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Working Group 3: What aspects of coastal ecosystems are significant globally?

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Working Group 3: What aspects of coastal ecosystems are significant globally?. Contributed by G.-K. Plattner, J. Kleypas, C. Nevison, A. Subramaniam. Coastal Zone Impacts on Global Biogeochemistry NCAR, June 2004. Outline: Key questions / areas.

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slide1

Working Group 3:

What aspects of coastal ecosystems are significant globally?

Contributed by

G.-K. Plattner, J. Kleypas, C. Nevison, A. Subramaniam

Coastal Zone Impacts on Global Biogeochemistry

NCAR, June 2004

outline key questions areas
Outline: Key questions / areas
  • How much do coastal zones matter for global atmospheric CO2?
  • How large is the impact on atmospheric chemistry and aerosols at different spatial scales?
  • e.g. N2O,CH4,DMS
  • Role of coastal salt marsh and mangrove swamps?
  • Role of river discharge?
the global carbon budget 1980 1999
The global carbon budget 1980-1999

(Sabine et al., SCOPE 2004)

coastal ocean and global carbon cycle
Coastal Ocean and Global Carbon Cycle
  • Conventional wisdom suggests that due to large river inputs of organic and inorganic carbon and due to fast local remineralization, the coastal oceans act as a net source of CO2 to the atmosphere.
  • Recent studies suggest a global net sink for atmospheric CO2(0.36Gt C yr-1; valuesrange from of 0.2 to 1 Gt C yr-1).
the global ocean carbon budget 1980 1999
The global ocean carbon budget 1980-1999
  • Units: Reservoirs in Gt C, Fluxes in Gt C yr-1

(Sabine et al., SCOPE 2004)

the global ocean carbon budget 1980 19991
The global ocean carbon budget 1980-1999
  • Estim. coastal fluxes:
  • - River input
  • inorg. ~0.6
  • org. ~0.5
  • - Sedimentation
  • ~0.4
  • - Net sea-air CO2 flux
  • ~0.36? (Chen, 2004)
  • - Export open ocean?
  • Units: Reservoirs in Gt C, Fluxes in Gt C yr-1

?

?

(Sabine et al., SCOPE 2004)

coastal ocean and global carbon cycle1
Coastal Ocean and Global Carbon Cycle
  •  The coastal zone fluxes represent the largest unknown in the CO2 balance of the oceans
  • Why?
  • Net fluxes of CO2 are small compared to gross fluxes
  •  difficult to measure
  • Global analysis of net air-sea gas exchange does not resolve coastal zones (Takahashi et al., 2002)
sea air co 2 flux annual mean
Sea-air CO2 flux: Annual mean

~106 measurements, 4ox5o grid

Global net CO2 flux : 1.5 GtC yr-1

coastal ocean and global carbon cycle2
Coastal Ocean and Global Carbon Cycle
  •  The coastal zone fluxes represent the largest unknown in the CO2 balance of the oceans
  • Net fluxes of CO2 are small compared to gross fluxes
  •  difficult to measure
  • Global analysis of net air-sea gas exchange does not
    • resolve coastal zones (Takahashi et al., 2002).
  • Large temporal and spatial (incl. meso- and submesoscale eddies) variability in the coastal ocean
slide11

Large variability of pCO2 in coastal systems: e.g. in an upwelling system (California)

(Friederich et al., AGU 2002)

coastal ocean and global carbon cycle3
Coastal Ocean and Global Carbon Cycle
  •  The coastal zone fluxes represent the largest unknown in the CO2 balance of the oceans
  • Net fluxes of CO2 are small compared to gross fluxes
  •  difficult to measure
  • Global analysis of net air-sea gas exchange does not
    • resolve coastal zones (Takahashi et al., 2002).
  • Large temporal and spatial (incl. meso- and submesoscale eddies) variability in the coastal ocean
  • Net sink or source of atmospheric CO2?
  • Models can’t help: coastal oceans not represented in current global ocean carbon cycle models
    •  see working group 4 outline
past present and future role
Past, Present and Future Role?

(Chen, SCOPE 2004; adapted from Ver et al. 1999)

summary
Summary
  • Significant river input of carbon (~0.6 Gt C yr-1 inorganic, ~0.5 Gt C yr-1organic) into coastal ocean
  • Sedimentation in the coastal zone is only ~0.4 Gt C yr-1
  • Recent studies nevertheless suggest a sink for atm. CO2of 0.36Gt C yr-1(range of 0.2 to 1 Gt C yr-1)
  • Export to open ocean?
  •  The coastal zone fluxes represent the largest unknown in the CO2 balance of the oceans
proposed outline key questions areas
Proposed outline: Key questions / areas
  • How much do coastal zones matter for global atmospheric CO2?
  • How much do coastal zones matter for other atmospheric compounds?
  • e.g. N2O, CH4, DMS
  • Topics:
  • Which coastal ecosystems are of relevance?
  • What’s their relative importance?
  • Role of biology vs. physical processes (incl. river discharge)?
  • Natural flux vs. anthropogenic perturbation?
the global carbon budget 1980 19991
The global carbon budget 1980-1999

(Sabine et al., SCOPE 2003)

preindustrial organic carbon cycle for coastal oceans
Preindustrial organic carbon cyclefor coastal oceans

(Chen, SCOPE 2004; after Rabouille et al., 2001)

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