Lesson video

Hello, my name is Mr. Marsh, and I'm here today to teach you all about the location and physical characteristics of cold environments.

So grab everything that you need for today's lesson and let's get going.

So by the end of today's lesson, you will be able to describe the location and physical characteristics of cold environments.

There are five key terms for today's lesson, and those are, "cold environments", "biome", "latitude", "tundra", and "climate".

Now, cold environments refers to those environments at higher latitudes and higher altitudes.

For example, the polar, tundra, and alpine biomes.

A biome is a global land area that is characterised by its plants, animals, and its climate.

Latitude refers to the angular distance of a place north or south of the Earth's Equator.

Tundra is a vast, flat, treeless arctic region, where vegetation growth is hindered by extreme low temperatures and short growing seasons.

And climate is the average weather conditions of a place over a long period of time, typically 30 years or more.

There are two learning cycles for today's lesson, and logically we'll start with the first, which is the location of cold environments.

Now, cold environments are biomes which are characterised by extremely low temperatures, typically below freezing for large parts of the year.

They are found at higher latitudes and at higher altitudes and include polar, tundra, and alpine biomes.

Polar biomes and large parts, but not all, of the tundra biome, are also characterised by low precipitation, by which I mean rainfall or snowfall.

These biomes often have less than 250 millimetres of precipitation, usually snowfall, per year, and this thereby defines them as deserts, or cold deserts, in this case.

A common misconception is that cold environments receive a lot of precipitation.

We see that snow, we see that ice, and naturally we think that it must receive a lot of snowfall throughout the year.

But again, this is actually a misconception.

Because in fact, some of the Earth's driest places are actually found within polar and tundra biomes.

For example, the McMurdo Dry Valleys, the image that you can see in front of you, located in Antarctica, receives less than 50 millimetres of precipitation per year, which is half the amount of precipitation that the Sahara desert actually receives.

So this really goes against this idea that the cold environments receive a lot of precipitation, when in fact, the opposite is true.

Alpine biomes are found at an altitude, which refers to the height above sea level, of 3000 metres or more.

We are therefore looking at very mountainous regions, those tall mountain regions, where we find alpine biomes.

So they're found on mountains above the tree line, where temperatures can drop to -30 degrees Celsius, and where precipitation can often be less than 300 millimetres of precipitation.

So again, it's an extremely dry area.

So a quick learn and check, and I would like you to identify all the biomes which can be classified as cold environments.

So read through the four options, and select all that apply.

Best of luck.

And the correct answers were, there were three correct answers.

So the polar, the tundra, and the alpine biomes can all be classified as cold environments.

Really, really well done, if you were able to select those three correct answers.

And another learning check.

True or false? Some cold environments are cold deserts.

So once again, pause the video here whilst you consider, and then select your answer.

And the correct answer is true.

Now, once again, I'd like you to pause the video whilst you consider your answer as to why this statement is true.

So pause the video here, please.

And the reason it is true is because cold environments that have less than 250 millimetres of precipitation per year can be categorised as cold deserts.

Really, really well done if you were able to select those two correct answers.

So cold environments cover almost 25% of Earth's total land area, thereby making it a significant or major global biome.

What I'd like you to do right now is pause the video whilst you consider any countries or mountain ranges which have cold environments, such as polar, tundra, or the alpine biome that you can see in front of you.

So pause the video here whilst you consider your own answer to that question.

So how did you get on with that previous question? Well, let's look at this map then and see if what I have in front of you tallies with what your own answers were.

So polar and tundra biomes are generally located in higher latitudes, between 60 degrees and 90 degrees north and south of the Equator.

These biomes can be found in the following areas.

So first of all, we can identify those lines of latitude.

We have the Arctic Circle at 66.

5 degrees north, and the Antarctic Circle at 66.

5 degrees south.

Now, if we look at our legend, we can see that the polar and tundra biomes are found in these areas around the Arctic Circle and the Antarctic Circle.

Basically around the North and South Poles.

So yes, they're generally found near these two lines of latitude.

We can also see that they are found largely across northern parts of North America and Europe, and in countries such as Canada and Russia.

Meanwhile, in Antarctica, we find the largest cold desert.

So alpine biomes can be found at any latitude, but only in high altitude, by which I mean height above sea level, regions, by which I mean mountainous regions.

And these can be found in the following areas.

For example, the Rockies can be found in North America, the Alps can be found in Europe, the Himalayas, which includes the world's tallest mountain above sea level, Mount Everest, in Asia.

And finally, the Andes in South America, that long strip of mountains stretching up and along the western coast of South America.

So a learning check.

Which statement most accurately describes the global distribution of polar and tundra biomes? So what I'd like you to do right now is read through the four options, pause the video whilst you consider, and then select your answer.

Best of luck.

And the correct answer was A.

The fact that they are located generally between 60 degrees and 90 degrees north and south of the Equator, essentially near and on the North and South Poles.

So really, really well done, if you were able to identify that answer.

Another learning check is, true or false? Alpine biomes are cold because of their extreme latitude.

So pause the video whilst you consider, and then make your answer.

And the correct answer was false.

Now, once again, I'd like you to pause the video whilst you consider your answer as to why this statement is false.

So pause the video here.

And the reason it is false is because alpine biomes are dependent on altitude, by which I mean height above sea level, and not latitude, distance from the Equator.

Therefore, alpine biomes can be found close to the Equator as well as in the higher latitudes, nearer the North and South Pole.

They can be found anywhere across the globe.

So really, really well done if you were able to get those two answers correct.

On now to our practise questions, and the first one asks you to use an atlas to add the correct name to label each of these seven alpine environments.

The names to use are Atlas, Rockies, Andes, Urals, Alps, Himalayas, and the Southern Alps.

Now the second question asks you to describe the distribution of the tundra biome, and it asks you to be sure to refer to hemisphere, lines of latitude, continents, and compass directions in your answer.

Now, Lucas has given an answer to the same question, but about the location of the alpine biome.

And this is what he says.

He says that, "The alpine biomes can be found in both hemispheres, and in almost every continent.

For example, the Andes alpine biome is found between 10 degrees north and 55 degrees south in western South America." So by looking at Lucas' answer, you can see how he's used hemispheres, continents, compass direction, and lines of latitude all in his answer.

So please pause the video here now whilst you attempt those two practise questions.

Best of luck.

And now some feedback.

So this was the location of those seven alpine environments.

Let's have a look at them now.

So we have the Rockies in North America, we have the Alps in Europe, we have the Andes in South America, we have the Ural mountains stretching across Russia, sort of separating Europe and Asia.

We have the Himalayas in Asia.

We have the Atlas Mountains in North Africa.

And finally, we had the Southern Alps in New Zealand.

So really well done if you were able to identify and locate those seven alpine biomes.

And the second practise question asks you to describe the distribution of the tundra biome.

Now your answer could have looked something like this.

It says, "Tundra biomes are found in both hemispheres, and can be found generally in higher latitudes, between 60 degrees and 90 degrees north and south of the Equator.

They can be found in Antarctica, northern North America, and northern Europe." So really, really well done, if you were able to get those few correct answers.

We're on now to our second learning cycle, which is the physical characteristics of cold environments.

Now, there are many elements which make up the physical characteristics of cold environments, and these include the climate, by which I mean the temperature or precipitation, the soil, the soil quality, including the nutrients, the different land forms, for example, glaciers can be found in cold environments.

And finally, the vegetation.

Each of these elements has distinct characteristics in cold environments.

For example, the climate in a cold environment is extremely cold.

It has low temperatures, typically below freezing for long periods of the year.

Meanwhile, precipitation is often below 1000 millimetres, or even less, as we discussed previously.

In polar biome it can even be less than 250 millimetres, thereby marking it as a desert, a cold desert.

The soil is either permanently, by which we mean permafrost, or temporarily frozen during the year, and it has incredibly low nutrients as well.

What this means is that the vegetation is very sparse and is very highly adapted to those cold and dry conditions that we find there.

Finally, the landforms. We have many different landforms in cold environments due to glacial erosion and deposition and periglacial landforms as well.

So cold environment landscapes, as we can see with these three images in front of you, they vary drastically.

We have tundra, alpine, and polar.

Now as you can see with tundra, there seems to be more vegetation.

This is due to the slightly warmer temperatures that we find there, at least for certain periods of the year.

With the alpine, we can see that this is clearly a mountainous region.

And finally, with the polar biome, we can see that due to the much colder temperatures all year round, we find a landscape which looks a lot more icy and snowy more often in the year.

So tundra, polar, and alpine biomes each have distinctive landscapes, but these landscapes are all the result of being cold environments.

This is the polar biome.

Let's try and break this down.

The winter temperatures here are the coldest.

They are often below 40 degrees, and summer temperatures often only up around zero degrees.

There is less than 250 millimetres of annual precipitation.

Yes, okay, it is wetter in the coastal regions, but generally this polar biome is extremely dry.

As previously mentioned, it being less than 250 millimetres per year marks it as a desert.

The land surface is permanently covered in ice, and the soil is permanently frozen.

This is known as permafrost.

And there are very few plants here.

All we typically have are lichens and mosses, and these are typically found only on the edges or on the fringes of the ice.

So on now to the tundra biome, and immediately what we can see with the image in front of you is that it has much more vegetation than the polar biome.

And this speaks volumes about the climate that we find there.

For example, the winter temperature goes as low as -20 degrees Celsius, which is very, very cold, but of course not as cold as the polar biome.

But the real difference is with those summer temperatures.

It gets above freezing point, up around 10 degrees Celsius, and this allows the snow and the ice there to melt to make way for at least a limited amount of vegetation growth.

Also, the precipitation is slightly higher in the tundra biome in comparison to the polar biome.

And again, this allows for more vegetation to grow.

Now, whilst the deeper soil, even in the tundra, remains frozen all year round, and we call this permafrost, the upper layer of the soil does thaw, and this allows a degree of vegetation to grow.

So what we find there are low-growing, flowering plants, and low bushes in those warmer regions.

And this is to deal again with those cold arctic winds.

And for this reason that the flowers and the vegetation there needs to be very low-growing, since also the roots won't be able to tap into those nutrients which are locked in that deep frozen soil.

So a learning check, it says to study the three images below and name the three biomes that characterise cold environments.

So pause the video here whilst you look at A, B, and C, and try to name those three biomes.

Best of luck.

And the three correct answers were, A was tundra, B was alpine, and C was polar.

Really, really well done if you were able to get those three answers correct.

So we now need to look at the climate of cold environments, and we're gonna look specifically at the polar biome.

We're gonna look at Antarctica.

Now there is a scientific station there called McMurdo, and we're gonna look specifically at the climate at this region.

What we can see then, first of all, with this climate graph, is that we need to break it down.

We can see two different types of graph combined to one.

Now the bar graph shows the precipitation, the rainfall, whilst the line graph shown here in red shows us the temperature.

And it shows us how the climate changes throughout the year from January to December, as identified with the X-axis across the bottom, which is showing us the different months of the year, January through to December.

So let's try to break down how the temperature changes in Antarctica, and straight away, when I look at the climate graph, I can see two clear seasons with temperature variation.

We can see how the line drops or decreases between May and September, and this is indicative of its winter.

We can see how the temperature drops between those months, whilst the summer, we can easily identify through the line going up and showing us that temperature increase.

And we can see, therefore, the summer existing between December and February.

Nevertheless, the average temperatures across the entire year are extremely cold, and never rise above zero degrees Celsius.

The peak is in December, of -3 degrees.

This is the warmest temperature found in Antarctica, and it is still below freezing.

Whilst the coldest is found in August, and its average temperature of -25 degrees Celsius really speaks volumes about how consistently cold it is in Antarctica.

Meanwhile, the precipitation.

Let us try to identify what is going on there.

We can see consistently low rainfall, or snowfall, in this case, across the entire year.

For example, the maximum rainfall is just 26 millimetres in November, whilst the minimum is only four millimetres.

The total precipitation then is roughly around 116 millimetres, which is well below that 250 millimetre threshold for it being defined as a desert.

Remember, Antarctica and many other polar environments and some tundra environments are or can be classed as cold deserts.

So Izzy and Aisha are having a debate about what the climate graph shows in Antarctica, and you need to decide which statement is correct.

So Izzy is saying that, "There are no clear seasons in Antarctica.

It is just always extremely cold." Aisha says that, "There are two clear seasons.

An extremely cold and extremely dry winter between May and September, and a warmer, but still cold, summer between November and February, which receives slightly more precipitation." So what I'd like you to do right now is once again read through those two responses and decide which person is correct.

Good luck.

So the correct answer is Aisha.

Yes, there are two clear seasons, as we can see in the climate graph in front of you.

We can see an extremely cold winter between May and September, and we can see a slightly warmer winter between February and December, even though it is still extremely cold, and we can see that across the whole year it is extremely dry, albeit there is slightly more precipitation in November and December.

So really, really well done if you are able to identify that correct answer.

So why is it then that the polar and tundra environments at those higher latitudes is so much colder than in other areas of our globe? It is all to do with the curvature of the Earth's surface, because this determines how concentrated or dispersed energy from the Sun is when it reaches the Earth.

Let us have a look a little bit more at this.

Let's first look at how the Sun interacts with areas at the Equator.

So what we can see here is that the Sun's rays hit Earth directly, so that the solar energy is much more concentrated, and this makes those areas along the Equator much, much warmer.

In contrast, though, the angle that the Sun hits the Earth means that the solar energy is much more dispersed at the poles, at the North and South Pole.

This means that the energy is spread out, and this means that the temperatures therefore are much, much colder.

So this is why the temperature decreases as we move away from the Equator, until, of course, we reach our North and South Pole, which is where we find our coldest temperatures.

Our seasons are caused by the tilt of the Earth, as you can see with this helpful diagram in front of you.

The tilt affects the amount of solar radiation or solar energy received at the poles at different periods of the year.

So at higher altitudes, this tilt is more pronounced and causes larger seasonal differences than at the Equator, for example.

And it is also another cause of the extreme cold temperatures found in higher latitudes, particularly during the winter.

For example, if we look at the diagram in front of you and we look at the left image of the Earth right there, we can see how the North Pole is facing or tilting towards the Sun.

This would be the North Pole's summer, and therefore it is receiving much more sort of focused and direct sunlight during those times.

So it has this season of growth during the summer.

But compare it to, perhaps, on the right hand image right there, the North Pole, and you can see how now, the Earth is tilting away from the Sun, and this would be its winter, and this causes an even more extreme drop in the temperature found there.

So a quick learning check.

It says, why do polar and tundra biomes have extremely low temperatures with large seasonal changes? There are two correct answers.

So what I'd like you to do right now is read through those three options, and select what you believe to be the two correct answers.

Best of luck.

And the two correct answers you were looking for were A and B.

So the reason why it is extremely cold up at the poles and why it has large seasonal differences is because, well, A, the Sun's rays hit Earth at an angle, so solar energy is less concentrated at these higher latitudes.

And B, the amount of solar radiation received at the poles changes drastically through the year.

Between the summer and the winter, there is drastic differences.

So really, really well done if you were able to identify those two correct answers.

Now, the reason why the alpine climate is cold is very different to the reason why the polar and tundra biomes are cold.

Because alpine climate is dependent on altitude, height above sea level, and not latitude.

The first thing to say is that temperature decreases with height.

For example, for every a hundred metres of altitude that we gain in elevation, the temperature drops on average 0.

6 degrees Celsius.

Now this is to do with the amount of air particles that we find the further up into the atmosphere we go, because the less air particles there are, the less heat is able to be transferred between those particles, and so heat ends up being lost.

So as a result, high mountain areas can be cold environments for this reason.

For example, Mount Kilimanjaro, which is 5,895 metres tall and is actually the world's tallest freestanding mountain, is located in Tanzania, which is very close to the Equator, in eastern Africa.

So you may think, "Well okay, it's near the Equator, therefore there's not gonna be any cold environments there." But as you can clearly see in the image in front of you, it does, it has that alpine biome, which we're currently discussing.

So on average, the temperature at the base of Mount Kilimanjaro is 27 degrees Celsius, but compare it to the top, at the summit, the temperature is on average -13 degrees Celsius.

So we've seen a 40 degree temperature change from the base of the mountain to the summit, and it all goes back to that reason of how, as you gain in elevation, temperature decreases.

Some cold environments, especially polar biomes, experience extremely low levels of precipitation.

But why is this? Well, it can be broken down into a number of different reasons.

The first and major reason is the fact that polar and tundra biomes are found at high pressure zones.

The second reason is the albedo effect.

And the third reason is the limited moisture transport.

So, quick learning check, what are the three reasons why the polar biome, and indeed some tundra biome areas, experience these low levels of precipitation? So pause the video here whilst you try to remember and recall the three correct answers.

And the three correct answers were the fact that they are found at high pressure zones, the fact that it has this albedo effect, and the limited moisture transport.

Now we're gonna try to look at these three reasons individually, to try to understand why it is that the polar and some areas of the tundra biome experience extremely low levels of precipitation.

So the first is that, as I said previously, the polar and tundra biomes are situated under a high pressure zone.

This is because warm air has already risen at 60 degrees north and south of the Equator.

Here, as that warm air rises, it cools, and releases its moisture as rain.

So areas at 60 degrees north and south of the Equator are extremely wet, because all of that moisture has sort of been dumped there.

However, the dry air now moves away from this latitude and descends at the poles, at zero degrees, which creates these high pressure zones, which we can see in the image in front of you.

The dry air in these high pressure zones means that there are very low levels of precipitation.

There just isn't the moisture in this air to create enough precipitation.

Next we have albedo.

Now the white ice and snow reflects sunlight, and thereby give cold environments a high albedo.

This keeps temperatures very cold and reduces the melting of sea ice and ice and snow generally, and thereby reduces evaporation, which would actually lead to cloud formation.

Therefore, less evaporation means less moisture rising into the air and the atmosphere, and therefore means less precipitation.

Most rain and snow comes from the ocean moisture, but the poles are very, very far from these warm, moist air sources.

In Antarctica, for example, the surrounding Southern Ocean, which has the Earth's strongest winds, acts as a massive barrier which prevents humid air from actually reaching the interior of Antarctica.

This is why the interior of Antarctica is actually the driest area on Earth.

Now, as we know, the poles are found at high pressure zones and this means that very few clouds actually form in cold environments, but especially polar biomes, as shown in the image in front of you.

This lack of a cloud blanket lets heat escape, albeit there isn't much heat to begin with, but it lets what minimal heat there is escape into the atmosphere, which causes nighttime temperatures to decrease even further, and thereby cause an even more extremely cold climate in the polar biomes.

So we now have two practise questions, and the first one says to study the image below, and what evidence can you identify that tells us this is from a tundra region and not a polar region? The second practise question asks you to describe the pattern of either precipitation or temperature in McMurdo station in Antarctica using the climate graph that you see in front of you.

In your description, you could include a seasonal pattern, you could include the both maximum and minimum of the temperature or the precipitation, and you could also include the range as well, which is the maximum minus the minimum.

So what I'd like you to do right now then is pause the video whilst you attempt these two practise questions.

Best of luck.

And now some feedback.

So the first question asked you to study the image below and you needed to look for evidence that would identify this picture as being from the tundra region and not the polar region.

So you may have noted some of the following.

The first one is that there is evidence of clouds, which is evidence of precipitation.

Now what we know is that in the tundra there is much more precipitation and cloud formation than in the polar biome.

So this is again, a little bit of evidence that perhaps suggests this is an image taken from the tundra.

Another evidence is the surface soil we can see, which is not frozen.

Again, indicative of the tundra rather than the polar biome.

We can also see that the snow has melted to leave surface water.

We can see these sort of puddles or lakes of water, which is melt water on the surface, which indicates also temperatures above freezing point.

And again, perhaps indicative of this picture being taken in the summer months.

And then finally, we can see green land surface, which indicates vegetation cover, for example, low-growing flowering plants that we tend to find in the tundra rather than the polar biome where very little to none vegetation grows.

Second, you are asked to describe the pattern of either precipitation or temperature in Antarctica using the climate graph below.

Now these are just what your answer may have included.

I've mentioned how there is a seasonal pattern.

You know, there is extreme cold between May and September, in the winter, but also that there is a warmer summer months between November and February.

The maximum is, in terms of temperature, in December, of -3 degrees.

And the minimum, the coldest is in August, of -25 degrees Celsius.

Therefore the range is 22 degrees Celsius, since of course 25 minus 3 equals 22.

In terms of the precipitation, you may have included this.

Again, there's a limited seasonal pattern, because the precipitation across the year is consistently low, between five and 10 millimetres each year, but there is a slightly higher precipitation amount between November and February.

There is though, one anomaly, which is the maximum in November, of 26 millimetres.

We can see that is drastically different from the other months.

The minimum is in October, of four millimetres, and therefore the range is 22 millimetres.

So really, really well done if you are able to include anything like that in your own answer.

So a learning summary then.

So you need to know that cold environments include polar, tundra, and alpine.

These generally receive little precipitation, especially the tundra and the polar biomes, which receive less than 250 millimetres per year.

The polar and tundra biomes are generally located between 60 and 90 degrees north and south of the Equator, while alpine biomes are found across the globe in high altitude mountainous locations.

Temperatures are consistently low because polar and tundra biomes are located in the higher latitudes, you know, far away from the Equator, and receive the least direct sunlight.

Where cold environments are located in high latitude, high pressure areas, they can also have very low levels of precipitation.

So really, really well done during today's lesson.

It was a pleasure to teach you, and I will see you on the next lesson.

Goodbye.