新定义美文阅读：
The Salinity of Ocean Waters
海水盐度
If the salinityof ocean waters is analyzed, it is found to vary only slightly from place to place. Nevertheless, some of these small changes are important.
假如大家剖析海水的盐度，会发现区域间只有轻微的变化，然而有的小的变化是要紧的。
There are three basic processes that cause a change in oceanic salinity. One of these is the subtractionof water from the ocean by means of evaporation-- conversionof liquid water to water vapor. In this manner the salinity is increased, since the salts stay behind. If this is carried to the extreme, of course, white crystals of salt would be left behind.
致使海洋的盐度变化的基本过程有三个，其中之一是通过蒸发的方法即把液态水转化为水蒸气来降低海洋中的水分。如此因为盐留了下来，所以盐度增大。当然，假如这种方法走向极端，将会剩下白色的盐晶体。
The opposite of evaporation is precipitation, such as rain, by which water is added to the ocean. Here the ocean is being dilutedso that the salinity is decreased. This may occur in areas of high rainfall or in coastal regions where rivers flow into the ocean.
与蒸发相反的是降水，如降雨，由此水被加入海中，海水被稀释，从而盐度减少。这种情形会发生在很多降雨的区域，或江河入海岸处。
Thus salinity may be increased by the subtraction of water by evaporation, or decreased by the addition of fresh water by precipitation or runoff.
因此，盐度通过蒸发降低水分而上升或通过降水或径流增加淡水成分而降低。
Normally, in tropical regions where the sun is very strong, the ocean salinity is somewhat higher than it is in other parts of the world where there is not as much evaporation. Similarly, in coastal regions where rivers dilute the sea, salinity is somewhat lower than in other oceanic areas.
通常来讲，在阳光非常强烈的热带区域，海水的盐度略高于世界上其它没热带那样多的蒸发的区域。同理，在江河稀释海水的海岸地带，海水盐度略低于其它海区。
A third process by which salinity may be alteredis associated with the formation and melting of sea ice. When sea water is frozen, the dissolvedmaterials are left behind. In this manner, sea water directly beneath freshly formed sea ice has a higher salinity than it did before the ice appeared.Of course, when this ice melts, it will tend to decrease the salinity of the surrounding water.
第三个可以变更盐度的过程与海洋中冰的形成和融化有关。海水冻结时，溶于其中的物质被留了下来。如此，在新形成的海水冰面的正下方的海水比在冰形成之前有更高的盐度。当然，当冰融化的时候，会减少周围水中的盐度。
In the Weddell Sea Antarctica, the densestwater in the oceans is formed as a result of this freezing process, which increases the salinity of cold water. This heavy water sinks and is found in the deeper portionsof the oceans of the world.
在南极洲边缘的威德尔海中，结冰过程增加低温海水的盐度，从而形成了浓度最大的海水。这类大密度的海水下沉，可以在世界海洋的深水域发现。
