Website Lecture 3 The Physical Environment Part 1

Transcription

1 Website Lecture 3 The Physical Environment Part 1 1

2 Lectures 3 & 4 1. Biogeochemical Cycling 2. Solar Radiation 3. The Atmosphere 4. The Global Ocean 5. Weather and Climate 6. Internal Planetary Processes Cycling of Materials Matter moves among organisms, ecosystems, and the abiotic environment Pools, compartments 2

3 Cycling of Materials Biogeochemical cycling Interactions between biological, geological, and chemical aspects of environment Five major cycles: Carbon, Nitrogen, Phosphorus, Sulfur, and Water (Hydrologic) The Carbon (C) Cycle 3

4 The Carbon (C) Cycle Global circulation of C between living and non-living environment Major processes Photosynthesis Respiration Soil, in particular Combustion of fossil fuels CO 2 dissolving into ocean Human Affects on C Cycle CO 2 was 0.029% of atmosphere (1700s) CO 2 is 0.04% (2014) Expected 0.06% by 2100 Higher CO 2 creates lots of feedbacks in environment > CO 2 dissolved in ocean 4

5 The Water (Hydrologic) Cycle The Water (Hydrologic) Cycle Cycles among organisms, atmosphere, land, and ocean All organisms use water 5

6 Transpiration Loss of water vapor from land plants 97% of plant water can be lost this way Human Affect on Water Cycle Air pollution may decrease precipitation Pumping, diverting surface and groundwater for irrigation Climate Change warming temperatures are melting polar ice caps Sea level rise Greater frequency of storms predicted 6

7 Solar Radiation Solar Radiation Sun provides energy for life, powers biogeochemical cycles, and determines climate 7

8 Solar Radiation Albedo The reflectance of solar energy off earth s surface Dark colors = low albedo Forests and ocean Light colors = high albedo Ice caps Solar Radiation Question! Why is the earth warmer at the equator that at the poles?????? 8

9 Solar Radiation Climate- Global Scale Temperate Tropics Beams of sunlight shine down directly overhead in tropical regions In the higher latitudes same amount of sunlight is spread over a much larger area. 9

10 Temperature Changes with Latitude Solar energy does not hit earth uniformly Due to earth s spherical shape and tilt Equator (a) High concentration Little Reflection High Temperature From (a) to (c) In diagram below Closer to Poles (c) Low concentration Higher Reflection Low Temperature What does this mean for climate? Tropics more sunlight striking the earth per unit area. Energy more concentrated - warmer. Temperate Areas less sunlight per unit area. Energy is less concentrated - cooler. As result, as you move away from the tropics, the average temperature gets cooler and cooler. 10

11 Temperature Changes with Season Seasons determined by earth s tilt (23.5 ) Causes each hemisphere to tilt toward the sun for half the year Northern Hemisphere tilts towards the sun from March 21 September 22 (warm season) The Atmosphere 11

12 The Atmosphere Content 21% Oxygen 78% Nitrogen 1% Argon, Carbon dioxide, Neon and Helium Greenhouse gases (CFCs, CO 2, CH 4 ) Density decreases with distance from earth Shields earth from high energy radiation Atmospheric Layers Layering is based upon temperature changes with altitude. 1. Troposphere (0-12km) Where weather occurs Temperature decreases with altitude 12

13 Atmospheric Layers 2. Stratosphere (12-50km) Temperature increases with altitude- very stable Ozone layer absorbs UV Where jets fly Atmospheric Layers 3. Mesosphere (50-80km) Temperature decreases with altitude 13

14 Atmospheric Layers 4. Thermosphere (80 480km) Gases in thin air absorb x-rays and short-wave UV radiation = very hot Source of aurora Reflects radio waves with need for satellites Atmospheric Layers 5. Exosphere (500km and up) Outermost layer Atmosphere continues to thin until converges with interplanetary space 14

15 Atmospheric Circulation Atmosphere is very dynamic! Air is in constant motion all over the planet Atmosphere is a giant heat engine Air movement powered by the sun. Atmospheric Circulation 15

16 Atmospheric Circulation This occurs at higher latitudes as well Moves heat from equator to the poles Coriolis Effect Earth s rotation influences direction of wind Earth rotates from East to West Deflects wind from straight-line path 16

17 Coriolis Effect Coriolis Effect Influence of the earth s rotation on movement of air and fluids Turns them Right in the Northern Hemisphere Turns them Left in the Southern Hemisphere How does it work?? Coriolis Effect 17

18 Coriolis Effect Earth is a sphere that rotates on it s axis. Greater circumference at the equator than at the poles Coriolis Effect Earth s surface is moving fastest at the equator. Earth s surface moves slower as you move towards the poles 18

19 Coriolis Effect Image you are standing on the equator with a magic paper airplane! Coriolis Effect You throw the plane directly north You think the plane will fly directly north 19

20 Coriolis Effect But it doesn t! Instead, it veers off to the east. Coriolis Effect If you turn around and throw the plane south, the same thing happens! 20

21 Why? 21

22 Coriolis Effect Earth s surface is moving fastest at the equator. Earth s surface moves slower as you move towards the poles, but the airplane is still moving at the same speed as the equator. Coriolis Effect 22

23 Coriolis Effect High altitude winds moving away from the equator 30º N 30º S Coriolis Effect winds 23

24 Coriolis Effect Surface winds moving toward the equator 30º N 30º S Coriolis Effect Surface winds moving toward the equator 30º N 30º S 24

25 The Global Oceans 25

26 Patterns of Ocean Circulation Prevailing winds caused by the earth s rotation produce ocean currents and generate large areas of circulating water gyres Example: the North Atlantic Ocean Trade winds blow west Westerlies blow east Creates a clockwise gyre in the North Atlantic Patterns of Ocean Circulation Westerlies Trade winds 26

27 Position of Landmasses Large landmasses in the Northern Hemisphere help to dictate ocean currents and flow Very little land in the Southern Hemisphere Vertical Mixing of Ocean Ocean water varies in density/temperature Gulf Stream and N. Atlantic Drift deliver heat from tropics to Europe Heat transferred to atmosphere, becomes denser, sinks ~8ºC cooler than surface current 27

28 Vertical Mixing of Ocean Ocean Conveyor Belt Affects regional and possibly global climate El Nino Southern Oscillation (ENSO) 28

29 Ocean Interaction with Atmosphere- ENSO El Niño-Southern Oscillation (ENSO) Periodic large scale warming of surface waters of tropical E. Pacific Ocean Every ~2-7 years The Usual Pattern of Ocean Circulation Surface winds normally carry water away from of N and S America over towards Asia and Australia. 29

30 Ocean Interaction with Atmosphere- ENSO East to West surface winds cause upwelling along the coast of South America This allows cold water from deep in the ocean to be pulled up to the surface near Peru. The movement of water across the equatorial Pacific results in ocean height being slightly greater in the west than in the east. 30

31 In El Nino years, the east to west trade winds get weak. The warm water in the western Pacific Ocean sloshes back toward the coast of South America. 31

32 Peruvian fisherman have long known that occasionally they would have years where the anchovy fisheries would fail. This always happened around Christmas--hence the name El Nino. In La Nina years, the east to west trade winds intensify and the upwelling off the west coast of South America resumes. 32

33 Because the winds, ocean heights, and surface temperatures cycle back and fourth in the equatorial Pacific ocean these cycles are now known as El Nino southern ocean oscillations (ENSO). ENSO Conditions Trade winds weaken and warm water expands eastward to South America Big effect on fishing industry off South America Floods in Peru May flood west coast of U.S. Australia and Indonesia have droughts La Nina (follows El Nino) Water in E. Pacific cools, west trade winds strengthen 33