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U.S. Eastern Continental Shelf Carbon Budget: Modeling,
Data Assimilation, and Analysis
U.S. ECoS Science Team*
ABSTRACT. We present results from the U.S. Eastern Continental Shelf Carbon Budget
(U.S. ECoS) Program, the main goal of which is to develop carbon budgets for the Mid- and
South- Atlantic Bights (MAB & SAB) along the eastern U.S. coast. A multi-disciplinary approach
has been adopted, combining the expertise of empiricists and modelers in a collaborative project
as part of the NASA Earth Interdisciplinary Science initiative. Main components of U.S. ECoS
are: (1) 3-D circulation/biogeochemical models; (2) historical in situ and satellite-derived data
analysis; (3) limited field measurements; (4) 1-D biogeochemical data assimilation; and (5) climate
change impacts.
The 3-D circulation model is shown to capture the observed fields of annual-mean salinity,
and the seasonal and spatial variability of surface temperature and mixed layer depth. Numerous
other circulation characteristics are also simulated, including the tidal mixing front and residual
circulation around Georges Bank, Gulf Stream intrusions in the SAB, and interactions of Gulf
Stream warm rings with the New England slope. The biogeochemical model captures the overall
spatial pattern and annual cycle in the surface ocean oxygen anomaly, as well as the annual-mean
pattern of surface ocean chlorophyll and semi-labile DOC. Distributions of the latter were
derived from seasonal algorithms linking remote-sensing reflectance, absorption of colored
dissolved organic matter, and DOC. Chlorophyll is generally too low in the SAB and the
subtropical gyre. The SAB is also difficult to observe from satellite because chlorophyll blooms,
driven by shelf-break upwelling, are often below the penetration depth of ocean color sensors.
The 3-D modeling results also suggest that POC is efficiently buried in the inner- and mid-shelf
while the mid- and outer-shelf export seasonally produced DOC to the open ocean at comparable
rates. Finally, 1-D assimilation of remotely sensed chlorophyll dramatically reduces model error
through optimization of model parameters, such as the maximum growth rate and C:chl ratio.
RESEARCH QUESTIONS
1) What are the relative carbon
inputs to the MAB and SAB from
terrestrial sources and in situ
biological processes?
2) What is the fate of DOC input
to the continental shelf from
estuarine and riverine systems?
3) What are the dominant food web
pathways that control carbon
cycling and flux in this region?
4) Are there fundamental
differences in the manner in
which carbon is cycled on the
MAB and SAB continental shelf?
*U.S. ECoS Science Team
Eileen Hofmann (ODU)
Project oversight, 1D modeling
Marjorie Friedrichs (ODU) Modeling, data assimilation
Chuck McClain (GSFC)
Project oversight, satellite data
Sergio Signorini (GSFC)
Satellite data analyses
Antonio Mannino (GSFC)
Carbon cycling
Cindy Lee (Stony Brook) Carbon cycling
Jay O’Reilly (NOAA)
Satellite data analyses
Dale Haidvogel (Rutgers) Circulation modeling
John Wilkin (Rutgers)
Circulation modeling
Katja Fennel (Rutgers)
Biogeochemical modeling
Sybil Seitzinger (Rutgers) Food web, nutrient dynamics
Jim Yoder (WHOI)
Food web, nutrient dynamics
Ray Najjar (Penn State) Data climatology, climate modeling
David Pollard (Penn State) Climate modeling
5) Is the carbon cycle of the MAB
and SAB sensitive to climate
change?
Latitude (North)
Source
Figure 1
Figure 1: This illustrates the
overall approach of this project,
which involves investigators with
different skills in data analysis
and model development.
Figure 5: We have developed several
new and simple metrics that characterize
the natural cycles of major annual
phytoplankton biomass and carbon
production events. One example is the
index of ‘month of maximum satellite
chlorophyll concentration’, which was
computed from a 9-year monthly
SeaWiFS climatology. This reveals that
the fall phytoplankton bloom (September
and October) in northern Gulf of Maine is
a more significant event in the annual
cycle than the spring bloom.
Figure 2: The biogeochemical model
used in this project is coupled to a
circulation model (Regional Ocean
Modeling System, ROMS v.3) that has
been implemented for the continental
shelf and adjacent deep ocean of the
U.S. east coast (Northeast North
American (NENA) Shelf Model).
Figure 6. Comparsions of
satellite-derived fields with
equivalent fields from NENA
show that the model captures
the north-south gradient in
SST, shows the general
north-south gradient in
chlorophyll distribution, but
underestimates concentrations
in the SAB except in the
mid-shelf, and captures the
spatial pattern in DOC
concentration.
Figure 3: Evaluation of the NENA model with
historical data. This shows that the circulation model
does a good job of capturing the spatial and temporal
variability of mixed layer depth and salinity. The
biogeochemical model simulates the annual cycle in the
surface ocean oxygen anomaly.
Figure 4: Various satellite data products have been
developed for analysis and for evaluation of the NENA
model. DOC algorithms were developed using field data from
the MAB, collected as part of this project.
Figure 8. Data assimilation using a
one-dimensional model is helping to
constrain model parameters.
Figure 7. The SAB continental shelf poses a
very unique challenge for satellite
measurement of chlorophyll a and,
consequently, primary production (PP)
estimates because the episodic summer
subsurface intrusions of nutrient-rich Gulf
Stream waters onto the shelf significantly
enhance biomass and carbon production below
the depths ‘visible’ to passive satellite ocean
color sensors, such as SeaWiFS and MODIS.
This project is
supported by the
NASA
Interdisciplinary
Science Program