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The Sea Around Us, Lecture 7, 4 Feb 2014 Ocean & Atmospheric Circulation, Its all about HEAT Here Comes the Sun! Around the Sun, REM Under the Sea Timeflies Tuesday Thanks to Victor T. A drop in the ocean Ron Pope Thanks to Meryem B.

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Read: Chap. 6 & 7 Course web site, Lecture Notes linkCourse web site OLA3 Due Today! Quiz 1, Friday Feb 7 Thanks to Michelle W. and Emma W. No Lecture on Thurs. Feb 6 (TAs will be here, 100 Thomas, to answer questions)

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What drives atmospheric and ocean Circulation? Lets examine how the spatial distribution of energy receipt and how the resulting temperature gradient drives ocean and atmospheric convection Well see how the winds (atmospheric circulation) drives circulation of ocean Surface Water! Lets examine how the spatial distribution of energy receipt and how the resulting temperature gradient drives ocean and atmospheric convection Well see how the winds (atmospheric circulation) drives circulation of ocean Surface Water!

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Global "Thermohaline" Circulation Circulation of ocean water driven by temperature and salinity differences

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The Ocean "Conveyor Belt" The "Conveyor" system is a very generalized view of the work done by surface and deep circulation in mass and heat transfer. Sinking of cold dense waters at high latitude Return of warm surface waters to replace them

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Energy from the Sun! http://earthguide.ucsd.edu/earthguide/diagrams/greenhouse/

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Energy Transfer to and from the Oceans Radiation Direct transmission from source with or without a medium Three types of heat transfer:

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Energy Transfer to and from the Oceans Three types of heat transfer: Radiation Direct transmission from source with or without a medium Advection or Convection Transport of material and its heat. Density-bouyancy driven movement of fluid

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Energy Transfer to and from the Oceans Radiation Direct transmission from source with or without a medium Advection or Convection Transport of material and its heat. Density-bouyancy driven movement of fluid Conduction Heat transfer by molecular motion. Only works for bodies in direct contact. Three types of heat transfer:

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Radiation Balance for the Earth Fig. 6.12 The Sun heats Earth more at the equator than at the poles! Did you see this link on the course web site? N. Pole S. Pole equator

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Radiation Balance for the Earth Earth's radiation balance is approximately at "steady state (comparing one year to the next) That is: outgoing rad= incoming rad (units are in percent of total radiation either incoming (solar) or outgoing (long-wave) Note role for latent heat transfer Dont worry about numbers, but note complexity Albedo=30%

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A temperature gradient is created from low (warmer) to high (colder) latitude This drives heat transfer But how is this heat transferred?

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The Ocean-Atmosphere Connection, Winds & Surface Currents

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What drives atmospheric and ocean Circulation?

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Radiation Balance for the Earth Albedo=30% Think about Solar Radiation Reaching the Sea Surface

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Solar Radiation Reaching Sea Surface (considers loss of reflected energy by clouds, etc.) Units are Watts/meter 2 --compare incoming patterns to outgoing in next slide

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Long-wave (infrared) radiation out Notice that higher energy loss values are association with tropics (warm), and values near the pole exceed incoming solar (previous slide).

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Average Sea Surface Temperatures So, the Temperature Pattern is Determined by Solar Energy Receipt but Must be Modified by Heat Transport \ Hot tropics Cold poles Strong Temperature gradient

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The Pattern of Surface Water Ocean Circulation Ocean Currents Transfer Heat

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GLOBAL ATMOSPHERIC CIRCULATION (WINDS) Large Scale Winds Transfer Heat, Note Air Pressure Zones

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Wind and Ocean Currents are driven by heat imbalance

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Which of the following are correct associations A) salinity and thermocline, density and pycnocline, and temperature and halocline B) salinity and halocline, density and thermocline, and temperature and pycnocline C) salinity and pycnocline, density and thermocline, and temperature and halocline D) salinity and halocline, density and pycnocline, and temperature and thermocline E) none of the above

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Which of the following is (are) correct? C. The sun radiates mostly short-wave energy (visible light), whereas the Earth radiates long- wave energy (infrared). D. So-called greenhouse gases absorb long-wave energy in the atmosphere and cause temperature to increase. E. All of the above. C. The sun radiates mostly short-wave energy (visible light), whereas the Earth radiates long- wave energy (infrared). D. So-called greenhouse gases absorb long-wave energy in the atmosphere and cause temperature to increase. E. All of the above. A.If more solar energy is retained by Earth than reflected or reradiated, Earths atmosphere will warm. B.On average, about 30% of incoming solar radiation is reflected back to space without an impact on Earth surface temperature.

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Which of the following statements is correct about the Earth? A. Incoming energy from the sun is the primary means of heating the tropics. B. Heat transfer from low to high latitudes plays an important role in the pattern of ocean currents and large scale winds C. Ocean currents and winds transfer heat from low to high latitudes D. all of the above E. none of the above.

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GLOBAL ATMOSPHERIC CIRCULATION (WINDS) Large Scale Winds Transfer Heat, Note Air Pressure Zones

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Warm air rises Air cools, sinks Rising air is replaced LOW Pressure 030 S 30 N

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Lets Consider Pressure Variations as a Cause for Winds Well draw the windfields around these low and high pressure cells. Whoa? Why do they look like that? Shouldnt winds blow directly from high to low pressure centers? (well talk about the Coriolis effect as a cause a bit later) Air should flow perpendicular to a pressure gradient, from high (H) to low (L) pressure.

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Winds around high pressure: clockwise in N. hemisphere and Counterclockwise in S. hemisphere Global Pattern of Winds on Earth! Low Pressure High Pressure Low Pressure

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Credit: NASA Recall the uneven heating of the Earths surface Lets examine how the Hadley Cell arises Heres the picture: why do winds blow this way? Required viewing: A year of Weather. Note large scale wind directions and storm circulation patterns from N. to S. Hemisphere. (animation) Thanks to Justin D.

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Warm air rises Air cools, sinks Rising air is replaced LOW Pressure 030 S 30 N

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Warm air rises Air cools, sinks Rising air is replaced LOW Pressure HIGH Rising air cools, which causes Rain drops to form! 030 S 30 N

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Air cools, sinks Divergent Wind Convergent Wind At Earths surface, wind moves away from Highs Pressure and toward Lows LOW Pressure HIGH 030 S 30 N Divergent Wind

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Air cools, sinks Divergent Wind Convergent Wind LOW Pressure HIGH 030 S 30 N Divergent Wind At Earths surface, wind moves away from Highs Pressure and toward Lows

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GLOBAL ATMOSPHERIC CIRCULATION (WINDS) Temperature gradients create pressure differences which drive winds

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Why is there generally low pressure over the equator and high pressure at 30 N and 30 S? A. Lots of solar energy reaches the equator and warms up the air, causing it to rise. B. The equator receives a surplus of energy relative to polar regions, and this causes winds, in the upper atmosphere, that blow North and South away from the equator C. Downward winds at 30 N and 30 S cause high pressure below them D. All of the above E. A and C

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Question: Why dont the tropics boil and the poles freeze over? A.Heat is Transferred from the tropics to the poles! B.Heat is received only in the tropics and not at the poles! C.Polar regions do not radiate heat. D.All of the above E.None of the above

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Solar energy received at Earths surface is high in the zones centered around about 20 N and S because: A.It is always summer there B.These areas are generally clear and not covered by clouds C.High pressure forms at the equator D.All of the above E.A and C

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Low Pressure High Pressure Low Pressure Global Pattern of Pressure Cells and Winds on Earth!

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Western Boundary Currents Gulf Stream, Kuroshio, Labrador, Kamchatka (Oyashio) Eastern Boundary Currents Canary, California Ocean Surface Currents Ocean's Role in Energy Transfer and Climate Regulation

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Western Boundary Currents Gulf Stream, Kuroshio, Labrador, Kamchatka (Oyashio) Eastern Boundary Currents Canary, California Ocean Surface Currents: Some Interesting Differences Between Eastern & Western Boundary Currents

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Gulf Stream as an example of a Western Boundary Current

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East Australian Current & Gulf Stream are examples of Western Boundary Currents

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Western boundary currents are intensified --transport warm water to higher latitudes

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Surface currents transport heat toward poles

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Example: The Gulf Stream Note these features: Sharp boundaries of currents (1 & 2) Eddies Warm-core rings (3) Cold-core rings (4) Labrador Current Gulf Stream This is a map of surface water temperature Surface currents transport heat toward poles

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Gulf Stream Heat Transfer: Is that all there is to it? OK, warm water flows toward the poles, but How does heat actually get transferred?? Two mechanisms: 1) Sensible heat transfer to atmosphere 2) Latent heat transfer (remember: evaporation- precipitation?)

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1) Pattern of solar energy absorption leads to temperature gradient 2) Heat transfer drives winds and ocean circulation. 3) Sensible heat transfer (wind, currents) and latent heat transfer to the atmosphere 4) Eastern and Western boundary currents Ocean's Role in Energy Transfer and Climate Regulation Key factors & processes

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Gustav Why do winds circulate around High and Low pressure systems?