183
for the untreated oil (Fig. 11.3a) indicates that within few days after the onset of
the simulation, the highest oil content is found in the subsea and upper 0–20 m
layer, which corroborates observations from the BP Gulf Science Data (Wade
et al. 2016; Paris et al. 2018). Bulk of weathered oil in excess of a thousand tons
(shades of red) near the release depth gradually spreads up in the water column to
around 400 m; the lower boundary of the bulk of oil mass shows subduction as
well. The bulk of the subsurface oil decreases rapidly after the oil release stops on
day 87, yet hundreds of tons of oil remain in the water column, including at depths
below the release height until through the end of 167-day simulation. Oil content
in the surface layer gradually diminishes as well, yet remaining at higher values
than in the ocean interior.
The SSDI-treated oil in DB_treated simulation leads to higher oil content below
the trap height but also initially in the 0–20 surface layer until about day 18
(Fig. 11.3c). At later times, the treated oil yields consistently lower oil mass in the
surface layer, which is then in agreement with the expected behavior of the DSD;
but this difference is by only a few thousand tons as compared to the untreated oil
content. Below the surface layer, treated oil yields lower (higher) amounts in the
water column interior above (below) the trap height most of the times due to downwelling currents, with some vertical fluctuations of the negative (positive) differences around that depth due to upwelling currents.
For the DB_FALL scenario, the major distinction in differential mass calculations from the DB_control case is seen in the intermediate depths, where a region
of positive-difference oil mass propagating upward from the release depth is
observed from approximately day 15 until after day 50 following the blowout
(Fig. 11.3d), after which the vertical extent and the upward “tongue” of positive
differences gradually diminish. This is also found in DB_control, yet at a noticeable lesser extent, on days 60–80 between about 900 and 1200 m. This distinctive
behavior of vertical oil content is explained by the different ocean circulation patterns in the DB_FALL case, where the oil is transported upslope or along the continental shelf slope. The positive differences likely result from smaller droplets being
involved in bathymetry- controlled upslope or upwelling movement that would otherwise stay at greater depths. Similar behavior of oil residues deposited on the
continental shelf slope was reported in Romero et al. (2017); another example in
Romero et al. (2015) shows chemically the impingement of the intrusion on the
continental shelf slope.
The vertical oil distribution and differential amounts in DB_VDROPJ_untreated
and DB_VDROPJ_treated simulations (Fig. 11.3e–f) look noticeably different from
the other cases. The primary reason is significantly larger droplet sizes up to 8 mm
in diameter that cause faster surfacing of the oil. Regardless of chemical dispersion,
the surface layer of the entire GoM and the trap height where oil droplets are
released at a single location 300 m above Macondo contains the highest oil mass
during the active blowout phase. The distinct time uniformity until the spill is contained on day 87 (Fig. 11.3e) is the combined result of large droplets surfacing too
fast to be affected by the lateral transport, the unconventional distribution of the
droplet size implemented from Gros et al. (2017). The vertical layering reflects the
2-hourly output frequency of the model and the droplet release frequency being
11 Far-Field Modeling of a Deep-Sea Blowout: Sensitivity Studies of Initial…
for the untreated oil (Fig. 11.3a) indicates that within few days after the onset of
the simulation, the highest oil content is found in the subsea and upper 0–20 m
layer, which corroborates observations from the BP Gulf Science Data (Wade
et al. 2016; Paris et al. 2018). Bulk of weathered oil in excess of a thousand tons
(shades of red) near the release depth gradually spreads up in the water column to
around 400 m; the lower boundary of the bulk of oil mass shows subduction as
well. The bulk of the subsurface oil decreases rapidly after the oil release stops on
day 87, yet hundreds of tons of oil remain in the water column, including at depths
below the release height until through the end of 167-day simulation. Oil content
in the surface layer gradually diminishes as well, yet remaining at higher values
than in the ocean interior.
The SSDI-treated oil in DB_treated simulation leads to higher oil content below
the trap height but also initially in the 0–20 surface layer until about day 18
(Fig. 11.3c). At later times, the treated oil yields consistently lower oil mass in the
surface layer, which is then in agreement with the expected behavior of the DSD;
but this difference is by only a few thousand tons as compared to the untreated oil
content. Below the surface layer, treated oil yields lower (higher) amounts in the
water column interior above (below) the trap height most of the times due to downwelling currents, with some vertical fluctuations of the negative (positive) differences around that depth due to upwelling currents.
For the DB_FALL scenario, the major distinction in differential mass calculations from the DB_control case is seen in the intermediate depths, where a region
of positive-difference oil mass propagating upward from the release depth is
observed from approximately day 15 until after day 50 following the blowout
(Fig. 11.3d), after which the vertical extent and the upward “tongue” of positive
differences gradually diminish. This is also found in DB_control, yet at a noticeable lesser extent, on days 60–80 between about 900 and 1200 m. This distinctive
behavior of vertical oil content is explained by the different ocean circulation patterns in the DB_FALL case, where the oil is transported upslope or along the continental shelf slope. The positive differences likely result from smaller droplets being
involved in bathymetry- controlled upslope or upwelling movement that would otherwise stay at greater depths. Similar behavior of oil residues deposited on the
continental shelf slope was reported in Romero et al. (2017); another example in
Romero et al. (2015) shows chemically the impingement of the intrusion on the
continental shelf slope.
The vertical oil distribution and differential amounts in DB_VDROPJ_untreated
and DB_VDROPJ_treated simulations (Fig. 11.3e–f) look noticeably different from
the other cases. The primary reason is significantly larger droplet sizes up to 8 mm
in diameter that cause faster surfacing of the oil. Regardless of chemical dispersion,
the surface layer of the entire GoM and the trap height where oil droplets are
released at a single location 300 m above Macondo contains the highest oil mass
during the active blowout phase. The distinct time uniformity until the spill is contained on day 87 (Fig. 11.3e) is the combined result of large droplets surfacing too
fast to be affected by the lateral transport, the unconventional distribution of the
droplet size implemented from Gros et al. (2017). The vertical layering reflects the
2-hourly output frequency of the model and the droplet release frequency being
11 Far-Field Modeling of a Deep-Sea Blowout: Sensitivity Studies of Initial…