U.S. Eastern Continental Shelf Carbon Budget: Modeling, Data Assimilation, and Analysis U.S. ECoS Science Team*

1
U.S. Eastern Continental Shelf Carbon Budget
Modeling, Data Assimilation, and Analysis U.S.
ECoS Science Team
ABSTRACT. The U.S. Eastern Continental Shelf
Carbon Budget (U.S. ECoS) Program, which began in
summer 2004, is funded as part of the NASA
Interdisciplinary Science Program. The overall
goal of this project is to develop carbon budgets
for the Mid-Atlantic Bight (MAB) and South
Atlantic Bight (SAB) along the eastern U.S.
coast. The U.S. ECoS program is structured
around five themes which are focused on 1)
development and implementation of circulation,
biogeochemistry, and carbon cycling models for
the east coast of the U.S. 2) analyses of
historical in situ measurements and
satellite-derived data 3) a limited field
measurement effort designed to provide
measurements for input to the biogeochemistry and
carbon cycling models 4) development and
implementation of data assimilative
biogeochemical and carbon cycling models and 5)
interfacing the circulation, biogeochemistry and
carbon cycling models with climate models. Our
research is particularly germane to NASAs carbon
cycle research focus topic and coastal research
initiative and the U.S. Climate Change Research
Program, all of which emphasize the North
American Carbon Program.
U.S. ECoS Science Team Eileen Hofmann
(ODU) Project oversight, 1D modeling Marjorie
Friedrichs (ODU) 1D modeling, data
assimilation Chuck McClain (GSFC) Project
oversight, satellite data Sergio Signorini (GSFC)
Satellite data analyses Antonio Mannino
(GSFC) Carbon cycling Cindy Lee
(SUNY-SB) Carbon cycling Jay OReilly
(NOAA) Satellite data analyses Dale Haidvogel
(Rutgers) Circulation modeling John Wilkin
(Rutgers) Circulation modeling Katja Fennel
(Rutgers) Biogeochemical modeling Sybil
Seitzinger (Rutgers) Food web and nutrient
dynamics Jim Yoder (URI) Food web and nutrient
dynamics Ray Najjar (Penn State) Oxygen data,
climate modeling David Pollard (Penn
State) Climate modeling

• RESEARCH
  QUESTIONS
• 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?
• 5) Is the carbon cycle of the MAB and SAB
  sensitive to climate change?

Figure 1
Sink
Figure 4
Figure 2 Simulated Chlorophyll
Source
Latitude (North)
Figure 5
Figure 2 SeaWiFS Chlorophyll
Longitude (West)
Comparisons of simulated monthly-averaged
chlorophyll concentrations with measured in situ
and SeaWiFS-derived chlorophyll values at
different sites in the MAB (Figure 4) show that
the biogeochemical model captures the chlorophyll
annual cycle. The biogeochemical model is
coupled to a carbon cycling model. The simulated
annual air-sea CO2 flux shows that the MAB and
SAB provide a net sink for carbon (Figure 5).
Additional simulations are ongoing to investigate
the processes that underlie this result.
The biogeochemical model used in this project
(Figure 1) is designed to investigate nutrient
cycling of the lower trophic levels of the MAB
and SAB. This model is coupled to a circulation
model that is based on the Regional Ocean
Modeling System (ROMS v.2) that has been
implemented for the continental shelf and
adjacent deep ocean of the U.S. east coast
(Northeast North American (NENA) Shelf Model).
Comparisons of simulated chlorophyll
distributions obtained with the coupled
circulation-biogeochemical model show features
that are similar to those seen in chlorophyll
distributions obtained from SeaWiFS measurements
(Figures 2, 3). The biogeochemical model is
currently being modified to include data
assimilation capability.
Figure 3
Figure 9
Figure 7
Satellite data analyses are an integral part of
the project and provide inputs and verifications
for the simulated distributions obtained from the
coupled model. One such example is the Western
North Atlantic POC composite (mg C L-1, log scale
is 0.01 to 5.0) for April 1998 (Figure 6) derived
from SeaWiFS normalized water leaving radiances
and the Clark empirical algorithm (D. Clark,
unpublished). Note the nearshore sources
(yellow-red high values) originating from rivers
and estuaries. The lowest values are in the
Sargasso Sea. The patchiness south of the Gulf
Stream may be due to POC advection by cold core
eddies.
The field sampling component of the U.S. ECoS
project is focused on Chesapeake Bay (Figure 9)
and includes measurements of DOC, POC, CDOM and
other nutrient and chlorophyll-related
parameters. results show that DOC is variable
and is lower in summer-fall than in winter-spring
(Figure 9). Measurements from Delaware Bay show
summer-fall differences in CDOM absorption
coefficients (Figure 10). The field sampling
program is providing measurements that are
critical to the biogeochemical and carbon cycling
models.
Satellite-derived data sets also provide an
approach for assessing seasonal and interannual
variability in primary production (Figures 7, 8),
and for comparing estimates of primary production
derived from different algorithms (Figure 7). In
situ data sets, such as the MARMAP data, provide
calibration for the satellite-derived values
(Figure 7).
Figure 6
Figure 8
Figure 10