Logo der Bayerischen Akademie der Wissenschaften

Geodesy and Glaciology

Menu

Mass balance of the Vernagtferner

The following graph shows the mass balance of Vernagtferner summed up since the start of regular observations in 1964.

The mass balance of the glacier is determined on the basis of measurements of snow accumulation and ice ablation during spring and autumn inspections. The data are reported to the World Glacier Monitoring Service and published in the Global Glacier Change Bulletin along with data from more than 120 other glaciers. The Vernagtferner is one of currently about 40 reference glaciers whose long and reliable time series form the basis of an observation network supporting the United Nations Framework Convention on Climate Change.

In principle, the mass balance of a glacier can be compared to maintaining a current account: The total amount of the glacier’s snow and ice at the beginning of the financial year represents the account’s current “credit” balance. The accumulation corresponds to the sum of the total annual income and is counted positively. The ablation, on the other hand, corresponds to the sum of the expenses and has a minus sign. The sign (plus or minus) of the balance between debits and credits determines whether the glacier has gained or lost mass. Accordingly, changes to the total amount are analogous to the new account balance. However, there is no overdraft facility with a glacier. Once the balance reaches zero, the glacier has disappeared.

Mass balance stripes

Along the lines of the Warming Stripes (see also here), which show temperature changes since the start of meteorological observations, mass balance stripes for Vernagtferner starting in 1964 are shown here. The stripes are meant to visualize the changes at first glance - without any numbers. Blue stands for mass increase, while red means mass loss. The colour scale is given by the extreme year 2003.

Mass balances 1964 - 2020

The following table shows the main parameters of the mass budget of the Vernagtferner for the budget years 1964/1965 to 2019/2020. The mass balance column is color-coded: here, too, blue shades correspond to a positive mass balance (mass increase) and red shades correspond to a negative mass balance (mass loss).

Year Area [km2] ELA AAR Balance [mm] Data Map
1964/65 9,52 2946 92 751    
1965/66 9,52 2940 93 632    
1966/67 9,52 3015 70 83    
1967/68 9,52 2995 86 301    
1968/69 9,46 3153 56 -307 Tabellen 1968/69  
1969/70 9,46 3113 61 -224 Tabellen 1969/70  
1970/71 9,46 3155 39 -424 Tabellen 1970/71  
1971/72 9,46 3028 79 137 Tabellen 1971/72  
1972/73 9,30 3185 43 -460 Tabellen 1972/73  
1973/74 9,30 2999 81 230 Tabellen 1973/74  
1974/75 9,30 3025 80 171 Tabellen 1974/75  
1975/76 9,30 3036 75 50 Tabellen 1975/76  
1976/77 9,30 2984 88 352 Tabellen 1976/77  
1977/78 9,55 3004 85 288 Tabellen 1977/78  
1978/79 9,55 3059 73 44 Tabellen 1978/79 Analyse  1978/79 107kb
1979/80 9,55 3027 77 140 Tabellen 1979/80  
1980/81 9,55 3101 72 -55 Tabellen 1980/81  
1981/82 9,35 3418 24 -845 Tabellen 1981/82  
1982/83 9,35 3304 25 -537 Tabellen 1982/83  
1983/84 9,34 3063 71 20 Tabellen 1983/84  
1984/85 9,34 3102 61 -112 Tabellen 1984/85  
1985/86 9,34 3291 19 -808 Tabellen 1985/86  
1986/87 9,34 3143 55 -290 Tabellen 1986/87  
1987/88 9,09 3230 39 -497 Tabellen 1987/88  
1988/89 9,09 3170 50 -312 Tabellen 1988/89  
1989/90 9,09 3283 32 -568 Tabellen 1989/90  
1990/91 9,09 3630 + 8 -1079 Tabellen 1990/91  
1991/92 9,09 3268 22 -858 Tabellen 1991/92  
1992/93 9,09 3225 37 -472 Tabellen 1992/93  
1993/94 9,09 3630 + 22 -1028 Tabellen 1993/94  
1994/95 9,09 3226 39 -398 Tabellen 1994/95  
1995/96 9,09 3225 40 -413 Tabellen 1995/96  
1996/97 9,07* 3220 41 -487 Tabellen 1996/97 Analyse  1996/97 204kb
1997/98 9,07 3280 30 -1003 Tabellen 1997/98 Analyse  1997/98 204 kb
1998/99 8,68 3097 56 -108 Tabellen 1998/99 Analyse  1998/99 212kb
1999/00 8,68 3123 48 -287 Tabellen 1999/00 Analyse  1999/00 212kb
2000/01 8,68 3128 47 -224 Tabellen 2000/01 Analyse  2000/01 177kb
2001/02 8,68 3122 53 -266 Tabellen 2001/02 Analyse  2001/02 214kb
2002/03 8,53 3600 + 0 -2133 Tabellen 2002/03 Analyse  2002/03 214kb
2003/04 8,36 3205 34 -407 Tabellen 2003/04 Analyse  2003/04 217kb
2004/05 8,36 3224 40 -523 Tabellen 2004/05 Analyse  2004/05 217kb
2005/06 8,36 3261 25 -882 Tabellen 2005/06 Analyse  2005/06 217kb
2006/07 8,17 3281 19 -966 Tabellen 2006/07 Analyse  2006/07 217kb
2007/08 8,17 3289 17 -843 Tabellen 2007/08 Analyse  2007/08 253kb
2008/09 8,17 3347 14 -959 Tabellen 2008/09 Analyse  2008/09 340kb
2009/10 7,92 3246 23 -680 Tabellen 2009/10 Analyse  2009/10 207kb
2010/11 7,92 3261 19 -955 Tabellen 2010/11 Analyse  2010/11 228kb
2011/12 7,55 3280 15 -1155 Tabellen 2011/12 Analyse  2011/12 228kb
2012/13 7,55 3148 35 -425 Tabellen 2012/13 Analyse  2012/13 342kb
2013/14 7,36 3127 57 -144 Tabellen 2013/14 Analyse  2013/14 342kb
2014/15 7,31 3241 15 -1268 Tabellen 2014/15 Analyse  2014/15 357kb
2015/16 7,16 3236 20 -781 Tabellen 2015/16 Analyse  2015/16 357kb
2016/17 7,08 3293 12 -1335 Tabellen 2016/17 Analyse 2016/17
2017/18 6,90 3306 9 -1419 Tabellen 2017/18 Analyse 2017/18
2018/19 6,90 3344 23 -929 Tabellen 2018/19 Analyse 2018/19
2019/20 6,85 3275 24 -824 Tabellen 2019/20 Analyse 2019/20

In addition to the main parameters of the mass budget, the table contains the total area of the glacier on which the analysis is based, the equilibrium-line altitude (ELA), the accumulation area ratio (AAR) and the specific net mass balance in mm water equivalent. In column Data the numbers for the different glacier parts. A legend (in German) can be found here. The analyses were carried out by Oskar Reinwarth, Ludwig Braun and Markus Weber. From the 2003/04 budget year onwards, Christoph Mayer has carried out the analyses.

To illustrate the development over the observation period, the specific mass balance values (balance column) are colour-coded. Negative values (red colours) mean a loss of mass, positive values (highlighted in shades of blue) mean a mass gain of the glacier. It can be seen that the glacier - after a weak growth period in the mid-1970s - has been steadily losing mass since the early 1980s. In addition, there has been a clear increase in mass budget years with extreme mass losses (more than 1 m of water equivalent across the entire glacier) over the last decade.

Total area of the glacier

The extent of the glacier area is an important reference value for assessing the mass balance. However, its change is not necessarily linked to the mass changes directly. Since ice masses are also transported dynamically, an increase or decrease of the ice mass does not have a direct effect on the area. Nevertheless, changes in the glacier boundaries occur over time, especially in peripheral areas.

The extent of the glacier area indicated in the table is not, however, always the current area at the end of the budget year, but the area at the time of cartographic mapping. It is this latter area that forms the basis of the analysis. This so-called contour plot cannot be updated every year, as aerial images must be available for this purpose.

Equilibrium Line Altitude (ELA)

The equilibrium line altitude (ELA) is a hypothetical variable determined by the height distribution of the specific net balance. It is the altitude at which the mass balance in the budget year in question is balanced or changes its sign. This contour line divides the glacier into two areas: above are the areas with a net gain in mass, below are the areas with mass loss. The mean height of the equilibrium line at the Vernagtferner is 3066 m, which corresponds to the altitude range in which the glacier area has the largest extent. If the current equilibrium line is above the long-term mean value, the total mass balance of the glacier is negative. If it is lower, mass growth can be observed. As this is a hypothetical parameter, the ELA can even be located above the ridge in extreme cases (e. g. 1993/94 and 2002/2003). During these years, the glacier loses mass over its entire elevation range.

AAR (Accumulation Area Ratio)

AAR stands for accumulation area ratio and indicates the ratio of the accumulation area to the total area as a percentage. As a rule of thumb, the mass budget of a glacier is balanced when the ratio of the size of the accumulation area to that of the ablation area is about 2:1. In this case, the AAR is 66%. For higher values, an increase in mass is expected, for lower values, a decrease in mass.