Читать книгу Oceans For Dummies - Joseph Kraynak - Страница 13

Earth has only one ocean, which is why we will refer to it as the ocean (singular) throughout this book. Geographically, it’s divided into four or five oceans, depending on who’s doing the dividing. Prior to the year 2000, text books recognized four oceans: the Atlantic, Pacific, Indian, and Arctic. Sometime around the year 2000, the International Hydrographic Organization designated a fifth ocean the Southern Ocean — a band that wraps around the world from the coast of Antarctica to 60 degrees south latitude (see Figure 1-1). Here’s a brief description of each of the five oceans, in order of size, because, well, size matters.

 Pacific Ocean: The largest of the five “oceans,” the Pacific stretches from the Arctic to the Southern Ocean and from east of Asia and Australia to the Americas. It covers more area than all the land on Earth combined and is more than double the surface area of the Atlantic Ocean. It also wins the deepest point in the ocean contest with the Mariana Trench, which is nearly 11 kilometers (about 7 miles) deep.

 Atlantic Ocean: This next largest ocean lies between the Americas and the continents of Europe and Africa. It’s home to the Bermuda Triangle, the Sargasso Sea, the Gulf Stream, and the hurricanes that rattle the Caribbean Islands and the southern and eastern coasts of the U.S. The North Atlantic is by far the most thoroughly explored, best understood, and most heavily fished of the five “oceans.”

 Indian Ocean: Nestled between Africa (to the west) and Australia (to the east) and between Asia (to the north) and the Southern Ocean (below it), the Indian Ocean ranks third in surface area but first in warmth.

 Southern Ocean: The Southern Ocean is relatively small, but its average depth is greater than the average depth of any of the other four oceans — four to five kilometers (2.5 to 3 miles) deep! It’s best known for its strong, sustained easterly winds, its huge waves (due to the strong, sustained winds), and its frigid environment; during its winter, nearly the entire surface of the Southern Ocean is frozen. It’s also home to the world’s largest ocean current — the Antarctic Circumpolar Current — and it is chock full of nutrients.

 Arctic Ocean: Surrounding the North Pole and bordering the northern edges of North America, Asia, and Europe is the Arctic Ocean. Most of it is located within the Arctic Circle, from the North Pole down to about 70 degrees northern latitude. It’s the smallest and shallowest of the five “oceans,” and for most of the year, most of its surface area consists of ice 1 to 10 meters (3 to 33 feet) thick. The Arctic Ocean is best known for its wildlife (including polar bears, whales, and seals) and for its natural resources (primarily oil).

©John Wiley & Sons, Inc.

FIGURE 1-1: The ocean’s five “oceans.”