How Do Surface Ocean Currents Affect Climate

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How Do Surface Ocean Currents Affect Climate – On the previous page, you learned about the different layers of the ocean: the surface ocean, the deep ocean, and the sediments on the sea floor. Here we will describe these layers, especially the major ocean currents and how they operate in the surface and deep ocean.

Recall from the Modern Atmosphere page that there are two main factors that drive the surface currents of our oceans: 1) differential heating between the equator and the poles, which creates winds, and 2) the Coriolis effect (an invisible force that repels objects as they move across the Earth’s surface ). In addition to these two forces, gravity also plays a role in creating surface currents. More precisely, ocean surface currents are currents that move water in the upper layer (several hundred meters) of the water column and can have local effects on weather and climate, which together can have a global effect on climate (long-term weather conditions). . models).

How Do Surface Ocean Currents Affect Climate

How Do Surface Ocean Currents Affect Climate

Main currents on the surface of the world’s oceans. Note that rotational systems operate in every ocean basin. Red lines indicate warm water and blue lines cold water. Image from “Physical Geology” by Stephen Earle, used under CC-BI 4.0 International License.

Why Are Ocean Currents Important?

Some of the main characteristics of ocean surface currents are eddy systems. Eddy currents, such as those in the North Atlantic and North Pacific, are very important features of the ocean, because they carry warm water from the equator to the poles to colder areas.

In particular, the western “branch” of eddy systems, called the Western Boundary Current, transports warm water to higher latitudes, releasing heat and moisture into the lower atmosphere. Moisture carried north and south of the equator by western boundary currents provides rain for areas along the coast. Some examples of Western Boundary Currents are the Gulf Stream in the Northern Hemisphere which flows along the east coast of North America and the East Australian Current in the Southern Hemisphere which flows along the east coast of Australia. These currents are fast flowing, occur deeper in the water column and tend to be very narrow. In the image on the left, the western boundary currents are colored red.

A sheep poses majestically against a sky of low clouds and fog on a rainy day in the west of Ireland.

As an example of a current western boundary bringing moisture north, consider the climate of Ireland. The country is at a relatively high latitude (about 53° N), but it doesn’t get much snow (for reference, New York is at 40° N), but it does get a lot of rain. This is due to the Gulf Stream and Norwegian Currents bringing warm water north of the equator, thus providing the moisture that falls on Ireland.

Future Changes To The Upper Ocean Western Boundary Currents Across Two Generations Of Climate Models

The opposite arm of the eddy is the eastern boundary currents, which are slower, wider and more extensive than the western boundary currents. Eastern boundary currents generally bring cooler water from higher latitudes back to the equator.

Another important current in our oceans is the Antarctic Circumpolar Current, or ACC, which flows clockwise around Antarctica in the Southern Ocean. The ACC flows almost unchecked around Antarctica (no land blocks its path) and is therefore a very strong current. In fact, it is the largest current in the world in terms of the amount of water transported (100-150 million cubic meters of water per second!!). Therefore, the ACC blocks the warm westerly boundary current that travels south of the equator, causing Antarctica to retain its large ice sheets.

Deep ocean currents, collectively called the thermohaline circulation, are very different from surface ocean currents. The term “thermohaline” refers to the differences in density of temperature (thermo) and salinity (halo) in different bodies of water (often called water masses). Unlike surface currents, which are driven by gravity, wind, and the Coriolis effect, the thermohaline circulation is driven by density differences. These currents are slow and occur deep in the water column.

How Do Surface Ocean Currents Affect Climate

Cross section from the North Atlantic Ocean (right) to the South Atlantic Ocean (left). Four bodies of water are represented here. The Gulf Stream is a surface current, more precisely the Western Boundary Current. Image from “Physical Geology” by Stephen Earle, used under CC-BI 4.0 International License.

Activity: Factors Affecting Climate

The Earth’s thermohaline circulation system generally affects the entire ocean and is important in transporting water and heat from the surface to the ocean depths and vice versa. For this reason, geoscientists often consider it a conveyor belt. The cross section on the left shows the four main water bodies. Note that the top of the water column, colored red and labeled “Gulf Stream,” represents the surface current (Western Boundary Current). This diagram looks across the Atlantic Ocean from the Arctic (right) to the Antarctic (left).

Deep water first formed in the North Atlantic Ocean (see image at right). The water here becomes denser than the surrounding water due to the repulsion of the salt water. Brine shedding occurs when seawater freezes but leaves salt behind. Because of this, the water around the ice becomes denser due to the increased salt content and then sinks under the less dense water brought north by the Gulf Stream.

Global thermohaline circulation. Red paths indicate warm surface currents, while blue paths indicate cold, deep ocean currents. Note that there are two areas of deep sea formation in the North Atlantic Ocean and one in the South Atlantic Ocean near Antarctica. The scale below shows the salinity of ocean water, measured in units of the practical salinity scale (PSS; a number without a scale, but the higher the number, the saltier the seawater). Image from “Physical Geology” by Stephen Earle, used under CC-BI 4.0 International License.

Deep water is also formed off the coast of Antarctica by the same process in the South Atlantic Ocean. Note in the cross-sectional image above that the bottom water of Antarctica is colder and therefore denser than the deep water of the North Atlantic, so it sinks and flows beneath it. In other words, the deep water that forms in the North Atlantic flows over the deep water that forms in Antarctica. Part of the deep water mass of the North Atlantic later rises near the coast of Antarctica. Deep-sea wells are important because, as mentioned above, they cause ocean mixing over millennia and also bring oxygen and other atmospheric gases (such as CO2) into the deep ocean.

Satellites Reveal Ocean Currents Are Getting Stronger, With Implications For Climate Change

But before it reappears, the deep water mass circulates through the ocean, from the North Atlantic Ocean, to the Indian Ocean, and then to the Pacific Ocean. So, in the Pacific Ocean, the bottom water is older and erupts again.

It is important to stop here before reading any further and reflect on the information you have read so far. The entire thermohaline circulation system depends on the sinking of dense, salty water in the Atlantic Ocean. The formation of dense water depends on the formation of ice. Ice formation depends on the cold climate.

Due to the thermohaline circulation system, along with surface currents, our oceans are able to mix over longer time scales and therefore absorb more CO2 from the atmosphere.

How Do Surface Ocean Currents Affect Climate

So what happens to the entire circulatory system when the climate starts to warm? Well, we’re glad you asked! Continue reading below to find out.

Climate Change: The Major Ocean Current That Regulates The Climate Shows Signs Of Collapse

It is not difficult to understand that as our Earth warms, so do our oceans. Warming oceans have huge implications for climate change, some of which we’ve already discussed. Another of these implications is ocean stratification, i.e. the increase in stratification of our oceans due to temperature differences. You may recall from the Ocean Layers and Mixing page that our oceans are somewhat layered due to differences in temperature and salinity. However, this is a good thing, because there is sinking, and therefore mixing of the deep, cold waters of the Atlantic.

It seems unreasonable to think that the thermohaline circulation system would stop or slow down, but there is evidence that this has happened in the geologic past.

But how could something like this happen and what does it mean for our Earth? Let’s remember that for the formation of a denser water mass, sea ice must form, which requires a cold climate. If the climate warms, sea ice will stop forming and begin to melt. The ice that originally formed did not include salt from the seawater, so the meltwater is essentially fresh water. This is why melted ice water is less dense because it does not contain salt.

Since meltwater is less dense, it floats to the surface of the ocean, where it heats up quickly. This warm water also causes the ice to melt, which brings more fresh water into the warming ocean. Eventually, enough ice melts to create a “freshwater lens” on the surface of the ocean in areas around the ice, where deep water forms. So, because the water is 1) warm and 2) less dense, it prevents deep water from forming due to upwelling

How Do Ocean Currents Affect The Biosphere?

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