Somali Current TYLER JANOSKI

First, let’s talk about the South-Asian Monsoon  Monsoon develops because of temperature differences between land and sea  Remember:  Land heats and cools much quicker than water  The center of Asia is extremely continental  Summer: Thermal low over Tibet  Air is forced upwards through heating  Subtropical high over the Indian Ocean  Winds flow northeastward  Winter: High pressure now over continental Asia  Air now rises over the Indian Ocean  Winds flow southwestward

Somali Current Formation  June to Sept: air flows towards low pressure in Asia  Jet of air called Findlater jet (or Somali Jet) forms from Western Intensification (it happens in the atmosphere too!) off coast of Somalia and Oman  Winds drive current from Southwest to Northeast  After Sept: winds die down  Dec-March: High pressure of Asia, air flows towards ocean  Current reverses direction and flows from Northeast to Southwest

Ekman Transport!  As we all know, the net transport of water is directed to the right of the wind stress  The flow in the Ekman layer during the summer is offshore  Cold water from the bottom Ekman layer flows up to replace it in upwelling  The strength of the winds and the Findlater jet create massive upwelling along the Somali coast  In the winter, the flow is directed on-shore, though it is weaker because of weaker winds  Cold air in the winter cools sea surface temperatures and promotes mixing

Comparison to other Western Boundary Currents  Somali current is the only Western boundary current that reverses direction  Relatively short because the Asian continent takes up most of Northern hemisphere above Indian ocean  Still experiences Western intensification (but only when it’s flowing Northeast in the summer)  Recorded speeds > 300cm/s  Upwelling during summer can lower temperatures by five degrees C  Upwelling=productive marine ecosystem

The Great Whirl  With the Somali Current forms an extremely large anticyclonic eddy called the Great Whirl  300km wide, extending almost 1000 m deep  Speed approx. 200cm/s  Researchers have discovered that it actually starts to form before the summer monsoon begins  Recently proposed theory: Rossby waves from previous monsoon propagate westward and concentrate energy off the coast  May play a role as predictor of monsoon strength  May influence the characteristics of the monsoon