That means that cold water will sink below warm water. Watch this video demonstration that shows cold water sinking below warm water. Salinity is a measure of how much salt there is in water. Ocean water has a salinity of about 3. That means that in a gm solution of salty water, there is 3.
Or, put another way, one litre of seawater contains 35 grams of salt - that is approximately 6 teaspoons. The other salts are made up of chlorine, sodium, magnesium, sulphur, calcium, and potassium. Salt water has more stuff in it than fresh water.
That stuff would be the salt, which makes the mass of water greater, without adding much to its volume. Increasing the mass by adding salt increases the density. Seawater is a little bit more dense than fresh water so it sinks beneath freshwater. This means that when rivers flow out into the sea the river freshwater floats on top of the sea water. However when the wind blows and the sea becomes rough, the two waters get all mixed up.
The winters in the Arctic and the Antarctic are extremely cold. The additional salt increases the density of the water below the ice. Once this cold very salty water is formed, because of its density, it sinks until it hits the ocean floor. This water flows along the bottom of the ocean toward the equator under warmer water layers. Unlike in the Modeling Thermohaline Water Flow Activity , large quantities of warm water are only on the surface of the ocean.
This is because the sun can only heat the top layer of water. Although hydrothermal vents on the ocean floor emit very hot water, they do not release the amounts of hot water demonstrated by the model. Models provide a way to understand systems that are too complex to observe directly, but they can oversimplify or focus on only a limited aspect of a complex concept.
Scientists can use models to help make predictions about the natural world. Motion of water in the ocean is affected by many factors. Thermohaline water flow plays a role in, but does not completely explain, global ocean circulation. Global ocean circulation is the result of many factors including density, wind, waves, tides, and the shape of the ocean floor.
This document may be freely reproduced and distributed for non-profit educational purposes. Skip to main content. Search form Search. Join The Community Request new password. Main menu About this Site Table of Contents.
Density Driven Currents. The content and activities in this topic will work towards building an understanding of how differences in salinity and heat energy affect ocean circulation. Water Layers and Currents Water forms layers in the ocean because of differences in density that are due to differences in temperature and salinity.
The largest waves occur where there are big expanses of open water that wind can affect. These large wave sites attract surfers, although occasionally, waves get just too big to surf. Some of the biggest waves are generated by storms like hurricanes. In , Hurricane Ivan created waves that averaged around 60 feet 18 meters high and the largest were almost feet In , hurricane Dorian also created a wave over feet high in the northern Atlantic.
To sailors, they look like walls of water. No one knows for sure what causes a rogue wave to appear, but some scientists think that they tend to form when different ocean swells reinforce one another. One was recorded by a buoy in and measured A classic tsunami wave occurs when the tectonic plates beneath the ocean slip during an earthquake.
The physical shift of the plates force water up and above the average sea level by a few meters. From a single tectonic plate slip, waves radiate outwards in all directions moving away from the earthquake. When a tsunami reaches shore, it begins to slow dramatically from contact with the bottom of the seafloor. As the leading part of the wave begins to slow, the remaining wave piles up behind it, causing the height of the wave to increase.
Though tsunami waves are only a few feet to several meters high as they travel over the deep ocean, it is their speed and long wavelength that cause the change to dramatic heights when they are forced to slow at the shore. Tsunami waves are capable of destroying seaside communities with wave heights that sometimes surpass around 66ft 20 m. Tsunamis have caused over , deaths since —over , people were killed by the giant earthquake off Indonesia in , and the damage caused to the Fukushima nuclear reactor in Japan by a tsunami in continues to wreak havoc.
The highest tsunami wave reached about 1, ft m , a product of a massive earthquake and rockslide. When the wave hit shore, it was said to destroy everything. There are also other, usually less destructive tsunami waves caused by weather systems called meteotsunamis.
These tsunami waves have similar characteristics to the classical earthquake driven tsunamis described above, however they are typically much smaller and focused along smaller regions of the oceans or even Great Lakes. Meteotsunamis are often caused by fast moving storm systems and have been measured in several cases at over 6 feet 2 meters high. A study found that smaller meteotsunami waves strike the east coast of the U. Tides are actually waves, the biggest waves on the planet, and they cause the sea to rise and fall along the shore around the world.
Tides exist thanks to the gravitational pull of the Moon and the Sun, but vary depending on where the Moon and Sun are in relation to the ocean as Earth rotates on its axis. The Moon, being so much closer to Earth, has more power to pull the tides than the Sun and therefore is the primary force creating the tides. Centrifugal force is the same force that smooshes riders to the outside walls of spinning carnival rides.
Meanwhile, Earth continues to spin. A specific point on the planet will pass through both of the bulges and both of the valleys. When a specific place is in the location of a bulge it experiences a high tide. When a specific place is in the location of a valley it experiences a low tide. During one planetary rotation or one day a specific location will pass through both bulges and both valleys, and this is why we have two high tides and two low tides in a day.
But, while Earth takes 24 hours to complete one rotation, it must then rotate an additional and 50 minutes to catch up with the orbiting Moon. This is why the time of high tide and the time of low tide change slightly every day. The Sun also has a part to play in causing the tides, and its location in relation to the Moon alters the strength of the pull on the ocean. This happens when the Moon is either on the same side of Earth as the Sun or directly on the opposite side of Earth.
Smaller-than-usual tidal ranges, called neap tides, occur when the gravitational force of the Sun is at a right angle to the pull from the Moon. The two forces of the Sun and Moon cancel each other out and create a neap tide. But continents obstruct the flow of water, causing this seemingly simple daily cycle to be a bit more complicated. Because of continental obstruction, some locations experience two tides a day that are more or less the same height known as semidiurnal tides , some locations experience one tide at one height and the second at a different height mixed semidiurnal tides , and some locations have so much interference from land that they only experience one high tide and one low tide per day diurnal tides.
The local geography can also affect the way the tides behave in a location. Shores around coastal islands and inlets may experience delayed tides compared to smoother surrounding coasts since the water must funnel in through constrained waterways. The intertidal zone , the coastal area tides submerge for part of the day, is home to many ocean creatures.
It takes a special set of adaptations to live a life half the time scorched by the Sun and the other submerged underwater. Moreover, the incoming tide promises a constant pounding by ocean waves. Shelled mollusks like periwinkles, muscles, and barnacles cling to rocks, sea stars wedge themselves in crevices, and crabs hide in fronds of algae. A red tide is not a true tide at all but rather a term used to describe the red color of an algal bloom. Algae are integral to ocean systems, but when they are supplied with excessive amounts of nutrients they can explode in number and smother other organisms.
The algae may produce toxins or they can die, decay, and the bacteria decomposing them take up all the oxygen. This massive growth of algae can become harmful to both the environment and humans, which is why scientists often refer to them as harmful algal blooms or HABs. Tidal movements are tracked using networks of nearshore water level gauges, and many countries provide real-time information with tidal listings and tidal charts.
Tides can be tracked at specific locations in order to predict the height of a tide, i. The tides there range from 11 feet 3. This erosion also releases nutrients into the water that help support marine life. The currents associated with the tides are called flood currents incoming tide and ebb currents outgoing tide. Having reliable knowledge about the tides and tidal currents is important for navigating ships safely, and for engineering projects such as tidal and wave energy , as well as for planning trips to the seashore.
Skip to main content. Credit: Pixabay. Are You An Educator? At Smithsonian Ocean, we have lesson plans, activities, and resources to help you engage your students in the wonders of our oceans. This is a map ocean surface currents from John James Wild, The major wind patterns drive oceanic currents.
Ekman transport creates a spiral as wind drags the surface of the ocean, which then drag deeper layers of water. Differences in temperature and salinity drive deep ocean currents.
Locals in Zebbug, Malta created salt pans where they can collect sea salt after the super salty Mediterranean Sea water has dried. Christine M. A rip current can be seen from up above.
Currents on the ocean surface are driven by wind, temperature, gravity, and the spin of Earth on its axis. Waves play an important role in the way coastal ecosystems function, and also provide tourism dollars because of their draw for surfers.
0コメント