MacDonald Ian R.

No Thumbnail Available
Last Name
First Name
Ian R.

Search Results

Now showing 1 - 3 of 3
  • Article
    Methods of oil detection in response to the Deepwater Horizon oil spill
    (The Oceanography Society, 2016-09) White, Helen K. ; Conmy, Robyn N. ; MacDonald, Ian R. ; Reddy, Christopher M.
    Detecting oil in the northern Gulf of Mexico following the Deepwater Horizon oil spill presented unique challenges due to the spatial and temporal extent of the spill and the subsequent dilution of oil in the environment. Over time, physical, chemical, and biological processes altered the composition of the oil, further complicating its detection. Reservoir fluid, containing gas and oil, released from the Macondo well was detected in surface and subsurface environments. Oil monitoring during and after the spill required a variety of technologies, including nimble adaptation of techniques developed for non-oil-related applications. The oil detection technologies employed varied in sensitivity, selectivity, strategy, cost, usability, expertise of user, and reliability. Innovative technologies ranging from remote sensing to laboratory analytical techniques were employed and produced new information relevant to oil spill detection, including the chemical characterization, the dispersion effectiveness, and the detection limits of oil. The challenge remains to transfer these new technologies to oil spill responders so that detection of oil following a spill can be improved.
  • Article
    Over what area did the oil and gas spread during the 2010 Deepwater Horizon oil spill?
    (The Oceanography Society, 2016-09) Ozgokmen, Tamay ; Chassignet, Eric P. ; Dawson, Clint N. ; Dukhovskoy, Dmitry S. ; Jacobs, Gregg ; Ledwell, James R. ; Garcia-Pineda, Oscar ; MacDonald, Ian R. ; Morey, Steven L. ; Olascoaga, Maria Josefina ; Poje, Andrew ; Reed, Mark ; Skancke, Jørgen
    The 2010 Deepwater Horizon (DWH) oil spill in the Gulf of Mexico resulted in the collection of a vast amount of situ and remotely sensed data that can be used to determine the spatiotemporal extent of the oil spill and test advances in oil spill models, verifying their utility for future operational use. This article summarizes observations of hydrocarbon dispersion collected at the surface and at depth and our current understanding of the factors that affect the dispersion, as well as our improved ability to model and predict oil and gas transport. As a direct result of studying the area where oil and gas spread during the DWH oil spill, our forecasting capabilities have been greatly enhanced. State-of-the-art oil spill models now include the ability to simulate the rise of a buoyant plume of oil from sources at the seabed to the surface. A number of efforts have focused on improving our understanding of the influences of the near-surface oceanic layer and the atmospheric boundary layer on oil spill dispersion, including the effects of waves. In the future, oil spill modeling routines will likely be included in Earth system modeling environments, which will link physical models (hydrodynamic, surface wave, and atmospheric) with marine sediment and biogeochemical components.
  • Article
    Natural and unnatural oil slicks in the Gulf of Mexico
    (John Wiley & Sons, 2015-12-28) MacDonald, Ian R. ; Garcia-Pineda, Oscar ; Beet, Andrew R. ; Daneshgar Asl, Samira ; Feng, Lian ; Graettinger, George D. ; French-McCay, Deborah P. ; Holmes, James ; Hu, Chuanmin ; Huffer, Fred W. ; Leifer, Ira ; Muller-Karger, Frank E. ; Solow, Andrew R. ; Silva, M. ; Swayze, Gregg A.
    When wind speeds are 2–10 m s−1, reflective contrasts in the ocean surface make oil slicks visible to synthetic aperture radar (SAR) under all sky conditions. Neural network analysis of satellite SAR images quantified the magnitude and distribution of surface oil in the Gulf of Mexico from persistent, natural seeps and from the Deepwater Horizon (DWH) discharge. This analysis identified 914 natural oil seep zones across the entire Gulf of Mexico in pre-2010 data. Their ∼0.1 µm slicks covered an aggregated average of 775 km2. Assuming an average volume of 77.5 m3 over an 8–24 h lifespan per oil slick, the floating oil indicates a surface flux of 2.5–9.4 × 104 m3 yr−1. Oil from natural slicks was regionally concentrated: 68%, 25%, 7%, and <1% of the total was observed in the NW, SW, NE, and SE Gulf, respectively. This reflects differences in basin history and hydrocarbon generation. SAR images from 2010 showed that the 87 day DWH discharge produced a surface-oil footprint fundamentally different from background seepage, with an average ocean area of 11,200 km2 (SD 5028) and a volume of 22,600 m3 (SD 5411). Peak magnitudes of oil were detected during equivalent, ∼14 day intervals around 23 May and 18 June, when wind speeds remained <5 m s−1. Over this interval, aggregated volume of floating oil decreased by 21%; area covered increased by 49% (p < 0.1), potentially altering its ecological impact. The most likely causes were increased applications of dispersant and surface burning operations.