Write about this. Have you ever experienced a very strong wind gust? What happened? Have you ever felt a gentle breeze? What did it feel like?

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1 Write about this. Have you ever experienced a very strong wind gust? What happened? Have you ever felt a gentle breeze? What did it feel like?

2 How wind works Winds flow on earth based on differences in pressures, everything flows high to low! The prevailing winds on Earth flow from areas of high pressure to areas of low pressure 14.7 lb/in2 is standard atmospheric pressure

3 What the heck is air pressure A column of air 1 square inch that extends all of the way to the end of the atmosphere exerts weight 14.7 lbs. What does psi mean?

4 Warm and cold air pressures Warmer air is typically less dense and higher in water vapor content (low pressure zone) Colder air is typically higher in density and lower in water vapor content (high pressure zone)

5 The climates on Earth what should this do for winds?

6 How about this.. Warm less dense air rises at the equator Cold dense air falls at the poles

7 Why does wind speed change? Pressure gradient : Horizontal difference between high and low pressure zones Steep gradient makes high wind Shallow gradient makes low wind

8 So why do wind patterns not flow due North or South? The Coriolis effect: Caused by the rotation of the earth on its axis Coriolis deflection Causes these simple flow patterns to be broken up and cause different wind patterns across earth s latitudes

9 Naming winds Winds are named for where they come from A person born in New York may call themselves a New Yorker or a person from Puerto Rico may call themselves Puerto Rican Winds born in the: North = Northerlies East = Easterlies South = Southerlies West = Westerlies

10 Winds are also named for what they do! Trade winds used by mariners, to help their ships move faster or in the proper direction Horse latitudes - low wind area throw off the horses save food and water for us Doldroms slow and lethargic winds Roaring forties areas with many wild winds

11 Sailing in the Doldrums

12 Artist s rendering of the roaring forties

13 Sailing in the trade winds

14 Why is Ocean Circulation Important? Transport ~ 20% of latitudinal heat Equator to poles Transport nutrients and organisms Influences weather and climate Influences commerce

15 Currents An ocean current is a continuous, directed movement of ocean water generated by the forces acting upon this mean flow, such as breaking waves, wind, Coriolis effect, temperature and salinity differences and tides caused by the gravitational pull of the Moon and the Sun. Depth contours, shoreline configurations and interaction with other currents influence a current's direction and strength.

16 There are two types of currents Wind driven currents make up approximately 10% of oceanic water flow Density driven currents make up approximately 90% of oceanic water flow Based on these factors Temperature Salinity Pressure

17 Surface currents Surface currents are created by wind drag on the surface of the water The area of contact between the wind and water is called the Fetch. The bigger the fetch the more energy that can be transferred

18 Power from wind 10 % oceanic water movement is powered by the wind Faster traveling air has more energy to transmit to the water beneath it The transfer of energy is not very efficient Water typically travels 3-4 % the speed of the wind above it

19 Example: wind speed = 50 kph Equation: 50 X = kph water current speed: kph

20 wind patterns + Coriolis equals Zonal wind Flow = movement of winds that is parallel to the lines of latitude

21 The currents are deflected by continents creating Circulation Gyres = large looping currents caused by a current being bent back on its self causing a loop of water

22 10% of ocean circulation is driven by wind

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24 Currents in the Real Ocean Currents rarely behave exactly as predicted by these theoretical explanations due to factors such as Depth shallow water does not permit full development of the Ekman spiral Density deeper currents moving in different directions influence the overlying surface movement

25 What do Nike shoes, rubber ducks, and hockey gloves have to do with currents?

26 Lost at Sea

27 Duckie Progress January shipwrecked in the Pacific Ocean, off the coast of China November half had drifted north to the Bering Sea and Alaska; the other half went south to Indonesia and Australia 1995 to spent five years in the Arctic ice floes, slowly working their way through the glaciers the duckies bobbed over the place where the Titanic had sunk they were predicted to begin washing up onshore in New England, but only one was spotted in Maine a couple duckies and frogs were found on the beaches of Scotland and southwest England.

28 North Pacific Subtropical Gyre

29 Upwelling and downwelling Vertical movement of water ( ) Upwelling = movement of deep water to surface Hoists cold, nutrient-rich water to surface Produces high productivities and abundant marine life Downwelling = movement of surface water down Moves warm, nutrient-depleted surface water down Not associated with high productivities or abundant marine life

30 Surface and Deep-Sea Current Interactions Unifying concept: Global Ocean Conveyor Belt

31 Heat Transport by Currents Surface currents play significant roles in transport heat energy from equatorial waters towards the poles May serve as heat sources to cooler overlying air, heat sinks from warmer Evaporation and condensation participate in latent heat exchanges

32 Matter Transport and Surface Currents Currents also involved with gas exchanges, especially O 2 and CO 2 Nutrient exchanges important within surface waters (including outflow from continents) and deeper waters (upwelling and downwelling) Pollution dispersal Impact on fisheries and other resources

33 Global ocean circulation that is driven by differences in the density of the sea water which is controlled by temperature and salinity.

34 White sections represent warm surface currents. Purple sections represent deep cold currents

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