Bell Ringer In your own words, define the following terms. In addition to a definition, discuss WHY each might be important. Ocean circulation Current Gyre Wave Tide

MARINE BIOLOGY Essential Question: How do Surface and Thermocline Circulation affect the Ocean? Learning Goals: Learn the components of Superficial and Thermocline Circulation Agenda: Bell Ringer Collect Homework Chapter 3 (Part 3) Classwork CNN/10 (3rd and 7th only) Upcoming: Chapter 3 (Part 4) Chapter 3 Test: 10/9 (B) & 10/10 (A)

Ocean Circulation – Surface & Thermocline (Part 3) Chapter 3 Ocean Circulation – Surface & Thermocline (Part 3)

Ocean Circulation Circulation can occur as waves, tides, currents and gyres. Circulation within the ocean is significantly driven by wind patterns. Winds are ultimately driven by sunlight energy.

Ocean Circulation (Cont.) As sunlight heats air, air rises. Hot air is less dense Cooler air rushes in to take the place of air that has risen. This movement is the source of winds. https://www.youtube.com/watch?v=uBqohRu2RRk – Bill Nye

The Winds Trade Winds: Located from the equator (0° - 30°) Westerly’s : Located in the Mid latitudes (30° - 60°) Easterlies : Located at the poles (60° - 90°) https://www.youtube.com/watch?v=Ye45DGkqUkE

Coriolis Effect Winds and the currents they drive are affected by the Coriolis effect. Because the earth spins continuously, anything that passes over the earth is deflected. In the NORTHERN Hemisphere wind is deflected to the RIGHT! In the SOUTHERN Hemisphere wind is deflected to the LEFT! https://www.youtube.com/watch?v=dt_XJp77-mk

Currents Currents are also a product of the wind. Current can be in surface layers of deeper water layers This deflection often causes currents to travel in circular patterns called gyres. https://www.youtube.com/watch?v=zYms4lHpgLc – spiral

Surface Currents All exposed surfaces of the ocean are subject to currents produced by the wind. Currents produced by the wind move at a 45° angle to the right due to the Coriolis effect This surface water current tugs on lower segments of water leading to an spiral (“Elkman Spiral”) Effect of the wind decreases with depth and is NOT felt passed a few hundred meters.

Elkman Spiral

Elkman Layer & Transport Elkman Layer: Upper Part of the Water Column affected by wind Elkman Transport: Microlayers moving together to produce a net movement of water 90° from the wind direction.

Equatorial Currents Due to the Trade wind movement towards the equator the current produced at the equator is parallel with the equator. The equatorial current moves along the equator East to West against the rotational spin of the earth

Major Ocean Surface Currents

Accidental Flotsam Current Study January (1992) Cargo ship in Pacific Ocean hit a wave & lost cargo. It was carrying toys from China to the United States. 29,000 Plastic Ducks among others Toys began washing up on shores around the world. November (1992): Sitka, Alaska 1995 : Hawaii, Japan, Bering Sea 2000 : East coast of United States Maine, Massachusetts 2007 : England

Accidental Flotsam Current Study On world map Write name and period # Sketch possible paths taken by the toys, where in the Pacific might they have been released? Describe in words how the toys could have made it to England. Could the toys journey all the way around the world? Why or why not? For homework, find the actual passage taken by the ducks and superimpose it onto your world map (use a different color, etc.)

Thermohaline Circulation Much of the Ocean surface waters are partially isolated from deeper waters due to density (temperature and salinity) Because denser sea water sinks, the ocean is usually stratified (layered) with the denser water at the bottom and the less dense at the surface. Deep water: Cold and dense Surface water : Warm and less dense.

Three Layered Ocean Surface Layer Intermediate Layer Deep Layer 100 – 200 meters (m) deep Mostly mixed by winds & waves Intermediate Layer 200 – 1000 meters (m) deep Deep Layer 1000 meters (m) + deep Thermoclines Transitions from warm to cold waters. Boundaries between layers Main thermocline is in the intermediate layer.

Stability and Overturn Much of the water column is stable. Stability is achieved through large differences in density between shallow and deeper water! Caused by a water column that has lost stability. Surface water becomes more dense and downwelling occurs. Downwelling occurs mostly during winter due to cold surface temperatures and water cold glacial water run off. Upwelling is the opposite.

The Great Ocean Conveyor Water settles in the column based on its density. Complete downwelling occurs only in the Atlantic South of Greenland & just North of Antartica. This is only temporary and drives the global thermohaline circulation. The oceans completely mix every 4000 years.