Image from NASA
It may seem unusually high, but almost half of the oil that makes its way into the ocean derives from natural sources. To find these oil slicks, scientists have long made use of satellite radar instruments. Upon reaching the surface, oil has a tendency to spread out into a thin layer, which causes a glint that can easily be seen by radar, explains the New Scientist's Catherine Brahic (see a short video here). Tracking and pinpointing these slicks is helpful for several reasons, one of which is because the seeps can become local carbon dioxide hotspots when the oil eventually disintegrates. On a large enough timeline, these hotspots could influence the direction of climate change.
The problem is that these satellite images cost a bundle and that it can be tricky for the satellite to be in the right place a the right time to capture the slick (they can revisit the same spot once every 8 to 16 days, as needed). Chuanmin Hu, a geologist at the University of South Florida, has found a solution: use a satellite instrument called MODIS (or Moderate Resolution Imaging Spectroradiometer) to provide near daily monitoring.
MODIS, which is found aboard NASA's Terra and Aqua satellites, scans the planet's entire surface every 1 to 2 days in 36 spectral bands (or groups of wavelengths) to help develop new global models and systems for climate change prediction. Here's a description of its functions and parameters:
The MODIS instrument is operating on both the Terra and Aqua spacecraft. It has a viewing swath width of 2,330 km and views the entire surface of the Earth every one to two days. Its detectors measure 36 spectral bands between 0.405 and 14.385 µm, and it acquires data at three spatial resolutions -- 250m, 500m, and 1,000m.
The many data products derived from MODIS observations describe features of the land, oceans and the atmosphere that can be used for studies of processes and trends on local to global scales. As just noted, MODIS products are available from several sources. MODIS Level 1 and atmosphere products are available through the the LAADS web. Land Products are available through the Land Processes DAAC at the U. S. Geological Survey EROS Data Center (EDC). Cryosphere data products (snow and sea ice cover) are available from the National Snow and Ice Data Center (NSIDC) in Boulder, Colorado. Ocean color products and sea surface temperature products along with information about these products are obtainable at the OCDPS at GSFC. Users with an appropriate x-band receiving system may capture regional data directly from the spacecraft using the MODIS Direct Broadcast signal.
Because the images it records are already freely available online, Hu and his colleagues believe MODIS could do the job; despite the images' lower resolution, they found that it could capture the presence of the oil seeps under the right conditions.
Though it may not be as precise as the other radar instruments that are currently in use, Hu says that MODIS would allow scientists to monitor the Gulf and other slick-heavy regions every 3 to 5 days. By being made freely available online, scientists from around the world could study their distribution and frequency to help predict how emission production, and climate change, might be affected. Of course, since it can produce a wide range of data products, scientists could also devise new uses for it in the future.
Via: Yale Environment 360: NASA Satellite Technology Can Monitor Natural Oil Seepage
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