Journal of Glaciology, Vol. 34, No. 118, 1988 IS THE LONGITUDINAL PROFILE OF STORGLACIAREN, NORTHERN SWEDEN, IN BALANCE WITH THE PRESENT CLIMATE? By PER HOLMLUND (Department of Physical Geography, University of Stockholm, S-106 91 Stockholm, Sweden) ABSTRACT. The main perturbation in the mass balance of Storglaciaren during the twentieth century was caused by a sudden 1°C increase in the summer mean temperature around 1910. Later perturbations of the climate have been of minor importance in relation to the mass balance. Annual field surveys suggest that the mass budget on Storglaciaren has been in near balance for the last 15 years. Because of this major step-like change, we can establish the validity of theoretical models giving response times for Storglaciaren of the order of 50 years. According to these models, Storglaciaren could by now have reached a profile in balance with the present climate. To study this problem, the emergence velocity was calculated and compared with the net balance. The result shows that the emergence velocity either balances or exceeds the net balance for the entire tongue except for the lowermost part, where it decreases to about half of the net balance. A slight further recession of the front position would thus be expected with today's climate. Calculated balance velocities also suggest that most of the present profile is close to a steady-state profile, if the mean annual sliding velocity is about 50% of the surface velocity. Lower sliding velocities would imply a thickening 425 .... . .... :.: .. .... . .. .... of the tongue and a thinning of the accumulation area during years of balanced mass budget. INTRODUCTION The purpose of this paper is to estimate whether or not the profile of Storglaciiiren is in balance with the present climate. The basic material for the study is the 42 year record of the mass balance of Storglaciaren. Prior to 1945, when the mass-balance study was initiated, only frontal position data were available. These show that the glacier reached a maximum forward position around 1910, followed by a mass loss and a retreat of the front caused by a 1°C increase in summer mean temperature (Holmlund, 1987). Since the mid-1970s, Storglaciaren has had a near-balanced budget and the recession velocity of the front has now (in the 1980s) declined to almost zero (Fig. I). A study of maps shows that the glacier became thinner at the tongue but thicker in its upper accumulation area between 1959 and 1980 (Holmlund, 1987, fig. 5). This paper will therefore deal mainly with the lower part of the glacier, in an attempt to estimate the state of today's profile. As discussed below, 200 StorglacHiren E .......... .. " - ... ..: . .:: ...... c 0 2 375 0> o x ............. Cl> ......... ... " ... "' ...... Cumulative mass change ... ... '--, Front position (scale to left) (scale to right) t-- Cl co , •••••• ••• ""\, Q) "''''' .::: ro '" -'-_ -400 '§ -'--, c ' ... ----, .2 325 300 1870 1890 1910 1930 Year 1950 1970 '--'- o c. -600 C o U: 1990 Fig. 1. Cumulative mass change of Storglaciiiren, 1878-1987. The dOLL ed line indicates calculated mass balance based on regression analysis. using temperature data from the met eorological sIGtion ill Karesuando, northern Sweden ( Holmlund, 1987). The solid line is the mass - balance data measured ill the field . The dashed line shows change (m) in the frontal position of the glaci er relative to the first survey in 1897 ( Schytt , 1979). 269 https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0022143000007000 Downloaded from https://www.cambridge.org/core. IP address: 168.151.112.56, on 24 Sep 2017 at 12:44:01, subject to the Cambridge Core terms of use, available at