Jökull

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Jökull - 01.12.1985, Qupperneq 23

Jökull - 01.12.1985, Qupperneq 23
this would indicate (1) that, at least in Haelavík, the glacier had retreated behind the present coastline around or before 9500 BP, and this (2) in turn would suggest that the upper till at Haelavík may date from the Younger Dryas. Whether the lower till is also of latest Weichselian age or if it represents the Weichselian maximum can not be said. The Haelavík tephra The blackish Haelavík tephra (Fig. 12) first appears with a very sharp lower contact, in both lacustrine/ fluvial (section 3 at Haelavík) and eolian sediments (section 2). In the latter case, deposited as a low dune consisting almost entirely of tephra, its thickness is approximately 0.5 m. In both the lacustrine/fluvial and the terrestrial sediments it gradually disappears upwards in the sections. According to the reasoning in the preceding chapter the age of the lacustrine/fluvial sediments where the tephra appears is around 9000 yeárs or somewhat youn- ger. The tephra is basaltic, and its chemical and chrono- logical relationship to other tephras on Iceland and to tephra beds deposited as deep-sea sediments (e.g. Kel- I°gg et al. 1978, Ruddiman and Mclntyre 1981) and on land in western Norway (Mangerud et al. 1984) will be the scope of a special study. It is possible that the tephra can be found elsewhere on the Vestfirdir peninsula, and found in connection with dateable organic material it could constitute an important marker horizon. little ice age climate and glaci- ation Research history Thórarinsson (1969) outlined the climatic oscillations ln Iceland since the colonization in the 9th century AD. According to him, the Little Ice Age cooling began already in the early 13th century and culminated in the 18th and 19th centuries. He based his conclusions on a multidisciplinary study involving geological, archaeological and historical evidence. Studies of the 0/180 ratios in ice-cores from the Greenland ice sheet have yielded similar results (Dansgaard et al. 1975). Meteorological evidence. Regular meteorological observations in Iceland began in 1845, when an observation post was estab- hshed at Stykkishólmur (Fig. 1). Eythórsson (1949), summing up the observations, noted that the mean annual temperature there reached its minimum between 1859 and 1888, with +2.7°C (mean values for the periods 1901 — 1930 and 1931-1960 were +3.4°C and 4.2°C (Eythórsson 1949, M.Á. Einarsson 1976)). Thor- oddsen (1911) published annual mean temperatures for Stykkishólmur, and Adalvík on Hornstrandir, for 1874—1901. The mean for Stykkishólmur was then + 3.0°C (M28) and for Adalvík +1.4°C (M2). According to M.Á. Einarsson (1976) the mean annual temperature at Hornbjargsviti during the period 1931 — 1960 was 1.1°C lower than at Stykkishólmur. He noted that fluctuation trends of temperature at Stykkishólmur have been detectable all over Iceland. Thus it seems (1) that the annual mean temperature on Hornstrandir is 1.0—1.5°C lower than at Stykkishólmur, (2) that temperature fluctuations on Hornstrandir probably are roughly in phase with the rest of Iceland, so that (3) the Little Ice Age temperature minimum on Hornstrandir (at least for the period after 1845) should have been reached sometime between 1860 and 1890. However, it is not certain that the temperature minimum exactly coincided with the Little Ice Age maximum glaciation, as pre- cipitation fluctuations have to be taken into considera- tion too. We have no precipitation values from Horn- strandir covering this period. Glaciological evidence. On northern Vestfirdir there are two types of glaciers which can provide information on the Little Ice Age climate and glacier oscillations; (1) the Drangajökull ice cap and its outlet glaciers, and (2) the small cirque glaciers. (1) Drangajökull: The outlet glaciers from Dranga- jökull (Fig. 1) have been monitored since 1931, and found to be sensitive to small scale climatic variations (Eythórsson 1935, 1949, Thórarinsson 1943, Bout et al. 1955, John 1977b, Rist 1983). Eythórsson (1935) came to the conclusion that these outlet glaciers reached their maximum extent in historical time, probably even in post-Weichselian time, during two separate readvanced culminating around 1756 and 1840. According to John (1975, 1977b) the Reykjafjördur outlet glacier on the north side of Drangajökull reached its most advanced position around 1850 rather than around 1756. He recognized three moraines from the Little Ice Age, which he „dated“ to 1840-1850, 1860-1870 and 1914- 1920. (2) Cirques: Little is known about glacier growth in the cirques on Hornstrandir during the Little Ice Age. Thoroddsen (1906, 1911) reported that in 1886 and 1887 large snow fields and old firns were common close to sea level in Adalvík and Fljótavík, although he could not JÖKULL 35. ÁR 21
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