Gyres rotate clockwise in northern hemisphere and counter clockwise in southern hemisphere. Western boundary currents are warm and transport heat away from equatorial regions. Eastern boundary currents are colder and move colder water towards equator.
Caption for Item 1: SATELLITES SEE GULF STREAM WARM WATERS This is a NASA satellite image of the warm waters of the Gulf Stream running up the U.S. eastern seaboard. The Gulf Stream shows up as a winding rope of orange and yellow (indicating warm waters) against the cooler green and blue waters. Credit: MODIS Ocean Group NASA/GSFC SST product by U. Miami
Caption for Item 4: NORTH ATLANTIC OCEAN CIRCULATION SYSTEM The Gulf Stream moves warm surface water from the equator north through the Atlantic, where the water cools and gets saltier. As it approaches the Norwegian Sea, it becomes dense enough to sink. It then slowly travels through the deep water southward into the Southern hemisphere, with the return flow to the North occurring at the surface. Credit: NASA GSFC
Ocean conveyor belt moves heat around the globe. One trip around the conveyor belt can take 1000 years or more.
Brings nutrient rich cold water to the surface nourishing marine life.
These two images show sea surface temperatures, blue is coldest water and red is warmest. On the left, a summer upwelling event reveals cold up-welled water near the coast with filaments streaming offshore. On the right, the same region without upwelling shows the relatively warm surface water of the California Current moving much closer to shore. Graphic courtesy of PISCO, the Partnership for Interdisciplinary Studies of Coastal Oceans , at Oregon State University
Salinity <ul><li>Amount of salts and minerals dissolved in water </li></ul><ul><li>Varies throughout </li></ul><ul><li>Average = 35 ppt or 3.5% </li></ul>
Density <ul><li>Salt water is more dense than fresh water </li></ul><ul><li>Cold water is more dense than warm water </li></ul><ul><li>Pycnocline – area of rapid increase in density with depth </li></ul>
Temperature <ul><li>Warm water expands and stays above colder water </li></ul><ul><li>Only fresh water evaporates or freezes. The salt is left behind. </li></ul><ul><li>Thermocline – area of rapid decrease in temperature as depth increases </li></ul>