Geography & Climate. All species have limits to their distribu9ons across the globe

Transcription

1 Geography & Climate All species have limits to their distribu9ons across the globe To understand species ranges, we need to understand the physical template and climate This is fundamental to biogeography 1

2 Geography: The Physical Template The Earth s crust changes across space and 9me. These changes are driven by two engines powered by different energy sources: 1) Energy stored in Earth s core is dissipated through the mantle and crust, moving and shaping the Earth s crust (we ll revisit this later in the term) 2) Energy from the sun strikes the Earth s surface and is absorbed and converted into heat We ll see how this influences global climate, wind pakerns and ocean currents (From Lomolino et al. 2010) 2

3 Climate reflects temperature and precipita9on Climate and tectonic change are the most important large- scale factors influencing species general distribu9ons. In the following lectures we ll look at how temperature and precipita9on vary at geographic and regional scales (From Lomolino et al. 2010) 3

4 Temperature and thermal energy Spherical shape of earth causes la9tudinal gradient in thermal radia9on The angle of incoming radiant energy affects the amount of heat absorbed Most intense hea9ng occurs where the incoming sunlight is perpendicular to the Earth s surface for two reasons: 1) The greatest amount of energy is delivered to the smallest surface area (a vs. a ) (From Lomolino et al. 2010) 2) Less radia9on is absorbed or reflected back into space because the distance traveled through the atmosphere is minimized (b vs. b ) 4

5 Temperature and thermal energy The angle of inclina9on of the earth s axis causes seasonality. What is the angle and how does this relate to the Tropic of Cancer and Capricorn? (From Lomolino et al. 2010) Looking at the figure on the right, what day of the year is it? 5

6 Cooling effects of eleva9on We examined la9tudinal varia9on in temperature and seasonality...what about al9tude? Why does Mount Kilamanjaro, near the equator in East Africa, have permanent ice at the top? This has to do with thermal proper9es of air... 6

7 Cooling effects of eleva9on As a climber goes up a mountainside, the length (and pressure) of the column of air above the climber decreases The pressure and density of air decreases with increasing al9tude column of air into atmosphere With reduced pressure, air expands and undergoes adiaba-c cooling Air at high al9tudes has less pressure, allowing it to expand and cool hkp:// view- from- the- top/ Lower pressure Higher pressure 7

8 Winds and Currents Differen9al hea9ng with la9tude drives the major atmospheric air circula9on, resul9ng in global wind pakerns. Here is how this works: 1) Equator is heated most intensively. Air at the equator expands as it is heated, becomes less dense than surrounding air and rises 2) Rising air reduces atmospheric pressure over the equator and surface air north and south of equator flows into area of reduced pressure 3) Rising heated air undergoes adiaba9c cooling, is pushed away from the equator, and descends at ~30 degrees N and S la9tude (From Lomolino et al. 2010) 8

9 Winds and Currents Differen9al hea9ng with la9tude drives the major atmospheric air circula9on, resul9ng in global wind pakerns. Here is how this works: 4) Circula9ng air masses produce surface winds blowing toward the equator between 0 and 30 degrees and toward the poles between 30 and 60 degrees 5) Surface winds do not blow due N or S because of the rota9on of the Earth (From Lomolino et al. 2010) 9

10 Winds and Currents Differen9al hea9ng with la9tude drives the major atmospheric air circula9on, resul9ng in global wind pakerns. Here is how this works: 6) Every point on the Earth s surface makes one rota9on every 24 hours. Because the circumference of the earth is ~40,000 km, a point at the equator moves from W to E at ~1700 km/h 7) Points at higher la9tudes travel a shorter distance with every 24- hour rota9on, moving at a slower rate than points at the equator 8) This induces the Coriolis effect, where surface winds are deflected toward the right in the NH and to the lef in the SH (From Lomolino et al. 2010) 10

11 Winds and Currents Coriolis Effect: the tendency for moving objects (e.g., wind and currents) to veer clockwise in the NH and counterclockwise in the SH. We see this effect easily between 0 and 30 degrees North and South la9tude (From Lomolino et al. 2010) 11

12 Winds and Currents Coriolis Effect: the tendency for moving objects (e.g., wind and currents) to veer clockwise in the NH and counterclockwise in the SH. We see this effect easily between 0 and 30 degrees North and South la9tude hkp://video.mit.edu/watch/the- coriolis- effect- 4407/ 12

13 Winds and Currents Surface winds ini9ate the major ocean currents: (1) Trade winds push ocean currents westward at the equator and (2) westerlies produce eastward currents at high la9tudes (N and S). The net results are circular ocean currents, clockwise in the NH and counter- clockwise in the SH. (From Lomolino et al. 2010) 13

14 Geographic precipita9on pakerns Global temperature, winds, and currents interact to influence global precipita9on Part of this has to do with cloud forma9on and adiaba9c cooling... As air warms, it can absorb more water vapor evaporated from land and water When air contains moisture and cools, there is a point at which the air is saturated with water vapor (dew point) Further cooling results in condensa9on and cloud forma9on. When water and ice par9cles are too heavy to remain airborne, they will fall as rain and snow. (From Lomolino et al. 2010) 14

15 Geographic precipita9on pakerns Horse La-tudes: warm, dry surface winds "dry- out" the land and create most of our great deserts near 30 o N and S la9tude (e.g., Mojave, Sonoran, Sahara, Gobi, and Great Sandy deserts). Tropical rains are heaviest when the sun is directly overhead and the rate of hea9ng is most intense (the spring and fall equinoxes). (From Lomolino et al. 2010) 15

16 Horse La9tudes and adjacent zones Two belts of rela9vely dry climates encircle the globe Over land, these belts are the world s deserts and Mediterranean climates (mild rainy winters and hot dry summers) Over oceans, these belts have hot air and likle wind The term may come from the days when Spanish ships transported horses to the West Indies hkp:// Ships would slow in mid- ocean in this la9tude, prolonging the voyage...water shortages would force crews to throw their horses overboard or eat them 16

17 Horse La9tudes and adjacent zones Deserts and Mediterranean climates are usually on the Western side of con9nents In winter, land is cooler than ocean water, westerly winds bring moisture- laden air that results in rainfall when air cools over land Horse la9tudes Horse la9tudes 17

18 Horse La9tudes and adjacent zones Deserts and Mediterranean climates are usually on the Western side of con9nents In summer, land is warmer than ocean water, westerly winds are cooler and can absorb lots of water and dry the land when they come onshore Horse la9tudes Horse la9tudes 18

19 Horse La9tudes and adjacent zones The world s driest deserts occur where westerlies bring cold currents and surface winds. In the winter, there is likle or no rainfall and summers are hot and dry. Atacama Desert (lef): 1 mm/year Namib Desert (right): 2-20 mm/year 19 (From Lomolino et al. 2010)

20 Regional precipita9on pakerns Regional topography also has important effects on precipita9on Monthly mean temperature and precipita9on Vancouver (49 15 N) Montreal (45 30 N) Temperature (degrees C) Temperature Precipitation Precipitation (mm) Temperature (degrees C) Temperature Precipitation Precipitation (mm) Jan Mar May Jul Aug Oct Dec Jan Mar May Jul Aug Oct Dec Month Month 20

21 Regional precipita9on Mountains, in par9cular, have complex effects on regional precipita9on Because we ll talk about mountains quite a bit, let s explore some details here (From Lomolino et al. 2010) 21

22 Regional precipita9on The adiaba-c lapse rate is the rate at which air cools as it rises. This lapse rate varies for many reasons, but generally, the lapse rate differs with and without condensa9on: (From Lomolino et al. 2010) 22

23 Regional precipita9on Once air loses moisture, passes over the crest of a mountain and descends, it warms at a higher rate. This creates a rainshadow effect on the leeward side of mountains. Rain shadow effect (e.g., tropical island of Puerto Rico) (From Lomolino et al. 2010) 23

24 But it s complicated... Mountains differ in temperature and precipita9on regimes for many reasons: la9tude, height and age, to name a few Let s make a comparison and look at these effects: Whistler, Pacific Range, Bri9sh Columbia, Canada Great Smoky Mountains, Appalachian Range, Tennessee- North Carolina, USA 24

25 Whistler vs. Great Smoky Mountains Whistler, Pacific Range, Bri9sh Columbia, Canada Great Smoky Mountains, Appalachian Range, Tennessee- North Carolina, USA La9tude: 51 degrees N Highest peak: 4019 m (13186 f) Age: 60 million years La9tude: 40 degrees N Highest peak: 2037 m (6684 f) Age: 480 million years 25

26 Whistler vs. Great Smoky Mountains Whistler, Pacific Range, Bri9sh Columbia, Canada Great Smoky Mountains, Appalachian Range, Tennessee- North Carolina, USA These mountains have different effects on regional precipita9on and climate: older mountains tend to be smaller with smaller rainshadow effects. 26

27 Revisit climate with a beker understanding of temperature and precipita9on By now, you should understand why we see the major climates exhibited here, but also why this map oversimplifies Earth s climate (From Lomolino et al. 2010) 27

28 Climate varia9on Seasonal and long- term varia9on in precipita9on are 9ed to changes in solar radia9on and current strength. El Nino Southern Oscilla-on (ENSO): period of weather change that occurs every 2-7 years due to strengthening of the equatorial countercurrent (cause s9ll under study). Increased rain (ofen 10x) in arid coastal regions of SA with reduced coastal upwelling. 28

29 Climate varia9on Seasonal and long- term varia9on in precipita9on are 9ed to changes in solar radia9on and current strength. El Nino Southern Oscilla-on (ENSO): period of weather change that occurs every 2-7 years due to strengthening of the equatorial countercurrent (cause s9ll under study). Increased rain (ofen 10x) in arid coastal regions of SA with reduced coastal upwelling. Atacama Desert 29

30 Climate varia9on Seasonal and long- term varia9on in precipita9on are 9ed to changes in solar radia9on and current strength. El Nino Southern Oscilla-on (ENSO): period of weather change that occurs every 2-7 years due to strengthening of the equatorial countercurrent (cause s9ll under study). Increased rain (ofen 10x) in arid coastal regions of SA with reduced coastal upwelling. Galapagos Islands 30

31 Climate varia9on Seasonal and long- term varia9on in precipita9on are 9ed to changes in solar radia9on and current strength. El Nino Southern Oscilla-on (ENSO): period of weather change that occurs every 2-7 years due to the strengthening of the equatorial countercurrent (cause s9ll under study). Increased rain (ofen 10x) in arid coastal regions of SA with reduced coastal upwelling. (From Grant and Grant 2002) 31

32 Climate change Global climate has changed frequently. Climate has clearly changed with cycles of glacia9on (more on this later). Change since last glacial max. has not exceeded about 1 o C per 1000 yrs. (From Gates 1993) 32

33 Climate reflects temperature and precipita9on This map should be more familiar now, with an understanding of la9tudinal varia9on in temperature and why we have deserts and rainforests at different la9tudes but also why this map oversimplifies Earth s climate and climate varia9on. (From Lomolino et al. 2010) 33

34 Climate and Climate Change References for this sec-on: Gates, D.M Climate Change and its Biological Consequences. Sunderland, MA: Sinauer Assoc. Grant, P.R., and B.R. Grant Unpredictable evolu9on in a 30- year study of Darwin s finches. Science 296: Lomolino, M.V., B.R. Riddle, R.J. WhiKaker, & J.A. Brown Biogeography (4 th ed., Chapter 2). Sinauer Associates, Inc., Sunderland, Mass. The Coriolis effect and the direc9on toilets drain in Norther & Southern Hemispheres: hkps:// 34