- The distance between the west and east coasts of the North Atlantic Ocean is quite short when compared with other oceans located on the same latitudes. This enables it to preserve the heat energy in the sea water.
- The predominantly west-east structure of European mountain ranges and inland seas facilitates the penetration of warm water from west to east.
The prevailing westerly winds greatly strengthen the penetration of the warm moist air carried by the Gulf Stream to Western Europe and even farther to the heart of Eurasia. In contrast, the effects of the Kuro Siwo Currents are much weaker since several mountain ranges running from north to south along the western coast of North America restrict the penetration of the warm moist air.
iv. In the southern hemisphere, although warm currents located along similar latitudes are formed, the temperature of sea water is lower than of their counterparts in the northern hemisphere because large quantities of cold water from the melting ice around Antarctica flow into these mid-latitude oceans.
v. The cold currents can be classified into the low-latitude and high-latitude categories. The low-latitude cold currents flow from the mid-latitudes to the tropic seas along the western coasts of the continents which enable the coastal lands in the tropics to enjoy a cool weather, particularly in the hot summer. The California Currents along the coasts of Portugal and Morocco, and the Peru Currents along the coast of Peru are good examples.
vi. The high-latitude cold currents also flow equatorwards from high latitudes but follow the eastern coast of the continents. They act as an agent to lower down the air temperature of the coastal lands. The Greenland Currents and Labrador Currents along the northern coast of Canada, and the Oya Siwo Currents along the coasts of Sea of Okhotsk and Sea of Japan are good examples.
World distribution of temperature (January and July)
The annual march of insolation between the summer and winter solstice creates very different patterns in hemispherical heating during January and July. The solar or latitudinal control of temperature is evident not only in the east-west trend of the isotherms in both cases.
The thermal effects of land and sea distribution, as well as that of the major ocean currents, also have an impact on global temperature distribution. This impact may be summarized as follows.
First, there is a more pronounced migration and concentration of isotherms over land masses than over the oceans.
Second, the annual range of temperature is greater in continental than in coastal locations. The annual range reaches an absolute maximum of over 55oC in north-east Siberia.
Third, the large heat storage of the oceans causes them to be warmer on average in winter, but colder in summer than land in the same latitude.
Finally, the influence of the main ocean currents is evident especially in winter (for warm currents) and summer (for cold currents). The outstanding effect of the warm North Atlantic Drift in pushing isotherms poleward in the North Atlantic in January is clearly shown. So is the pronounced equatorward displacement of isotherms along the coast of Peru and Chile in January (southern summer) by the cold Peruvian Current.
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