Climate and weather

Kangerlussuaq lies at approximately the same latitude (68ºN) as the Lofoten Islands in Norway, where sea ice does not occur and extensive forests are clothe the adjacent mainland. In common with other areas on the western side of the Atlantic basin, Kangerlussuaq is very much colder, being strongly influenced by the East Greenland current, the main outflow from the Arctic Ocean, which carries large amounts of drift ice. This is the single most important factor both for the climate as well as for the traveller. Throughout the whole of East Greenland, drift ice is present for most of the year and vegetation is generally minimal, trees or even bushes being absent north of Skjoldungen, many hundreds of kilometres to the south.

At the time of Wager's discovery of the Skaergaard intrusion in 1930, and indeed up to relatively recent times, the area had been extremely inaccessible, among the most isolated areas of our planet outside Antarctica. The drift ice which, after growing and ageing for several years in the Arctic Ocean, eventually gets caught in a current which takes it through the Fram Strait between Spitsbergen and Greenland and down the East Greenland coast. This current is the major outlet from the Arctic Ocean and has a profound effect on the North Atlantic climate; it also carries the world's heaviest drift ice. Those who have travelled by sea to Skærgård will always remember the transition west of Iceland between the grey, chilliness of the North Atlantic to the biting cold and crystal clear light (if not foggy) of the Arctic as the ship crosses this oceanic boundary and the first drift ice begins to appear. Soon the ship may well find itself stopped by an impenetrable mass of ice, with flows reaching several kilometres in diameter and many metres in thickness. From this point on further progress is determined by the skill of the skipper in finding open leads, or by the whims of wind and current. Even the largest ice-breakers have difficulty in forcing ice of this thickness.

Drift ice conditions vary markedly from year to year, but it is seldom before the end of July, when a lead opens off Kangerlussuaq, that a ship can approach Skærgård. Nevertheless, the sea is normally quite open by the end of August and a big Atlantic swell begins to make itself increasingly felt along the outer coast and can make landings impossible. However, Kangerlussuaq itself always contains so much ice - glacier-derived brash ice and bergs of all sizes - that the swell does not penetrate far into the fjord.

This fjord is heavily glaciated with a number of tidewater glaciers, of which the Kangerlussuaq Glacier is the biggest. Draining about 50,000 km³ of the Inland Ice, it is one of the major ice producers of Greenland, calving about 15 km³/a. Recent ship-borne studies of the fjord, largely aimed at elucidating sedimentary conditions, have been made by Andrews et al. (1994) and Syvitski et al. (1996), from which this information is taken. Among other things, they found that sedimentation rates in the Holocene may average about 50 m/ka, an extraordinarily high rate.

Just south of Kangerlussuaq is the Polaric Glacier (known to the Inuit as Apulileertip Apusia), which is also highly productive and frequently a severe hindrance to navigation from the south.

The geomorphology of the area has been discussed by Brooks (1979). Kangerlussuaq reaches depths of almost 1000 m, has a marked trough on the adjacent shelf, excavated when it extended far out beyond the present coastline and was grounded during the Pleistocene. Prominent nick marks can be seen on the fjord walls marking the earlier thickness of this glacier.

Climate

Several features of the Kangerlussuaq climate, that cannot be found readily in the literature are worth mentioning here. Unfortunately the meteorological records from the Skærgård station have not proved accessible either in Denmark or the USA so our knowledge comes from the Wager and Deer overwintering from 7th August, 1935 to 19th August, 1936 (Manley, 1937). Records from Nordre Aputitêq (Apulileeq) during the period 1958 to its closure in 1981 and subsequent automatic observations are less useful, as the weather at Aputitêq is known to be considerably different from that at Skærgård, notably in having an almost complete absence of storms from the land, a high incidence of fog and north-easterly storms at times of depressions.

Skaergaard lies in the climatic type known as "maritime Arctic" which, in contrast to the high Arctic, is characterized by less stable weather with influxes of maritime air masses bringing heavy precipitation. The proximity to the maritime environment means also that the temperatures are less extreme than further to the north. Nevertheless, in contrast to, for example Iceland, the weather is extremely stable with periods of good weather that can last many weeks. Likewise, temperatures are polar by any standards and there are only a few weeks each summer when the temperature does dot fall below zero at night. The annual mean temperature is -5ºC with maximum temperatures in summer of up to +15ºC and minimum temperatures in winter of -30ºC to -35ºC. Normally, winter ice in the fjord lasts until July when dog sledging is still possible, but by September skins of ice form on the water on clear nights, even though it may be much later that the ice becomes thick enough to withstand the winds and currents. Even in the middle of winter open water forms when storms break up the ice.

It is important to realize that the figures given above are averages and variability is great. Thus in 1974 a maximum temperature of 18ºC was recorded, but in 1972 and 1973 no temperatures higher than 10ºC were recorded. Observations from Nordre Aputitêq (Apulileeq) for the period 1971-1978 (the last years of manned operation) are summarized in Fig. 8.

Precipitation is generally moderate, about 800 mm, and most falls as snow, although in January 1936 the temperature rose above zero and rain was recorded. Most precipitation falls in concentrated bursts, when a depression passes up the Denmark Strait. During Wager & Deer's overwintering in 1935-36, significant amounts of precipitaion occurred on only 86 days during the year, mostly in the autumn and spring. Precipitation recorded over a period of years from other East Greenland stations (as mentioned above, the Skærgård data have not proved accessible, but are expected to be similar in this respect), show that the most striking feature is the great variability. For example, in the month of June, precipitation varies from 160 mm down to only about 20 millimetres. Ammassalik had over 1400 mm of precipitation in 1972 and 1976, while 1974 had only 900 mm and 1971 only 800. Wager & Deer's overwintering year appears to have been fairly average, except for January and September which were unusually dry. The great variability is doubtless due to Kangerlussuaq's position close to the boundary between high Arctic and maritime Arctic areas. When the high Arctic weather systems move south, the weather is dry, in other years the maritime air masses establish themselves farther north and the weather can be very wet. In short, it is difficult to predict whether a given month will be wet or dry or to predict the extent of summer snow cover, which is strongly influenced by precipitation (- rain is the most effective agent for snow melting).

Winds are generally very light and the majority of days are wind-still on a regional basis. However, local winds are very noticeable (particularly when the temperatures are low and the air is close to the dew point). Under fine weather conditions, warm air rising from insolated rock inland cause strong winds to blow up the fjords from the outer coast. These winds die down at night and are negligible in the early part of the day. In short, they are classic "sea breezes". They are confined to the fjords as it can frequently be observed that a short distance out from the mouth of Miki Fjord the water becomes mirror calm, although in the fjord it is being whipped up by a strong, cold breeze. . They are never very thick so that about 200 m up the mountain calm conditions generally prevail. The cold, ice-filled waters also give rise to a strong temperature inversion such that at a height of a few hundred metres the air is much warmer than at sea level, where a clammy fog frequently obscures the sun and is a severe hindrance to navigation. Such inversions are sometimes marked by thin layers of cloud, which are a characteristic of overcast days when the fjord wind is less strong. When flying by helicopter we have registered as much as 6ºC increase in temperature in rising 300m. The temperature inversion has a marked effect on vegetation which becomes more noticeable higher up the hillsides, being virtually absent at sea level.

Another type of wind that, once experienced, will not to be forgotten, is the dreaded "piteraq", a powerful catabatic wind that originates on the inland ice, which rises at this latitude to about 3000 m high. The air becomes cooled by contact with the ice so that even in summer the air temperature might be between -20 and -30ºC. This cold air streams off the dome-shaped ice cap and becomes channelled into the major fjords. Kangerlussuaq is specially favoured because the Kangerlussuaq glacier drains a huge bowl-shaped area of ice. By the time the wind reaches sea level it is relatively warm (often markedly so) due to adiabatic compression, very dry, and of hurricane force. This weather is characterised by a deep blue sky, very clear and dry atmosphere and intense sunlight. Cigar-shaped clouds perpendicular to the wind direction can usually be seen towards the inland ice. Such winds show up well on satellite images in the infra-red bands, due to their higher temperature relative to the surrounding air masses. Their occurrence appears to be related to the passage of depressions, up the Denmark Strait. Experience is that during periods of fine weather, these winds blow almost continuously in the inner parts of the fjord, especially along its western side (Kærven and particularly Gardiner Plateau are especially prone to such winds) and extend to the outer parts of the fjord but sporadically and then they generally miss Skærgård. On these occasions, the wind out in the fjord is heard as a dull roaring sound and clouds of spray whipped up from the water can be seen, although locally it may be calm. Occasionally, these hurricanes sweep in over Skærgård and, if not taken down, tents are rapidly destroyed. They almost always strike early in the day after a period of wet, overcast weather. Within minutes after the first gust, the sky has become a deep, cloudless blue and people may have difficulty in standing. In the autumn, waterfalls, augmented by recent rain, are turned to ice within a short time and any snow rapidly sublimes. In summer, "piteraqs" do not last for more than one day and the weather is dry and sunny. That the western side of the fjord is more affected by such winds is due to the Coriolis force.

In contrast, the most depressing weather for field geologists living in tents generally comes from the east to north-east when the storms known as "neqajak" occur. Very different from the "piteraq" conditions , such weather is characterised by heavy cloud, humid air and heavy precipitation. During these periods, which normally last for three to four days, the wind offshore can occasionally also reach hurricane force. Fortunately however, Skærgård is well protected from these winds, although the dampness and raw cold have a very demoralizing effect on campers.