INSTITUTIONEN FOR NATURGEOGRAFI
OCH KVARTARGEOLOGI
DETER
MIN
I
N
G GLACIER MASS BALANCE
FROM SUR
ROG
ATE VARIABLES
A
CASE STUDY ON STOR
G
LACIAREN USIN
G
ELA
AND
AAR
DIRK-SYTZE KooTSTRA
EXAMENSARBETE I NATURGEOGRAFI
5TOCKHOLMS UNIVERSITET
EXAMENSARBETE
N-57
Institutionen for naturgeografi och kvartargeologi
Stockholms universitet
Denna uppsats utgor Dirk-Sytze Kootstras examensarbete i naturgeografi vid Institutionen for
naturgeografi och kvartargeologi, Stockholms universitet. Examensarbetet omfattar 20 poang
( ca 20 veckors heltidsstudier). Handledare har varit docent Regine Hock, Institutionen for
naturgeografi och kvartargeologi, Stockholms universitet. Examinator for examensarbetet har
varit professor Arjen Stroeven, Institutionen for naturgeografi och kvartargeologi, Stockholms
universitet
F orfattaren ar ens am ansvarig for uppsatsens innehall.
Stockholm, den 25 januari 2005
Lars-Ove Westerberg
Studierektor
Abstract
The purpose of this report is to give an overview on methods using surrogate variables to obtain glacier mass balance and to test one of the methods on Storglaciaren, a small valley glacier in
northern Sweden. Surrogate variables used for detecting mass balance are meteorological
variables like temperature and precipitation, variables related to snowlines on the glacier like
equilibrium line altitude (ELA) and accumulation area ratio (AAR), and albedo of the glacier surface. The shortcoming of all methods using surrogate variables is that they need calibration with mass balance data. The stability of parameters in the obtained relationships is unknown and it is well possible that parameter values will change under a different climate. The obtained relationships between the surrogate variables and mass balance are site-specific. Therefore testing
of the methods on more glaciers is needed. A method was tested on Storglaciaren The tested
method (Dyurgerov 1996) uses ELA and AAR as surrogates. The method consists of substitution of long-term observations of annual mass balance (B0) and ELA or AAR by transient values of
mass balance and ELA or AAR measured repeatedly during the ablation season. The special thing about this method is the use of transient measurements which makes it possible to obtain a relationship between mass balance and ELA or AAR within one melt season. Detailed fieldwork, including mapping of mass balance and AAR, was carried out on Storglaciaren during the
summer of 2004. Both long-term and transient relationships between mass balance and AAR or ELA have a strong linear correlation. However the relationship obtained from transient values from the melt season of 2004 was significantly different from the long-term relationship of mass
balance and AAR. Various analyses indicate that this deviation was not caused by errors in the transient mass balance calculations or that 2004 was an abnormal year. It remains unclear why the
mass balance-AAR relationships would be different for the transient and the long-term cases. There does not seem to be an obvious physical reason for the different relationships.
