Presentation on theme: "Deep Water Circulation Also known as thermohaline circulation."— Presentation transcript:
Deep Water Circulation Also known as thermohaline circulation
Deep Water? Where: ◦ below pycnocline – high layer of density change in the vertical dimension layer ◦ about 90% of global ocean Compared to Shallow Currents they move very slow. When surface water becomes dense enough it sinks initiating deep ocean currents
T-S diagram Temperature-Salinity ◦ Origin of water can be determined by specific characteristics of water. ◦ Densest seawater is cold and a little salty AABW NADW
Sources of Deep Water Antarctic Bottom Water (AABW): ◦ densest water mass (very cold) ◦ forms around Antarctica and sinks to seafloor North Atlantic Deep Water (NADW) ◦ Less dense than AABW ◦ Norwegian Sea water sinks and mixes with other North Atlantic water masses North Atlantic Intermediate Water (NAIW) Formed at Arctic Convergence Zone Above NADW Antarctic Intermediate Water (AAIW) ): Formed at Antarctic Convergence Zone Above NADW
Worldwide Deep-Water Circulation Mixes Shallow Water with Deep Water. ◦ Upwelling Brings nutrients up ◦ Downwelling Brings O 2 Down
The “Conveyor Belt” Combination of surface ocean circulation and deep-ocean circulation ◦ North Atlantic: Gulf Stream transports warm seawater pole ward ◦ Cooling of this water means it sinks and flows southward ◦ Joins deep water around Antarctica ◦ Mixed water flows northward into Pacific and Indian oceans ◦ Upwelling water flows west and north into Atlantic Ocean
Turning off the Conveyor belt If surface water did not sink, oceans would be warmer ◦ More Tropical Storms and Hurricanes ◦ Less Fish If ocean were warmer, NADW might not sink as readily ◦ No up welling ◦ No downwelling Less transfer of warm water to high latitudes.
Summary – Deep Water Circulation Huge volumes of seawater move at slow speeds T-S diagram helps identify sources of water Two Main Sources of Deep Water ◦ Antarctic Bottom Water ◦ North Atlantic Deep Water Mixes with Surface Water at High Latitudes where the pycnocline is weaker.
Summary - The “Conveyor Belt” Mixes Deep and Shallow Currents ◦ Happens where the pycnocline is weaker ◦ Allows for Upwelling and Down welling Sinks in North Atlantic Rises in Indian and North Pacific Turning it off would be bad ◦ Warmer oceans – more storms. ◦ Less heat transfer to poles ◦ Less up and downwelling.