Ocean Water notes

Salinity refers to the total amount of dissolved solids in the water. It's measured in PPT or parts per thousand. For instance, are salinity in the oceans, ranges from 35 PPT to 38 PPT. 33 PPT means that for every part every thousand parts water you would have 33 parts dissolved salts. The average salinity of our oceans is 35 PPT. So that's the most important figure to remember here that average 35 parts per thousand. So salinity can change an easy way to think of this is to imagine mixing salt in a couple of warm water at your house and trying to drink it. If it tastes really salty and really terrible, you could add a little bit of water so it would taste quite so salty. So salinity increases or decreases depending on the amount of water. So salinity will increase if you take water away. The water would taste more salty will be more salty if you take water away. In nature, water is removed from the oceans by evaporation or freezing. That means that salinity decreases when water is added in nature, water can be added to the ocean in three ways, which would be precipitation, runoff from rivers and melting. Water temperature also varies. It varies by latitude, meaning how close you are to the equator. 

So the water at the equator is much warmer than the water at the poles because it's being heated more efficiently. And it also varies by depth because the water is much warmer at the surface where it's being heated by the sun. Water in the deep ocean stays very cold. The thermocline refers to a later of water in which the temperature is decreasing rapidly. This happens about 300 meters to a thousand meters deep depending on where you are. How close to the equator. If you are near the poles, there is no thermocline because the water at the surface is cold, the water deep in the ocean is just as cold. This graph shows the thermocline, notice on the Y axis, it's showing depth of the water, so you have sea level right here, and this is meters of depth in the water. So the temperature stays pretty warm at the top, this top layer where the sunlight can penetrate about 300 meters, and then it the temperature quickly drops when the sunlight can no longer heat the water, and then the rest of the way down the water just stays quite cold. The picnic line is a similar layer, and but in this case, instead of a rapid change in temperature, it's a rapid change with density, in the case of density of the density increases with depth because that cold dense water sinks lower. The picnic line happens at the same area as the thermal climb, and again, like the thermal pine, there is no picnic line at higher altitudes near the poles. Other things in the water are the organisms. 

Organisms in the water range from microscopic bacteria and algae to the largest organisms alive, which are blue whales. Altogether over 250,000 marine species have been identified. These organisms are classified according to where they live and how they move. For instance, plankton are organisms in the ocean that can float. Nectin or organisms that can swim. And bent those organisms refer to those things that live at the bottom of the ocean. Again, plankton are those things that drift with the current, they can't swim on their own. So this would include organisms like algae and bacteria, anything that can't swim against the current. Some of these plankton can swim vertically, but again, if the current comes through to move them, they can't fight the current. Next in are things that can swim or move independently of a current. They include things like adult fish, squid, marine mammals, and reptiles. Hydrothermal vents are places on the ocean floor where earth's interior heat is warming the water to very high temperatures. And there are hundreds of species that have adapted to live near these vents and this picture you see things called tube worms and these are very interesting organisms because they're the only things on the planet that can live without sunlight. 

They get their energy from the earth's interior. Now that we've talked about what's in the water, let's talk about how the water moves. The ocean water is constantly in motion. There are two main types of currents. The first of those are surface currents, which are caused by wind blowing across the water. When the currents move from low latitudes near the equator to higher latitudes, moving toward the poles, they transfer heat. They can move lots of energy from the equator north and southward. An example of a surface current is the Gulf Stream, which flows near Great Britain, and it causes Great Britain's climate to be warmer in the winter than it would otherwise be at that latitude. Here's a picture of the warm. Water being pumped northward and the cooler water being blown back toward the equator. Another way that the water moves is through deep ocean circulation, sometimes this is referred to as a conveyor belt. This happens when cold dense water at the poles sinks to the bottom of the ocean and slowly moves toward the equator. At the equator, the warmer less dense water rises to the surface and moves back to the poles. 

So again, water in the ocean is constantly being circulated. Another way in which water can move is through upwelling. Upwelling happens when winds blow usually on the western coast of a continent, the winds start blowing the surface water out further to the ocean and the cold water from deep layers has to rise up to replace that water that's being blown out to sea. Now this is very helpful for organisms that live in these areas. When things die in the ocean, they sink down to the bottom, and decay. And when things decay, those nutrients can be used for new organisms to grow and multiply and reproduce. So those nutrients are very important to things that are living and growing. So when this cold water rises up, it brings lots of nutrients to the surface, causes lots of plankton to feed on those nutrients and then the neck and can feed on that plankton. So fishermen really like these periods of upwelling because it gives a boon to the organisms living in that area. Another way that ocean waters constantly moving is by waves. Waves obtain energy and motion from the wind. So waves are caused by the wind blowing across the water. 

The size of the wave depends on three things. That's the wind speed, the length of time that the wind blows, and the distance which wind blows across the water. Fetch refers to the distance the wind is blown across the water. So the. Faster the wind speed, the longer time it blows and the greater distance, the greater the waves can be. Two ways to describe waves, the wave height, as you can see in this picture is a vertical distance from the trough to the crest of a wave. The wavelength is a horizontal distance between two crests as in this picture or two troughs. The constant motion of the waves changes the shore, it erodes transports and drops that sediment back down, so shorelines are constantly being reshaped the sediment like sand on the beaches is constantly being moved. For instance, this graphic shows long shore current. Notice as the wave hits the shore, it pushes some of the sand, this direction, when the water receives, it drops some of the sand back down. So over time, when waves hit the shore day after day after day, little bits of sand are moved this direction. So eventually this beach will become thinner as that sand gets moved this direction.