Warm summers… but long, dark, cold winters. Here in the far north of the major continents,
we find the widest temperature ranges to be found anywhere on earth.
One of the last great wildernesses, the few cities that are here are the coldest on the planet.
A place of snow, swamp, lake and trees.
These are the lands of the boreal forest. The taiga. Welcome to the sub-arctic.
In our journey from equator to pole, we have spent the last two episodes looking at the
climates found within the great continents, the cool deserts and the mixed woodlands and grasslands
of the humid continental. It’s now time to take a look at the last of these, the coldest
and most northerly of them, the climate of the endless coniferous forests of North America
and Eurasia. The climate itself is referred to as sub-arctic
by most climatologists, but because of the almost exclusive biome of coniferous forest
that mark these zones, it often goes by the name of such forests, which are called boreal
forest or taiga, the latter word coming from Russian, and which should not be confused
with… tiger. Incidentally, tigers live in the taiga – the Siberian Tiger is the largest
cat on the planet… This climate zone houses the world’s largest
extent of forests – with almost a third of all trees planetwide found here. They cover
in a virtually unbroken sea of dark green, the entire width of the northern continents,
from Alaska to Labrador in North America, and from Norway to Siberia and Kamchatka in
Eurasia. But opposite to their equatorial cousins - the Tropical Rainforests - these
regions have the lowest biodiversity of anywhere on earth, being dominated by often single
species trees, such as larch, fir, pine and spruce.
This climate type also occurs in comparatively tiny pockets in more southerly alpine areas,
as a result of altitude cooling, specifically in the Rocky Mountains in North America, the
Pyrenees, Alps and Carpathians of Europe and the Tibetan plateau in Asia.
In the Koppen Climate Classification, there are, like the humid continental climates to
their immediate south, six divisions of the sub-arctic climate, separated by patterns
of rain and snow and winter temperature. Dominating these six is the one called Dfc, which has
year round precipitation – rain in summer, snow in winter, and where at least one full
month of the year has an average day/night temperature of 10°C (50°F). This variant
accounts for almost 90% of sub-arctic climate coverage, spanning the entire width of the
northern continents. In the northern Far East, Dfc is supplanted
by Dwc, having similar temperatures, but with a monsoon influence pattern of precipitation,
with dry winters and wet summers. Yes, the Asian Monsoon makes it this far north, such
is the extent of the world’s largest weather system.
10°C might seem like a chilly summer day, but this is a day/night average, and the peak
daytime temperature can often exceed 20°C, equivalent to that of the Oceanic climates
such as Britain. Winters are a different story, however. Far
from the ocean, and so far north that winter days can be very short, and the nights long,
temperatures plummet to -20°C or below as a 24-hour average.
And things only get worse in north-eastern Siberia. Here, we need a colder set of Koppen
designations – Dfd and Dwd, because it is here that the winter temperatures fall to
the lowest recorded anywhere outside Antarctica. In this classification, winter day/night averages
must be below -38°C, and night lows in winter often fall below -50°C. Yet, due to continentality,
and long hours of sub-arctic sunlight, summers here are still surprisingly warm, with peak
day temperatures above 23°C. There is a town in north eastern Siberia that
you’ve probably never heard of. But to anyone familiar with climate study, it is well known.
Its name is Verkhoyansk, and it is home to the widest recorded temperature range on the
planet. Here you can see its rather impressive graph, with a temperature range of summer
day to winter night being a staggering 72°C. But this only shows averages. The highest
ever recorded temperature here was 37.3°C, while the lowest was -67.6°C – that’s
a range of almost 105°C! The amount of rain falling within these climate
zones is usually low in comparison to others, due to continentality. But because of the
low average annual temperatures, evaporation of water is low, allowing the growth of hardened
coniferous trees which have specialised in their evolution to thrive in these extreme
climates. If thrive could be said, because the growing season in these cold climes is
limited to just a few short months in summer, and so the trees can take decades to grow
to any reasonable size, and usually live for centuries.
So, where in the world are the sub-arctic climate zones? In short they dominate the
northern hemisphere between 50-70 degrees in latitude.
In North America, all but the north coast of Alaska is covered by this climate, along
with most of the northern half of the great Canadian plains, from the Yukon in the west
to Labrador in the east. In Europe, this climate dominates Scandinavia,
with most of Iceland, all but the oceanic west coast in Norway, the northern two thirds
of Sweden and all but the southern fringe of Finland coming under its sway. Iceland
is the only notable exception to the rule of the sub-arctic being covered with pine
forest. Once, this island was forested in the same way, but the dependency on the human
settlements here on local materials resulted in almost total deforestation of the land
centuries ago, leaving a bleak landscape in its place.
As we continue east into Russia, the majority of this enormous country is blanketed by the
taiga, with the band widening from the northern half of European Russia in the west to encompass
all but the frigid northern coasts in the centre and east, in one of the most famous
and forbidding regions in the world – Siberia. The subarctic climate extends all the way
to the Kamchatka peninsula in the Far East before finishing at the Bering Straits, a
stone’s throw from Alaska, where we began.
As mentioned, and obvious from all you have seen in video so far, this climate is virtually
synonymous with the boreal forest, or taiga. Patterns in this seemingly homogenous forest
do exist, however. Different species of trees tend to dominate different regions - spruces
in North America, for example, while eastern Siberia and its extreme winter temperatures
is dominated by the hardiest conifers of all…
In the south the taiga gradually gives way to mixed woodland and deciduous forest, such
as in Eastern Canada, or to grasslands where there is more aridity, such as in Central
Russia or east of the Rockies. In the north, even the trees eventually give way to the
barren grasses of the Tundra, which we’ll take up in the next episode.
Due to the low evaporation rates in this land of weak sun, the rain and snow that does fall
in the flat basins that dominate the upper latitudes tends to persist, forming large
swamps, bogs or lakes. If you’ve ever looked at a map of Finland or Northern Canada, then
you’ll have noticed this. Because of the long winters, the ground is
permanently frozen below a certain depth. This is known as permafrost. The depth at
which it is frozen depends on latitude – with more southerly regions having soil with a
thinner layer of ice at a deeper level compared to more northerly areas where the ice is thicker
and closer to the surface. On average, the ground stays frozen just a few feet below
the surface. We’ll talk more about the permafrost in the next episode.
Farming in such conditions is extremely difficult and there is no farming on any scale worth
mentioning in these bleak regions. These factors in combination make the sub-arctic
a forbidding place in regard to human settlement, and so these areas are consequently very sparsely
populated, the exceptions being where the location has specific strategic advantage
or where rich natural resources are found. There are only four cities of any size worthy
of mention here. Anchorage Alaska has grown over the last hundred years as a rail and
aviation hub, and with its coastal location, the climate is relatively moderate under the
maritime influence. Murmansk, a significant strategic naval base on the arctic coast of
Russia by Scandinavia, and the largest city above the arctic circle, is similarly moderated
by an ice-free sea. This is not true for the other two major cities
in the sub-arctic. Norilsk, a metallurgical mining centre in Northern Siberia is the most
northerly city above 100,000 population and is regarded as the coldest city in the world
by its average temperature year round of nearly minus 10 degrees celsius. Lastly, Yakutsk,
a diamond mining centre in Eastern Siberia has the coldest winters of any major city
in the world with a day/night average in January of almost minus 39 degrees celsius. Fun times.
So there you have the sub-arctic climate zone, and its dominant biome the taiga. I hope this
has given you some ideas for your next holiday.
Please leave your comments, especially if you’re one of the rare breed that have survived
in this forbidding zone of earth – I’d love to hear of your experiences. If you enjoyed
the video, please click the like button and share it with your friends or fellow students.
And if you haven’t already done so, click the subscribe button so you don’t miss future
episodes. Thanks again for watching, and I’ll see
you in the next episode, where we’ll be journeying even further into the forbidding
arctic – the bleak and treeless lands of the tundra. Until then, stay alive!