Do you know what I've been thinking about lately?
Hanging out on a tropical beach with sand between my toes and a cool breeze blowing through my hair.
I mean, strictly in the interests of science
Because the breeze in my hair and the wind
and even the big cycles going on out there in the ocean
are all great ways of understanding currents.
A few episodes ago we learned that the
uneven heating of land and water creates wind by forming different pressure zones.
The air above the land is warmer and less dense
so it rises.
And the air over the water is cooler and heavier.
The cool air rushes in toward the low pressure zone
over the land forming a lovely sea breeze.
But you may have noticed that you don't need a beach to feel a breeze.
Nope wind is everywhere.
Air is constantly moving all around the world in cycles or currents
Sometimes they're small, like a light breeze blowing off the sea
and sometimes they're massive, might rivers of wind
Let's see how currents move around the world
You know Earth is a sphere
so the Sun's rays hit the middle of the Earth straight on
This part of Earth receives direct sunlight
Meanwhile, Earth's poles receive indirect sunlight
Or sunlight coming in at an angle
Here the light is spread out over a larger area and is less intense
This mean's Earth's Equator is much warmer than the poles
I mean, you wouldn't pack a swimsuit for a trip to the Arctic
And you know that when we different temperatures, we're going to have different pressure zones
The area around the Equator is a low pressure zone
Here the warm air rises and slowly moves toward the poles
Now if Earth weren't spinning on an axis
And if it didn't tilt and wasn't covered in water
Then the warm air at the Equator would just rise toward the poles and
And the cool air would move in at the Equator, where the warm air just left.
This would create two giant air currents called cells
But of course things on Earth are much more interesting
The Sun hits the Equator causing warm air to rise
And the air moves away from the Equator
But it doesn't have to get all the way to the poles
About 1/3 of the way there the air cools falls
And moves toward the Equator again creating a smaller cell
Another cell is created in the mid-latitudes and another at the poles
In each cell cold air sinks and warm air rises.
There are six cells circling in Earth's atmosphere
At the boundaries of these cells, something really weird starts to happen.
We get jet streams
Wha
Air in these cells is trying to get from one pressure zone to another
Since there's a big temperature difference between air over the poles and over the mid-latitudes
But the Earth is spinning faster at the Equator than at the poles
If you were to stand at the Earth's axis on the North Pole
You would spin more slowly than if you were standing at the Equator
So as air rises over the Equator and makes its way toward the poles
It keeps moving eastward at the same rate
Even though the higher it goes, the slower Earth is spinning
This creates ribbons of very fast-moving air called jet streams
Jet streams move in wiggly patterns across Earth
caused by the interaction with other high- and low-pressure systems
And also with seasonal changes
These streams are usually six to fourteen kilometers off the ground
And cane reach speeds of 442km/h
Simple enough but of course there's more
We know from our little trip to the beach that there are other factors here
Remember our nice sea breeze?
Those small differences between high and low pressure
Caused by the heating of the land and water taking place on all the coastlines
Around the world, makes air patterns more complex
And jet streams and wind patterns aren't the only currents flowing around Earth
Water actually moves a lot like air
Warm, light water rises as cold, salty, heavy water sinks
And just like with air the Sun heats the water that's at the Equator
And that warm water spreads out toward the poles
Cold water moves slowly down to the Equator where it will warm again,
In an endless cycle.
This massive movement of water called ocean currents helps regulate
Global temperatures just as much as air circulation.
All of this interaction between the land air and water creates some complex
Wind weather and climate patterns.
These currents make large parts of Earth livable
Without them, the poles would be far too cold
And the Equator scorching hot
So currents are little complicated and messy and always on the move
They're caused by uneven heating of the Earth's surface
Whether that's between land and water
Or between the poles and the Equator.
And they're all driven by energy from the Sun
Without that energy our air and water would be still
All of these complex currents blowing and flowing around
All over the places makes it hard to predict where the wind will blow and
What kind of weather you'll have next week.
But that's a problem we'll explore in another episode
And until then I'm going to keep planning my beach vacation