Environmental Engineering Reference
In-Depth Information
until approximately August 1, 2010, when it reattached to the LC for a second time.
Ultimately, only a small amount of surface oil was reported to have entered the north-
ern LC/LCR system. Altimetry-derived observations show that this LCR, sometimes
referred to as Eddy Franklin according to a naming protocol followed by some
operational forecasters, eventually translated to the west and became undetectable
early in 2011.
The scale of the DWH event required the use of satellite data to evaluate the impact
of large oil spills on coastal and marine ecosystems. Satellite observations provided
an important tool to conduct pre- and post-event evaluations of ecosystem processes.
Current efforts are also focusing now on the investigation of the potential impact of
oil on photosynthesis of plant species in the intertidal zone and of phytoplankton in
offshore areas.
1.5 Conclusions
Hydrographic and satellite observations together with numerical model outputs
played a key role in support of monitoring efforts during the DWH oil spill. The
combined suite of observations and model outputs analysis can continually provide
information about key parameters, such as ocean currents, frontal regions, water
masses, and oil spill extent at the surface. This chapter presented important results
on how the combined use of all available data and analysis were employed to monitor
the surface oil areal extent and surface ocean currents in support of the restoration
and recovery efforts, which were originally carried out under operational constraints
involving short timelines and data resource availability.
Experimental Marine Pollution Surveillance (EMPS) reports, which provided an
outer boundary of the extent of the surface oil, were used in this study to investigate
the variability of the extent of surface oil using satellite imagery from both active
and passive sensors and from supplementary information, such as overflights and in
situ observations which were key for the assessment of numerical models. Results
obtained from these reports show that the maximum surface area extent of the oil
spill at the surface was approximately 47
10
3
km
2
, while the combined affected
×
10
3
km
2
. The oil spill surface extent exhibited large
variability. The largest increase of surface oil occurred between April 22 and May
22, 2010, at an average rate of 1.3
surface area was at least 130
×
10
3
km
2
per day. On the other hand, the largest
decrease in the extent of surface oil started on June 26, 2010, at an average rate of 4.4
×
×
10
3
km
2
) occurred during
several periods between late May and the end of June. The southernmost extension of
the surface oil spill extent reached approximately 85
ⓦ
W27
ⓦ
Nduring the beginning of
June. Although smaller potential surface oil slicks were also identified to the south by
MPSRs, only a few of them were observed from in situ and overflight observations,
partly due to limited resources to evaluate them.
Real-time surface current fields derived from satellite altimetry were used to mon-
itor conditions during the oil spill. In this work, delayed-time altimetry observations
10
3
km
2
per day. The largest surface extensions (
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40
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