**5. The 1987 Red Tide event as viewed in SSTs and numerical model output**

In **Figure 5**, employing NOAA AVHRR-derived Sea Surface Temperature images (SST), courtesy of Dr. Steven Baig of NOAA's Atlantic & Oceanographic Laboratory *On the Possibility of Non-Local and Local Oil Spills Striking the Shores of North Carolina... DOI: http://dx.doi.org/10.5772/intechopen.106679*

#### **Figure 5.**

*NOAA AVHRR imagery of Gulf Stream waters with frontal filaments. (a) Left panel, October 05, 1987, image showing two filaments; (b) October 09, 1987, image showing three filaments. (SST images were provided by Dr. S. Baig, AOML). The magenta coloring is employed to depict the location of the Gulf Stream and its Frontal Filaments.*

(AOML) that outlined the Gulf Stream and its frontal features, we see the presence of GSFs. At the time, these SST maps were a product that was hand drawn by Dr. Baig of AOML as a public service particularly the fishing industry. In the upper panel, two GSFs are shown to have been located between 32° and 33.5° on October 05. In the **Figure 5** lower panel, a third GSF has appeared and the three frontal features are between 32.25° and 34.25°. The southernmost GSF in **Figure 5** upper panel moved to Onslow Bay offshore waters as shown in **Figure 5** lower panel. An additional GSF had by then formed east of Cape Romain, SC. For the GSF located offshore of Onslow Bay to have propagated there from its previous location offshore of Charleston, SC, it would have had a phase speed of approximately 42 cm/sec or 36 km/day. If this phase speed of propagation is representative of the speed of parcel movement along the western wall of the Gulf Stream, the Gulf Stream frontal zone, then it would have taken a patch of water and its constituents 45 days to go from Naples, Fla., to Onslow Bay. We will test this with our numerical model scenario present below.

From the above data-based hypothesized description, Red Tide dinoflagellates could have been loaded into the Loop Current in the Gulf of Mexico offshore of Naples, Fla., and eventually could have been positioned in a large Gulf Stream Frontal Filament (GSF) offshore of Onslow Bay on Oct. 09. If the dinoflagellates were located in surface layer waters of the GSF, then the obvious question occurs: How could the dinoflagellates have been transported out of the filament and across Onslow Bay, a distance of 90–110 km (56–68 mi.) by October 31 when the Red Tide was first observed on the NC beaches? To address this question, we must ask an additional one. What physical processes could exist at this time of year that would move one-celled, microscopic drifters across the width of Onslow and Long Bays? We next employ a numerical atmospheric and ocean current model system to simulate the events of 1987.

In our numerical model simulation, we employ two different reconstructed wind fields, so as not to appear to bias the atmospheric driving force. On the oceanic side, we employ the Regional Ocean Model System (ROMS) ocean circulation model [13]. **Figure 6** depicts the seeding of coastal waters on the West FL shelf with Red Tide plants that are assumed passive tracers. Two model simulations were conducted to offer comparisons. One simulation employed the North American Regional Reconstruction (NARR) winds (https://www.emc.ncep.noaa.gov›mmb›rreanl›index.

#### **Figure 6.**

*Patch of red tide cells dumped into the ROMS Ocean current model in the surface waters of the west coast of FL on August 24, 1987, with a triple-nesting approach in the ROMS Ocean currents model.*

html) and the second, the European Centre for Medium-Range Weather Forecasts (ECMWF) winds (https://www.ecmwf**.**int)*.*

**Figure 7** presents the NARR wind fields used in the model experiment, by way of example. As the winds on the west FL shelf were consistent from late August to early September, we present that sequence. In **Figure 8**, the numerical model simulations employing the NARR winds versus the ECMWF winds (which are not shown) are presented. They are quite comparable, providing credence to our mechanical windforcing hypothesis.

In the numerical model experiments, two conclusions are reached: (1) the atmospheric winds in late August and early September 1987 on the West Florida Shelf were sufficient to transport the Karina Breve cells from the west coast of Florida to the Loop Current to the Florida Current—and into Gulf Stream system; (2) the combination of the wind effects, from Cold Fronts in the GOM and ETCs; on the other hand, the effect of the Gulf Stream meanders and frontal filaments are necessary to transport the passive tracer from the Gulf Stream to the inshore area of the NC and SC coasts. We next consider the atmospheric wind fields along the southeastern Atlantic Seaboard in the fall 1987.

*On the Possibility of Non-Local and Local Oil Spills Striking the Shores of North Carolina... DOI: http://dx.doi.org/10.5772/intechopen.106679*

**Figure 7.** *NARR-based wind fields over the west coast of FL on August 24 1987, during the numerical passive tracer experiment.*

#### **Figure 8.**

*The passive tracer wind-driven numerical model experiments employing the NARR versus the ECMWF driving fields, both driving the ROMS Ocean currents model. (a) Left panel, the passive K-breve algae; (b) right panel, a surface oil spill in the GOM being transported to the southeastern Atlantic seaboard.*
