Ocean Surface Circulation Motion in the Ocean, Part I, or Why does the ocean have currents, and why do they move in circles? Jack Barth (barth@coas.oregonstate.edu) NASA web site: http://oceanmotion.org [...]...Consequences of Coriolis 3 Moving fluids (atmosphere and ocean) turn to the right in the Northern Hemisphere 3 Moving fluids (atmosphere and ocean) turn to the left in the Southern Hemisphere Global Wind Circulation westerlies trades trades westerlies Wind-Driven Ocean Circulation 3 Steady winds produce waves and set the surface water in motion 3 Moving water is deflected to the right... around the gyres Northern Hemisphere Gyres westward intensification ~1000 meters Surface Circulation Upwelling and Oregon’s Ocean 3Winter winds from the south -downwelling 3Summer winds from the north -upwelling Winter Summer Oregon’s Summer Thanks to Alan Dennis (COAS/OSU) Cold, nutrient-rich water near the Oregon coast: leads to phytoplankton blooms chl (mg/m3) T (ºC) Barth (2007) Equatorial Divergence... cm/second = 1 km/day R Lumpkin (NOAA/AOML) 106 m3/sec (Sverdrup) = all the rivers Gulf Stream - Benjamin Franklin 1760s Sailing times to and from Europe Gulf Stream from satellite So, do the gyres just follow the winds? 3 Not exactly! But the winds get the motion in the ocean started 3 The oceans respond by flowing and turning 3 Water piles up in the center of gyres several meters high Global Wind Circulation... blooms chl (mg/m3) T (ºC) Barth (2007) Equatorial Divergence Equatorial Divergence Antarctic Circulation How do we track ocean circulation? 3 Fixed Buoys measure current speed and direction 3 Drifters travel with the currents and transmit their location Beach Swap Meets! . Circulation: ➨ Surface Circulation Wind-driven ➨ Deep Circulation – Density-driven Density of water is influenced by Temperature and Salinity, so density- driven circulation is often called. Circulation Temperature and Pressure ✦ As the Earth’s surface is heated, air is warmed, expands and rises (Low Pressure) ✦ Warm air carries water vapor ✦ In the upper atmosphere the air cools and sinks. from a rotating reference frame ✦ Gustave-Gaspard Coriolis (1835) ✦ Familiar from merry-go-rounds ✦ Significant only for large distances (not toilets and billiards!) animation