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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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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


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)


Modern annual carbon budget for continental margins
Modern annual carbon budgetfor continental margins

(Chen, SCOPE 2004)


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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