Did you ever ask yourself: how do large bodies of water affect climate?
Probably not, but did you ever wonder why cities at coasts are warmer in winter and colder in summer than cities inland? It all has to do with the nearby ocean.
The properties of water in combination with the ocean currents influence the areas near oceans.
Mainly oceans and seas, but big lakes too, can have great impacts on the climate in certain regions.
A nearby water body does not only have a lot of influence on the temperatures but also on the precipitation.
All over the world, water affects climate. Mainly the proximity to large bodies of water and the prevailing wind direction decides the influence on the climate. But sometimes ocean currents and mountains can be of importance too. Generally speaking, coastal areas are wetter and have more temperate temperatures.
Water is different from land, in the sense that the heat capacity or thermal capacity of water is higher than that of land. The heat capacity is specific to each substance.
Essentially, it’s the value expressed in Joules per Kelvin (J/g*K). To put it into words, the value expresses the amount of energy needed to warm one gram of the substance with one Kelvin.
For water, this value is a little above 4, so it takes 4 Joules of energy to warm one gram of water with one Kelvin.
For air, for example, the heat capacity is about 1. Even more important, for land, the heat capacity is generally below 1.
But this value depends somewhat on the type of soil. That’s also why on a cold winter night, the ground temperature descents faster than the temperature at eye height.
Influence of Heat Capacity on Water Temperature
It takes more energy to warm water than it does to warm land. So, when sunrays transfer energy to the earth, water takes longer to warm than land does.
In summer, the temperatures above a body of water will be lower than the temperatures above land, because there is an exchange of temperature between the lowest layers of the atmosphere and the water.
The opposite is true for winter, land regions are then generally colder ocean regions.
This is because it does not only take longer for water to warm, but it also takes longer for water to cool down. Temperatures near water are always more temperate than inland.
The higher heat capacity of water is the cause of its more temperate temperatures.
The heat capacity is not the sole reason for the differences in temperature between water and land.
Water is a liquid, while the soil is solid. Water particles can move around, not only horizontally, but also vertically.
The best way to explain this is with an example. At the start of the summer, when water temperatures are rising due to the higher air temperatures, most warming happens at the surface layer of the water body.
The lower layers of the sea are still cold. When vertical motions mix the water, temperatures will even out more. The surface water will cool slightly, while the lower layers will warm slightly.
This effect takes place in deeper and bigger water bodies.
That’s why large bodies of water affect the climate more than small ones. Your backyard pond will not affect the climate in your village or city.
Horizontal Movement of Water: Ocean Currents
Besides the vertical movement of water, which accentuates the temperate temperatures of water bodies, there is the horizontal movement of water.
When looking at the earth’s oceans and seas, these movements are called ocean currents.
This predictable and continuous movement of water across the globe is the result of wind, the Coriolis effect, water density and gravity.
The ocean currents transport water, the main important factor here is the area from where the water comes.
If the water is transported from warmer areas near the equator to colder regions, we speak of a warm ocean current. An example of this is the warm gulf stream, which affects Western Europe and the East Coast of the USA.
The opposite is the cool ocean current, transporting colder water from colder areas to warmer ones. Examples are the California ocean current on the USA’s West Coast and the Benguela ocean current that affects western Africa.
The ocean currents transport water from one region to another, affecting seawater temperatures.
The climate isn’t warming at the same rate across the whole earth. Mainly at the North Pole, the warming has been going at a far higher rate because of arctic amplification.
Due to the smaller differences in temperature between the equator and the North Pole, especially the gulf stream of the Northern Atlantic could slow down.
This of course has great impacts on the regions surrounding it. But how does the water from these water bodies exactly affect the climate in the surrounding regions?
Oceans cool and warm much more slowly than land. Regions near coasts will thus have more temperate climates than inland regions on the same latitude.
For example, Brussels and Kyiv lay at about the same latitude. In Brussels the average maximum temperature in February is 43°F (6°C), in Kyiv, it’s 30°F (-1°C). This while summer temperatures are higher in Kyiv.
The main reason for this difference is the proximity to the sea or ocean. Brussels lays at about 68 miles (110km) from the North Sea. Kyiv is located about 260 miles (420km) from the Black Sea.
But this isn’t the full story. Another important factor regarding the influence of water bodies is the prevailing wind direction. In Brussels, the prevailing wind direction in the winter is southwest, straight from over the ocean.
In Kyiv on the other hand, the wind blows mostly from the west. West of Kyiv there are about 1,200 miles (2,000km) of the continent.
That only enlarges the differences in temperature between Brussels and Kyiv. On top of this, the North Sea near Brussels is warm due to the warm Gulfstream.
The proximity to a large body of water in combination with the prevailing wind direction affects the temperatures.
If there is water in the vicinity, it can evaporate. When it evaporates, there is more moisture in the air. This means that there is a higher chance of clouds and precipitation.
But this is not always the case, the chance of precipitation has also to do with once again the temperatures of the water and the prevailing wind direction.
If the wind blows from over the waterbody, the chances of precipitation are bigger than if the wind blows from overland.
When colder air moves over a relatively warm body of water, convection takes place and the coastal areas can get exposed to prolonged periods of precipitation.
Areas that are exposed to warm ocean currents, will receive more precipitation. For example, the cold Benguela ocean current to the west of Africa borders a desert.
Generally speaking, areas near water bodies receive more precipitation.
How do large bodies of water and mountains affect climate? When there is a mountain range located right along a coastline, a special phenomenon can occur.
This phenomenon is called orographic lift and can occur at all-mountain ranges but is mostly seen near large bodies of water.
When the wind blows over the ocean, the air gets moist. When this air collides with a mountain range, the moist air is forced to move upwards.
When going upwards, the temperature goes down. Colder air can hold less moisture, so moisture starts to precipitate out in the form of rain and/or snow.
At the other side of the mountain range, conditions are dry, and deserts are common. A great example of this is the Andes mountains in Southern South America.
The proximity to water bodies affects climates all around the world. Generally, regions near coasts and with a prevailing wind direction from over the body of water receive more precipitation and have more moderate temperatures year-round.
Read Next: How Do Hurricanes Affect the Hydrosphere?
From the basic properties of water to the vertical and horizontal movement of water.
There are a lot of factors that influence the answer to the question: how do large bodies of water affect climate?
Areas near large bodies of water, generally receive more precipitation and more moderate temperatures. But because of the interesting geography of the earth, there are exceptions to this rule.