Atlantic Ocean Essay Research Paper Atlantic Ocean — страница 2

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the bottom topography. In addition, a number of deep channels cut across the continental rise. Ocean sediments are composed of terrigenous, pelagic, and authigenic material. Terrigenous deposits consist of sand, mud, and rock particles formed by erosion, weathering, and volcanic activity on land and then washed to sea. These materials are largely found on the CONTINENTAL SHELVES and are thickest off the mouths of large rivers or off desert coasts. Pelagic deposits, which contain the remains of organisms that sink to the ocean floor, include red clays and Globigerina, pteropod, and siliceous OOZES. Covering most of the ocean floor and ranging in thickness from 60 m (200 ft) to 3,300 m (10,900 ft), they are thickest in the convergence belts and in the zones of UPWELLING. Authigenic

deposits consist of such materials as MANGANESE NODULES. They occur where sedimentation proceeds slowly or where currents sort the deposits. WATER CHARACTERISTICS The salinity of the surface waters in the open ocean ranges from 33 to 37 parts per thousand and varies with latitude and season. Although the minimum salinity values are found just north of the equator, in general the lowest values are in the high latitudes and along coasts where large rivers flow into the ocean. Maximum salinity values occur at about 25 deg north latitude. Surface salinity values are influenced by evaporation, precipitation, river inflow, and melting of sea ice. Surface water temperatures, which vary with latitude, current systems, and season and reflect the latitudinal distribution of solar energy,

range from less than 2 deg to 29 deg C (28 deg to 84 deg F). Maximum temperatures occur north of the equator, and minimum values are found in the polar regions. In the middle latitudes the area of maximum temperature variations, values may vary by 7 deg to 8 deg C (12.6 deg to 14.4 deg F). The Atlantic Ocean consists of four major water masses. The North and South Atlantic central waters constitute the surface waters. The sub-Antarctic intermediate water extends to depths of 1,000 m (3,300 ft). The North Atlantic deep water reaches depths of as much as 4,000 m (13,200 ft). The Antarctic bottom water occupies ocean basins at depths greater than 4,000 m (13,200 ft). Water in the North Atlantic circulates in a clockwise direction, whereas water circulation in the South Atlantic is

counterclockwise–a reflection of the Coriolis force. The South TIDES in the Atlantic Ocean are semidiurnal; that is, two high tides occur during each 24 lunar hours. The tides are a general wave that moves from south to north. In latitudes above 40 deg north some east-west oscillation occurs. CLIMATE The climate of the Atlantic Ocean and adjacent land areas is influenced by the temperatures of the surface waters and water currents as well as the winds blowing across the waters. Because of the oceans’ great capacity for retaining heat, MARITIME CLIMATES are moderate and free of extreme seasonal variations. Precipitation can be approximated from coastal weather data and air temperature from the water temperatures. The oceans are the major source of the atmospheric moisture that

is obtained through evaporation. Climatic zones vary with latitude; the warmest climatic zones stretch across the Atlantic north of the equator. The coldest zones are in the high latitudes, with the coldest regions corresponding to the areas covered by sea ice. Ocean currents contribute to climatic control by transporting warm and cold waters to other regions. Adjacent land areas are affected by the winds that are cooled or warmed when blowing over these currents. The Gulf Stream, for example, warms the atmosphere of the British Isles and northwestern Europe, and the cold water currents contribute to heavy fog off the coast of northeastern Canada (the Grand Banks area) and the northwestern coast of Africa. In general winds tend to transport moisture and warm or cool air over land

areas. Hurricanes develop in the southwestern North Atlantic Ocean. HISTORY AND ECONOMY The Atlantic Ocean appears to be the youngest of the world’s oceans. Evidence indicates that it did not exist prior to 100 million years ago, when the continents that formed from the breakup of the ancestral supercontinent, Pangaea, were being rafted apart by the process of SEAFLOOR SPREADING. The Atlantic has been extensively explored since the earliest settlements were established along its shores. The Vikings, Portuguese, and Christopher Columbus were the most famous among its early explorers. After Columbus, European exploration rapidly accelerated, and many new trade routes were established. As a result, the Atlantic became and remains the major artery between Europe and the Americas.