28 



OCEANOGRAPHY: 



thing to a universal solvent. This solvent action 

 allovk's much of the chemically complex activity of 

 protoplasm, living substance. In addition, any mate- 

 rial in solution will enter into chemical reactions 

 faster than will those not in solution. 



Certain properties of water cause the earth to be an 

 environment where particular kinds of organisms can 

 survive. First, water contracts as it cools to 4°C.; 

 further cooling from 4°C. to freezing expands it 9 

 per cent. This expansion causes ice to be lighter than 

 water per unit volume; hence, ice is able to float in the 

 liquid phase of water. If ice were to sink, the oceans 

 would be frozen solid, in which case earth would be a 

 frozen planet, devoid of most of its present life. 



Second, water has the capacity to absorb and store 

 large amounts of heat. This causes seasonal climatic 

 changes to be relatively insignificant as compared to 

 what they would be otherwise, because large bodies 

 of water moderate air temperature by first storing and 

 later releasing heat. 



The third property of water that contributes to the 

 maintenance of life is its quality of neither gaining 

 nor losing heat rapidly. Because of this and the 

 second mentioned property, water reduces the tem- 

 perature extremes of air, keeping the atmospheric 

 temperature range within limits suitable for life. 



Finally, the freezing and boiling points of water 

 are much above those of most chemicals. This means 

 that under normal earth conditions water is a liquid 

 — the rarest state of matter — and is able to provide 

 an essential medium for life processes. Therefore, 

 earth's life is dependent upon the sea, the source of 

 the earth's water. 



TEMPERATURE 



Most of the ocean has a uniformly cold tempera- 

 ture. Below one mile, the temperature is about 35° F. 

 Above one mile, there is a gradual temperature rise 

 to about 39° F. at the 600-foot level. From 600 feet 

 upward, there usually is a rapid change to the sur- 

 face. The surface temperature of ocean water ranges 

 from about 28° F. in the polar regions to about 80° F. 

 at the equator. 



Below 600 feet the ocean's temperature tends to 

 remain constant throughout the year. However, sur- 

 face waters regularly display some seasonal variation. 

 In about three-fourths of the surface the range be- 

 tween annual minimum and maximum is 8° F. Near 

 latitudes 40° north and south, the range is about 



12° F., and close to the equator it is only a couple of 

 degrees. In certain localized, midlatitude situations, 

 climatic conditions can produce seasonal variations of 

 25° to 35° F. On the other hand, daily surface tem- 

 peratures vary insignificantly, generally no more than 

 2° to 4° F. Greater variations are extremely rare. 



Ocean temperatures are much more stable than 

 those upon the land (Figure 3.1). This stability is 



HEAT LOSS 



ov\/ specific heat 

 no currents 



HEAT GAIN 



ow evaporation 

 low specific heat 

 no currents 



Figure 3.1 Differential heat losses and gains between land and water. 



due to the physical property of water which causes 

 neither significant gain nor loss of heat. In contrast, 

 the properties of rocks and soils are such that great 

 temperature fluctuations are possible, but the greatest 

 possible extremes are not realized. Even within conti- 

 nents, the ocean is effective in reducing the potential 

 ranges of temperature. 



