Research Note Glacier mass balance investigations in the balance years 1984-85 and 1985-86 JON OVE HAGEN A N D OLAV LIESTOL Hagen, J . 0. & Liestel, 0. 1987: Glacier mass balance investigations in the balance years 1 9 8 4 8 5 and 198S86. Polar Research 5 n . s . , 261-265. As in previous years Norsk Polarinstitutt has carried out mass balance investigations on Storbreen and HardangerjOkulen in mainland Norway and on Breggerbreen and LovCnbreen in Svalbard. More than 20 years of measurements show that the glaciers both in mainland Norway and in Svalbard are retreating. Both in 1985 and in 1986 the glaciers in Norway had a negative net balance. A t Storbreen the mean annual net balance value 1949-86 is -0.30 m in water equivalents, while o n Hardangerj0kulen the mean value 1963-86 is -0.02 m . The two glaciers measured in Svalbard also had negative net balance in 1985 and in 1986. Both measured glaciers have had negative balance nearly all years since the measurements started in 1966. The mean value is close to - 4 0 g/cm2 or - 0 . 4 m on both. Jon Oue Hagen and Olau Liestol. Norsk Polarinsritutt, P . O . Box 158. 1330 Oslo Lufrhaun, Norrr.ap. Glaciers in Norway Storbreen Storbreen is situated in Jotunheimen in southern Norway. Mass balance measurements started in 1949. In 1985 the winter accumulation was measured in the beginning of May. The result was 120 g/cm2, which is 85% of the mean value since 1949. The ablation gave a summer balance of 160 g/cm’ which was close to the mean. The net balance result was -40 g/cm2 or -0.4 m water equivalents. In 1986 the winter accumulation measured in the beginning of June was only 105g/cm2, or 1.05 m in water eq., which is one of the lowest values that has ever been measured on this glacier, and it was only 77% of the mean value since 1949. The summer ablation was 137g/cm2 or 1.37111. The result was a negative net balance of -32 g/cm2 or -0.32 rn, while the mean has been -30g/cm2. The net balance result from 1986 is shown in Fig. 1. The equilibrium line was then 1770 m a.s.1. The cumulative net balance for the whole period 1949-1986 is then -1104g/cm2 or -11.04m of water layer over the whole glacier. The area of the glacier is 5.3 km2 so the total volume of ice shrinkage is 65 x 106m3. That means that the ice surface on average has lowered 12.3 m over the whole glacier and given an extra quantity of 1.5 x 106m3 water to the river from the glacier every year. A new glacier map in the scale 1 : 10,000 has been constructed from air photos taken in 1985. The former map was constructed in the same scale on the basis of photos from 1968. The volume change during these 17 years could then be cal- culated. The mean annual shrinkage of the glacier surface was 0.31 m, which is very close to the measured net balance value. Hardangerjv kulen Hardangerjekulen is situated south and west of Storbreen. Both the winter and the summer bal- ance on Hardangerjekulen usually have the higher values. Mass balance has been measured every year since 1963. In 1985 the winter balance was 140g/cm2 or 1.40 m water eq., which is7476 of the mean winter accumulation of 1.90 m. The summer balance was calculated to 190 g/cm2, which is very close to the mean ablation. The result was a net balance of -50g/cm2 or -0.50 rn water eq. The winter accumulation in 1986 was less than normal too, 1.54m, which is 80% of the mean 262 Hagen & Liestd Storbreen 1985 _ _ ~ m a s I i Fig. 1. Net mass balance at Storbreen 1985/86 in relation to height above sea level. Table I . Spcctfic mass balance in water equivalents (m) for Austre Br~ggerbreen and Midtre Lovtnbrcen 1967-1986 Year Austre Brdggerbreen Midtre Lovenbreen b, h. b, b, b. 1966-67 1 9 6 7 4 1968-69 1969-70 1970-71 1971-72 1972-73 197.3-74 1974-75 1975-76 1976-77 1977-78 1978-79 1979-80 1980-81 1981-82 1982-83 1983-84 1984-85 1985-86 1967-86 0.77 0.57 0.37 0.65 0.95 0.74 0.75 0.78 0.72 0.76 0.75 0.77 0.7s 0.46 0.64 0.70 0.69 0.93 0.98 0 71 0.40 1.42 0.67 1.33 0.91 1.23 1.26 0.82 1.67 1.09 1.17 0.87 1.31 1.48 1.27 1.01 0.68 0.97 1.42 1.48 1.30 1.17 -0.65 -0.10 -0.93 -0.54 -0.58 -0.31 -0.08 -0.92 -0.31 -0.45 -0.11 -0.56 -0.71 -0.52 -0.55 -0.04 -0.27 -0.73 -0.55 -0.32 -0.46 0.48 0.41 0.36 0.70 0.98 0.82 0.70 0.83 0.75 0.80 0.81 0.80 0.83 0.51 0.66 0.75 0.74 0.98 1.06 0.74 0.51 1.25 0.89 1.16 1.20 1.59 1 .w 1.10 0.84 1.29 1.46 1.26 0.97 0.64 0.92 1.42 1.46 1.27 1.11 0.84 -0.03 -0.84 -0.53 -0.46 -0.22 -0.02 -0.89 -0.21 -0.35 -0.04 -0.48 -0.66 -0.43 -0.46 0.02 -0.17 -0.6X -0.48 -0.21 -0.37 Glacier mass balance investigations 263 Brcggerbreen m a s I 1600 1984 85 Loverbreen m a s I I tm 2- ?I: ‘.O 1.1 q: ~ n w a i e r eq 22 ~ m 0 1.0 20 mwaier eq Fig. 2. Mass balance variations in relation t o height in 1984/85 on Austre Breggerbreen and Midtrc Lovinhreen. 61 ogyerbreen Lovenl reen ma.s.1 rea disirihution I I I I I I I 2.0 1.0 10 7.0 mwaler eq m - 1.0 0 1.0 20 mwaler eq 11 I , Fig. 3. Mass balance variations in relation t o height in 1985/86 on Austre Breggerbreen and Midtre Lovtnbreen. 264 Hagen & Liest01 value. The summer melting was also less than normal, and total ablation was 1.60 m . T h e result was a net balance close to zero, -0.06 m . The cumulative net balance of the observation period 1963-86 is -0.50 m . Hardangerjskulen is thus nearly in climatic equilibrium. Glaciers in Svalbard Brmggerbreen During the winter 1984/85 the snow accumulation was about 130% of the mean value of the obser- a slightly higher deficit t h a n t h e average for the previous 18 years. T h e following winter 1985/86 also had heavy snowfall. The winter balance was 0.98 m , which is the highest winter precipitation since the regis- trations started in 1967, 140% of t h e mean. But the summer of 1986 was warm, thc ablation was 1.30m, and thus there was o n e more year of negative net balance, -0.32 m. T h e cumulative net balance since 1967 then becomes -9.23m (see Table 1). T h e distribution of snow accurnu- lation in 1985-86 is shown in Fig. 5 , and t h e mass balance variations related to height can b e seen in Fig. 3. , , Fig. S. Distribution of the snow accumulation on Br0g- 0 5 0 0 1000 h4 Fig. 4 Distribution of the snow accumulation on Lo\Cnbreen in 1985;86 vation period 1967-84, giving a specific winter balance b, = 0.93 m , measured in water equiv- alents. The following summer was warmer than normal and the specific summer balance was b, = 1.48 rn. The result was a net balance b, = -0.55 m , which in spite of the great snowfall was Glacier mass balance investigations 265 Based on air photos from 1977 a glacier map was constructed in the scale 1 : 20,000 with counter interval 10 m. One of the stakes was plotted on the map and surveyed in 1985. The vertical dif- ference of the glacier surface was then 5.20111. The cumulative net balance during the same period was 4.95 rn in water equivalents, which is 5.50m of ice. The direct measurements on the map thus agreed well with the annual mass bal- ance measurements. Loven breen Due to a little higher average elevation LovCn- breen usually has slightly higher winter accumu- lation and a slightly lower ablation in the summer. Thus the net balance usually is a little less negative than on Br~ggerbreen. These two years have been no exception. In 1985 the winter balance was 0.98 m and the summer balance was 1.46 m , which resulted in a negative net balance of -0.48m. Both the accumulation and the ablation were about 30% above the mean values. In the snow-rich winter of 1986 the accumu- lation was 1.06m, but in the following warm summer the ablation was 1.27 m. Accordingly the net balance was -0.21 m (Figs. 2, 3 and 4). The mean net balance on LovCnbreen is then -0.37m, while it is -0.46m on BrQggerbreen (Table 1). The equilibrium line during these 20 years of measurements is then a little above 400m a.s.l., which is about 100m above an equilibrium line that would keep the net balance at zero.