SATELLITE ESTIMATION OF COASTAL PCO2 AND AIR-SEA FLUX OF CARBON DIOXIDE
IN THE NORTHERN GULF OF MEXICO
Abstract
A key to better constraining estimates of the ocean sink for fossil fuel
emissions of carbon dioxide is reducing uncertainties in coastal carbon
fluxes. A contributing factor in uncertainties in coastal carbon fluxes
stems from the under sampling of seasonality and spatial heterogeneity.
Our objectives were to i) assess satellite-based approaches that would
expand the spatial and temporal coverage of the surface ocean pCO2 and
sea-air CO2 flux for the northern Gulf of Mexico, and ii) investigate
the seasonal and interannual variations in CO2 dynamics and possible
environmental drivers. Regression tree analysis was effective in
directly relating surface ocean pCO2 to satellite-retrieved (MODIS Aqua)
products including chlorophyll, sea surface temperature, and
dissolved/detrital absorption. Satellite-based assessments of sea
surface pCO2 were made spanning the period from 2006-2010 and were used
in conjunction with estimates of wind fields and atmospheric pCO2 to
produce regional-scale estimates of air-sea fluxes. Seasonality was
evident in air-sea fluxes of CO2, with an estimated annual average CO2
flux for the study region of -4.3 + 1.1 Tg C y-1, confirming prior
findings that the Gulf of Mexico was a net CO2 sink. Interannual
variability in fluxes was related to Mississippi River dissolved
inorganic nitrogen inputs, an indication that human- and climate-related
changes in river exports will impact coastal carbon budgets. This is the
first multi-year assessment of pCO2 and air-sea flux of CO2 using
satellite-derived environmental data for the northern Gulf of Mexico.