AEROGRAPHER'S MATE 3 & 2 



at the surface and the major part of the sound 

 path is in nearly stable water. 



MAJOR CURRENT SYSTEMS 



Ocean currents transport vast quantities of 

 water with differing characteristics from one 

 region of the earth to another. Since three- 

 fourths of the earth's surface is composed of 

 water, it is not difficult to understand why the 

 Aerographer's Mate must become familiar with 

 ocean current systems and the effects they 

 have on certain regions. 



Ocean currents are established and main- 

 tained primarily by the stresses exerted by 

 the prevailing winds over the surface of the 

 sea. Moving water obeys the same laws of 

 deflection as moving air. It is deflected to the 

 right in the Northern Hemisphere and toward 

 the left in the Southern Hemisphere. The earth's 

 rotation provides the basic cause for this pattern 

 of deflection. The prevailing winds along the 

 ocean surface also determine some of the 

 circulation characteristics. Thus, an oceanic 

 circulation that roughly corresponds to the 

 atmospheric circulation is maintained. 



The orientation of coastlines often modifies 

 this circulation. Since the air circulation over 

 the oceans in middle latitudes is chiefly anti- 

 cyclonic (more pronounced in the Southern 

 Hemisphere than in the Northern Hemisphere), 

 we can expect the oceanic circulation at these 

 latitudes to be the same. At higher latitudes, 

 where the flow is principally cyclonic, the 

 oceanic circulation follows this cyclonic pattern, 

 although not as closely as the anticyclonic 

 pattern of the lower latitudes. In regions with 

 a pronounced monsoonal flow, the ocean currents 

 respond to this flow. The following statements 

 can be made concerning general distribution 

 of ocean currents. 



At middle (below 40° lat) and low latitudes, 

 continents have warm currents which flow 

 poleward along their east coasts and cold 

 currents flowing equatorward along their west 

 coasts. This is true in both hemispheres. 



In the Northern Hemisphere at high latitudes, 

 continents have cold currents flowing equator- 

 ward along their east coasts and warm currents 

 flowing poleward along their west coasts. In 



monsoonal regions, ocean currents vary with 

 the seasons. The presence of an irregular 

 coastline will cause deviation in the general 

 distribution of ocean currents. 



The circulation of ocean waters acts to 

 transport heat from one latitude belt to another 

 in a manner similar to the heat transported 

 by the primary circulation of the atmosphere. 

 The cold waters of the Arctic regions move 

 to warmer sections of the earth, while the 

 warm waters of the low latitudes move toward 

 the poles. 



An example of this effect on climate is 

 shown by the comparatively mild climate that 

 exists in the area of northwest Europe. The 

 coast of Norway, as far north as it is, is 

 mild enough that its ports on the Atlantic are 

 ice-free for the most part during the long 

 winter. This is due to the effect of the ocean 

 current which sweeps the Atlantic Ocean from 

 the equatorial regions. The cold ocean current 

 off the coast of California is a decisive factor 

 in giving cities such as San Francisco such cool 

 temperature readings in summer. 



Meteorologists are normally more interested 

 in the effect of the surface temperature of the 

 ocean's water than in the manner in which the 

 waters have arrived at a particular locality. 

 Even so, ocean currents and their relationship 

 to the prevailing winds of the weather picture 

 must be understood. Figure 16-9 shows the 

 surface currents of the oceans during February 

 and March. 



NORTH ATLANTIC CURRENTS 



Movements of the waters of the North 

 Atlantic Ocean are dominated by the NORTH 

 EQUATORIAL CURRENT and the GULF STREAM 

 SYSTEM. 



North Equatorial Current 



The North Equatorial Current is located in 

 the trade wind belt of the North Atlantic Ocean, 

 The chief sources of the flow are the north- 

 easterly currents off the west coast of north- 

 western Africa. These currents of water of 

 relatively high density and low temperatures are 

 from the North Atlantic Current, and they help 

 to cause the temperatures of the northwest 

 coast of Africa to be lower than normally would 



386 



