The ocean as a storehouse of water
The oceans are, by far, the largest reservoir of water on earth—over 96% of all of Earth's water exists in the oceans. In terms of the water cycle, almost all water that is in the atmosphere (about 90%) comes from evaporation from the oceans.
Not only do the oceans provide evaporated water to the water cycle, they also allow water to move all around the globe. Ocean currents move massive amounts of water throughout the oceans, and the movement of water affects everything from the climate to the environments where life thrives both in the oceans and on the continents.
The Gulf Stream in the Atlantic Ocean, for example, moves warmer water from the Gulf of Mexico northward and eastward, ending up on the coasts of northern Europe. Much of Europe would be much colder if it was not for the Gulf Stream.
The water cycle sounds like it is describing how water moves above, on, and through the Earth ... and it does. But, in fact, much more water is "in storage" for long periods of time than is actually moving through the cycle. The storehouses for the vast majority of all water on Earth are the oceans. It is estimated that of the 332,500,000 cubic miles of the world's water supply, about 321,000,000 is stored in oceans. That is about 96.5 percent of all Earth's water. It is also estimated that the oceans supply about 90 percent of the evaporated water that goes into the water cycle.
Not only do the oceans provide evaporated water to the water cycle, they also allow water to move all around the globe. Ocean currents move massive amounts of water throughout the oceans, and the movement of water affects everything from the climate to the environments where life thrives both in the oceans and on the continents.
The Gulf Stream in the Atlantic Ocean, for example, moves warmer water from the Gulf of Mexico northward and eastward, ending up on the coasts of northern Europe. Much of Europe would be much colder if it was not for the Gulf Stream.
The water cycle sounds like it is describing how water moves above, on, and through the Earth ... and it does. But, in fact, much more water is "in storage" for long periods of time than is actually moving through the cycle. The storehouses for the vast majority of all water on Earth are the oceans. It is estimated that of the 332,500,000 cubic miles of the world's water supply, about 321,000,000 is stored in oceans. That is about 96.5 percent of all Earth's water. It is also estimated that the oceans supply about 90 percent of the evaporated water that goes into the water cycle.
The water in the oceans is saline (saltwater), but, what do we mean by "saline water?" Saline water contains significant amounts of dissolved salts. In this case, the concentration is the amount (by weight) of salt in water, as expressed in "parts per million" (ppm). Water is saline if it has a concentration of more than 1,000 ppm of dissolved salts; ocean water contains about 35,000 ppm of salt.
The volume of the oceans does change ... slowly
Of course, nothing involving the water cycle is really permanent, even the amount of water in the oceans. Over the "short term" of hundreds of years the oceans' volumes don't change much. But the amount of water in the oceans does change over the long term. During the last Ice Age, sea levels were lower, which allowed humans to cross over to North America from Asia at the (now underwater) Bering Strait.
During colder climatic periods more ice caps and glaciers form, and enough of the global water supply accumulates as ice to lessen the amounts in other parts of the water cycle. The reverse is true during warm periods. During the last ice age glaciers covered almost one-third of Earth's land mass, with the result being that the oceans were about 400 feet lower than today. During the last global "warm spell," about 125,000 years ago, the seas were about 18 feet higher than they are now. About three million years ago the oceans could have been up to 165 feet higher.
The volume of the oceans does change ... slowly
Of course, nothing involving the water cycle is really permanent, even the amount of water in the oceans. Over the "short term" of hundreds of years the oceans' volumes don't change much. But the amount of water in the oceans does change over the long term. During the last Ice Age, sea levels were lower, which allowed humans to cross over to North America from Asia at the (now underwater) Bering Strait.
During colder climatic periods more ice caps and glaciers form, and enough of the global water supply accumulates as ice to lessen the amounts in other parts of the water cycle. The reverse is true during warm periods. During the last ice age glaciers covered almost one-third of Earth's land mass, with the result being that the oceans were about 400 feet lower than today. During the last global "warm spell," about 125,000 years ago, the seas were about 18 feet higher than they are now. About three million years ago the oceans could have been up to 165 feet higher.