Satellite observations of coastal p co 2 and air sea flux of carbon dioxide
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Satellite observations of coastal p CO 2 and air-sea flux of carbon dioxide. Presenter: Steven E. Lohrenz Department of Marine Science The University of Southern Mississippi [email protected] Contributors: Wei-Jun Cai, Wei-Jen Huang – UGA

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Satellite observations of coastal p co 2 and air sea flux of carbon dioxide

Satellite observations of coastal pCO2 and air-sea flux of carbon dioxide

Presenter: Steven E. Lohrenz

Department of Marine Science

The University of Southern Mississippi

[email protected]

Contributors: Wei-Jun Cai, Wei-Jen Huang – UGA

John Lehrter, Mike Murrell, Jan Kurtz – EPA

ACE Workshop

6 June 2011


Acknowledgements

Acknowledgements

  • Support provided for this effort from NASA, NSF, NOAA, and EPA

  • This work supports is aligned with goals and objectives of the Ocean Carbon and Biogeochemistry and North American Carbon Program


Overview

Overview

  • The role of coastal margins in the global carbon budget

  • Satellite algorithms for estimating pCO2 in coastal waters

  • Applications of the approach in the Gulf of Mexico

  • Conclusions and Recommendations


Importance of coastal margins global carbon budgets

Importance of Coastal Margins Global Carbon Budgets

“The North American Carbon Program therefore requires marine observations and diagnostic models focused on understanding the role of coastal systems on adjacent ocean basins and on atmospheric CO2 distributions.” - Wofsy and Harris (2002)

Need for improved estimates of “North American coastal ocean and continental margin air-sea fluxes, land-ocean and coastal open ocean exchange, and biogeochemical cycling…in order to close the carbon budget over North America” - Doney (2004)


Importance of coastal margins in the nacp

Importance of Coastal Margins in the NACP

  • Specific coastal objectives included:

    • “better estimates of air-sea fluxes and their impact on the CO2 concentrations of continental air masses,

    • “estimates of carbon burial and export to the open ocean,

    • “elucidation of factors controlling the efficiency of solubility and biological pumps in coastal environments,

    • “quantification of the influence of margin biogeochemical processes on the chemical composition of open ocean surface waters, and

    • “the development of coupled physical biogeochemical models for different types of continental margins.”

Denning, 2002


Current efforts

Current Efforts

  • Ocean Component of NASA Carbon Monitoring System

    • “The quantity of carbon exchanged between the land and ocean remains an unknown in the global carbon budget,” NASA Carbon Monitoring System Scoping Study Workshop Report, 13-14 July 2010

  • Carbon Cycle Science Plan Update

    • understanding how natural processes and human actions affect the carbon cycle, on land, in the atmosphere, and in the oceans


Synthesis activities addressing coastal carbon

Synthesis Activities Addressing Coastal Carbon

  • Numerous other reviews:

    • Borges et al., 2005;

    • Chen and Borges, 2009;

    • Cai, 2011

Liu et al. (2010)

Hales et al. (2008)

Chavez et al. (SOCCR, 2007)

Crossland et al. (2005)


Significance of coastal ecosystems to global c cycling

Significance of Coastal Ecosystems to Global C Cycling

  • Global riverine C exports to the ocean approach or exceed 0.9 Pg C a-1 (McKee et al., 2003; Cai, 2011)

  • Roughly half of this is organic carbon

  • This is a substantial flux between land and ocean ecosystems and represents a substantial fraction ofthe net ocean atmospheric uptake of carbon (-1.6 Pg C a-1 (Takahashi et al., 2009)


Significance of coastal ecosystems to global c cycling1

Significance of Coastal Ecosystems to Global C Cycling

  • It has been argued that much of this carbon is respired in shelf environments

  • However, recent syntheses (Borges et al., 2005; Liu et al., 2010; Cai, 2011) have shown that most shelves (except in low latitudes) act as a net sink for CO2

  • Increasing levels of atmospheric CO2 may have contributed to the current state of continental shelves as net sinks for atmospheric carbon (Cai, 2011)


Significance of coastal ecosystems to global c cycling2

Significance of Coastal Ecosystems to Global C Cycling

  • In contrast to shelf ecosystems, inner shelf and estuarine waters appear to be a net source of carbon (Borges et al., 2005; Chen and Borges, 2009; Cai, 2011)

  • However, there is some debate as to whether these estuarine and systems are net atmospheric sinks given high productivity of salt marsh and mangrove ecosystems (Cai, 2011)

  • It also seems likely that riverine carbon is largely transported beyond these near shore systems to shelf and ocean waters


Significance of coastal ecosystems to global c cycling3

Significance of Coastal Ecosystems to Global C Cycling

  • Clearly, there remains large uncertainty in the contribution of coastal ecosystems to global carbon budgets and the exchanges and transformation of carbon along the land-water interface

  • The high heterogeneity of these systems necessitates a combination of in situ and satellite approaches

  • Coastal ecosystems also pose serious challenges to satellite based methods given their optical complexity


Satellite observations of coastal p co 2 and air sea flux of carbon dioxide

  • Coastal zones are subject to increasing variability and human impacts including rising CO2

Land

Carbon Management

Land Use and Land Cover Change

Agriculture, Fertilizer

Energy and Biofuels

Population Growth

Water Resource Management

Land-Ocean Exchange

Boundary Effects on Continental Air Masses

Coastal Ocean Exchange

Coastal Margin

Air-Sea Exchange

Eutrophicationand Hypoxia

Ocean Acidification

Sea Level Rise Impacts

Coastal Habitat Loss

Water Quality

Fisheries

Ocean Carbon Reservoir

Air-Sea Exchange

Carbon Sequestration?


Overview1

Overview

  • The role of coastal margins in the global carbon budget

  • Satellite algorithms for estimating pCO2 in coastal waters

  • Applications of the approach in the Gulf of Mexico

  • Conclusions and Recommendations


Satellite algorithms for estimation of p co 2 and air sea flux of carbon

Satellite Algorithms for Estimation of pCO2 and Air-Sea Flux of Carbon

  • Various approaches that use combinations of in situ and satellite observations:

    • Climatologies (e.g., Chavez et al., 2007; Takahashi et al., 2009)

    • Simple regression (Olsen et al., 2004)

    • Multiple regression (Lefevre et al., 2002; Ono et al., 2004; Sarma et al., 2006; Chierici et al., 2009)

    • PCA – regression (Lohrenz and Cai, 2006; Lohrenz et al., 2010)

    • Neural net – SOM (Telszewski et al., 2009; Evans et al., 2011)

  • Satellite observations allow for the extrapolation of in situ observations in time and space


Overview2

Overview

  • The role of coastal margins in the global carbon budget

  • Satellite algorithms for estimating pCO2 in coastal waters

  • Applications of the approach in the Gulf of Mexico

  • Conclusions and Recommendations


Applications in the gulf of mexico

Applications in the Gulf of Mexico

  • The Gulf of Mexico example:

    • Gulf of Mexico a net source?

      • 0.014 Pg C a-1 (Chavez et al., 2007 – climatology)

    • More recent observations (Wanninkhof et al., 2007; Lohrenz et al., 2010) suggest seasonally variable conditions and a possible weak net sink


Satellite observations of coastal p co 2 and air sea flux of carbon dioxide

  • Compare to Lohrenz and Cai (2006) for June 2003:

    • Plume: -6.8- -7.7 mmol m-2 d-1

    • Shelf: -4.9 - -5.5 mmol m-2 d-1

Lohrenz et al., 2010


Satellite observations of coastal p co 2 and air sea flux of carbon dioxide

MODIS

SST,a412,Chl

T,S,Chl

PCA

PCA

pCO2

Map

pCO2

Map

Empircal

Algorithm

Empircal

Algorithm

MODIS

Products

+

In situ

pCO2

In situ

pCO2

  • These earlier studies relied on regressions between in situ observations:

  • An alternative approach is to relate directly to satellite observations:

MODIS

Products

+


Satellite observations of coastal p co 2 and air sea flux of carbon dioxide

  • In situ surveys show seasonal patterns in northern Gulf (Cai et al.)


Seasonal patterns in fluxes in the northern gulf of mexico

Seasonal patterns in fluxes in the northern Gulf of Mexico


Seasonal patterns in fluxes in the northern gulf of mexico1

Seasonal patterns in fluxes in the northern Gulf of Mexico


Overview3

Overview

  • The role of coastal margins in the global carbon budget

  • Satellite algorithms for estimating pCO2 in coastal waters

  • Applications of the approach in the Gulf of Mexico

  • Conclusions and Recommendations


Conclusions

Conclusions

  • The U.S. coastal margins are economically critical regions and coastal regions are subject to extreme environmental variability and increasing human impact

  • Coastal carbon processes may have a significant impact on the continental carbon budget, but large uncertainties remain in air-sea fluxes and land-ocean exchanges

  • Satellite ocean color as well as other satellite-derived products (e.g., SST, winds) will be invaluable in helping to constrain temporal and spatial variability in air-sea flux of carbon dioxide; ACE will have advanced capabilities for coastal applications

  • pCO2 and air-sea flux of carbon dioxide represent products directly relevant to oceanic uptake of carbon

  • Such measurement approaches provide a context for understanding other aspects of ocean productivity and carbon cycling


Recommendations

Recommendations

  • Strategies should be developed to combine field and satellite observations to generate improved estimates of air-sea fluxes using novel experimental designs that are part of an overall flight program

  • Complementary field and satellite-based efforts are needed to understand biogeochemical factors influencing the relative importance of biological and solubility pumps and land-ocean-atmosphere fluxes

  • The fate of riverine and estuarine carbon as well as should be a focus of efforts to constrain carbon budgets


Satellite observations of coastal p co 2 and air sea flux of carbon dioxide

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