Jökull


Jökull - 01.12.1956, Page 12

Jökull - 01.12.1956, Page 12
papers as the variations of Svínafellsjökull— Skaf tafellsjökull): 1934-35 0 m 1935-36 - 10 „ 1936-37 O co 1 1937-45 o GO CM 1 1945-47 no measurements 1947-48 + 50 m 1948-49 + 20 „ 1949-50 - 45 „ 1950-51 - 7 „ 1951-52 - 4 „ 1952-53 + 7.5 „ 1953-54 - 23 „ 1954-55 - 32 „ 1955-56 O CM 1 ENTONNOIRS ON KVÍÁRJÖKULL. At the end of his paper Björnsson describes some peculiar features on the surface of Kvíár- jökull. These are circular or somewhat ellipse- shaped depressions, commonly 20—30 m broad and 6—8 m cleep with rather steep slopes and a flat bottom. In the bottom is a narrow water furrow. These depressions are founcl in great number on the relatively ílat southwestern part of the glacier tongue, W of the median moraine. I may here add that these depressions are visible on an aerial photo taken by P. Elannes- son May 28tli 1938 (published in Thorarinsson 1943, p. 31), which supports Björnsson’s state- ment that these depressions have existed at least two decades. Depressions of this type have been described from Gorner Glacier and some other glaciers in the Alps. They are also known from Malaspina Glacier (Alaska) ancl Tasman Glacier (New Zea- land). They have been especially studied on Gorner Glacier (Renaud 1936) where they are termecl entonnoirs. However, their formation seems not yet to be quite satisfactorily ex- plained. REDUCTION OF KVÍÁRJÖKULL SINCE AB. 1870.' The map fig. 7 is based on the Danish General Staff map of 1904 (sheet 87 Öræfajökull SA), the U. S. Army Service maps of 1950 (6018 I and 6018 IV), based on aerial photography 1945 and Á. Bödvarssons aerial photos of Sept. 15, 1945. The sections figs. 8 and 9 are based on the same maps. Tlie dash lines marking the exten- sion and thickness of the glacier ab. 1870 must be regarded as approximate. The extension of the glacier at that time must however have been practically the same as its maximum one in Postglacial Time. The following figures are based on the 1904 and 1950 maps. IvVÍÁRJ ÖKULL. Area below the 1100 m con- tour 1904 ............... 11.1 km2 Area below the 1100 m con- tour 1945 ............... 9.5 „ Total areal loss 1904—1945 . . 1.6 „ (14,5%) Frontal areal loss 1904—1945 . 1.0 „ (9.0%) Max. frontal recession 1904— 1945 .................... 0.55 km Average thinning along section C—D 1904-1945 ........... 60 m The average thinning below the present 200 m contour ab. 1870—1945 may be estimated 80— 10

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Jökull

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