An international team of scientists says they’ve developed a method of using satellites to peer beneath of ocean’s surface to study underwater currents.

Using sensor data from several U.S. and European satellites, researchers from the University of Delaware, NASA’s Jet Propulsion Laboratory, and the Ocean University of China have developed a method to detect super-salty, submerged eddies called Meddies that occur in the Atlantic Ocean off Spain and Portugal at depths of more than a half mile.

Such warm, deep-water whirlpools are part of the ocean’s complex circulatory system, and help drive the ocean currents that moderate Earth’s climate.

The research marks the first time scientists have been able to detect phenomena so deep in the oceans from space, using a new multi-sensor technique that can track changes in ocean salinity.

The initial results of the project are reported in the April issue of the American Meteorological Society’s Journal of Physical Oceanography.

Surface currents, shown below, are driven by the winds. Warm water is red and cold water is blue. The Trade Winds propel ocean water westward along the equator, and when it strikes a continent, it is diverted poleward. However, a narrow return flow also occurs along the equator. In mid-latitudes the currents are driven eastward by the Westerlies. The opposing wind belts cause currents in all the ocean basins to form gyres, or giant loops. 

Thermohaline (Deep) Circulation

  • Evaporation makes water more saline and denser
  • Freezing makes water more saline and denser
  • Cold water is denser than warm water

A combination of surface and deep flow creates a giant global heat conveyor. The coldest and densest water forms off Antarctica and flows along the ocean floors until it reaches an obstacle. Then it rises and joins the surface circulation. As water loops around the North Pacific gyre, it becomes extremely warm. Even though the amount of water that passes from the Pacific to the Indian Ocean is not great, the amount of heat it carries is. It cools a bit rounding Africa, then warms in equatorial latitudes and carries  water up the Atlantic into the Arctic. Finally the water cools and sinks, mixes with cold bottom water, and begins the cycle again.