Mapping Dissolved Organic Carbon in Eastern U.S. Coastal Waters Using Ocean Color Satellite Data

River runoff of dissolved organic carbon (DOC) into the oceans is significant and can play a very important role in the global carbon cycle since the carbon reservoir of DOC in the ocean is comparable to carbon dioxide [CO2] in the atmosphere. A fraction of DOC Chromophoric Dissolved Organic Matter (CDOM) is capable of absorbing visible and ultraviolet light and can be detected by ocean color satellite sensors. Various investigators have reported a relationship between DOC concentrations and absorption by CDOM, but the parameterization of this relationship appears to vary regionally and seasonally due to photochemistry.

This project investigates the relationships between DOC and CDOM and between carbon and ocean color. Data from historical and ongoing fieldwork will be used to study the spatial and seasonal distribution of DOC, along with inherent and apparent optical properties, for the coastal and continental shelf regions along the east coast of the U.S.

The scientists will also investigate photodegradation of DOC to dissolved inorganic carbon (DIC) during summer and link it to bleaching of CDOM. The combined dataset will be used to develop an algorithm to map DOC from the DOC-to-CDOM dependence using satellite ocean color sensors. Yearly time-series of DOC maps for the east coast of the U.S. will then be constructed, allowing scientists to explore the spatial and temporal variability, as well as long-term changes in this parameter with a strong emphasis on the processes driving DOC distribution, transformation and transport.

This proposal addresses an area of primary interest for NASA in the North American Carbon program by bringing remote sensing to bear on characterization of carbon stocks, transport and transformations of terrestrially derived organic carbon in the coastal waters off the eastern United States.

Caption

SeaWiFS image of chlorophyll concentrations in the Mid and South Atlantic Bights (MAB and SAB, respectively) from October 9, 1999. A fresh water plume is seen as a jet of high chlorophyll extending from the Outer Banks.

The OCT99MAB cruise track and stations occupied during the entire cruise are shown in red with the stations sampled on the same day as this image shown in white. In-situ measurements showed this jet had extremely high CDOM absorption and was the runoff after three Hurricanes (Dennis, Floyd, and Irene) had passed over North Carolina.

Credit

Ajit Subramaniam, Lamont Doherty Earth Observatory at Columbia University

Caption

Chlorophyll concentrations in the South Atlantic Bight (SAB) derived from MODIS data. The stations visited on the MAY05SAB field survey on May 12 and 13, 2005, are indicated by * and + respectively. The high apparent chlorophyll concentrations seen along the coast may be a consequence of the record rainfall over the southeast U.S. in spring 2005.

Credit

Ajit Subramaniam, Lamont Doherty Earth Observatory at Columbia University

Contacts:

Ajit Subramaniam
Principal Investigator
Lamont Doherty Earth Observatory at Columbia University
ajit@ledo.columbia.edu

Rossana Del Vecchio
Co-Investigator
University of Maryland Earth System Science Interdisciplinary Center
rossdv@wam.umd.edu

James Nelson
Co-Investigator
Skidaway Institute of Oceanography
nelson@skio.peachnet.edu

Science Goals: This research will map DOC (and terrigenous CDOM) to compile a long-term dataset and better define the processes driving the distribution, transformation and transport of dissolved organic carbon in the coastal ocean off the eastern U.S.

• The spatial and temporal variation of DOC (and CDOM) and water leaving reflectance will be investigated for the eastern U.S. coastal waters.
• Loss of DOC upon light exposure will be estimated for each region
• Regional algorithms for retrieving DOC concentrations from CDOM absorption based on ocean color will be developed.
• These algorithms will be applied to the coastal ocean color datasets to provide the yearly data set to study the seasonal and interannual changes DOC concentration along the east coast of the U.S.

Partners:

This research is funded through NASA's North American Carbon Cycle Science program and is a joint effort among the Lamont Doherty Earth Observatory, University of Maryland and Skidaway Institute of Oceanography.

When:

Sporadic missions will be conducted over a three-year period (2005-2007)

Where:

Field surveys will be conducted at several locations off the eastern U.S. coastline, especially over the South Atlantic Bight near Savannah, Georgia.

Links:

For more information about the North American Carbon Program (NACP) and U.S. Global Change Research Program (USGCRP):

http://www.usgcrp.gov/

For more information about the Lamont Doherty Earth Observatory:

http://www.ldeo.columbia.edu/

For more information about the University of Maryland Earth System Science Interdisciplinary Center:

http://www.essic.umd.edu/

For more information about the Skidaway Institute of Oceanography:

http://www.skio.peachnet.edu/