Date of Award

Summer 8-2011

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)

Department

Marine Science

Committee Chair

Dr. Stephan D. Howden

Committee Chair Department

Marine Science

Committee Member 2

Dr. Laodong Guo

Committee Member 2 Department

Marine Science

Committee Member 3

Dr. Steven E. Lohrenz

Committee Member 3 Department

Marine Science

Abstract

With the continued increase of carbon dioxide (CO2) emissions, researchers are concerned with accumulation of excess CO2 within the atmosphere. The ocean is an important sink for the drawdown of atmospheric CO2 concentrations. Due to high spatial and temporal variability, CO2 fluxes in the coastal ocean are not as well characterized as those for the open ocean. More specifically, data for the northern Gulf of Mexico (GOM) coastal region is lacking. A time series analysis of air-sea CO2 flux rates from May through December 2009 was conducted using data collected by The University of Southern Mississippi’s Central Gulf Ocean Observing System 3-meter discus buoy, located within the northwest Mississippi Bight region (MBR). Data collected by the buoy included wind speed and direction, sea surface temperature, sea surface salinity, pressure, and pCO2. Four hypotheses were addressed. One hypothesis was the region was a weak net sink for atmospheric CO2 with an alternative hypothesis that the region was a net source that varied seasonally. Air-sea CO2 flux rates calculated from the buoy data indicated the northwest MBR was a weak net source during the month of July, but was overall a net sink for CO2 from May through December. The mean daily CO2 flux rate from May through December ranged from -4.23 to -5.96 mmol m-2 d-1. A third hypothesis was uptake of CO2 in the coastal northern GOM would exceed release of CO2 in the remainder of the GOM. Net annual flux for the entire coastal northern Gulf of Mexico region was estimated at approximately -3.78 to -5.33 Mt C yr-1, while the net annual flux for the remainder of the GOM was estimated at approximately 14.33 to 19.82 Mt C yr-1. Sea surface salinity, net primary productivity, and wind speed were the environmental variables which had the strongest correlations with CO2 flux rates. Although air-sea flux calculations should use the wind speed relative to surface water, the wind speed relative to fixed geographic coordinates (Eulerian reference frame) is customarily used. The final hypothesis was surface currents would have an appreciable affect on CO2 flux rates throughout the region. An investigation of CO2 flux rates computed from wind speeds relative to surface water resulted in a decrease in CO2 flux rates of 2.06 to 2.84%. This difference in CO2 flux rates was statistically significant; however, fell within the margin of error involved in estimating the Eulerian flux rates.

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