The average salinity of the ocean is 35 parts per thousand (ppt); most of the Gulf of Mexico averages 28 to 32 ppt. However, some areas of the Gulf of Mexico average 36 ppt. There are many influences on the salinity within the Gulf of Mexico. More than 30 rivers contribute freshwater to the Gulf. The Mississippi River makes the greatest contribution.

Brine pools and seeps from the bottom of the Gulf of Mexico basin contribute higher salinity water to the Gulf and significantly raise the salinity near these features. Ecosystems and the life forms that exist in high salinity environments are very different from those found elsewhere. It is interesting to investigate those life forms and their adaptations for survival in such hostile environments. One well known brine seep is located near the East Flower Garden Banks, and an even larger one is located at the Orca Basin. These seeps have a salinity of 200 ppt and 250 ppt, respectively.

The Brine Pool and other brine lakes in the Gulf of Mexico are caused by dissolution of buried salt deposits created during a time when the Gulf dried out. There is a brine seep located 233 feet below the surface on the margin of the East Flower Garden Bank. Living conditions for most marine organisms are not good here since the lake's water is highly saline, has high levels of hydrogen sulfide and dissolved hydrocarbon gases, and no oxygen. The lake has an outflow into a canyon that contains a mixing stream, which dilutes the brine to lower salinity, adds oxygen and diminishes the toxic hydrogen sulfide.  The lake, about 80 feet in diameter, is only 10 inches deep. The canyon begins at the end of the depression where the lake sits. There, water from the brine seep flows over a small waterfall and down the canyon, which extends roughly 200 feet to the edge of the bank. 

The dominant organisms in the brine lake are sulfide-oxidizing bacteria that live at the very thin interface that separates the dense brine lake from the normal seawater above. Fish and other animals generally cannot tolerate the sulfide of the canyon brine stream, but some fishes such as angelfish, butterflyfish and cottonwick are able to swim in and out of the brine stream to feed. Large red snappers and groupers often swim very close and even dive into the full-strength brine of the lake.

Each generation inherits problems from the generation that preceded it.  World War I gave rise to World War II; WWII gave rise to the Cold War and the myriad global conflicts that continue around the globe to this day.  Industrialization has given rise to a variety of environmental problems that the present (perhaps future) generation must solve if humans are to continue to live on this planet in health and safety.  Consider farms and yards and golf courses with their fertilizers, insecticides, and herbicides or pastures and feed lots with eroded topsoil and animal wastes or industrial sites with toxic emissions and accidental spills.  For example, could anyone have predicted the deleterious effects of mall parking lots on local watersheds?

A hurricane is an intense tropical weather system.  It has a well-defined eye and sustained winds of a minimum of 74 miles per hour.  It takes an almost exact set of weather conditions for a hurricane to form. (NOAA).  Some of these conditions are warm water (81 degrees F), light upper level winds, and a pre-existing disturbance of thunderstorms.  Hurricanes start off as a tropical wave-a cluster of thunderstorms.  After these thunderstorms get some organization and have winds sustained at 35mph for a minimum of a minute these storms are known as a tropical depression.  Continued organization and winds of 40 mph sustained will classify the storm as a tropical storm where it is given an official name.  Once the sustained winds have reached 74 mph and the eye becomes more defined the tropical storm is classified as a hurricane.

Hurricanes have different names for them all over the world.  Hurricanes are also known as typhoons, sever tropical cyclones, and severe cyclonic storms.  In the northern hemisphere hurricanes rotate in a counterclockwise motion while in the southern hemisphere hurricanes rotate in a clockwise motion.  The Atlantic hurricane season lasts from June first to November 30.  There is an increase in storm activity in July and August because of the increase in water temperature. (NOAA).  Hurricanes usually average 300 miles wide and hurricane force winds can be felt 25 to 150 miles from the eye of the storm while tropical storm-force winds can extend 300 miles for the eye of the storm depending on the intensity of the hurricane.  The eye of a hurricane is normally between 20-40 miles across and is relatively clam.  The winds are the greatest at the eye wall.  The northeast corner of the storm is the most dangerous part of the storm because it has the highest storm surge due to its counterclockwise rotation. 

Hurricanes are uncontrollable, but with increased warning systems lives have been saved.  When hurricanes move over land, surface circulation can be reduced by friction and the main moisture sources are cut of, so the storm’s fury slowly comes to an end.  If the storm, however, moves back into warmer water, the storm can re-intensify. 

Background information for this lesson should be obtained from:
NOAA Hurricane Education: Storm Surge Student Activities and Teacher Resources Website: http://www.climate.noaa.gov/education/hurricanes/stormsurge.pdf

Tsunami is a Japanese word meaning “harbor waves”.  Also called tidal waves, tsunamis are produced by earthquakes, landslides, volcanoes, and other disturbances of the ocean floor.  They can have wave lengths of 150 miles and can travel over 400 miles per hour.  On the open ocean they are only 1 meter tall, but get higher when they approach land.

In 1883, the explosion of Krakatoa produced a huge tsunami. Over 35,000 people died.  Over 300,000 people died on Dec. 26 th 2004, when a tsunami occured in the Indian Ocean because of an earthquake which measured 9.0 on the Richter scale.  Millions of survivors were left homeless and unemployed. 

In many ways the Gulf of Mexico is like every other part of the ocean, but there are differences.  This presentation (lesson) discusses the origins of the Gulf of Mexico and makes some comparisons to other parts of the world’s ocean in the context of the four traditional disciplines of oceanography:  geology, physics, chemistry, and biology.   (Taken from the introduction in “The Gulf of Mexico:  Understanding America’s Sea,” a COSEE presentation by Jessica Kastler, PhD, 2008.)
Students will discuss the Seven Essential Principles of Ocean Literacy before proceeding with the lesson (http://coexploration.org/oceanliteracy/).

Ocean surface currents are primarily driven by winds which are directly influenced by the Coriolis Effect.  Deep ocean currents on the other hand are caused by differences in density, determined by salinity and temperature.  This lesson reviews the surface and deep ocean currents with students.  Students are then introduced to the Loop Current of the Gulf of Mexico: 

CIRCULATION AND CURRENTS OF GULF OF MEXICO

Water enters the Gulf through the Yucatan Strait, circulates as the Loop Current, and exits through the Florida Strait eventually forming the Gulf Stream. Portions of the Loop Current often break away forming eddies or 'gyres' which affect regional current patterns. Smaller wind driven and tidal currents are created in nearshore environments.

Drainage into the Gulf of Mexico is extensive and includes 20 major river systems (>150 rivers) covering over 3.8 million square kilometers of the continental United States (Moody, 1967). Annual freshwater inflow to the Gulf is approximately 10.6x1011 m3 per year (280 trillion gallons). 85% of this flow comes from the United States, with 64% originating from the Mississippi River alone. Additional freshwater inputs originate in Mexico, the Yucatan Peninsula, and Cuba.
Source:  http://www.gulfbase.org/facts.php

Resources:
The Loop current
http://oceancurrents.rsmas.miami.edu/atlantic/loop-current.html

NOAA National Ocean Service: Education on Currents
http://oceanservice.noaa.gov/education/kits/currents/lessons/currents_tutorial.pdf
Chemistry in the Gulf of Mexico
http://www.gomr.mms.gov/PDFs/2006/2006-018.pdf