Some basic Information about Arctic polar Regions
The climatic system
To understand the Arctic climate fully, it has to be placed in a more global context. To do that, we talked to the climatologist, André Berger, who is a tenured lecturer at the Université Catholique de Louvain in Belgium. He is also a former president of the Georges Lemaître Institute of Astronomy and Geophysics, and author of a reference work entitled Le climat de la Terre: un passé pour quel avenir? (The Earth's Climate what does the past mean for the future?).
" In fact, the climate system is like an enormous tank in which matter, energy and a quantity of movement are all stored as they are continually in the process of being converted and redistributed. When all is said and done, the energy that is required to form and develop movements in the atmosphere and the oceans, as well as to maintain all of the processes that go with them, comes from the Sun. Which is why it is essential to monitor the development of solar radiation by way of the climate system.
The fraction of solar energy that is absorbed by the climate system (approximately seven-tenths) is converted into heat; in turn, the system will then emit an equivalent amount of thermal radiation (in a balanced situation). The intensity of this depends in particular on the temperature of the bodies emitting the radiation. In fact, the infrared radiation emitted by the surface of the Earth is re-absorbed by the components of the atmopshere (mainly steam and carbon dioxide), which then defines, via the greenhouse effect, the average overall temperature of the air at the Earth's surface. (...)
To understand the Earth's climate fully, we first have to analyse its average energy balance. The majority of solar radiation entering the Earth's system (342 watts per sq.m.) has a short wavelength, with the maximum being visible. On average and across the whole of the Earth in a year, 30% of this radiation is reflected back towards space, while the remaining 70% (237 Wm-2) is absorbed by the ozone in the stratosphere, by steam, clouds and aerosols in the troposphere (68 Wm-2) and by the Earth's surface (169 Wm-2). This means that to maintain an energy balance, infrared radiation needs to be re-emitted back into space in a quantity equivalent to the amount of solar radiation that has been absorbed. The surface emits 390 Wm-2, 20 of which will pass through the atmosphere directly into the "atmospheric window", while the remainder is absorbed by the troposphere. In turn, having absorbed (68+370 Wm-2), the atmosphere will re-emit 217 watts per sq.m. of it back into space and 327 towards the Earth's surface. A quick check on the radiation balance sheet demonstrates that the surplus in surface energy (106 Wm-2) has to be set off by non-radiation processes such as evaporation (90 Wm-2) and conduction 16 Wm-2), with an equilibrium being re-established by way of this convective coupling between the Earth's surface and the atmosphere..."
(Extract from "The Earth's climate: what does the past mean for the future?", André Berger, De Boeck University, Brussels, 1992, pp. 208 to 211)
Poles: balanced radiation deficit
However, this balanced situation does not prevail everywhere on Earth. In the polar regions, the radiation balance at the top of the atmosphere is negative. This fact is linked to a loss of energy that can be explained in two ways.
First, solar radiation expends a maximum amount of energy in reaching the poles, because passing through the atmosphere takes place increasingly on the diagonal and hence takes longer as the poles are approached. The quantity of energy received per unit of the Earth's surface is lower in polar regions than it is in equatorial regions - and all the more so as the remaining energy is spread over an ever-increasing surface area due to the rounded shape of our planet and its degree of tilt.
Snow and ice also play a role. While - as we have seen - the surface of the Earth and the atmosphere reflect an average of 30% of the sun's radiation, this reflection is accentuated in the vicinity of the poles by the whiteness of the snowy mantle, which bounces the majority of incident light (or albedo) back into space.
To establish a balance of energy, the polar regions, where the radiation balance at the top of the atmosphere is negative, receive the energy that compensates for the inter-tropical regions, where there is a surplus. An energy cycle of colossal power is generated by the huge difference in temperature that exists between cold regions and hot regions, which are heated up by the Sun. The result of this is the transfer of an enormous quantity of heat. This is produced by the ocean and atmospheric currents, which interact with one another.
Arctic: unequal seasons and low altitude
These variables have an effect on the Arctic climate. It is a climate that is characterised by the disparity of its seasons. Also, the tilt of the Earth in relation to the Sun, creates seasons with highly variable lengths in the region: winter lasts approximately nine months, summer is only a third of that, while spring and autumn are merely transitional periods that last a matter of weeks.
Harsh though it is, the Arctic climate would be much more so if it did not benefit from the heat mentioned above that comes from the non-polar regions.
Does the essentially marine nature of the Arctic - which, unlike the Antarctic, is an ocean surrounded by various masses (continents and the Greenland icecap) - also contribute to moderating the harshness of the climate? You might well think so when you think that the specific heat of the water is well above that of the ground.
"I really do not believe in the explanation that says it is because the Arctic Ocean is covered in ice in winter," explains André Berger. "I think it is the altitude of the Antarctic that makes it so much colder at the South Pole."
Nonetheless, the huge disparities recorded in the Far North are substantial. Proof of this can be seen in the heart of Siberia (where temperatures vary between a minimum of -67.8°C and an absolute maximum of 36.7°C at Verhoïansk) or in Canada, which has even more extreme temperatures than the North Pole, where the thermometer fluctuates between -40°C et 0°C.