| 1. |
- Holmlund, Erik S., et al.
(författare)
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Constraining 135 years of mass balance with historic structure-from-motion photogrammetry on Storglaciaren, Sweden
- 2019
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Ingår i: Geografiska Annaler. Series A, Physical Geography. - : Informa UK Limited. - 0435-3676 .- 1468-0459. ; 101:3, s. 195-210
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Tidskriftsartikel (refereegranskat)abstract
- Geodetic volume estimates of Storglaciaren in Sweden suggest a 28% loss in total ice mass between 1910 and 2015. Terrestrial photographs from 1910 of Tarfala valley, where Storglaciaren is situated, allow for an accurate reconstruction of the glacier's surface using Structure-from-Motion photogrammetry, which we used for past volume and mass estimations. The glacier's yearly mass balance gradient and net mass balance was also estimated back to 1880 using weather data from Karesuando, 170 km north-east of Storglaciaren, through neural network regression. These combined reconstructions provide a continuous mass change series between the end of the Little Ice Age and 1946, when field data become available. The resultant reconstruction suggests a state close to equilibrium between 1880 and the 1910s, followed by drastic melt until the 1970s, constituting 76% of the 1910-2015 ice loss. More favourable conditions subsequently stabilized the mass balance until the late 1990s, after which Storglaciaren started losing mass again. The 1910 reconstruction allows for a more accurate mass change series than previous estimates, and the methodology can be used on other glaciers where early photographic material exists.
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| 2. |
- Holmlund, Per, et al.
(författare)
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Recent climate-induced shape changes of the ice summit of Kebnekaise, Northern Sweden
- 2019
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Ingår i: Geografiska Annaler. Series A, Physical Geography. - : Informa UK Limited. - 0435-3676 .- 1468-0459. ; 101:1, s. 68-78
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Tidskriftsartikel (refereegranskat)abstract
- The ice summit of Kebnekaise is slowly melting down as a consequence of climate change. In August 2018 this peak, which for a long time has been the highest in Sweden, reached an elevation a few decimetres lower than the nearby situated northern summit in solid rock. It has become a symbol of the fragility of nature. Its areal extent and shape have varied over time and its height has ranged within approximately 15 m during the twentieth century. Since the turn of the century, the ice summit has decreased to a new lower and smaller level but the changes are not uniform, and they show a complex relation between weather parameters and the shape and size of the summit. Layers in the ice include climate information of past changes. But what changes are we able to determine by examining gradually exposed dust layers, or by coring the summit. In this paper, we are analysing the late changes in shape and volume of the ice summit and we place the results into a paleo climate discussion. We have used photogrammetric methods to map the geometry of the summit at different dates when data has been available. We have also done a multiple regression to analyse the relation between the summit elevation and the net mass balance of the nearby located Storglaciaren. The correlation is good from mid 1970s until now but weak prior to that. It is herein explained by former uncertainties of the geographic position of the summit.
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| 3. |
- Linderholm, Hans W., 1968
(författare)
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Editorial
- 2019
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Ingår i: Geografiska Annaler, Series A: Physical Geography. - : Informa UK Limited. - 0435-3676 .- 1468-0459. ; 101:2
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 4. |
- Sugden, David E., et al.
(författare)
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Plucking enhanced beneath ice sheet margins : evidence from the Grampian Mountains, Scotland
- 2019
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Ingår i: Geografiska Annaler. Series A, Physical Geography. - : Informa UK Limited. - 0435-3676 .- 1468-0459. ; 101:1, s. 34-44
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Tidskriftsartikel (refereegranskat)abstract
- Concentrations of boulders are a common feature of landscapes modified by former mid-latitude ice sheets. In many cases, the origin of the boulders can be traced in the up-ice direction to a cliff only tens to hundreds of metres distant. The implication is that a pulse of plucking and short boulder transport occurred beneath thin ice at the end of the last glacial cycle. Here we use a case study in granite bedrock in the Dee Valley, Scotland, to constrain theory and explore the factors involved in such a late phase of plucking. Plucking is influenced by ice velocity, hydrology, effective ice pressure, the extent of subglacial cavities and bedrock characteristics. The balance between these factors favours block removal beneath thin ice near a glacier margin. At Ripe Hill in the Dee Valley, a mean exposure age of 14.2 ka on blocks supports the view that the boulder train formed at the end of ice sheet glaciation. The late pulse of plucking was further enhanced by ice flowing obliquely across vertical joints and by fluctuations in sub-marginal meltwater conditions. An implication of the study is that there is the potential for a wave of ice-marginal plucking to sweep across a landscape as an ice sheet retreats.
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