DaylightDAYLIGHT
In southern Greenland the period of greatest daylight occurs in the months of May, June and July, whilst the warmest and driest month is August. The expedition was planned to take advantage of all these factors, arriving in Greenland on the 8th July and departing on the 19th August.
The amount of daylight experienced, noticeably decreased throughout our stay. On our first day, (camping on the shores of Narsaq Fjord), the amount of full daylight was in excess of 20 hours, with the remainder of the day occurring as twilight. By the time we arrived on the shores of Ikka (six days later and further north), we were starting to experience longer hours of twilight followed by about 4 hours of darkness. When we left Ikka (on the 15 August) we were experiencing a lengthy period of twilight and over 6 hours of darkness. The period of twilight before dusk was compounded by a high mountainous ridge on the western side of the fjord, which cut out any sunshine in the early evening. The periods of twilight, however had no real affect on any the activities carried out, other than to reduce the amount of light penetration on dives.
THE NIGHT SKY
During the periods of full night, the skies were almost always cloudless. Venus was in the ascendant and usually visible. Satellites came speeding over on a regular basis and the occasional meteor shower was also seen. Furthermore, though we were told not to expect it, we were rewarded on the last three consecutive nights of our stay in the Ikka area with spectacular displays of the Aurora Borealis, albeit in monochrome green.
The temperatures experienced were fairly constant for any part of the day. Day time temperatures, whilst not freezing were normally quite cold and usually required the wearing of two layers of clothing, the underlayer being a thermal one. The arrival of the evening twilight brought with it a rapid decline in temperature and at night it was usually several degrees below zero.
Temperatures were not recorded on a regular basis, but as a guide, the recorded highs and lows were 20oC (daytime) and -4oC (late evening) respectively.
The fjord was generally subject to a local weather system. The start and finish of a normal day were usually very calm. In the morning this was often accompanied by some low cloud, whilst the late evenings were mostly cloudless and very cold. The day itself was usually breezy but none the less, quite sunny. As with most camping 'holidays', however, we did get the occasional bit of rain. The worst of which was a period of over 24 hours of continuous rain, (which saw the fresh water layer of the fjord increase by over a metre and small streams turn into boulder moving torrents) and was accompanied by gale force winds that flattened several of our tents, including our 'Diving Bell' - an old fashioned bell tent, containing all our dive kit.
F&#ouml;hn / Lee-Wave effect These gale force winds were attributed to the F&#ouml;hn effect, a well known feature of local weather systems in mountainous environments. It is usually a mechanism responsible for the warm dry wind which occurs to the leeward side of mountains or hills. At its simplest, the fohn principle can be thought of as the air precipitating its moisture on the hills and giving cloud free (and therefore sunny) weather on the lee side.
However, in approximately 1/10 of cases, it results in the 'lee-wave effect'. In these cases the rising air meets a resistance to its upward motion, which in turn forces the air to descend. Hence the air 'bounces' up and down. If moisture is present, then every time the air rises a lee-wave cloud is formed. These clouds are often lens or cigar shaped, at least in cross section. The undulations in air flow are standing waves and the cloud can thereby stay in the same position relative to the mountains. The winds too are particularly strong and gusty, where they descend.
In Ikka the fohn effect results from very strong winds emanating from the ice sheet, and as we were warned are preceded by a fairly rapid rise in temperature. In our case, the temperature rose to 16oC at night, when temps would normally be expected to be below zero, and were preceded in the late afternoon by the ominous cigar shaped clouds.
We were told that in the winter, the fjord is covered by a 60cm to 1m thick 'sheet' of ice. From our aerial photographs, this ice sheet is still very much in evidence during the spring, however there was no permanent ice in the fjord during our summer stay.
On the other hand the surrounding seas and the larger, less restricting fjords, were full of ice, which was coming from the summer thaw of the local glaciers. Our stay was not entirely ice free, however and we did get a couple of small bergs coming to visit us.
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