Thermohaline or Deep Ocean Circulation draft



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Thermohaline or Deep Ocean Circulation - DRAFT

(Thanks to Turtle Haste for this activity)

Background:
Circulation in the ocean is unified through the global conveyor belt which connects ocean surface and thermohaline circulation transporting heat and salt on a global scale. Deep ocean circulation is driven primarily by slight differences in seawater density that is caused by variations in temperature and salinity, referred to as thermohaline circulation.
Thermohaline circulation involves the creation and movement of unique water masses. These are large homogeneous volume of water that processes a characteristic range of temperature and salinity. Most deep waters masses form at high latitudes at the ocean surface where they acquire their unique low temperature and salinity. For example, in the North Atlantic, the combined chilling of ocean water, evaporation and formation of sea ice produces the North Atlantic Deep Water (NADW). The newly formed water sinks and when it reaches an area where the surrounding area has the same density the water mass begins to flow along “horizontally” channeled by sub-marine features. These waters gradually warm and mix with overlying waters as they flow towards lower latitudes rising slowly at the rate of only a few meters per year. In the deep, waters move slowly in comparison to the well-defined gyres of surface currents. Water at the bottom of the Pacific can be 1500 years old and may take as long as 1,000 years to move through the conveyor. The identification of these water masses allows scientists to monitor the transport of water on a global scale.
Diagram from the United Nations Environmental Project



Robert Simmon, NASA. Minor modifications by Robert A. Rohde (Public Domain)

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