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Topic 3 The Water Planet

Topic 3 The Water Planet. GEOL 2503 Introduction to Oceanography. Earth? Wouldn’t “Ocean” be a better name?. Water on the Earth’s Surface. 71% of the Earth is covered by the oceans (139 million square miles)

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Topic 3 The Water Planet

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  1. Topic 3The Water Planet GEOL 2503 Introduction to Oceanography

  2. Earth? Wouldn’t “Ocean” be a better name?

  3. Water on the Earth’s Surface • 71% of the Earth is covered by the oceans (139 million square miles) • More than one-half of the world's population lives within 60 miles (100 km) of the ocean. • Volume of water in the oceans = 1.37 billion cubic kilometers = 329 million cubic miles

  4. Volume of Earth: • approx: 1,100,000,000,000 cubic kilometers • Volume of oceans: • 1,370,000,000 cubic kilometers • Oceans make up only 0.125% of Earth’s volume

  5. Source: Gleick, P. H., 1996: Water resources. In Encyclopedia of Climate and Weather, ed. by S. H. Schneider, Oxford University Press, New York, vol. 2, pp.817-823. How much water exists in the oceans?One estimate of global water distribution:

  6. Sphere Depths • Assume Earth is a perfectly smooth ball • The oceans would cover the globe to a depth of 2646 meters (ocean sphere depth). • Add all of the remaining water from the land and the atmosphere would increase the depth by 75 meters to 2721 meters (total water sphere depth).

  7. Sphere depth

  8. The Global Ocean Atlantic Pacific Indian Continents can be considered as islands in a single, world ocean.

  9. Ocean The illustration shows how water evaporates from the ocean, land, and rivers. The evaporated water condenses in the cooler altitudes and falls to the ground as rain or snow. See http://ga.water.usgs.gov/edu/watercycle.html.

  10. The Hydrologic Cycle • Reservoirs—the places in which water resides -oceans -lakes -rivers -groundwater -glaciers -atmosphere -snow packs -sea ice See previous slide and USGS web page

  11. The Hydrologic Cycle • Hydrologic cycle – typically know as the water cycle • Evaporation water changes from a liquid to a gas as water vapor. • Precipitation water that falls to the ground in many forms – ice, snow, rain, hail. • Excess water on land returns to the ocean by rivers

  12. What is Residence Time? • Rate of removal from reservoirs must equal rate of addition to reservoirs • Residence Time—time that water spends in any one reservoir • Oceans oven have a residence time of thousands of years because of their size. • Small reservoirs, such as the atmosphere, have short residence times, days to weeks.

  13. The Distribution of Land and Water • 70% of Earth’s landmasses are in the Northern Hemisphere • Most of this land lies in the middle latitudes • The Southern Hemisphere is the water hemisphere • Land in the water hemisphere is located in the tropical latitudes and the polar region

  14. The Oceans • Three main oceans -Pacific Ocean -Atlantic Ocean -Indian Ocean • The Arctic Ocean, considered the fourth ocean, is really an extension of the North Atlantic

  15. Figure 02_22

  16. The Pacific Ocean • Most surface area • Largest volume • Deepest in terms of single deepest spot • Deepest in terms of average depth • Circular shaped • Covers one-third of the globe

  17. The Challenger Deep in the Mariana Trench is the deepest spot in the world.

  18. The Atlantic Ocean • Shallowest, rectangular shape • Has the most shallow adjacent seas -Arctic Ocean -Gulf of Mexico -Caribbean Sea -Mediterranean Sea • Covers about one-fifth of the globe

  19. The Indian Ocean • Smallest area • Very deep • Triangular shaped • Located mostly in the South Hemisphere • Covers about one-seventh of the globge

  20. The Arctic Ocean • Really a sea—an extension of the Atlantic Ocean

  21. A Fifth Ocean? • In the spring of 2000, the International Hydrographic Organization decided to delimit a fifth world ocean—the Southern Ocean (recall Balboa and the South Sea) • It is the southern portions of the Atlantic Ocean, Indian Ocean, and Pacific Ocean. • The Southern Ocean extends from the coast of Antarctica north to 60 degrees south latitude • Northern boundary defined by an ocean current, not by land, so many do not consider this a true ocean

  22. The Hypsographic Curve • The hypsographic curve—graph of the depth/elevation versus Earth’s area • 29% of the Earth’s surface is above sea level • 71% of the Earth’s surface is below sea level • 80% of land is below 2,000 meters elevation • 80% of the seafloor is deeper than 2,000 meters • Hints at composition of crust

  23. Figure 02_23

  24. Hypsographic curve – 2 views Cumulative curve

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