The ocean is a significant sink of atmospheric CO2 and thus, a complete understand of carbon dioxide flux through the air-sea interface is a particularly pressing and time sensitive issue. However, the study of air-sea gas exchange is multifaceted. The following cartoon attempts to capture the complexity of this research problem: On the leeward side of the spilling breaker, air flow separation occurs and turbulence dominates within the separation bubble [Veron et al., 2007]. Mean CO2 concentration profiles have a logarithmic structure in the turbulent layer and a linear structure near the interface where molecular transport dominates. The vertical distribution of stress in the atmospheric layer is crtitcal for parameterizing gas flux and is shown on the right hand side. Notice the wavy sea surface makes quantifying these stresses difficult. However, molecular exchange does not tell the entire story as bubble-mediated exchange plays a major role.

Thus, the objective of the project is to further quantify the contributions of the surface sea state (fetch) and bubbles make on the atmospheric and oceanic gas transfer process. To do so, three specific goals were established. The first goal is to determine if the interfacial air-sea gas transfer is fetch dependent. To achieve this goal, the momentum stress model developed by [Mueller and Veron, 2009] and [Mueller and Veron, 2010] will be expanded upon to include the CO2 transfor via molecular and turbulent processes. The second goal is to calculate the diffusive gas transfer for one entrained bubble at a prescribed depth in the water column. The primary assumption made to achieve this goal is that bubble motion is driven only by buoyancy. The figure below shows the volume of CO2 in a bubble placed at 100 cm in the water column with a prescribed radius of 1000mm as it ascends at terminal velocity. Note the CO2 concentration in the water column is assumed to be equal to that of the atmosphere for this experiment. The solid line used the flux equation from [Memery and Merlivat, 1985] whereas the dashed line uses my flux equation which account for hydrostatic pressure changes with depth.

The final goal is to bring everything together and quantify the role of bubbles in the air-sea CO2 transport under a modeled wave field. This will be done using an initial bubble distribution which is not only a function of radius, but also varies with depth. The bubble plumes generated by breaking waves will be binned with a characteristic bubble from each used to calculate the gas transfer. Wave spectral statistics will allow results to be applied to the generated, fetch-dependent wave field.

Tidal harmonics were computed using a year of observations from three CODAR Coastal Observing Systems deployed along the Delaware, Maryland, and Virginia coast under support from the Integrated Ocean Observing System (IOOS). The resulting tidal current estimates were then removed from the raw HF Radar (CODAR) current estimates to render a composite of the mean surface circulation pattern for this coastal ocean region. We found that tidal currents in this region account for up to 60% of the total current variability, particularly at the mouth of the Chesapeake Bay. Using the tidal harmonics, a year’s worth of daily progressive vector diagrams were analyzed in order to ascertain the level of ‘jitter’ that one could expect from obtaining hourly images from a geostationary hyperspectral ocean color satellite such as NASA’s GEO-CAPE mission.  The figure (below) gives a quick, and crude, indication of the ‘jitter’ or variability. 

The purpose of this internship was to identify flooded areas using AMSR-E observations. Seven different wavelength-signals are typically used to extract a flood index—the vertical and horizontal 6.9 GHz, 10.7 GHz, and 18GHz signals, along with the 36.5 GHz vertical signal.  Using the Change Vector Analysis (change detection), along with various arrangements of the signals and their sequential structure, the hypothesis is that it is possible for flooded areas to be identified. Experiments using a band ratio of the 6.9 GHz horizontal frequency to the 36.5 GHz vertical frequency have confirmed that flood detection is possible using these techniques, although resolution issues remain.

The purpose of the internship was to analyze the projected climate over the Chesapeake Bay Watershed by the IPCC AR4 models.  As a means of doing this the A2 and B1 emission scenarios were chosen because they represent the largest range of direction in all the emission scenarios.  By removing some poorly performing models versus the 20th century data, the mean model was able to undergo a statistically significant improvement.  With an improved mean model, it is projected that mean annual temperature will increase across the watershed by 4.65 degrees Celsius under the A2 emissions scenario and 2.49 degrees Celsius under the B1 scenario by the end of the century.  Additionally, annual precipitation is projected to increase by 5.04% under the B1 scenario and 7.18% under the A2 scenario with the greatest increases projected for winter and spring.  These results lack error analysis but given an initial look the climate projections over the watershed and, provided a starting point for the Maryland Commission on Climate Change.