Slowing Currents in the Gulf Stream

• The Gulf Stream, together with its northern extension the North Atlantic Drift, is a warm and swift Atlantic ocean current that originates in the Gulf of Mexico and stretches to the tip of Florida.
• It then follows the eastern coastlines of the United States and Newfoundland before crossing the Atlantic Ocean as the North Atlantic Current.
• The Gulf Stream system conveys warm surface water from the equator to the north and the deeper cold, low-salinity water down south.
• It works like a giant conveyor belt.
• A recent study has revealed the slowing of the Gulf Stream system.
• Increased rainfall and melting of the Greenland Ice sheet may have likely contributed to the observed slowing down of the Gulf Stream.

More About Oceanic Currents:

• Ocean currents are the horizontal flow of a mass of water in a fairly defined direction over great distances.
• They are like streams of water (like rivers) flowing through the main body of the ocean in a regular pattern.
• Ocean currents (Avg speed 3.2 km to 10 kmph) with higher speeds are called streams and currents with lower speeds are called drifts.

Ocean currents are categorized as warm or cold on the basis of relative temperature w.r.t the surrounding water:

• Warm currents generally flow from equatorial regions toward poles. Eg. Kuroshio current, Gulf stream
• Cold currents generally flow from polar regions towards the equator. Eg. Oyashio Current, Labrador current.

The circulation of the ocean currents depends on the following factors:

• Planetary Winds: A major role in ocean currents is played by the frictional drag of surface water by planetary winds.
  • Most of the currents of the world tend to follow the direction of planetary winds.
  • Differences in Density: Differences in water density affect the vertical mobility of ocean currents. The less-dense water of the equator rises and moves towards the poles (warm current) while the cold and dense waters of the poles sink and move towards the equator (cold current). Similarly, water with lower salinity (lower density) flows on the surface while an undercurrent of high salinity flows towards the less dense water - eg. the current between the Mediterranean Sea with higher salinity and Atlantic Ocean with lower salinity.
  • Earth’s Rotation: The earth’s rotation deflects air to its right in the northern hemisphere and to its left in the southern hemisphere. Similarly, ocean water is also affected by Coriolis force.
  • So, all the ocean currents follow a clockwise direction in the northern hemisphere and an anticlockwise direction in the southern hemisphere.
  • Coastlines and Bottom Reliefs also affect the direction of currents. Eg. The Equatorial current after being obstructed by Brazilian coast bifurcates into two branches.
  • Heating by the Sun: Heating by solar energy causes the water to expand.
  • That is why, near the equator the ocean water is higher in level than in the middle latitudes. This causes a very slight gradient and water tends to flow down the slope.
• Ocean currents and mixing by winds and waves can transport and redistribute heat to deeper ocean layers.
• Currents are also important in marine ecosystems because they redistribute water, heat, nutrients, and oxygen about the ocean.