Posted by: leahbiery | May 21, 2010

What is the Loop Current?

By J. Bruce Neill, Ph.D. and Leah Biery, Sanibel Sea School

Mired in the morass of the Gulf oil blowout is the Gulf Loop Current. Over the course of the ongoing disaster in our backyard, you’ve probably heard reports that oil could enter the Loop Current and make its way to the Florida Keys, where it could impact fragile mangrove, seagrass, and coral reef ecosystems.

A diver enjoying the Florida Keys.

After hearing that something “could” or “might” happen, it is easy to assume that it probably won’t, but on Tuesday, May 19th, officials at the National Oceanic and Atmospheric Administration announced that surface oil has entered the Loop Current and will likely arrive in the Florida Keys within 10 days.  Some oceanographers predict that traces of oil could reach Key West as early as Sunday, May 23rd.

The Gulf of Mexico basically has a single entrance and a single exit.  Most saltwater enters the Gulf of Mexico from the Caribbean Sea through a narrow passage between the Yucatan Peninsula and Cuba – called the Yucatan Channel, or the Straits of Yucatan.  The water that flows through this passage is called the Yucatan Current.

Much of the Yucatan Current roughly follows the shoreline of the Yucatan Peninsula north and west and continues to the western Gulf. The eastern part of the Yucatan Current flows along the northern edge of Cuba; it is called the Florida Current.

A third, central portion of the Yucatan Current flows northward, then to the east, eventually turning south towards the Florida Keys.  This is the now famous Gulf Loop Current.

The Loop Current and the Florida Current combine and flow between the southern tip of Florida and Cuba as the Gulf Stream.  It is joined and pushed along by an Atlantic current (the Antilles Current) to flow northward along the eastern seaboard of North America, eventually flowing to Europe.

Currents in the Gulf of Mexico.

By now, you’ve probably realized that ocean currents are very complex.  Oceans are better thought of as a series of fairly discrete rivers flowing in their own directions stacked on one-another between the surface and the ocean floor.  To make things more complicated, not only do currents flow differently at different depths, they vary horizontally over space as well.  So we have a series of adjacent rivers flowing in separate directions, stacked on even more rivers flowing in their own directions.

The Loop Current is a surface current, typically 100 – 200 miles offshore at the latitude of Lee County, although prevailing weather patterns can cause it to meander significantly.  However, it is rarely less than 100 miles from our shores, so it is likely to bypass Lee County and deposit oil in the Tortugas, the Marquesas and the Keys.  You may be thinking, whew, we lucked out – but not so fast.

BP is releasing oil from a pipe 5000 feet below the surface of the ocean.  It is not simply rising to the surface where we can scoop it up. Remember all those stacked currents?  In all likelihood, a significant amount of oil is being transported below the surface on deeper currents in other directions.  It is likely that oil carried by deeper currents will end up in Lee County over the coming weeks or months.

So what do we do?  We wait, and we plan for the worst and hope for the best.  Most importantly, we learn from this horrific event and act to avoid similar disasters in the future.

In the meantime, find and practice ways to conserve energy.  Investigate solar hot water heaters, drive your car less, and turn your thermostat up a degree or two.  Go out and enjoy our pristine beaches.

As often as possible, ride your bike instead of driving.

Simple answers would be nice, but unfortunately there are none.  Let’s push our leaders to support ways to reduce our reliance on fossil fuels.

Perhaps this is our chance to take the lead, and let our leaders follow.

A helpful video of Gulf currents…!


  1. Very interesting piece on the Loop Current; informative and helpful. Thank you for posting.

    Regarding the earlier articles about oil spill clean-up and fossil fuels/energy policy, I think it is difficult to have this conversation without providing the broad context first and rationally tabling both sides of the debate. SCCF doesn’t provide both sides either.

    Climate change risks, economic security, enabling people to come out of poverty through energy use, energy supply, environmental protection, oil spill response, roles of companies and governments — all of these elements are wound up in this very complex issue of energy policy.

    As you are aware, sustainable development is a pattern of resource use that aims to meet human needs while preserving the environment so that these needs can be met not only in the present, but also for future generations (Bruntdland Commission). To me, this means that we can’t just halt energy production because of the environment – it would cripple world economies. But, we also have to take necessary steps to identify and then effectively manage the risks. BP recognizes this – they push energy efficiency too in their own operations and their R&D programs. They didn’t want this to happen and clearly they didn’t believe this could happen. They were wrong. We have been safely drilling in the Gulf of Mexico for over 30 years – which doesn’t get a lot of airtime. Have you read their sustainability report?

    Now, about supply/demand fundamentals (a reality-check) … Global energy demand is expected to climb by 35% by 2030 due to OECD nations. Fossil fuels will remain the dominant wedge of the world’s supply due to it’s abundance and cost. Natural gas is the cleanest fossil fuel and will likely be a bridging fuel for power generation until revolutionary technologies are developed over the coming decades. Nuclear will grow as well. Solar, wind, and biofuels will grow quickly but will be a relatively small part of the supply wedge. It will take decades to transition, just like it took decades to transition from wood, coal to oil.

    For the near term, let’s not forget the collective reaction when gasoline hits $4/gal. It is unacceptable to the people of America.

    What is striking about the BP incident is that oil spill response appears to be grossly inadequate. This response capability rests with the companies and governments at the federal, state, and local levels. We should be outraged that they didn’t have an adequate plan in place and hold those leaders accountable. You do realize, with all those ships coming into Florida to meet our energy needs, a spill can still occur. None of this is without risk. Are we ready?

    Seems to me there is too much grandstanding and not enough being done in terms of contingency planning.

    Agree with your point on energy efficiency – that’s a win-win.

    Forgive my ignorance, but is Sanibel Sea School an advocacy group and does this get incorporated into the kid’s curriculum? It would be good know. Thanks.

    • Thank you for reading our blog. Sanibel Sea School is a marine education nonprofit dedicated to marine conservation through transformative education, communication, and research. We offer a variety of field-based educational programs for children and adults.

      We are not an advocacy group, nor are we affiliated with any political group or party. Our staff members and supporters come from many different backgrounds, but we all agree that the ocean is worth protecting. We do our best to provide accurate, unbiased information that will educate our clients and supporters on a wide variety of ocean-related issues and equip them to act as good stewards of marine ecosystems.

      We take advantage of every opportunity to teach people about the ocean, and the oil spill offers a valuable chance to facilitate conversations about energy consumption, clean energy, and how these things affect coastal and marine environments. We will incorporate these topics into our curriculum in an age-appropriate manner centered on good ocean stewardship.

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