On January 28th, 2008, reports of 'tarballs' washing up on shorelines throughout central California arrived via beach monitoring agencies and the public. These floating bits of oil are dime to dinner plate sized.
The beaches where tarballs were found - as of January 29th, 2008 - is made available courtesy of Glen Watabayashi (NOAA) (at right). The sightings have decreased in Monterey and Santa Cruz Countiey, but continue especially in San Mateo County. The San Mateo County Dept of Environmental Health closed two beaches as a result of the oil washing ashore and warn that this may continue for months.
The U.S. Coast Guard, with the aid of the California Department of Fish and Game (CDFG) and others, initially mobilized crews to spot and clean-up tar on the beaches. These agency's personnel worked along with contractors and local volunteers who had helped with the November 2007 Cosco Busan Oil Spill in SF Bay. Fifteen cubic yards of tar was collected by these efforts. Soon after, CDFG determined the tarballs to be derived from seafloor areas of Monterey rock formation oil deposits. Therefore, they are from a natural source and not a result of the Cosco Busan Oil Spill (or any other spill). Because the source was not an oil spill, the funds devoted to the cleanup effort by the Coast Guard were removed and local agencies took over where necessary (or possible).
The Monterey formation extends throughout many portions of central California offshore, thus the exact source of the oil seepage from the seafloor is difficult to determine. Some researchers believe that Monterey Bay contains oil seeps that may cause tarballs. Other scientists think the large seeps in the Santa Barbara Channel, which cause consistent issues on beaches in that area, may be the source. This would require strong and consistent northerly currents to bring the tarballs to the Monterey Bay and areas further north. If currents are moving the tarballs south, it is likely that the source is such known seeps as Pt. Montara (south of SF) or Pt Reyes (north of SF).
Information provided by the high frequency radar units of the Coastal Ocean Current Monitoring Program (COCMP), now sheds light on the subject of the tar source (see image on left). The pattern of current direction and speed during late January, was strongly northward from Santa Barbara to San Francisco for 3-5 days. The currents were moving at an average speed of around 70 km/day. This current speed and direction, over the time indicated, would be sufficient to move tarballs from the Santa Barbara Channel area as far north as San Francisco.
Additionally, it has been observed that tarballs have washed ashore in these areas at around the same time (Jan-Feb) in at least the last few years. These events may correspond to seasonal changes in prevaling ocean current direction. As current data continues to be collected, this relationship may become more clear.
Sources of further information:
KTVU News http://www.ktvu.com/news/15165922/detail.html
Visit the real-time CeNCOOS surface currents page here
For more information contact CeNCOOS (CeNCOOS_Communications@mbari.org).