interannual air-sea flux variability
• Significant oceanic variability driven by natural
  climate modes (ENSO, NAO, PDO)
• Timing, magnitude mechanisms of mid to
  high-latitude variability?

Atmospheric Inversions,
Baker (in prep.)
1 PgC/yr
Equatorial Pacific
Global Ocean
Global Ocean
Ocean Models, LeQuere et al. (2002)
Feely et al. (2001)
29
Land-Ocean Interface

• Global impacts of coastal air-sea CO2 fluxes and
  offshore carbon export not well known (but
  several mechanisms proposed)
• Complicated because of river inputs, estuarine
  cycling, coastal upwelling, and small time/space
  scales

AVHRR SST
30
Scientific Basis for Mitigation Strategies
Direct CO2 injection -local effects -sequestration
time-scales
Caldeira Wickett
Iron fertilization -carbon export
sequestration -ecosystem response
SOIREE (Boyd et al., 2001)
31
Numerical Modeling
Pre-JGOFS -box and 1-D uptake models -preliminary
global 3-D tracer and simple biogeochemical
models (e.g., nutrient restoring -solubility pump
with fixed circulation
Present -coupled ecological-BGC models (iron,
functional groups) -Ocean Carbon Model
Intercomparison Project (OCMIP) -strong data
constraints -climate change response -inverse
modeling
32
Formal Model-data Evaluation Framework
OCMIP international model-model model-data
intercomparison of dozen global 3-D
models -physics, tracers (14C, CFCs), Canthro,
DIC, alkalinity, O2, macro-nutrients
33
Inverse and Diagnostic Models
Combine global survey data and circulation model
in dynamically consistent way
Pre-industrial air-sea fluxes and transport
Gruber et al.
34
Elements of a Carbon Data Assimilation System
Observing Network
Data Delivery Network
Data Synthesis
Information
35
Basin-scale CO2 Experiments
Doney et al. (2000)