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Oil-spill threat - are our waters safe?

Published:Thursday | June 17, 2010 | 12:00 AM

A statement from the Guyana-based CARICOM secretariat said that the foreign ministers will talk about the oil spill, which followed an explosion on April 20 on an offshore rig belonging to British Petroleum (BP).

"All efforts to stem the flow of oil from the underwater well have failed and there are concerns in the Caribbean that the oil slick will reach its shores eventually, given the flow of currents," said the CARICOM secretariat - The Gleaner, June 10, 2010

So are we really in danger of the slick globs of oil that has so far washed up on all the shores bordering the Gulf of Mexico, ruining our pristine white sands and fragile coral reefs? While some may say no and others yes, this is just a look of the factors that could make the situation a possibility, and they include: ocean current patterns and weather patterns.

An ocean current is a continuous, directed movement of ocean water generated by the forces acting upon this mean flow, such as breaking waves, wind, Coriolis force, temperature and salinity differences and tides caused by the gravitational pull of the moon and the sun. There are two types of ocean currents: surface ocean currents and deep ocean currents.a

Surface ocean currents are generally wind driven and develop their typical clockwise spirals in the northern hemisphere and counter-clockwise rotation in the southern hemisphere because of the imposed wind stresses. In wind driven currents, the Ekman spiral effect results in the currents flowing at an angle to the driving winds. The areas of surface ocean currents move somewhat with the seasons; this is most notable in equatorial currents.

Deep ocean currents are driven by density and temperature gradients. Thermohaline circulation, also known as the ocean's conveyor belt, refers to the deep ocean density-driven ocean basin currents. These currents, which flow under the surface of the ocean and are thus hidden from immediate detection are called submarine rivers.

  • The current flow and the spill site

A closer look at the current flow in an around the Caribbean will reveal a north-westerly flow from the eastern Caribbean to the Gulf of Mexico that loops around and heads north to Florida and up the eastern United States (US) coastline. This particular current has a name called The Loop Current and it has clockwise flow that extends northward into the Gulf of Mexico and joins the Yucatan Current and the Florida Current.

The location of the spill site is approximately 100 miles off the coast of Mississippi, deep in the Gulf of Mexico. Despite this, the oil flow has dispersed along all of the states bordering the gulf and managed to drift into the Loop Current. The following diagram from NOAA shows the spill site and the oil dispersion far into the waters of the gulf.

From the diagram we can see that the oil is drifting north and spreading along the coast of the US southern states, far from the Caribbean flow and the loop flow, at the moment, however this is projected to change over time. With the dispersion of oil though spreading quicker north then south it is expected to reach The Loop current eventually. This will result in a more rapid flow of the oil slicks to other regions that are in proximity to this flow, and other tangential currents, the more important question is where will it flow? Below are screenshots of a computer model simulating the oil spill and the projection of the oil flow for the coming weeks and up to three months if not stopped.

As you can see from the pictures as the oil disperses further from the spill site it will likely travel southward to join The Loop Current and follow this stream along the Atlantic coast away from the Caribbean. The major part of the oil spill is not expected to flow latitude of the northern tip of Cuba, and not easterly enough to affect all the Bahamian islands, therefore using the surface current flow model only, we can safely conclude that Jamaica is in the clear, at least at this stage.

  • Hurricanes in the mix

The spill occurred well over a month before the June 1 start of the hurricane season, so the amount of oil leaked into the gulf of Mexico is estimated at 30,000 to 40,000 barrels a day, that is well over 80 million gallons of oil since the deepwater accident. To compound the problem, this season is predicted to be one of the most active seasons in recent years with 14-23 named storms (winds 39mph or higher)eight-14 hurricanes (winds 74mph or higher)three-seven major hurricanes (winds of at least 111 mph). Blow shows a history of hurricane paths of strength three and above that has passed though the Caribbean and the Gulf of Mexico.

The diagram shows that generally the hurricanes will follow a north-westerly path much like the direction of the surface and deepwater currents, which it drives. Thus if any hurricane were to occur, it may actually act like a cleaner pushing oil slicks away from the Caribbean back into the Gulf of Mexico, or it may accelerate the flow into the The Loop current flow.

  • Still good idea to plan

While the imminent threat to solid beaches and wildlife at this time seems unlikely, it is still better to plan rather than wait and see, we need to formulate a response plan in any event to protect the beaches that sustain the economy and wildlife.

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