Temperature of Ocean Waters

The temperature distribution at different parts of the ocean show vertical and spatial variations. Like land, the ocean water also heats up due to solar energy. As compared to the land, the cooling and heating process takes place at a much slower pace on the ocean. 

Factors that determine the temperature distribution 

Latitude: As we move towards poles from the equator, the temperature of the surface water gets reduced. It is because insolation gets reduced as we move closer to the poles. 

Irregular distribution of water and land: The oceans that lie in the Southern Hemisphere receive less heat as they are less connected to a larger landmass as compared to the oceans of the Northern Hemisphere. 

Effect of Wind: The wind passing from the land to the surface water of the oceans, propel the water water from the coast and upwell the cold from beneath the surface. This gives rise to longitudinal variation in its temperature.

On the contrary, the winds passing towards the ocean gather the warm water close to the coast. This increases the temperature of ocean water. 

Ocean Currents: Cold ocean currents tend to reduce the temperature of the warmer areas and similarly warm currents tend to enhance the temperature of colder regions. The Gulf stream, which is an example of warm current, increases the temperature of Europe’s west coast and North America’s east coast. The Labrador ocean currents are an example of cold current reducing the temperature of North America’s north-east coast. 

The seas that lie in the lower latitudes and are enclosed experience a higher temperature as compared to the open seas. Also, the seas that lie in the higher latitudes and are enclosed experience a lower temperature as compared to the open seas.

Vertical and Horizontal Distribution of Temperature 

If we study ocean water’s temperature-depth profile, it reflects that the temperature tends to lower in the deeper areas. The profile exhibits a boundary between the deeper layers and surface waters. 

Vertical Distribution of Temperature 

Generally, the boundary starts at 100 to 400 meters below the surface and goes up to hundreds of meters below. Thermocline is that region of the boundary where the rapid reduction in the temperature begins.

Usually, approximately 90% of the ocean water lies beneath the thermocline. As we move towards this zone, the temperature reaches closer to 0-degree Celsius. 

Across the low and middle latitudes, the ocean’s temperature structure can be categorized into 3 layers. These layers start at the surface and end at the bottom of the ocean. 

1st layer: It showcases the topmost layer of ocean water that is warm and about 500 meters thick. The temperature of this layer can vary between 20 to 25-degree Celsius. Tropical oceans have this layer all year. However, this layer is evident only in the summer in the oceans that lie in the middle latitude.

2nd layer: This layer falls below the top layer and is known as the thermocline layer. A quick fall in temperature is noted with increasing depth here. The thermocline layer is generally 500 to 1000 meters thick. 

3rd layer: This layer falls below the 2nd layer and is usually quite cold. In the Antarctic and Arctic region, the temperatures are usually close to 0-degree Celsius even at the surface. Therefore, the temperature varies slightly with the increase in the depth. In these areas, only one cold layer is formed from the top (surface water) to the bottom (ocean floor).

Horizontal Distribution of Temperature 

• On average, the temperature of the ocean’s surface water is around 27-degree Celsius. The temperature gradually reduces as we start from the equator and move towards the poles

• The temperature decreases by 0.5-degrees per latitude as the latitude increases

• At 20-degree latitude, the temperature is about 22-degree Celsius on average. At 40-degree latitude, the temperature reduces to 14-degree Celsius. The temperature drops at 0-degree Celsius at the poles

• The oceans that fall in the southern hemisphere usually have a lesser temperature than the oceans of the northern hemisphere

• The temperature is the highest towards the north of the equator

• The annual temperatures of southern and northern hemispheres are 16-degree Celsius and 19-degree Celsius respectively. The difference exists due to the irregular distribution of water and land in these hemispheres

• The ocean has the maximum temperature at its surface as the sun’s heat is transmitted directly to the surface. The heat reaches to the lower surface through a process known as convection

• As we move closer to the depth of 200 metres, the fall in temperature is quite steep. However, the rate of fall in temperature slows down after that

Conclusion

3-4 degrees Celsius is the average temperature of the ocean. It’s because sunlight only penetrates the upper 200 fathoms, where temperature changes are most noticeable. For the rest of it, the oceans’ temperatures are rather stable. The vast majority of ocean waters are between 1.5° and 4.6°C in temperature. At the surface and at considerable depths, the temperature of the oceans changes, much like it does on land. There is a very narrow temperature range in the ocean because water warms and cools considerably more slowly than land.