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If the salinity of ocean waters is analyzed, it is found to vary only slightly from place to place. Nevertheless, some of these small changes are important. There are three basic processes that cause a change in oceanic salinity. One of these is the subtraction of water from the ocean by means of evaporation conversion of 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. The opposite of evaporation is precipitation, such as rain, by which water is added to the ocean. Here the ocean is being diluted so that the salinity is decreased. This may occur in areas of high rainfall or in coastal regions where rivers flow into the ocean. Thus salinity may be increased by the subtraction of water by evaporation, or decreased by the addition of fresh water by precipitation or runoff. 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. A third process by which salinity may be altered is associated with the formation and melting of sea ice. When sea water is frozen, the dissolved materials are left behind. In this manner, sea water directly materials 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. In the Weddell Sea Antarctica, the densest water 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 portions of the oceans of the world. |
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rú guǒ wǒ men fēn xī hǎi shuǐ de yán dù, huì fā xiàn dì qū jiān zhǐ yǒu qīng wēi de biàn huà, rán ér yǒu xiē xiǎo de biàn huà shì zhòng yào de. dǎo zhì hǎi yáng de yán dù biàn huà de jī běn guò chéng yǒu sān ge, qí zhōng zhī yī shì tōng guò zhēng fā de fāng shì jí bǎ yè tài shuǐ zhuǎn huà wéi shuǐ zhēng qì lái jiǎn shǎo hǎi yáng zhōng de shuǐ fèn. zhè yàng yóu yú yán liú le xià lái, suǒ yǐ yán dù zēng dà. dāng rán, rú guǒ zhè zhǒng fāng shì zǒu xiàng jí duān, jiāng huì yú xià bái sè de yán jīng tǐ. yǔ zhēng fā xiāng fǎn de shì jiàng shuǐ, rú jiàng yǔ, yóu cǐ shuǐ bèi jiā rù hǎi zhōng, hǎi shuǐ bèi xī shì, cóng ér yán dù jiàng dī. zhè zhǒng qíng xíng huì fā shēng zài dà liàng jiàng yǔ de dì qū, huò jiāng hé rù hǎi àn chù. yīn cǐ, yán dù tōng guò zhēng fā jiǎn shǎo shuǐ fèn ér shàng shēng huò tōng guò jiàng shuǐ huò jìng liú zēng jiā dàn shuǐ chéng fèn ér xià jiàng. yì bān lái shuō, zài yáng guāng hěn qiáng liè de rè dài dì qū, hǎi shuǐ de yán dù lüè gāo yú shì jiè shang qí tā méi yǒu rè dài nà yàng duō de zhēng fā de dì qū. tóng lǐ, zài jiāng hé xī shì hǎi shuǐ de hǎi àn dì dài, hǎi shuǐ yán dù lüè dī yú qí tā hǎi qū. dì sān ge kě yǐ biàn gēng yán dù de guò chéng yǔ hǎi yáng zhōng bīng de xíng chéng hé róng huà yǒu guān. hǎi shuǐ dòng jié shí, róng yú qí zhōng de wù zhì bèi liú le xià lái. zhè yàng, zài xīn xíng chéng de hǎi shuǐ bīng miàn dí zhèng xià fāng de hǎi shuǐ bǐ zài bīng xíng chéng zhī qián yǒu gèng gāo de yán dù. dāng rán, dāng bīng róng huà de shí hòu, huì jiàng dī zhōu wéi shuǐ zhōng de yán dù. zài nán jí zhōu biān yuán de wēi dé ěr hǎi zhōng, jié bīng guò chéng zēng jiā dī wēn hǎi shuǐ de yán dù, cóng ér xíng chéng le nóng dù zuì dà de hǎi shuǐ. zhèi xiē dà mì dù de hǎi shuǐ xià chén, kě yǐ zài shì jiè hǎi yáng de shēn shuǐ yù fā xiàn. |