The Earth System Connections among the great spheres

Transcription

1 The Earth System Connections among the great spheres

2 Our Home Planet About 4.5 billion years old Only planet presently known to support life Has well-defined continents and ocean basins Very dynamic, both internally and externally A closed system!

3 Earth As A Closed System Mass conserved within system (no gain or loss) Closed system: exchange of energy but negligible exchange of mass with surroundings

4 Four Spheres Within Closed System Within this closed system are four major, interlinked components: Geosphere Hydrosphere Atmosphere Biosphere Energy and matter are exchanged between these components. In this course, our focus will be on the biosphere. So while we re thinking about it

5 Why can Earth sustain life? Not too close or far from Sun, thus preventing life from freezing or frying Large enough to hold atmosphere Abundance of water Temperature range to allow water to exist in liquid (very important) as well as gaseous, and solid forms. The interaction of the four components or spheres of the Earth system. The origin of life is a separate issue, which we will discuss later.

6 Earth s Four Spheres

7 Geosphere Geosphere: The solid, inorganic Earth, including Earth s surface and layers of its interior. The Earth is composed of nested shells that are classified according to their chemical and mechanical characteristics.

8 Earth s Layers: Composition and Mechanical Characteristics Primarily silica plus light metallic elements Composition crust Mechanical Characteristics lithosphere asthenosphere brittle solid solid (but nearly liquid) Primarily silica plus iron and magnesium mantle mesosphere solid Primarily iron and nickel core outer core inner core liquid solid

9 Geosphere: Chemical and Mechanical Characteristics Combined Note: Lithosphere contains both crust and uppermost (brittle) layer of mantle

10 Some important roles of the geosphere: 1. Contributor of particulate matter (e.g. volcanic ash) to atmosphere. 2. Ultimate contributor of salts to the ocean (due to ions being released from weathered rock). 3. Ultimate source of nutrients for all living things. 4. Important contributor of atmospheric gases (from volcanoes) 5. Movement of plates produces barriers that aid in the isolation of population of organisms (and therefore influences evolution).

11 The Dynamic Geosphere Processes that occur beneath Earth s surface are manifest in earthquakes and volcanism. These phenomena are linked to the movement of tectonic plates that, in turn, is driven by internal Earth processes. Earthquakes Volcanoes Plate Boundaries

12 Hydrosphere Hydrosphere:The hydrosphere is composed of all of the water in the Earth system, including water in the oceans, rivers, lakes, air, and below Earth s surface. 97 percent of the earth's water is in the oceans. Surface temperatures of oceans (blue= coldest red= warmest) The remaining 3 percent is fresh water (mostly in ice sheets, but also in the air as vapour, and below Earth s surface as groundwater). The presence of liquid surface water makes our planet unique.

13 Hydrosphere Some important roles of the hydrosphere: 1. Moderates climate 2. Transfers heat 3. Organisms need water to transport nutrients and waste 4. Water is essential in many of Earth s processes, from mineral formation to the weathering and erosion of rock.

14 Atmosphere Atmosphere: The atmosphere is the body of gases that surrounds our planet. Most of our atmosphere is located close to the earth's surface where it is most dense. The air of our planet is 79% nitrogen and just under 21% oxygen; the small amount remaining is composed of carbon dioxide and other gases. Also has a layered structure (but we won t get into this right now)

15 Some important roles of the atmosphere: 1. Contains the gases that living things need for survival (e.g., carbon dioxide for photosynthesis, and oxygen for aerobic respiration). 2. Transfers heat. 3. Ozone in stratosphere protects living things from excess ultraviolet radiation. 4. Plays a part in weathering and erosion.

16 Biosphere Biosphere: The sphere that includes all living organisms. Plants, animals, and microbes are all part of the biosphere. It also includes organic matter not yet decomposed. Most of Earth s life is found from about 3 metres below the ground to 30 meters above it and in the top 200 metres of the oceans and seas. But life can thrive in the most unlikely places, from hot springs to ice caps.

17 Some important roles of the biosphere: 1. Aids in weathering (e.g. formation of acids in soil). 2. An important sink for certain elements (especially carbon). 3. Mediates the formation of some minerals. 4. Photosynthesis maintains the oxygen content of the atmosphere.

18 A Recent Addition to Biosphere: Human Activity The presence of humans and the extent of human influence can be appreciated by looking at satellite photos. Even at night, evidence of human activity can be seen. White dots: major centres of human population Yellow patches: fires from slash-and-burn farming Red patches: natural gas burning in major oil fields

19 Interconnectedness of Spheres To appreciate how strongly interconnected the Earth s spheres really are, we need only to think about what happens to substances within the system. For example, the carbon cycle. Note that at any given point in time, carbon occurs in all of the great spheres.

20 Other Circumstances: Earth s Spin and Tilt Earth is not just a static lump of rock! As it spins on its tilted axis, it different areas of Earth are exposed to different amounts/intensities of the Sun s energy. This gives us seasons.

21 Example 1 Considering Interactions Between the Spheres Identify some interactions that are represented in this picture

22 Example 2 What about this picture?

23 Example 3 or this one?

24 Small-scale example: A forest fire

25 Interactions Between Spheres: Cause and Effect Initial Conditions Geosphere: The ground could have been very permeable, preventing moisture from being retained in the upper part of the soil profile. Hydrosphere: The area could have been prone to fire due to lack of precipitation. Atmosphere: The fire could have started due to a lightning strike. Biosphere: Dead wood, leaves and needles may have enhanced the ability of the fire to start and spread.

26 Relevance to Geosphere 1. Heat from the fire causes rocks to crack (therefore enhancing weathering). 2. Soil erosion is also enhanced by the removal of vegetation. 3. Ash particles from the fire alter the chemistry of the soil.

27 Relevance to Atmosphere 1. Smoke and ash particles are carried by wind to other areas. 2. Increased precipitation elsewhere is enhanced due to the ash particles acting as nucleation centres for water droplets. 3. Gaseous pollutants such as carbon dioxide (CO 2 ) are produced during the burning of the vegetation and carried into the air by the wind.

28 Relevance to Hydrosphere Heat from the fire further removes moisture from the air, soil, and vegetation through the process of evaporation. Increased siltation of streams due to enhanced erosion (particles are then deposited as sediment).

29 Relevance to Biosphere 1. Immediate destruction of habitat in burn area. 2. Smoke in the air may have coats the lungs of animals, including people, and affects their ability to breathe. 3. Ash particles in water clogs the gills of fish and other aquatic organisms.

30 Relevance to Biosphere 4. On the positive side, nutrients released from ash from the fire can, on the long term, benefit future plant communities. 5. Also, seeds of some plants may require that their outer shells be burned before they can germinate (so the forest fire benefits these plants).

31 Global Effects These types of interactions not only apply to local scenarios, but also influence changes on global scale. Examples of events that may have something to do with interactions between components of the Earth system: 1. Initiation of ice ages 2. Mass extinctions 3. Global climate change 4. El Nino events. We will look at some of these things in detail as the course progresses.

32 The Earth s Atmosphere

33 The Earth and its Atmosphere This chapter discusses: 1. Gases in Earth's atmosphere 2. Vertical structure of atmospheric pressure & temperature 3. Types of weather & climate in the atmosphere

34 Solar Energy as Radiation Figure 1.1 Nearly 150 million kilometers separate the sun and earth, yet solar radiation drives earth's weather.

35 Earth's Atmosphere Thin Gaseous envelope Figure % of atmospheric gases, including water vapor, extend only 30 kilometer (km) above earth's surface. Most of our weather, however, occurs within the first 10 to 15 km.

36 Composition of Atmosphere Nitrogen - 78% Oxygen - 21% Water Vapor 0 to 4% Carbon Dioxide -.037% Other gases make up the rest

37 Atmospheric Gases Nitrogen, oxygen, argon, water vapor, carbon dioxide, and most other gases are invisible. Clouds are not gas, but condensed vapor in the form of liquid droplets. Ozone is the primary ingredient of smog! Ground based smog, which is visible, contains reactants of nitrogen and ozone.

38 Variable & Increasing Gases Figure 1.3 Nitrogen and oxygen concentrations experience little change, but carbon dioxide, methane, nitrous oxides, and chlorofluorocarbons are greenhouse gases experiencing discernable increases in concentration. CO2 has risen more than 18% since Fossil fuels are the biggest problem!

39 Atmospheric Greenhouse Effect The warming of the atmosphere by its absorbing and emitting infrared radiation while allowing shortwave radiation to pass through. The gases mainly responsible for the earth s atmospheric greenhouse effect are water vapor and carbon dioxide.

40 Aerosols & Pollutants Human and natural activities displace tiny soil, salt, and ash particles as suspended aerosols, as well as sulfur and nitrogen oxides, and hydrocarbons as pollutants. Figure 1.6

41 Pressure & Density Gravity pulls gases toward earth's surface, and the whole column of gases weighs 14.7 psi at sea level, a pressure of mb or in.hg. The amount of force exerted Over an area of surface is called Air pressure! Air Density is The number of air Molecules in a given Space (volume)

42 Atmospheric pressure decreases rapidly with height. Climbing to an altitude of only 5.5 km where the pressure is 500 mb, would put you above one-half of the atmosphere s molecules. Vertical Pressure Profile

43 Lapse Rate The rate at which air temperature decreases with height. The standard (average) lapse rate in the lower atmosphere is about 6.5 C per 1 km or 3.6 F per 1000 ft.

44 Temperature Inversion An increase in air temperature with height often called simply an inversion. Radiosonde an instrument that measures the vertical profile of air temperature in the atmosphere (sometimes exceeding 100,000 ft)

45 Atmospheric Layers 8 layers are defined by constant trends in average air temperature (which changes with pressure and radiation), where the outer exosphere is not shown. 1. Troposphere 2. Tropopause 3. Stratosphere 4. Stratopause 5. Mesosphere 6. Mesopause 7. Thermosphere 8. Exosphere

46 Atmospheric Layers Tropopause separates Troposphere from Stratosphere. Generally higher in summer Lower in winter. Figure 1.7 Troposphere Temp decrease w/ height Most of our weather occurs in this layer Varies in height around the globe, but Averages about 11 km in height.

47 The troposphere is the lowest major atmospheric layer, and is located from the Earth's surface up to the bottom of the stratosphere. It has decreasing temperature with height (at an average rate of 3.5 F per thousand feet (6.5 C per kilometer); whereas the stratosphere has either constant or slowly increasing temperature with height. The troposphere is where all of Earth's weather occurs. The boundary that divides the troposphere from the stratosphere is called the "tropopause", located at an altitude of around 5 miles in the winter, to around 8 miles high in the summer, and as high as 11 or 12 miles in the deep tropics. When you see the top of a thunderstorm flatten out into an anvil cloud, like in the illustration above, it is usually because the updrafts in the storm are "bumping up against" the bottom of the stratosphere

48 Atmospheric Layers Stratosphere Temperature inversion in stratosphere Ozone plays a major part in heating the air At this altitude Figure 1.7

49 Atmospheric Layers Mesosphere Middle atmosphere Air thin, pressure low, Need oxygen to live in this region. Air quite Cold -90 C (-130 F) near the top of mesosphere Figure 1.7

50 Atmospheric Layers Thermosphere Hot layer oxygen molecules absorb energy from solar Rays warming the air. Very few atoms and molecules in this Region. Figure 1.7

51 The Stratosphere and Ozone Layer Above the troposphere is the stratosphere, where air flow is mostly horizontal. The thin ozone layer in the upper stratosphere has a high concentration of ozone, a particularly reactive form of oxygen. This layer is primarily responsible for absorbing the ultraviolet radiation from the Sun. The formation of this layer is a delicate matter, since only when oxygen is produced in the atmosphere can an ozone layer form and prevent an intense flux of ultraviolet radiation from reaching the surface, where it is quite hazardous to the evolution of life. There is considerable recent concern that manmade flourocarbon compounds may be depleting the ozone layer, with dire future consequences for life on the Earth. The Mesosphere and Ionosphere Above the stratosphere is the mesosphere and above that is the ionosphere (or thermosphere), where many atoms are ionized (have gained or lost electrons so they have a net electrical charge). The ionosphere is very thin, but it is where aurora take place, and is also responsible for absorbing the most energetic photons from the Sun, and for reflecting radio waves, thereby making long-distance radio communication possible.

52 Atmospheric Mixture & Charge Additional layers include: a) the homosphere with 78% nitrogen and 21% oxygen b) the poorly mixed heterosphere c) the electrically charged ionosphere

53 Radio Wave Propagation Figure 1.9 (Ionosphere Radio Prop) AM radio waves are long enough to interfere with ions in the suncharged D layer, but at night the D layer is weak and the AM signal propagates further, requiring stations to use less power.

54 Weather & Climate Weather is comprised of the elements of: a) air temperature b) air pressure c) humidity d) clouds e) precipitation f) visibility g) wind Climate represents long-term (e.g. 30 yr) averages of weather.

55 Satellite Instruments Meteorologists may study larger weather patterns with space borne instruments, while ground-based tools often measure a single point. (GOES SAT) Meridians Longitude Latitude Middle Latitudes 30-50N Middle-latitude cyclonic storm Hurricane Thunderstorm Tornado most violent disturbance in atms Figure 1.10

56 Surface Weather Map Meteorologists generate diagrams of observed weather from ground-based instruments. Figure 1.11 This surface map overlaps in time with the previous satellite image. Low High Fronts Wind Direction

57 History of Meteorology Meteorology is the study of the atmosphere and its phenomena Aristotle wrote a book on natural philosophy (340 BC) entitled Meteorologica Sum knowledge of weather/climate at time Meteors were all things that fell from the sky or were seen in the air meteoros : Greek word meaning high in air

58 Impacts of Weather 1/5 Figure 1.12

59 Impacts of Weather 2/5 Figure 1.13

60 Impacts of Weather 3/5 Figure 1.14

61 Impacts of Weather 4/5 Figure people die each year In US from flash floods

62 Impacts of Weather 5/5 Lightning strikes earth 100 times every second Figure 1.16