Deep Ocean Currents (Great Ocean Conveyer Belt) Differential Solar Heating Deep Ocean Currents • There are areas in the oceans where surface water becomes denser than the water below it and sinks • This causes a system of slow deep water currents • In order for sea level to remain constant, if water sinks in one area, it must rise somewhere else • Areas where deep water rises to the surface are called areas of upwelling Sinking of Surface Water • Surface water sinks in areas where warm, salty water is carried toward the poles by currents • This water cools and becomes cold, salty water which makes it denser than the water below it • So it sinks forcing deep water to flow away from that area thus starting the deep current Example • • • • Tropical Atlantic is very salty Gulf Stream moves this water north Water cools along the way By the time it reaches the area between Iceland and Europe, it has cooled enough to become very dense • Surface water sinks to the bottom – feeding deep currents North Atlantic Deep Water Formation Great Ocean Conveyor Belt • The deep current system connects all the oceans • Called the Great Ocean Conveyor • Has enormous effects on: – World climate (heat transfer) – Fishing industry (upwelling areas are great fishing grounds) Great Ocean Conveyor Belt Conveyor and Climate Change • Scientists are concerned that global warming could affect the ocean conveyor system and make abrupt climate change more likely • Melting of ice is making polar seas less salty • This could interfere with sinking – slowing down the conveyor • On the other hand, tropical waters are becoming saltier or denser • Ultimate result??? Can’t be sure • The following illustration describes the flow pattern of the major subsurface ocean currents. Near surface warm currents are drawn in red. Blue depicts the deep cold currents. Note how this system is continuously moving water from the surface to deep within the oceans and back to the top of the ocean. • One complete circuit of this flow of sea water is estimated to take about 1,000 years. • the ocean "conveyor belt", refers to the cycle in which surface waters sink, enter deep water circulation, then resurface after slowly flowing through the deep ocean.