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 39 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 balances 1964 - 2017

The following table shows the main parameters of the mass budget of the Vernagtferner for the budget years 1964/65 to 2016/17. The mass balance column is color-coded: 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] Tables Analysis

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 als PDF-Datei

Analyse  2009/10 207kb

2010/11

7,92

3261

19

-955

Tabellen 2010/11 als PDF-Datei

Analyse  2010/11 228kb

2011/12

7,55

3280

15

-1155

Tabellen 2011/12 als PDF-Datei

Analyse  2011/12 228kb

2012/13

7,55

3148

35

-425

Tabellen 2012/13 als PDF-Datei

Analyse  2012/13 342kb

2013/14

7,36

3127

57

-144

Tabellen 2013/14 als PDF-Datei

Analyse  2013/14 342kb

2014/15

7,31

3241

15

-1268

Tabellen 2014/15 als PDF-Datei

Analyse  2014/15 357kb

2015/16

7,16

3236

20

-781

Tabellen 2015/16 als PDF-Datei

Analyse  2015/16 357kb

2016/17

7,08

3282

20

-1297

Analyse 2016/17

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. 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 (yellow to orange to red) mean a loss of mass, positive values (highlighted in shades of blue) mean a mass gain of the glacier. The values highlighted in shades of green are largely balanced, i.e. the ice mass of the glacier remains constant. Years with extreme mass losses (more than 800 mm) are highlighted in red. 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 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.