Illustration The M Factory © Smithsonian Institution Great Ocean Conveyor - temperature driven large-scale (global) circulation and formation of North Atlantic Deep Water (cold deep water current) North Atlantic Deep Water forms near Iceland where waters are cooled by strong winds, becoming very cold (and dense) and sink – mainly temperature driven Illustration The M Factory © Smithsonian Institution

Ice formation causes salty dense water to sink at the poles – temperature and salinity driven (Illustration by Jayne Doucette, Woods Hole Oceanographic Institution

Mediterranean Outflow Water is a deep water mass at about 1000m that results from high salinity, not temp. The high evaporation rate in the Mediterranean increases salinity. As the water leaves the Mediterranean basin it spreads into the Atlantic. Mediterranean Outflow Water is saltier (38 parts per thousand) than the North Atlantic Deep Water, but much warmer, so it floats above it. The Mediterranean is a distinct water mass in the global ocean. Images:http://www.eng.warwick.ac.uk/staff/gpk/Teaching-undergrad/es427/rice.glacier.edu-oceans/GLACIER%20Oceans-%20--%20Densitydriven.htm

Salinity Profile of the North Atlantic at 1000m depth Mediterranean Outflow and salinity profile - Salinity driven current at 1000m Salinity Profile of the North Atlantic at 1000m depth

Mouth of the Amazon - fresher water plume stretching out 1000km into the ocean. Murkey, brown water is sediments being carried by the freshwater outflow on the surface.   Image: rst.gsfc.nasa.gov/Sect17/Sect17_4.html

Plankton in San Francisco Bay: Estuary Model Fresh water i Mouth of Estuary (ocean water) Salinity (ppt) Depth (m)

Plankton - derived from Greek for “drifters”; Plankton - derived from Greek for “drifters”; living organisms that can not swim against the ocean currents. - can choose to move up and down in water column in response to environmental conditions

Plankton swimming up

Plankton more likely to swim down

Plankton swimming up and down