People have always been attracted to the ocean. It provides us with food, recreation, and time spent along the coast feeds our souls. Although we love the sea, one of our challenges is that first dip in the sea that freezes our toes and catches our breath. Temperatures may be steaming, but the ocean is always cool, if not downright cold.
The ocean is cold because water has a high specific heat capacity. Cold polar currents travel through the water, decreasing the temperature. The sea loses energy to the air, and the wind blows reducing the sea’s temperature. The wind pushes water away and results in the upwelling of cold water.
We do not know a lot about the ocean, but one thing we can explain is why ocean water is cold. The explanation involves some understanding of physics, but fortunately, the concepts are easy to grasp.
Why Is The Ocean Colder Than The Land?
In physics, there is a concept known as specific heat capacity, which refers to the amount of energy required to increase the temperature of a kilogram of a substance by one degree. Each kind of substance has a different specific heat capacity.
Water has a higher heat capacity than land or soil. Another way to explain this is to say that more energy is needed to heat water by one degree than to heat land.
The result is that when the sun shines, the land heats up quicker than the ocean, so the sea will always feel cold compared to the land.
In the same way, the environmental air also heats up quickly, making it feel warm and sometimes hot. The ocean is always cold in contrast to the air. Water needs four times the energy to heat up compared to air.
The contrasts between the warmth of the air and the land and the colder ocean will mean that the sea always feels chilly when we enter it. We are moving from a warm medium, the air, and land, into a cooler medium, the water.
Ocean Currents Affect The Overall Water Temperature
Ocean currents are the movement of streams of water within the ocean. They occur for various reasons, but the pertinent point of our discussion is where these currents arise.
Some currents originate in the polar regions, and they are understandably freezing. They move north from Antarctica and south from the Arctic through the world’s oceans. These icy currents decrease the temperature of the water resulting in a very cold ocean.
Some cold currents are the:
- The Benguela current from Antarctica moves north along the west side of Africa, bringing cool, dry conditions to the area.
- Antarctica current
- The Peru current moves north from Antarctica along the western shores of South America.
- The California current moves southwards from Alaska down the western seaboard of the USA.
- The cold Labrador current moves south along the east coast of Canada.
The ocean areas that these currents move through make them colder than some other areas of the ocean. There are warm currents that originate near the equator. They carry warm water through the seas, increasing the ocean’s temperature
Why Do Different Oceans Have Different Temperatures?
It is easy to see the effects of currents by comparing the oceans’ temperature on either side of a continent. This is clearly seen in southern Africa, where the Benguela current on the west makes the Atlantic Ocean much colder. The Indian Ocean on Africa’s east coast is warmed by the Agulhas current that originates at the equator.
It is the currents which result in oceans with different temperatures. Even though the water in some oceans may be warmer, all water in the sea is still colder than the land and air because of the effects of specific heat capacity.
Does The Wind Make The Oceans Cold?
The wind plays an influential role in the temperature of the oceans. The energy from the sun heats the water surface, and the top layers of the water vaporize (or evaporate). The warm water vapor and air molecules move upwards, and cold air sinks in to replace the warm air. In this way, the water loses heat to evaporation.
As warm air rises, differing air pressure systems develop, and winds arise. Winds blow from high pressure (cold air) areas to low pressure (warm air). Warm air is being constantly moved away from the surface water, which results in a decrease in water temperature.
The wind is also responsible for blowing warm surface water away from areas. Coldwater from deeper in the ocean rushes in to fill the void. This is known as upwelling, and it can occur along coastlines and in the open ocean.
Why Is The Ocean So Cold When You Scuba Dive?
The deeper water in the ocean is always colder because it receives less solar radiation. The sunlight and heat energy can only penetrate the top layers of the sea.
Water lower down does not receive the heat energy from the sun. The deeper you dive in the sea, the colder it is because it gets minimal to no solar heat.
How Does Latitude Affect Ocean Temperature?
Tropical oceans near the equator receive many hours of sunlight each day, allowing them to warm up considerably. Oceans near the polar regions receive very few hours of sunlight throughout the year, and the water is freezing as a result.
Perceptions Make The Water Feel Colder
When our skin is warm and we encounter the water from the ocean, our nervous system notes the contrast. We generally perceive the water to be colder than it is because of the temperature difference.
If you have been in the water for some time, your skin will have lost heat, but you perceive the water to be warmer because there is less contrast. We instinctively know this, as we will say, “it is cold, but I just need to get used to it.”
The water in the ocean always feels cold because the temperature is less than the land and air temperature due to the effects of specific heat capacity. Cold ocean currents and upwelling all decrease the temperature of the sea. Heat is lost through evaporation, and the wind further reduces the ocean’s temperature.