Reducing
Uncertainty in the Marine Carbon Cycle by Coupling Satellite and
In-Water Robotic Measurements
School of Marine
Sciences oceanographers are currently carrying out a coupled
underwater glider – above-water satellite remote sensing study
of the phytoplankton Spring Bloom in the Gulf of Maine. From
mid-March to mid-May one of the two UMaine gliders – either Nemo
or Dory – will run transects between GoMOOS Buoy E and Wilkinson
Basin.
Both gliders have
sensors that measure chlorophyll fluorescence (proxy for
phytoplankton concentration), colored dissolved material
fluorescence (CDOM, proxy for dissolved organic carbon), optical
backscattering (proxy for particle concentration), temperature,
salinity, and oxygen. In addition Dory measures spectral
upwelling and downwelling light. Additional optical and
chemical measurements will be measured at GoMOOS Buoy E on the
glider deployment / retrieval cruises to validate the optical
proxies for carbon-cycle components. Stratification indices
will be computed to assess the role played by stratification in
the evolution of the bloom. Satellite imagery of ocean color
and sea-surface temperature will be collected using the
satellite antenna of the roof of Aubert Hall and analyzed for
water-leaving radiance, standard pigment products, optical
backscattering coefficients, colored dissolved and particulate
detrital concentrations. Together, the glider and satellite
data will be merged to generate a new 4-D (space and time) view
of the evolution of the Spring Bloom in the Gulf of Maine.
While
local in scope, this project provides critical insight into
reducing major uncertainties about both the Gulf of Maine and
the global carbon cycle. Four major challenges to accurate
space-based assessment of marine productivity that can be
addressed today with existing underwater glider technology are:
1) verification of derived products within different bio-optical
regimes; 2) determination of key biogeochemical stocks in the
entire euphotic zone; 3) actual measurement of input variables
for productivity models; 4) continuity of stock measurements
during periods of cloudiness. The coupling of underwater
measurements from gliders with satellite data will improve
accuracy in quantifying key biogeochemical stocks and input
variables for satellite-based productivity models. The expected
outcomes of this study are a reduction in uncertainty in
productivity estimates on the local level and a demonstration of
how the coupled use of satellites and in-water robotic gliders
can be best used to reduce specific components of uncertainty.
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