Weather, wet and wild

The word ‘weather’, in Old English, means wind or breeze, but if you look closely at it you can find the word ‘water’ hidden within.  While that may seem like a coincidence it is interesting to think that scientists actually find out a lot about weather by looking at water.

Over 70 per cent of the planet earth is covered in water and almost 97 per cent of that water is in our oceans. So it comes as no surprise that ocean currents, the movement of water through the ocean, has a significant impact on weather across the planet.

Because so much of the planet’s surface is water much of the sun’s heat is absorbed by it. In the tropical waters around the equator the ocean acts as a gigantic solar panel, not only capturing the heat of the sun but storing it. This heat can then be distributed to colder areas of the planet as oceans move from one place to another.

Gyres are ocean circulation patterns created by winds moving the surface of the ocean in the same direction they are blowing. These spinning currents move cold water from the north and south poles to the hot equator where the water is warmed and sent back to the poles. The temperature of the ocean affects the temperature of the air so cold water cools the land as it moves towards the middle of the planet and warm water warms the land as it returns to the top of the world. 

Fast fact: Gyres move clockwise, above the equator, in the Northern Hemisphere and counter clockwise, below the equator, in the Southern Hemisphere. 

Another result of the sun heating the ocean is that ocean water is in a constant state of evaporation as water molecules change into a gas state and lift into the air. This evaporation leads to rain and storms that can be carried by the winds long distances over water and land. Almost all rain that falls on land start off in the ocean.              

 Without ocean currents to redistribute the sun’s heat, temperatures would be more extreme around the planet.  The poles would be extremely cold without the heat flowing up from the equator and the equator would be extremely hot without the cooling waters coming down from the poles. Without this redistribution less of the planet could support life.

Chinooks

A perfect example of how the ocean affects weather in areas far removed from the shore are the warm winds that can blow across the Canadian prairies in the cold winter months. Known as Chinook winds they develop in the Pacific Ocean and blow in an easterly direction toward the Rocky Mountains. As they climb up the mountain the air cools, dropping snow or rain. Once it has reached the summit the air is drier and drops down the other side of the mountain, warming as it picks up speed during its descent. These winds can be as much as 10 degrees Celsius warmer than the air they displace, and traveling at speeds of up to 128 kilometres an hour. The change is so extreme and so rapid that any snow the Chinook encounters is more likely to evaporate than melt!

Article originally published in Brainspace Magazine Winter 2018/19

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