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) 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

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

OceanSurface area in square miles Surface area in square kilometers Of all oceans Pacific64,000,000166,000, % Atlantic31,600,00082,000, % Indian28,400,00073,600, % Southern13,523,00035,000,0009.5% Arctic4,700,00012,173,0003.3% Total142,223,000368,773, % USA3,794,0839,826,630 Georgia59,441153,952

How much water exists in the oceans? One estimate of global water distribution: 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 Water sourceVolume, in cubic mi Volume, in cubic km Percent of total water Oceans, seas and bays321,000,0001,338,000, Total global water332,500,0001,386,000,000100

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).

Sphere depth

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

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

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

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

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.

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

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

Figure 02_22

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

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

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

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

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

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

OceanSurface area (square miles) Surface area (square kilometers) Of all oceans Pacific 64,000, ,000, % Atlantic 31,600,000 82,000, % Indian 28,400,000 73,600, % Southern 13,523,000 35,000, % Arctic 4,700,000 12,173, %

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

Figure 02_23

Hypsographic curve – 2 views Cumulative curve