The use of airborne longwave-infrared hyperspectral imagery (allowing high cloud/nighttime observations) to assess methane emissions from Gulf of Mexico platforms and areas of ocean surface contaminated by spilled oil to varying extents will be used in this RAPID project. SEBASS (Spatially Enhanced Broadband Array Spectrograph System) will be flown on a Twin Otter over the oil leak site at various altitudes and over the course of one week.
The Twin Otter aircraft will also carry equipment to enable in situ whole air sampling at a range of altitudes and downwind distances from the Deepwater Horizon site. In addition, the Twin Otter flights will be coordinated with NASA's ER-2 that will be flying the AVIRIS (Airborne Visual Infrared Imaging Spectrometer). The ER-2 flights are covered under a separate RAPID. ER-2 and Twin Otter flight paths and flight times will overlap to look at data consistency and different spatial scales and resolutions. This is part of a three-pronged approach that the Atmospheric Chemistry Program is coordinating in response to the Gulf Oil Leak to estimate trace gas emissions.
The 20 April 2010 destruction and foundering of the Deepwater Horizon oil exploration platform resulted in an environmental catastrophe in the Gulf of Mexico that is expected to have far-reaching impacts. The Aerospace Corporation deployed an airborne high-resolution thermal-infrared imager to the Gulf region to participate in a rapid-response exercise aimed at assessing gaseous emissions (methane) and the spatial extent and weathering characteristics of the growing sea-surface oil spill (see accompanying figure). Imagery was also acquired over the coastal Louisiana wetlands and barrier island environments prior to their anticipated inundation by crude oil. This was done in order that future revisits of the area could effectively track recovery of the affected wetlands using the pre-oil data as a baseline. The airborne field campaign itself was conducted over the 20-27 May 2010 period. Extensive analysis revealed no observations of methane in the airborne data. While initially puzzling, this result comports with the many other field studies mounted within the spill zone. The underlying causes for the lack of observed methane continue to be investigated by the community at large. Suggestions under consideration include that the methane released by the Deepwater Horizon event was sequestered at the sea bed through clathrate (solid methane hydrate) formation or that it was metabolized by marine methanotrophic bacteria. Elsewhere, the observation of spectral features at the sea surface that identify as hydrocarbon compounds provides a demonstration of a thermal-infrared oil slick detection technique that is operable throughout the full diurnal cycle, i.e., including the nighttime when visible imagers are not effective.
