| 1. |
- Alexanderson, Helena, et al.
(författare)
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The Seven Islands, Svalbard: glaciation at the margin
- 2018
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- On the Seven Islands, north of Nordaustlandet, Svalbard, decreasing snow cover has made previously inaccessible stratigraphic sections in coastal cliffs possible to investigate. Sections on two of the islands, Phippsøya and Parryøya, reveal mainly raised marine deposits, representing one or more coarsening upward sequences (emergence cycles) at each site, which in turn imply preceding regional glaciations (cf. Alexanderson et al. in press). Optically stimulated luminescence (OSL) ages are pending but radiocarbon (14C) ages and correlation to a previously studied site on Phippsøya (Forman and Ingólfsson 2000) suggest at least two events that occurred during the late Weichselian-early Holocene and prior to 40 14C ka BP, respectively. These results, along with observations of postglacial land uplift and of transport of erratic boulders to the islands, provide information on the glacial history and dynamics of an area close to the margin of the Svalbard-Barents Sea ice sheet.ReferencesAlexanderson, H., Henriksen, M., Ryen. H.T., Landvik, J.Y. and Peterson, G. in press. 200 ka of glacial events in NW Svalbard: An emergence cycle facies model and regional correlations. arktos. Forman, S.L. and Ingólfsson, Ó, 2000. Late Weichselian glacial history and postglacial emergence of Phippsøya, Sjuøyane, northern Svalbard: a comparison of modelled and empirical estimates of a glacial-rebound hinge line. Boreas 29, 16-25.
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| 2. |
- Farnsworth, Wesley R., et al.
(författare)
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Dynamic Holocene glacial history of St. Jonsfjorden, Svalbard
- 2017
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Ingår i: Boreas. - : Wiley. - 0300-9483. ; 46:3, s. 585-603
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Tidskriftsartikel (refereegranskat)abstract
- Evidence of a dynamic Holocene glacial history is preserved in the terrestrial and marine archives of St. Jonsfjorden, a small fjord-system on the west coast of Spitsbergen, Svalbard. High-resolution, remotely sensed imagery from marine and terrestrial environments was used to construct geomorphological maps that highlight an intricate glacial history of the entire fjord-system. The geomorphology and stratigraphy indicate an early Holocene local glacier advance constrained to the Lateglacial–early Holocene transition. Identification and 14C dating of the thermophilous bivalve mollusc Modiolus modiolus to 10.0±0.12 cal. ka BP suggest a rapid northward migration of the species shortly after deglaciation. Further evidence enhances the understanding of the onset and subsequent climax of the Neoglacial-Little Ice Age in inner St. Jonsfjorden. The present-day terminus of Osbornebreen, the dominating glacier system in St. Jonsfjorden, is located over 8.5 km up-fjord from its Neoglacial maximum extent. Cross-cutting relationships suggest subsequent advances of all the smaller glaciers in the area following the break-up of Osbornebreen. Glacial deposits, landforms and their cross-cutting relationships observed in both terrestrial and marine settings imply a complex and highly dynamic environment through the later part of the Holocene.
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| 3. |
- Flink, Anne E., et al.
(författare)
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Holocene glacial evolution of Mohnbukta in eastern Spitsbergen
- 2018
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Ingår i: Boreas. - : Wiley. - 0300-9483 .- 1502-3885. ; 47:2, s. 390-409
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Tidskriftsartikel (refereegranskat)abstract
- Submarine geomorphology is one of the main tools for understanding past fluctuations of tidewater glaciers. In this study we investigate the glacial history of Mohnbukta, on the east coast of Spitsbergen, Svalbard, by combining multibeam-bathymetric data, marine sediment cores and remote sensing data. Presently, three tidewater glaciers, Heuglinbreen, Konigsbergbreen and Hayesbreen calve into Mohnbukta. Hayesbreen surged at the end of the Little Ice Age, between 1901 and 1910. The submarine landform assemblage in Mohnbukta contains two large transverse ridges, interpreted as terminal moraines, with debrisflow lobes on their distal slopes and sets of well-preserved geometric networks of ridges, interpreted as crevasse-squeeze ridges inshore of the moraines. The arrangement of crevasse-squeeze ridges suggests that both landform sets were produced during surge-type advances. The terminus position of the 1901-1910 Hayesbreen surge correlates with the inner (R.2) terminal moraine ridge suggesting that the R.1 ridge formed prior to 1901. Marine sediment cores display C-14 ages between 5700-7700cal. a BP derived from benthic foraminifera, from a clast-rich mud unit. This unit represents pre-surge unconsolidated Holocene sediments pushed in front of the glacier terminus and mixed up during the 1901 surge. An absence of retreat moraines in the deeper part of the inner basin and the observation of tabular icebergs calving off the glacier front during retreat suggest that the front of Hayesbreen was close to flotation, at least in the deeper parts of the basin. As the MOH15-01 core does not penetrate into a subglacial till and the foraminifera in the samples were well preserved, the R.1 ridge is suggested to have formed prior to the deposition of the foraminifera. Based on these data we propose that a surge-type advance occurred in Mohnbukta in the early Holocene, prior to 7700cal. a BP, which in turn indicates that glaciers can switch to and from surge mode.
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| 4. |
- Flink, Anne E., et al.
(författare)
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Past ice flow in Wahlenbergfjorden and its implications for late Quaternary ice sheet dynamics in northeastern Svalbard
- 2017
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 163, s. 162-179
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Tidskriftsartikel (refereegranskat)abstract
- Wahlenbergfjorden is a fjord situated in the western part of Nordaustlandet in northern Svalbard. It leads into the 400 m deep Hinlopen Strait located between Nordaustlandet and Spitsbergen. High-resolution multibeam bathymetric and sub-bottom data, as well as sediment cores are used to study the past extent and dynamics of glaciers in Wahlenbergfjorden and western Nordaustlandet. The submarine landform assemblage in Wahlenbergfjorden consists of landforms characteristic of subglacial, ice marginal and proglacial conditions. Glacial lineations indicate that Wahlenbergfjorden was occupied by streaming ice during the LGM and most likely acted as an ice stream onset zone. Westward ice flow in the fjord merged with the ice stream in Hinlopen Strait. Absence of ice recessional landforms in outer Wahlenbergfjorden suggests relatively fast deglaciation, possibly by flotation of the glacier front in the deeper parts of the fjord. The inner part of Wahlenbergfjorden and Palanderbukta are characterized by De Geer moraines, indicating episodic retreat of a grounded glacier front. In Palanderbukta, longer still stands of the glacier terminus resulted in the formation of larger terminal moraine ridges. The inner part of Wahlenbergfjorden was deglaciated prior to 11.3 +/- 55 Cal. ka BP. The submarine landform assemblages in front of Bodleybreen, Etonbreen, Idunbreen, Frazerbreen and Aldousbreen confirm that these glaciers have surged at least once during the Holocene.
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| 5. |
- Flink, Anne Elina, et al.
(författare)
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The evolution of a submarine landform record following recent and multiple surges of Tunabreen glacier, Svalbard
- 2015
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 108, s. 37-50
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Tidskriftsartikel (refereegranskat)abstract
- This study focuses on the glacial landform record associated with recent surge events of Tunabreen - a calving tidewater glacier in Tempelfjorden, Spitsbergen. Submarine geomorphology and recent terminal fluctuations of Tunabreen's glacier front were studied using high-resolution multibeam-bathymetric data and a range of published and remote-sensing sources, including topographic maps, satellite images and aerial photographs. The retreat moraines in the inner part of Tempelfjorden have been correlated with glacier terminus positions during retreat from the 2004 surge maximum. Glacier surface velocity and ice-front positions derived from high-resolution TerraSAR-X satellite data show ice movements at the glacier front during minor advances of the front in winter when calving is suppressed. This suggests that the moraines have formed annually during quiescent phase winter advances. Tunabreen has experienced three surges since the Little Ice Age (LIA). This is in contrast with most Svalbard surging glaciers which have long quiescent phases and have typically only undergone one or two surges during this time. The landform record in Tempelfjorden is distinguished from previously studied glacier-surge landsystems by four, well-preserved sets of landform assemblages generated by the LIA advance and three subsequent surges, all of which partly modify earlier landform records. Based on the unique landform record in Tempelfjorden, a new conceptual landsystem model for frequently surging glaciers has been put forward improving our understanding of the dynamics of the surging glaciers and, most importantly, how they can be distinguished from the climatically-controlled glaciers in the geological record.
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| 6. |
- Gowan, Evan J., et al.
(författare)
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ICESHEET 1.0 : a program to produce paleo-ice sheet reconstructions with minimal assumptions
- 2016
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Ingår i: Geoscientific Model Development. - : Copernicus GmbH. - 1991-959X .- 1991-9603. ; 9:5, s. 1673-1682
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Tidskriftsartikel (refereegranskat)abstract
- We describe a program that produces paleo-ice sheet reconstructions using an assumption of steady-state, perfectly plastic ice flow behaviour. It incorporates three input parameters: ice margin, basal shear stress and basal topography. Though it is unlikely that paleo-ice sheets were ever in complete steady-state conditions, this method can produce an ice sheet without relying on complicated and unconstrained parameters such as climate and ice dynamics. This makes it advantageous to use in glacial-isostatic adjustment ice sheet modelling, which are often used as input parameters in global climate modelling simulations. We test this program by applying it to the modern Greenland Ice Sheet and Last Glacial Maximum Barents Sea Ice Sheet and demonstrate the optimal parameters that balance computational time and accuracy.
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| 7. |
- Holmes, Felicity A., et al.
(författare)
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Relating ocean temperatures to frontal ablation rates at Svalbard tidewater glaciers : Insights from glacier proximal datasets
- 2019
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Ingår i: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Fjord-terminating glaciers in Svalbard lose mass through submarine melt and calving (collectively: frontal ablation), and surface melt. With the recently observed Atlantification of water masses in the Barents Sea, warmer waters enter these fjords and may reach glacier fronts, where their role in accelerating frontal ablation remains insufficiently understood. Here, the impact of ocean temperatures on frontal ablation at two glaciers is assessed using time series of water temperature at depth, analysed alongside meteorological and glaciological variables. Ocean temperatures at depth are harvested at distances of 1 km from the calving fronts of the glaciers Kronebreen and Tunabreen, western Svalbard, from 2016 to 2017. We find ocean temperature at depth to control c. 50% of frontal ablation, making it the most important factor. However, its absolute importance is considerably less than found by a 2013-2014 study, where temperatures were sampled much further away from the glaciers. In light of evidence that accelerating levels of global mass loss from marine terminating glaciers are being driven by frontal ablation, our findings illustrate the importance of sampling calving front proximal water masses.
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| 8. |
- How, Penelope, et al.
(författare)
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Calving controlled by melt-under-cutting : detailed calving styles revealed through time-lapse observations
- 2019
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Ingår i: Annals of Glaciology. - : Cambridge University Press (CUP). - 0260-3055 .- 1727-5644. ; 60:78, s. 20-31
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Tidskriftsartikel (refereegranskat)abstract
- We present a highly detailed study of calving dynamics at Tunabreen, a tidewater glacier in Svalbard. A time-lapse camera was trained on the terminus and programmed to capture images every 3 seconds over a 28-hour period in August 2015, producing a highly detailed record of 34 117 images from which 358 individual calving events were distinguished. Calving activity is characterised by frequent events (12.8 events h(-1)) that are small relative to the spectrum of calving events observed, demonstrating the prevalence of small-scale calving mechanisms. Five calving styles were observed, with a high proportion of calving events (82%) originating at, or above, the waterline. The tidal cycle plays a key role in the timing of calving events, with 68% occurring on the falling limb of the tide. Calving activity is concentrated where meltwater plumes surface at the glacier front, and a similar to 5 m undercut at the base of the glacier suggests that meltwater plumes encourage melt-under-cutting. We conclude that frontal ablation at Tunabreen may be paced by submarine melt rates, as suggested from similar observations at glaciers in Svalbard and Alaska. Using submarine melt rate to calculate frontal ablation would greatly simplify estimations of tidewater glacier losses in prognostic models.
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| 9. |
- Jakobsson, Martin, et al.
(författare)
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In memoriam of Tom Flodén : obituary
- 2017
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Ingår i: GFF. - : Taylor & Francis. - 1103-5897 .- 2000-0863. ; 139:3, s. 241-242
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 10. |
- Kirchner, Nina, et al.
(författare)
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High-resolution bathymetric mapping reveals subaqueous glacial landforms in the Arctic alpine lake Tarfala, Sweden
- 2019
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Ingår i: Journal of Quaternary Science. - : Wiley. - 0267-8179 .- 1099-1417. ; 34:6, s. 452-462
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Tidskriftsartikel (refereegranskat)abstract
- In Arctic alpine regions, glacio-lacustrine environments respond sensitively to variations in climate conditions, impacting, for example,glacier extent and rendering former ice-contact lakes into ice distal lakes and vice versa. Lakefloors may hold morphological records of past glacier extent, but remoteness and long periods of ice cover on such lakes make acquisition of high-resolution bathymetric datasets challenging. Lake Tarfala and Kebnepakte Glacier, located in the Kebnekaise mountains, northern Sweden, comprise a small, dynamic glacio-lacustrine system holding a climate archive that is not well studied. Using an autonomous surface vessel, a high-resolution bathymetric dataset for Lake Tarfala was acquired in 2016, from which previously undiscovered end moraines and a potential grounding line feature were identified. For Kebnepakte Glacier, structure-from-motion photogrammetry was used to reconstruct its shape from photographs taken in 1910 and 1945. Combining these methods connects the glacial landform record identified at the lakefloor with the centennial-scale dynamic behaviour of Kebnepakte Glacier. During its maximum 20(th) century extent, attained c. 1910, Kebnepakte Glacier reached far into Lake Tarfala, but had retreated onto land by 1945, at an average of 7.9 m year(-1).
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