CHAPTER
19
Norway
Liss M. Andreassen, Frank Paul, and Jon Endre Hausberg
ABSTRACT
The Norwegian Water Resources and Energy
Directorate (NVE, Norges vassdrags- og energidirektorat) has initiated glacier mapping in mainland Norway using band ratio thresholds applied to
Landsat imagery. The method works well when
applied to glaciers having sparse debris cover. A
larger challenge has been the interpretation and
identification of individual glaciers and linking
the new inventory to previous inventories that use
different drainage divides. Assessing area changes
between repeat inventories required much manual
work and glaciological expert knowledge. The
amount of seasonal snow is a critical point when
selecting satellite scenes for a new glacier inventory
and for area change assessments. The observed glacier area changes differ between two study regions
in Norway. Whereas a selection of 300 glaciers in
the Svartisen region had an overall area change
from 1968 to 1999 close to zero, the area reduction
in Jotunheimen was 10% (4% per decade) from
1980 to 2003.
19.1
INTRODUCTION
Glaciers cover nearly 1% of the total land area in
mainland Norway. They have importance for
hydropower production, climate research, tourism,
but are also a source of natural hazards. In particular, glacier influence on river discharge and hydropower production has resulted in an extensive
glacier measurement record in Norway. Monitoring
of Norwegian glaciers includes field measurements
of glacier mass balance and length changes as well
as overall surveys from aerial and spaceborne
imagery to create glacier inventories.
The Norwegian Water Resources and Energy
Directorate (NVE) is the regional GLIMS center
for mainland Norway. To gain an updated overview of the present state of glacier cover and glacier
changes since the previous inventories, NVE started
mapping present glacier extent using Landsat
imagery within the framework of the GLIMS initiative. In this chapter we present results of this work
and demonstrate how the new Landsat-derived
glacier outlines in combination with topographical
maps were used to quantify glacier changes.
19.2
REGIONAL CONTEXT
The glaciers in mainland Norway are found in highmountain regions in both southern and northern
parts of the country (Fig. 19.1). Previous inventories report a total of 2,113 glacier units (1,627
glaciers) covering an area of 2,609 km 2 (Østrem
et al. 1988). The largest ice masses in Norway are
428
Norway
Figure 19.1. (Left) Map of Norway showing the location of the Landsat images used in the new glacier inventory
for Norway with the two scenes presented in this chapter shaded in gray (S ¼ Svartisen/Blåmannsisen and
J ¼ Jotunheimen). Glaciers are shaded in blue. (Right) Mean annual precipitation of Norway (mm) between
1961 and 1990. Dataset delivered from http://www.senorge.no/
ice caps (or plateau glaciers) with Jostedalsbreen
(488 km 2 ) being the largest contiguous ice mass in
mainland Norway as well as in mainland Europe
(Fig. 19.2). Other common glacier types in Norway
are cirque, mountain, and valley glaciers, which are
typical glacier types in Jotunheimen, the highest
elevated region in Norway (Fig. 19.3).
The long coastline of Norway and the rugged
topography strongly influence Norway’s climate,
and climate conditions vary greatly within the
country. Whereas temperature decreases from
south to north due to increasing latitude, precipitation decreases from west to east due to the shading
effect of coastal mountains (Fig. 19.1). Mean
equilibrium line altitude (ELA) thus increases with
distance from the western coast and decreases
from south to north (Østrem et al. 1973, 1988).
The strong gradient of precipitation from west to
east is also confirmed by long-term observations
of mass balance along a west–east profile in southern Norway. The observations reveal a clear gradient in mean summer and winter balance, with
maritime glaciers located closer to the west coast
having a much higher mass turnover than those
located in drier continental regions (Andreassen
et al. 2005).
19.2.1 Glacier observations
The first reliable observations of glaciers in Norway
date from the first half of the 18th century when
advancing glaciers caused serious damage to several
farms (for an overview see Hoel and Werenskiold
1962). Systematic observations of Norwegian
glaciers started around 1900, when glacier length
change measurements were initiated (e.g., Øyen,
1906). The first mass balance investigations in Norway began at Storbreen in Jotunheimen in spring
1949 (Liestøl, 1967). In the 1960s, systematic mass
balance studies were initiated at selected additional
glaciers and a glacier division was established at
NVE to investigate the contribution of glaciers to
runoff in connection with the planning of hydropower production. The mass balance and length
change measurements as well as other glaciological
investigations are published in annual reports by
NVE (e.g., Kjøllmoen et al. 2008). Photographic
monitoring of glaciers provides additional and
Regional context 429
Figure 19.2. Red, green, blue (RGB) composite of bands 5, 4, 3 of a Landsat ETMþ scene from 2006 showing the
Jostedalsbreen ice cap in southern Norway (N ¼ Nigardsbreen). Figure can also be viewed as Online Supplement
19.1.
valuable information about recent glacial changes
(e.g., Winkler et al. 2009).
Cartographic and remote-sensing methods have
also been used to monitor glaciers, both to obtain
detailed maps of mass balance glaciers and to calculate geodetic mass balance (e.g., Kjøllmoen and
Østrem 1997, Andreassen et al. 2002, Geist et al.
2005). The first satellite images of glaciers in Scandinavia were taken in 1972 by the Multispectral
Scanner (MSS) on board Landsat 1. The obtained
images were suitable for mapping the transient
snow line (TSL), and the TSL at the end of the melt
season was used as a proxy for net balance (Østrem
1975, Østrem and Haakensen 1993).
19.2.2 Glacier changes
Most Norwegian glaciers reached their Little Ice
Age (LIA) maximum extent in the 18th century
(e.g., Hoel and Werenskiold 1962, Grove and
Battagel 1983, Matthews 2005). Since then all
glaciers have retreated, although several intermittent periods of readvances have occurred, the latest
in the 1990s after a period of mass surplus on
coastal glaciers (see overviews in Andreassen et
al. 2005, Nesje et al. 2008). Retreat was particularly
strong in the 1930s. As an example, Storbreen in
Jotunheimen has lost about 40% of its length and
25% of its area since its LIA maximum extent at
about 1750 (Fig. 19.4). Mass balance investigations
reveal that maritime glaciers accumulated a large
mass surplus between 1962 and 2000, while continental glaciers with a smaller mass turnover had a
mass deficit over the same period. Between 1989
and 1995 all monitored glaciers had a transient
mass surplus except for Langfjordjøkelen, the
northernmost glacier in the network. This mass
surplus was caused mainly by an increase in winter
430
Norway
Figure 19.3. RGB composite of bands 5, 4, 3 of a Landsat TM scene from 2003 showing the glaciers in Jotunheimen in southern Norway (S ¼ Storbreen).
precipitation, which is closely linked to the positive
North Atlantic Oscillation (NAO) index in this
period (e.g., Hurrell 1995, Rasmussen et al. 2007).
Since 2000, all monitored glaciers had a net mass
deficit, with negative net balances for all glaciers in
2002, 2003, and 2006 due to a combination of
higher summer ablation and lower winter accumulation than usual. In 2005 and 2007, however,
maritime glaciers in southern Norway had again a
positive net balance. Estimates using recent climate
scenarios have shown that predicted warming will
have significant implications for Norwegian
glaciers, and many glaciers are projected to disappear or be greatly reduced in volume in the next 100
years (Nesje et al. 2008). Particularly sensitive are
glaciers with a flat accumulation area as outlets
from ice caps, such as Nigardsbreen (Oerlemans
1997; for location see Fig. 19.2N) and Hardangerjøkulen (Giesen and Oerlemans 2009).
19.2.3 Previous glacier inventories
Previous detailed inventories of the glaciers in Norway were based on vertical aerial photos and topographical maps. Inventories were compiled in the
1960s of southern Norway (Østrem and Ziegler
1969) and in early 1970s of northern Scandinavia
(Østrem et al. 1973). A second glacier inventory for
southern Norway was completed in the late 1980s
(Østrem et al. 1988). The inventories consist of
tabular data and sketch maps displaying all identified glaciers. The inventory tables are available
digitally, but not the glacier outlines from the
inventories.
19.2.4 Digital glacier outlines from
topographical maps (N50)
Digital data (contour lines, lakes, rivers, glacier
outlines) from the main topographic map series of
Norway at the scale 1:50,000 (N50) assembled by
the Norwegian mapping authorities (Statens kartverk) are available for all of Norway and were used
as background data for analyses and for assessing
area changes. The N50 maps are based on aerial
photography, and the date of the maps varies for
each region. The glacier outlines from N50 do not
necessarily differentiate between glaciers and
(perennial) snowfields, so snow ridges outside the
glaciers are often included in the glacier areas when
they have direct contact to them.
Methodology (derivation of glacier outlines from Landsat)
431
Figure 19.4. Orthophoto showing Storbreen in Jotunheimen in 2004 and the retreat of the glacier since its
maximum Little Ice Age extent (LIA). The 2003 outline is derived from a Landsat TM image.
19.3
METHODOLOGY (DERIVATION
OF GLACIER OUTLINES FROM
LANDSAT)
19.3.1 Selection of Landsat scenes
Successful mapping of glacier outlines from optical
remote-sensing data requires cloud-free scenes from
the end of the ablation period that have been
acquired in a year without snow outside the perimeters of glaciers (e.g., Raup et al. 2007, Racoviteanu et al. 2009). Hence, one of the major
challenges in Norway is to find appropriate satellite
scenes for glacier mapping due to the frequent cloud
cover at the end of the ablation period (August/
September). In addition, persistent seasonal snowfields considerably reduce the number of appropriate scenes as snow hinders clear glacier
identification. As an example, it took 22 years
before Landsat 5 finally acquired a near-perfect
scene for glacier mapping of the Jostedalsbreen
ice cap in September 2006 (Fig. 19.2). In recent
years, however, a selection of Landsat scenes with
satisfactory conditions for glacier mapping has
been chosen for the GLIMS work in Norway
(Fig. 19.1). The scenes have been used to compile
a new glacier inventory of Norway and provide
Norwegian glacier outlines to the GLIMS glacier
database. Data from the first two processed scenes
covering the Jotunheimen and Svartisen region
were included in the GLIMS database in 2007. In
this contribution we focus on the results from these
two scenes, a Landsat 7 ETMþ from September 7,
1999 covering Svartisen and a Landsat 5 TM scene
from August 9, 2003 covering Jotunheimen (Fig.
19.1). The scenes were delivered by Norsk satellittdataarkiv (Norwegian Satellite Data Archive) and
were already orthorectified. The quality of orthor-
432
Norway
Table 19.1. Landsat scenes used for glacier mapping and change analysis in this chapter. RMS error is given in
pixels (30 m cell resolution).
Region
Path/Row
Date
Sensor
Delivered by
Cloud
(%)
CP/GCP
RMS xy
Jotunheimen
199/17
August 9, 2003
L5/TM
Norsk satellittdataarkiv
0
14
0.64
Svartisen
199/13
September 7, 1999 L7/ETMþ Norsk satellittdataarkiv
0
13
0.50
ectification was tested by the authors using 13–14
independent check points (CPs) which revealed high
quality, the resulting RMSE of the CPs was only
0.50–0.64 pixel (pixel size 30 m) (Table 19.1). Both
scenes had appropriate snow and cloud conditions
for glacier mapping; the scene from 2003 had even
near-excellent snow conditions (i.e., nearly no seasonal snow outside the perimeters of glaciers).
19.3.2 Glacier-mapping methods
In a pilot study in the Jotunheimen region the
applicability of standard glacier-mapping methods
were tested using thresholded ratio images from the
raw digital numbers of bands TM3/TM5 and TM4/
TM5 (Bayr et al. 1994). Glacier outlines obtained
using these methods have previously been reported
as accurate for debris-free glaciers (Albert 2002,
Paul et al. 2002, Paul and Kääb 2005). The derived
outlines from Jotunheimen were compared with a
RGB composite of the Landsat image from 2003 and
with digital orthophotos from 2004 to find the most
suitable method in this region (Andreassen et al.
2008). Ratio images of TM3/TM5 gave the best
results. In Fig. 19.5 the good quality of the automatic
method is illustrated for Hellstugubreen (Jotunheimen), where orthophotos from 2004 showed
precise agreement with automatic mapping (the
Landsat image and orthophotos were taken one year
apart, during which time the front terminus of Hellstugubreen retreated 5 m). An additional threshold
in ETM band 1 was used for the Svartisen scene to
improve the mapping of glacier ice in cast shadow as
was previously applied for Baffin Island (Paul and
Kääb 2005). In the Blåmannsisen region the method
successfully mapped glacier boundaries even under
Figure 19.5. Mapped glacier outlines from the Landsat TM image from 2003 using a thresholded band ratio image
(TM3/TM5) for a subset in the Jotunheimen region. (Left) Outlines with the Landsat image in the background.
(Right) Outlines with an orthophoto from 2004.
Case studies and special topics
difficult conditions like bare ice in cast shadow under
thin cirrus clouds (Paul and Andreassen 2009). For
both scenes we also applied a median filter (3 3
kernel) to the classified image to reduce noise in
shadow and to remove isolated pixels. However,
the filter also closes isolated gaps (e.g. due to rock
outcrops or a thin medial moraine) and reduces the
size of small glaciers to some extent (Paul et al. 2002,
Paul and Kääb 2005). Very few glacier outlines had
to be corrected for debris cover in both regions.
Greater effort, however, was required for correction
of lakes that were wrongly classified as glaciers, a
well-known problem when using the 3/5 ratio (Paul
and Kääb 2005, Raup et al. 2007). Corrections were
also applied to a few glaciers in cast shadow. Finally,
manual corrections were also made for obvious
(seasonal) snowfields attached to glaciers.
19.4
CASE STUDIES AND
SPECIAL TOPICS
19.4.1 Glacier size distribution
Fig. 19.6 shows percentages by number and by area
per size class for identified glacier units larger than
0.01 km 2 in the Jotunheimen and Svartisen study
regions. The sample sizes were 417 and 489 glaciers,
respectively. Total area of the Jotunheimen glaciers
(345 km 2 ) was only half that in the Svartisen sample
(633 km 2 ). The Jotunheimen region is dominated
by many small glaciers, typical mountain glaciers
(size class 1–5 km 2 ) which cover 48% of the total
area, but only 17% of the total number. Glaciers
smaller than 0.5 km 2 form 68% of the sample, but
they only represent 14% of the area in this region.
433
In Jotunheimen only one glacier unit was larger
than 10 km 2 (covering 4% of the area), while in
the Svartisen region 12 glacier units were larger
than 10 km 2 and covered 43% of the total area.
Many of the largest units in the Svartisen region are
connected to the three major ice masses (Vestisen,
Østisen, and Blåmannsisen), which together cover
453 km 2 or 72% of the total area.
19.4.2 Assessing area changes in
Jotunheimen and Svartisen
Comparison of the new Landsat-derived glacier
inventory with previous inventories was not
straightforward as the previous inventories only
existed as tabular data with glacier extents printed
on sketch maps. For many of the smallest glaciers
it was often uncertain to which glacier the point
information stored in the glacier inventories
belonged to. Furthermore, glacier basins were
impossible to reconstruct precisely from the sketch
maps in the inventories. Although many of the
glaciers could still be identified as a result of place
names and map information, many glaciers had to
be left out of the comparison. Therefore, glacier
change analysis was done by comparing the new
Landsat-derived outlines with previous glacier outlines from N50 maps. In the Svartisen region these
outlines were mainly from 1968, in the Jotunheimen
region the maps were from 1966–1983. Examples of
area changes since the N50 survey are illustrated for
glaciers in Jotunheimen in Fig. 19.7.
The resulting changes in glacier sizes for the
Jotunheimen and Svartisen region revealed significant differences (Fig. 19.8). In the Jotunheimen
Figure 19.6. Bar graph showing the normalized part of the glacier area and number per size class for two different
regions in Norway: Jotunheimen in southern Norway (sample of 417 glaciers) and Svartisen in northern Norway
(489 glaciers).
434
Norway
Figure 19.7. RGB composite of bands 5, 4, 3 of a Landsat TM scene from 2003 with derived outlines from 2003 in
black and glacier outlines from topographical maps, N50, in white (mapping date: 1976 and 1981 for this part). Dots
denote identified glaciers for the new inventory. Figure also available as Online Supplement 19.2.
region (sample of 355 glaciers) the glaciers generally
decreased, total reduction of 10% (4% per decade)
from 1980 (N50) to 2003 (Landsat), whereas in
the Svartisen region (sample of 300 glaciers) there
was virtually no change in glacier size (1.1% or
0.35% per decade) from 1968 (N50) to 1999
(Landsat). Note that the periods are different, so
the results are not directly comparable even when
referring to decadal change rates. The scatter of
individual changes was large in both regions and
strongly increased towards smaller glaciers (Fig.
19.8).
The analyses from Jotunheimen suggested that
in northern parts of the region area reduction was
probably overestimated as the N50 dataset tended
to include many snowfields due to the poor snow
conditions prevailing when these glaciers were
mapped in this region (Andreassen et al. 2008).
Therefore, the scatter in area changes of the smallest glaciers may partly be caused by differences in
snow conditions for the two different mapping years
as well as differences due to human interpretation.
In the Svartisen region, the overall changes of the
two largest ice caps, Vestisen and Østisen, are close
to zero. Some of the outlet glaciers increased their
size, while others retreated. In particular, small
glaciers (<1 km 2 ) increased their size, partly by
more than 40%. In the Jotunheimen scene, the
four largest ice caps reduced in area from 15%
(the Holåbreen complex), 11% (Harbardsbreen),
2% (Smørstabbreen), and 1% (Spørteggbreen).
Note that the periods of comparison differ as the
N50 maps are from different years. Area loss in
Smørstabbreen was mainly caused by retreat along
two of its main tongues, while other parts showed
no significant reduction since 1981.
19.4.3 Uncertainties
While glacier mapping in the Jotunheimen and
Svartisen regions was straightforward and gave
satisfying results, the major challenges in these
regions (in addition to finding suitable cloud-free
images) were related to adverse snow conditions
and comparison with previous inventories that used
different drainage divides. Human intervention is
Acknowledgments 435
Figure 19.8. Relative area changes in the regions: Jotunheimen (left) and Svartisen (right). Note that the periods
differ for the two regions: for Jotunheimen it is 1980 to 2003, for Svartisen it is 1968-1999.
the most critical part in glacier mapping: first,
during preprocessing (selection of a proper scene
and a threshold for classification) and, then, during
postprocessing (manual editing and selection of
samples for statistical analysis).
There are also several uncertainties in the area
change assessments, as we compared glacier areas
derived from different sources (Landsat data and
topographic maps derived from aerial photography) and under different snow conditions. Thus,
the area changes calculated may partly be due to
methodological differences or human recognition
rather than real glacier changes. The selection process used to recognize a glacier is subjective and
hence will influence the value of the average absolute and relative change of glaciers. Results from
the Jotunheimen region showed that small changes
in glacier area (3%) for a mountain glacier of size
5 km 2 are not necessarily a reliable measure of
glacier shrinkage or increase, but could instead be
due to different interpretation by the operator(s) as
well as differences in snow conditions at the time of
image acquisition (Andreassen et al. 2008).
19.5
CONCLUSIONS
In recent years NVE has started to map current
glacier extents in mainland Norway by Landsat
imagery using thresholded band ratios. First results
from the GLIMS work in Norway have demonstrated that the technical process of glacier mapping
using Landsat imagery is straightforward and accurate in these regions when there is sparse debris
cover on the glaciers. More of a challenge is the
interpretation and identification of individual
glaciers and linking the new inventory to previous
inventories that used different drainage divides.
Assessing area changes between repeat inventories
required much manual work and glaciological
expert knowledge. To obtain new and reliable
glacier outlines, optimum snow conditions are
mandatory and an experienced operator vital. The
amount of remaining seasonal snow is critical when
selecting satellite scenes for a new glacier inventory
and for area change assessments.
The area changes observed differed strongly
between the two studied Norwegian regions.
Whereas a selection of 300 glaciers in the Svartisen
region had an overall area change from 1968 to
1999 close to zero, the area reduction in Jotunheimen was 10% (4% per decade) from 1980
(N50) to 2003.
19.6
ACKNOWLEDGMENTS
The work in Norway is funded by NVE and partly
by the Norwegian Space Center and ESA as part of
the Cryorisk and CryoClim projects. Geir Brånå at
Statens Kartverk provided digital aerial photos
(orthophotos). The work of F. Paul was supported
by a grant from the ESA GlobGlacier project
(21088/07/I-EC). Andreas Kääb is thanked for his
advice which helped us in setting up the new
remote-sensing derived inventory. We would also
like to thank Solveig H. Winsvold who contributed
strongly to the completion of the glacier inventory
436
Norway
of Norway which is now published as a book
(Andreassen et al. 2012) and included in the
GLIMS database since 2012.
19.7
REFERENCES
Albert, T. (2002) Evaluation of remote sensing techniques
for ice-area classification applied to the tropical Quelccaya ice cap, Peru. Polar Geography, 26, 210–226.
Andreassen, L.M., Elvehøy, H., and Kjøllmoen, B. (2002)
Using aerial photography to study glacier changes in
Norway. Annals of Glaciology, 34, 343–348.
Andreassen, L.M., Elvehøy, H., Kjøllmoen, B., Engeset,
R.V., and Haakensen, N. (2005) Glacier mass balance
and length variations in Norway. Annals of Glaciology,
42, 317–325.
Andreassen, L.M., Paul, F., Kääb, A., and Hausberg,
J.E. (2008) The new Landsat-derived glacier inventory
for Jotunheimen, Norway, and deduced glacier
changes since the 1930s. The Cryosphere, 2, 131–145.
Andreassen, L.M., Winsvold, S.H., Paul, F., and Hausberg, J.E. (2012) Inventory of Norwegian Glaciers (NVE
Report No. 38), Norwegian Water Resources and
Energy Directorate, Oslo, Norway.
Bayr, K.J., Hall, D.K., and Kovalick, W.M. (1994)
Observations on glaciers in the Eastern Austrian Alps
using satellite data. International Journal of Remote
Sensing, 15(9), 1733–1742.
Geist, T., Elvehøy, H., Jackson, M., and Stötter, J. (2005)
Investigations on intra-annual elevation changes using
multitemporal airborne laser scanning data: Case
study Engabreen, Norway. Annals of Glaciology, 42,
195–201.
Giesen, R.H., and Oerlemans, J. (2010) Response of the
ice cap Hardangerjøkulen in southern Norway to the
20th and 21st century climates. The Cryosphere, 4, 191–
213.
Grove, J.M., and Battagel, A. (1983) Tax records from
western Norway, as an index of Little Ice Age environmental and economic deterioration. Climatic Change,
5, 265–282.
Hoel, A., and Werenskiold, W. (1962) Glaciers and Snowfields in Norway (NP Skrifter No. 114), Norsk Polarinstitutt, Tromsø, Norway, 291 pp.
Hurrell, J.W. (1995) Decadal trends in the North Atlantic
Oscillation: Regional temperatures and precipitation.
Science, 269, 676–679.
Kjøllmoen, B. and Østrem, G. (1997) Storsteinsfjellbreen:
Variations in mass balance from the 1960s to the 1990s.
Geografiska Annaler, 79A(3), 195–200.
Kjøllmoen, B. (Ed.), Andreassen, L.M., Elvehøy, H.,
Jackson, M., Giesen, R.H., and Winkler, S. (2008)
Glaciological Investigations in Norway 2007 (NVE
Report No. 1, 2008), Norges Vassdrags- og Energidirektorat (Norwegian Water Directorate), Oslo, 91
pp. þ appendices.
Liestøl, O. (1967) Storbreen Glacier in Jotunheimen,
Norway (NP Skrifter No. 141), Norsk Polarinstitutt,
Tromsø, Norway, 63 pp.
Matthews, J.A. (2005) ‘‘Little Ice Age’’ glacier variations
in Jotunheimen, southern Norway: A study in regionally controlled lichenometric dating of recessional
moraines with implications for climate and lichen
growth rates. Holocene, 15, 1–19.
Nesje, A., Bakke, J., Dahl, S.O., Lie, Ø., and Matthews.
J.A. (2008) Norwegian mountain glaciers in the past,
present and future. Global and Planetary Change, 60,
10–27.
Oerlemans, J. (1997) A flow-line model for Nigardsbreen:
Projection of future glacier length based on dynamic
calibration with the historic record. Annals of Glaciology, 24, 382–389.
Paul, F., and Andreassen, L.M. (2009) A new glacier
inventory for the Svartisen region (Norway) from
Landsat ETMþ data: Challenges and change assessment. Journal of Glaciology, 55(192), 607–618.
Paul, F., and Kääb, A. (2005) Perspectives on the production of a glacier inventory from multispectral satellite
data in the Canadian Arctic: Cumberland Peninsula,
Baffin Island. Annals of Glaciology, 42, 59–66.
Paul, F., Kääb, A., Maisch, M., Kellenberger, T.W., and
Haeberli, W. (2002) The new remote sensing-derived
Swiss glacier inventory, I: Methods. Annals of Glaciology, 34, 355–361.
Østrem, G. (1975) ERTS data in glaciology: An effort to
monitor glacier mass balance from satellite imagery.
Journal of Glaciology, 15(73), 403–15.
Østrem, G., and Haakensen, N. (1993) Glaciers of
Norway. In: R.S. Williams and J.G. Ferrigno (Eds.),
Satellite Image Atlas of Glaciers of the World (USGS
Professional Paper, 1386-E-3), U.S. Geological Survey,
Reston, VA, 53 pp.
Østrem, G., and Ziegler, T. (1969) Atlas over breer i SørNorge (Atlas of Glaciers in South Norway) (Meddelelse
20), Hydrologisk avdeling, Norges Vassdrags- og
Elektrisitetsvesen (Norwegian Water Resources and
Energy Directorate, Oslo, Norway), 207 pp. [in Norwegian].
Østrem, G., Haakensen, N., and Melander, O. (1973)
Atlas over breer i Nord-Skandinavia (Glacier Atlas of
Northern Scandinavia) (Meddelelse 22), Hydrologisk
avdeling, Norges Vassdrags- og Energiverk (Norwegian Water Resources and Energy Directorate, Oslo,
Norway) 315 pp. [in Norwegian].
Østrem, G., Dale Selvig, K., and Tandberg, K. (1988)
Atlas over breer i Sør-Norge (Atlas of Glaciers in South
Norway), Hydrologisk avdeling, Norges Vassdrags- og
Energiverk, Meddelelse 61, 180 pp. [in Norwegian].
Øyen, P.A. (1906) Klima und Gletscherschwankungen in
Norwegen. Zeitschrift für Gletscherkunde, 1, 46–61 [in
German].
Racoviteanu, A.E, Paul, F., Raup, B., Singh Khalsa, S.J.,
and Armstrong, R. (2009) Challenges in glacier map-
References 437
ping from space: Recommendations from the Global
Land Ice Measurements from Space (GLIMS) initiative. Annals of Glaciology, 50(53), 53–69.
Rasmussen, L.A., Andreassen, L.M., and Conway, H.
(2007) Reconstruction of mass balance of glaciers in
southern Norway back to 1948. Annals of Glaciology,
46, 255–260.
Raup, B.H., Kääb, A., Kargel, J.S., Bishop, M.P., Hamilton, G., Lee, E., Paul, F., Rau, F., Soltesz, D., Khalsa,
S.J.S. et al. (2007) Remote Sensing and GIS technology
in the Global Land Ice Measurements from Space
(GLIMS) Project. Computational Geosciences, 33,
104–125.
Winkler, S., Elvehøy, H., and Nesje, A. (2009) Glacier
fluctuations of Jostedalsbreen, western Norway,
during the past 20 years: The sensitive response of
maritime mountain glaciers. The Holocene, 19(3),
395-414.