Spørteggbreen is a small ice cap just east of Jostdalsbreen, Norway’s largest ice cap. The Norway Glacier atlas chronicles the area of the 10 glaciers that comprise the ice cap at 23.8 square kilometers in 2006 (Andreassen and Winsvold, 2012). The Norwegian Water Resources and Energy Directorate (NVE) has an excellent glacier monitoring program that monitors 10 glaciers that drain Jostedalsbreen from 2008-2013 the net change was retreat on all 10. This is exemplified by Tunsbergdalsbreen. In 2014, 33 of 38 glaciers observed in Norway retreated and 5 did not change. Laumann and Nesje (2014) examined Spørteggbreen during the Holocene. They noted the glacier disappeared from 7300 years before present and reformed approximately 5400 years before present. Their model simulates minor changes from 2011 to 2050. Here we focus on changes to the southwest side of this ice cap using Landsat imagery from 1988-2014 and implications for the near future.
Norway Glacier atlas image looking southwest toward Jostdalsbreen. The foreground is the main Sporteggbreen, the new lake is in midground and then the separated southwest extension. There is no retained snowcover evident on the southwest extension and it is thin.
In 1988 at the southwest side of Spørteggbreen the main ice cap joins the southwest extension of the ice cap in a small lake at the red arrow. At the purple and yellow arrow are small peripheral proglacial lakes. The green arrow indicates a narrow section in the southwest extension. In August 1998 there is substantially more snow and lake ice, which makes identification of change difficult. In 2010 the southwest extension is well separated by a lake from the main ice cap, red arrow. This lake is m across, with the glaciers reaching the shore at both ends. The lakes at the purple and yellow arrow have also expanded. The width of the narrow section of the southwest extension has narrowed from 600 m to 300 m. In 2014 the main Spørteggbreen Ice Cap no longer reaches the eastern shore of the lake, red arrow. The lake is 750 m across. The lake at the purple arrow is now equivalent to the glacier that ends in the lake and is m long. The width of the glacier at the narrow section is down to 200 m. The most noteworthy item is that in this mid-September image the ice cap has 25% of its area still covered in snowpack, note the areas marked with pink letter A. The other areas are either firn from previous years or bare glacier ice. By the end of the melt season at the end of the month this will likely be closer to 20% . Remember a glacier typically needs 55-65 % snowcover to be have an equilibrium balance. This will lead to a large negative balance and thinning right to the top of the ice cap. This was the case in 2013 as well. Hence, the Spørteggbreen Ice Cap is currently experiencing significant volume and area losses. The retreat is not as large in terms of distance as on nearby Tunsbergdalsbreen.
1988 Landsat image.
1998 Landsat image
2010 Landsat image
2014 Landsat image
Vestisen Glacier is the second largest glacier of the Oksindan Icecap flows west. The glacier drains west into the Rossaga River, which has a Statkraft Hydropower plant, though upstream of the glacier inflow. Here we examine Landsat imagery from 1992-2014 to observe recent changes.
Vestisen Mapcarta view
In 1994 the glacier terminus is at the red arrow. The areal extent of snowcover is more than 50% of the glacier area, blue arrow. A small glacier to the north is connected to the Vestisen at the pink arrow. The purple arrow is a small bedrock ridge that intrudes into the glacier a small distance from the south, and the yellow arrow is a small side terminus of the glacier. In 1999 the snowcovered area is 35% of the glacier. The region of firn, snow that survived the first summer, but is not ice yet, green arrow, is extensive suggesting that the 1999 mass balance was more negative than recent years. In 2006 the ridge at the south edge of the glacier has expanded at the purple arrow. At the pink arrow the connection to the glacier to the north is still comprised of glacier ice. In early september of 2014 the snowcovered area is very low at 15-20% of the glacier. The glacier has separated from the glacier to the north at the pink arrow. A small outcrop of rock has appeared amidst a secondary terminus at the south side of the glacier, yellow arrow. The ridge intruding into the southern edge of the glacier is now 300-400 meters longer and is wider. A lake has formed at the main terminus. This lake has formed due to a combination of thinning and retreat of the terminus, a retreat of 250-300 m has occurred. The Mid-September 2014 image indicates the snowcovered area, blue arrow is down to 5%. The firn area, green arrow, that represents snow that had survived previous summers, is being consumed by the substantial melt of the 2014 season. To have an equilibrium mass balance glaciers in Norway need to be 55-60% snowcovered at the end of the melt season. Glacier mass balance will be quite negative in 2014, which will lead to further retreat of the main terminus and secondary terminus regions, NVE will continue its long term mass balance monitoring that will report on the particular quantities. The retreat here is less than that of Austsre Oksindbreen, just to the northeast, but it is poised for greater retreat in the near future, with poorer retained snowcover. The glacier is following a pattern of thinning and retreat over the last 15 years in Norway. The Norwegian Water Resources and Energy Directorate (NVE) reports that 23 of 24 Norway glaciers examined consistently since 2000 have retreated significantly.
1994 Landsat image
1999 Landsat image
2006 Landsat image
2014 early September Landsat image
2014 Late September Landsat image
Austre Okstindbreen is the largest glacier of the Okstindan Icecap. It flows north from the 1700 m to a terminus in a proglacial lake at 900 m. The lake drains into Grasvatnet. The glacier had a sustained retreat of 2 km from 1908-1980, emplacing annual moraine ridges during the 1950-1968 period (Worsley and Ward, 1974). The other main glacier of the Oksindan Icecap is Vestisen. Knudsen and Theakstone (1988) identified a series of glacier dammed lake draining events from 1976-1987, with glacier retreat this is no longer occurring. Jacobsen et al (1997) noted that the lower glacier in particular had slowed down from 1976 to 1995. They also reported during a series of positive balance years the ELA averaged 1250 m. The Norwegian Water Resources and Energy Directorate (NVE) reports annual terminus of this glacier, noting a 118 m retreat from 2010-2013. Here we examine changes in the glacier from 1994-2014 using Landsat imagery.
Google Earth Image
In 1994 the glacier terminates at the red arrow, the snowline (purple dots) is at 1300 m. The width of the glacier at the eastward turn, yellow arrow is 1500 m. In 1999 the glacier has retreated a short distance and the snowline is at 1400 m. In 2006 the proglacial lake has continued to expand. The glacier width at the east turn is 1300 m. The snowline is at 1450 m. In 2014 the snowline is at 1550 m. The glacier width at the yellow arrow is down to 1100 m. The retreat from the red arrow is 400 m, which is 20 meters/year. The persistent high snowline above 1300 m in images that are not even at the end of the melt season indicate a significant rise. The 400 m reduction in the width of the glacier at the east turn, which is 1.5 km above the terminus, indicate the retreat will continue. The glacier retreat parallels that of Norway glaciers in general since 2000, with 23 of 24 glaciers examined consistently by (NVE) retreating during this interval, one was close to equilibrium. Engabreen, Tunsbergdalsbreen and Blamannsisen.
1994 Landsat image
1999 Landsat image
2006 Landsat image
2014 Early September Landsat image
2014 Mid-September Landsat image
Lodalsbreen is an outlet glacier from the northeast region of the Jostedalsbreen Icecap of Norway. This particular outlet is difficult to reach and not often investigated, for this icecap in general all 10 glaciers observed from 2000-2010 have retreated (Norwegian Water Resources, 2010). Recent work by Nussbaumer et al (2011) and Imhof et al (2011) have focussed on the changes in terminus postion of Jostedalsbreen glaciers since the Little Ice Age including Lodalsbreen. The glacier reached a maximum around 1750 and has retreated 4.5 km up to 2006 as noted in the second image below modified only slightly from Nussbaumer et al (2011). The third image indicates Lodalsbreen and the western tributary and the large accumulation zone of Jostedsalsbreen that feeds the many outlet glaciers, image source is the WGMS-UN publication Global Glacier Change:s Facts and Figures. The glacier was 6 km long in 2005. A comparison of 1989, 2000, 2002, 2010 and 2012 Landsat imagery indicates the retreat of the main tongue, purple arrow for 1989 and yellow arrow 2010 and western tributary that was previously joined to the glacier, red arrow at 1989 terminus. From 1989 to 2010 Lodalsbreen has retreated 240 meters. The western tributary terminated in the valley bottom at 750 meters above sea level in 1989, and by 2010 has retreated 500 meters up the valley wall to 1000 meters above sea level. Most of the retreat of the tributary has been since 2000. The retreat of this glacier is similar to that of other Norwegian glaciers in the area, Tunsbergdalsbreen and Midtdalsbreen . The Jostedalsbreen has a large accumulation area above 1500 meters that feeds the many outlet glaciers, which are no in danger of disappearing with current climate.
The Norwegian Water Resources and Energy Directorate (NVE) has an excellent glacier monitoring program. Of these ten drain the largest ice cap in Norway the Jostedalsbreen, from 2008-2013 the net change was retreat on all 11. The largest outlet glacier Tunsbergdalsbreen is not one of the closely monitored glaciers. This glacier flows southeast from the icecap, is 18 km long and terminates at 670 meters in a new proglacial lake.
Examination of Tunsbergdalsbreen in Landsat imagery from 1989, 2003, 2011 and 2014. The violet arrows indicate the terminus. In 1989 no lake is evident. By 2003 the lake has begun to develop and has icebergs in it. In 2011 the lake is 400 meters across and has numerous icebergs in it. In 2014 the lake has expanded to a length of 700 m. The glacier is fed by several tributaries coming off the ice cap. At the #3 green arrow, bedrock is by 2010 in the midst of an icefall from the upper ice sheet that was underneath the glacier in 1989 and 2003. At green arrows #1 and #2 the area of bedrock exposure is expanding, indicating thinner and less ice draining from the ice cap into the tongue of the Tunsbergdalsbreen. In 2003, 2011 and 2014 the snowline is at 1450 m, too high to sustain the glacier, the negative mass balance will drive further retreat.
1989 Landsat image
2003 Landsat image
2011 Landsat image
2014 Landsat image
A closeup of the terminus from Google Earth indicates a number of debris covered ice bergs in the lake. This combined with the observed thinning upglacier indicates that retreat will continue. Exposure of bedrock upglacier occurs because of thinning, which only occurs because of mass balance loss which also results in velocity and discharge reductions.
At present the Tunsbergdalsbreen is the focus of an ongoing field project that aims to monitor the glacier on an annual basis documenting the impact of climate change. This project is focussing on monitoring the elevation of the glacier surface, the ice velocity and the front position. Video of the project are also worth examining. In two of these images below, the red arrows in each indicate the thin relatively uncrevassed lower reach. The low slope suggests the lake basin will continue to expand as this area is lost. These are 2013 images and in fact some of this retreat has occurred. Upglacier of the red arrows there is limited crevassing but the slope does increase.
In 2010 -2014 glacier mass balances across Norway were negative. The nearby Sporteggbreen Glacier is experiencing signficant area and volume loss.
2012 Google Earth Image.
Images above from Pål Gran Kielland at the Norsk Bremuseum, a partner in the Tunsbergdalsbreen Project.