Del Castillo, Carlos: NASA (Project Lead)
Gregg, Watson: NASA GSFC (Institution Lead)
Miller, Richard: East Carolina University (Institution Lead)
Project Funding:
2007 - 2010
NRA: 2006 NASA: Ocean Biology and Biogeochemistry
Funded by NASA
Abstract:
The SO is an important sink of CO2 due to cooling of warm sub-tropical waters and
primary productivity enhanced by high concentrations of nutrients. The Antarctic
Circumpolar Current plays a major role in the global ocean circulation, and the Antarctic
Convergence creates a distinct body of water with unique biogeochemical conditions, and
plays a crucial role in the air/sea flux of CO2. Colored dissolved organic matter (CDOM)
is an important component of the oceanic carbon pool, including in the SO. It is the
subject of many research efforts based on traditional field and laboratory methods, and
remote sensing techniques. It is well known that the photolysis of recalcitrant CDOM
results in the formation of CO2, CO, and labile, low-molecular-weight compounds in
quantities sufficiently large to be relevant to the carbon budget. Here we propose a
multidisciplinary approach to answer the following questions: 1-What is the annual
variability in abundance and distribution of CDOM in the SO?; 2-What physical
processes control the abundance and distribution of CDOM? 3-How much CO2 and CO is
produced from the photolysis of CDOM? Question 1 will be answered using historical
ocean color data from SeaWiFS, MODIS-AQUA, and MERIS. We will use field and
laboratory measurements, and radiative transfer modeling to develop a regional CDOM
algorithm for the SO. The algorithm will be use to reprocess imagery from the
aforementioned sensors from launch trough 2008, and the data will be merged to reduce
the effect of prevalent cloud cover in the region. Clearly, differences between sensor
outputs will be analyzed and reported. Question 2 will be answered through a
combination of ocean circulation modeling and remote sensing. The ocean circulation
model and data assimilation system will be developed for the GasEx cruise region from
existing, similar, setups in the subpolar North Atlantic ocean. A package to simulate
upper ocean CDOM will be included. From this perspective CDOM, is, essentially, a
passive tracer with (complex) sources and sinks. The sources and sinks will be treated as
weakly constrained parameters to be determined in the DA The model will use inputs
from field measurements, and from remote sensing estimates of wind vectors, SSH, and
SST, and photolysis loss term for CDOM. The model will be run retrospectively, and
resulting CDOM field maps will be compared with remote in-situ and remote sensing
measurements of CDOM. Question 3 will be answered in two modalities. In the first
approach, we will estimate the photoproduction of CO2 and CO along the cruise track
using underway measurements of CDOM, solar irradiance, radiative transfer modeling,
and published values of photoproduction quatum efficiencies (Φ) for the gases. In the
second approach we will use remote sensing estimates of CDOM (question 1), solar
irradiance, radiative transfer modeling and published values of Φ to produce historical
maps of CO2 and CO photoproduction.
More details may be found in the following project profile(s):