It means that by definition the whole of Greenland remains within polar climatic limits, where average monthly temperatures do not exceed 50˚F (10˚C).
50˚F (10˚C) is chosen as the natural value, because this is the temperature below which real forests cannot grow and flourish. In other words Arctic areas are those north of the forest line!
That all said, summer temperatures in Greenland really do not vary much – ranging between 43-46˚F (6-8˚C) in most locations. At the heads of fjords in inland areas of the country, local temperatures can be higher. This is especially seen in the southernmost part of the country, where temperatures in July does at times exceed 50˚F (10˚C) in sheltered valleys. These areas are indeed where Greenland’s few woods are found!
Summer temperatures can also be higher further to the north – the airstrip at Kangerlussuaq has a July average of 53˚F (11.6˚C).
THE MIDNIGHT SUN
Curiously enough the inland area of North Greenland – nearly as close to the North Pole as you can get – is the area least likely to have summer night frosts. At a time when even South Greenland can experience summer night frosts, there is a guaranteed frost-free period of 70 days in the northernmost areas. That is because, in North Greenland the sun shines round the clock from April until September and because of this, in midsummer the average temperature difference between midday and midnight is only 34˚F (1˚C).
Now, the temperature-equalizing role of the midnight sun is less the further south you are. But, even in places on the edge of the polar circle such as Maniitsoq and Ammassalik, there is on average 22 hours of daylight around July 1st!
THE POLAR NIGHT
In the wintertime there are major climatic differences.
Nanortalik, Greenland’s most southerly town, has an average January temperature of -37˚F (-3˚C), while average temperatures at Station Nord during March (the coldest month) are -91˚F (-33˚C)!
Of course the northernmost areas experience the most extreme effects of the polar nights. But northern towns along the west coast are also affected. Upernavik has polar nights for about 80 days; Uummannaq for about 60; while a town like Ilulissat has approximately 45 days. Obviously, temperatures drop sharply in places where the sun does not rise above the horizon.
There are also significant variations in precipitation between south and north. In general the climate is wet in the south and dry in the north.
The type of terrain, and whether it is a coastal or inland area also play a major part in terms of local precipitation levels. Coastlines have a far wetter climate. Coastal mountains receive noticeably the most precipitation in areas where ice-free land is the widest. The inland lies sheltered from precipitation. Measurements taken at Kangerlussuaq clearly illustrate this. Around the coast, annual precipitation is 37.4 inches (950 mm), but up the fjords it is only 4.9 inches (125 mm)!
For the Arctic, Greenland is not a very windy place! There can be many totally calm days –but, at the same time there are areas of the country that rank as some of the most windswept in the northern hemisphere.
The most extreme of natural wind phenomena is the piteraq. Although the name is generally used throughout Greenland it is actually the local name in the Ammassalik region for a very powerful wind blowing from inland. It is also a simpler term to use than the equivalent scientific name: a katabatic wind.
A piteraq can occur all over Greenland, but is at its most powerful in the Ammassalik region. A constant high pressure lies above the ice sheet, generated by the intensity of the radiated heat from the ice sheet. The result is that winds blow continually outwards towards the edge. This wind is normally light, but if a strong low pressure passes along the coast, extremely high winds – a piteraq – can be triggered by the large variations in atmospherically pressure.
Piteraq wind speeds vary considerably. At their most powerful, wind speeds can peak at over 124 mph (200 kph), equivalent to wind speeds found in northern tropical storms!
Foehn winds occur in most mountainous regions, and are common in Greenland both in summer and winter.
As with the piteraq, the strength of Foehn winds varies. Some are not particularly severe and seem just like any ordinary fresh breeze – others can be violent and produce severe storm-force winds. Foehn winds are hot and dry winds that blow down from mountain regions over low-lying land. Almost without exception, Foehn winds in Greenland blow from the inland ice out towards the coast.
In winter, a Foehn wind can drive temperatures up to well above freezing point, and in springtime it can cause snow to melt rapidly. The latter is beneficial for plants, which reap the benefits of an extended growing season, Conversely a Foehn wind in winter can be disastrous for animals. After a brief thaw, brought about by a Foehn wind, winter conditions return to normal. Wet snow freezes to armour-like ice, which can be so think that in some cases neither animals nor birds can break their way through it. Foehn winds accounted for the mass destruction of the musk oxen in Northeast Greenland, and probably caused reindeer to become extinct in the same area.
Nature usually provides its own advance warning of Foehn winds – mostly by the formation of lenticular clouds. If such clouds appear it is worth reconsidering any outside activities!