Zasięg czoła lodowca Tungnaár w czasie małej epoki lodowej na tle zlodowaceń Islandii : Extent of the Tungnaárjökull snout during the Little Ice Age against the glaciations in Iceland

• Main Authors: Andrzejewski, Leon, Molewski, Paweł
• Format: Text
• Language: Polish
• Published: Słupskie Prace Geograficzne, Nr 4 (2007), 35-43 2007
• Subjects: FOS Natural sciences; Jökulgrindur; Tungnaárjökull; Vatnajökull; glacier; Ice Sheet; Iceland
• Online Access: https://dx.doi.org/10.34858/spg.4.2007.003; https://spg.apsl.edu.pl/baza/wydawn/spg04/andrzejewski_molewski.pdf

W artykule zaprezentowano wyniki badań nad zasięgiem lodowca Tungnaár (stanowiącego zachodnią część lodowca Vatna) w okresie małej epoki lodowej na tle współ- czesnego stanu zlodowacenia Islandii. Obecnie lodowce pokrywają na Islandii 11 785 km2, co stanowi 11,4% powierzchni wyspy. Powierzchnia ta zmienia się w zaleŜności od bilansu lodu, który jest zdeterminowany przez czynnik geotermalny oraz warunki klimatyczne i fi- zjograficzne. Autorzy skorelowali istniejące w rejonie lobu Tungnaár formy i osady glacjalne i fluwioglacjalne, co umoŜliwiło wyznaczenie na jego przedpolu sześciu zróŜnicowanych stref morfogenetycznych. W okresie małej epoki lodowej zasięg lodowca Tungnaár był więk- szy niŜ współcześnie i zdeterminowany orografią podłoŜa lodowca i jego aktywnością. : The paper presents the extent of the Tungnaárjökull (western part of the Vatnajökull) dur- ing the Little Ice Age against the contemporary views over the glaciations of Iceland. In the Plio-Pleistocene period, i.e. between 3.3-0.7 Ma ago, nine glacial-interglacial cy- cles are distinguished on the area of Iceland. Each cycle lasted about 180 ka on average. It is assumed that five consecutive glacial-interglacial cycles, which lasted from 120 to 140 ka, took place on Iceland during the earlier 700 ka, i.e. in the Upper Pleistocene period. The ul- timate expansion of the ice sheet on the area of Iceland took place during the Vistulian (Weichselian) glaciation, which lasted here from 120 to 10 ka ago. The present morphology of Iceland is largely the effect of volcanic and glacial activity during the above mentioned pe- riod. The maximum of the Vistulian glaciation falls to 25-30 ka BP, and its decline proceeded in stages at the turn of the Late Glacial and Holocene (Fig. 1). Contemporary glaciers of Ice- land spread over 11,785 km2, which makes up 11.4% of the island’s total surface. They show diverse dynamics and ice balance, which is determined by the geothermal factor as well as climatic and physiographic conditions. Moreover, another characteristic feature of many Ice- landic outlet glaciers is their sudden surge-advance. The forefield of the Tungnaárjökull is located at the altitude of 700-900 m above sea level. It spreads from north to south for over 28 km, while its width ranges from about 1 km in the northern part to over 2.5 km in the middle and southern parts (Fig. 2). The snout of the glacier shows a lob character. The orography of the volcanic basement of the glacier’s fore- field, especially the NE-SW course of the Upper Pleistocene volcanic ridges, determines sig- nificantly both spreading and dynamics of the glacier’s snout. The analysis of the develop- ment and correlations of glacial and fluvioglacial forms/deposits as well as their relation to the volcanic relief became the basis for distinguishing six diverse morphogenetic zones at the Tungnaárjökull forefield (Fig. 2). During the Little Ice Age the extent of the Tungnaárjökull was much larger than contem- porarily and was predominantly determined by the orography of the volcanic substratum and the forefield of the glacier (Fig. 2). In the northern part of the forefield the layout of the vol- canic ridges, parallel to the glacier’s snout, limited its advance. Within the zone number 1 the snout of the glacier was 800 to 900 m to north-west from its contemporary location. In the zone number 2 and, partially, number 3, the glacier advanced over the volcanic ridge of the Jökulgrindur by 150-200 m, the extent of which was larger than the contemporary one by about 1,200-1,300 m. In the zone number 4, where the direction of the advance was concor- dant with the direction of the ridges of the volcanic substratum, the glacier’s extent was the largest. Its snout was located about 2,300 m to the west of its modern location. In the zone number 5, which is limited by the volcanic ridges perpendicular to its snout and found both under and at the forefield of the glacier, the extent of the glacier during the Little Ice Age was diverse and larger than the contemporary one by 1,200 m at the most. In the zone 6, however, where are no large orographic barriers found, the extent increased again up to about 1,400 m. : Nr 4 (2007): Słupskie Prace Geograficzne, 35-43