| 1. |
- Alexanderson, Helena, et al.
(author)
-
The Seven Islands, Svalbard: glaciation at the margin
- 2018
-
Conference paper (other academic/artistic)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.
|
|
| 2. |
- Farnsworth, Wesley R., et al.
(author)
-
Dynamic Holocene glacial history of St. Jonsfjorden, Svalbard
- 2017
-
In: Boreas. - : Wiley. - 0300-9483. ; 46:3, s. 585-603
-
Journal article (peer-reviewed)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.
|
|
| 3. |
- Farnsworth, Wesley R., et al.
(author)
-
Holocene glacial history of Svalbard : Status, perspectives and challenges
- 2020
-
In: Earth-Science Reviews. - : Elsevier BV. - 0012-8252. ; 208
-
Journal article (peer-reviewed)abstract
- We synthesize the current understanding of glacier activity on Svalbard from the end of the Late Pleistocene (12,000 yrs. before present) to the end of the Little Ice Age (c. 1920 AD). Our glacier history is derived from the SVALHOLA database, the first compilation of Holocene geochronology for Svalbard and the surrounding waters, including over 1,800 radiocarbon, terrestrial cosmogenic nuclide and optically stimulated luminescence ages. Data have been categorized by geological setting, uniformly (re-)calibrated, quality assessed and ultimately used to constrain glacier fluctuations (deglaciation, ice free conditions, glacier re-advances and ice marginal positions). We advance existing knowledge by mapping the extent and distribution of ice-cover during the Holocene glacial maximum and the glacial minimum, as well as present retreat rates (and percentages) within Early Holocene fjord-systems. Throughout the Holocene, Svalbard glaciers have responded to a varying combination of climatic, environmental and dynamic driving factors which influence both the extent and behavior of ice margins. We discuss the complexities of glacier systems and their dynamics in response to changes in climate. This review provides a holistic state of the art of Holocene glaciers on Svalbard, suitable for orienting future works which address gaps in our current knowledge.
|
|
| 4. |
- Flink, Anne E., et al.
(author)
-
Holocene glacial evolution of Mohnbukta in eastern Spitsbergen
- 2018
-
In: Boreas. - : Wiley. - 0300-9483 .- 1502-3885. ; 47:2, s. 390-409
-
Journal article (peer-reviewed)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.
|
|
| 5. |
- Flink, Anne E., et al.
(author)
-
Past ice flow in Wahlenbergfjorden and its implications for late Quaternary ice sheet dynamics in northeastern Svalbard
- 2017
-
In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 163, s. 162-179
-
Journal article (peer-reviewed)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.
|
|
| 6. |
- Flink, Anne Elina, et al.
(author)
-
The evolution of a submarine landform record following recent and multiple surges of Tunabreen glacier, Svalbard
- 2015
-
In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 108, s. 37-50
-
Journal article (peer-reviewed)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.
|
|
| 7. |
- Gowan, Evan J., et al.
(author)
-
ICESHEET 1.0 : a program to produce paleo-ice sheet reconstructions with minimal assumptions
- 2016
-
In: Geoscientific Model Development. - : Copernicus GmbH. - 1991-959X .- 1991-9603. ; 9:5, s. 1673-1682
-
Journal article (peer-reviewed)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.
|
|
| 8. |
- Holmes, Felicity Alice, 1995-
(author)
-
Glacier-Ocean Interactions in the Arctic : Contemporary calving and frontal melt from field observations, remote sensing, and numerical modelling
- 2022
-
Doctoral thesis (other academic/artistic)abstract
- Globally, glaciers are losing mass as a result of the changing climate, with this mass loss having a considerable societal impact through rising sea levels. Glaciers which terminate in the oceans are particularly vulnerable to changing external conditions as a result of high sensitivity at their marine margins. Both changing meteorological patterns as well as changing ocean heat content and transport have been previously identified as potential drivers for contemporary rapid glacier retreat and acceleration. However, uncertainties remain and provide motivation for studies which improve our process understanding. Here, we use a combination of field data, remotely sensed data, and targeted numerical modelling experiments to investigate marine terminating glacier response to external changes. This is done in order to address uncertainties around mass loss at the inaccessible glacier-ocean interface. In particular, focus is paid to the processes of submarine melt and calving, together referred to as frontal ablation. Submarine melt is the melting of glacier termini by warm ocean waters below the waterline, whilst calving is the breaking off of icebergs from glacier termini. The two processes are interlinked, with submarine melting undercutting the glacier terminus and contributing to calving, whilst calving events can expose larger areas of the glacier margin to submarine melt. To look for relationships between frontal ablation and external forcings, four glacier-fjord systems were studied to varying extents; two grounded glaciers in Svalbard (Kronebreen and Tunabreen) and two glaciers with floating ice tongues in Greenland (Ryder glacier and Petermann glacier). Both submarine melt and calving were examined at various different scales, both temporally and spatially. Specifically, analysis was carried out from the scale of individual calving events up to decadal long time series of glacier margin change. Much of the data used focused on specific glaciological variables such as satellite-derived velocities, margin positions, model simulations, and time-lapse photography of calving events. However, as glaciers and their adjacent fjord or ocean environments impact on each other, data such as water temperatures were also collected from glacier proximal fjord environments. The results from both the observational data and model experiments suggest that ocean temperatures are of great importance for the frontal ablation of glaciers in the Arctic, but that the relationship is complex. Heterogeneous glacier response to external forcings highlights how site specific factors such as bathymetry and fjord geometry can add an additional layer of complexity and make it challenging to scale up results from one glacier to an entire region. However, there are some strong indications that it is the presence of warm air temperatures in conjunction with warm ocean temperatures that is most important for driving frontal ablation - highlighting the need to situate glacier behaviour within a wider environmental context.
|
|
| 9. |
- Holmes, Felicity A., 1995-, et al.
(author)
-
Impact of tides on calving patterns at Kronebreen, Svalbard – insights from three-dimensional ice dynamical modelling
- 2023
-
In: The Cryosphere. - 1994-0416 .- 1994-0424. ; 17:5, s. 1853-1872
-
Journal article (peer-reviewed)abstract
- Understanding calving processes and their controls is of importance for reducing uncertainty in sea level rise estimates. The impact of tidal fluctuations and frontal melt on calving patterns has been researched through both modelling and observational studies but remains uncertain and may vary from glacier to glacier. In this study, we isolate various different impacts of tidal fluctuations on a glacier terminus to understand their influence on the timing of calving events in a model of Kronebreen, Svalbard, for the duration of 1 month. In addition, we impose a simplified frontal melt parameterisation onto the calving front in order to allow for an undercut to develop over the course of the simulations. We find that calving events show a tidal signal when there is a small or no undercut, but, after a critical point, undercut-driven calving becomes dominant and drowns out the tidal signal. However, the relationship is complex, and large calving events show a tidal signal even with a large modelled undercut. The modelled undercut sizes are then compared to observational profiles, showing that undercuts of up to ca. 25 m are plausible but with a more complex geometry being evident in observations than that captured in the model. These findings highlight the complex interactions occurring at the calving front of Kronebreen and suggest further observational data and modelling work is needed to fully understand the hierarchy of controls on calving.
|
|
| 10. |
- Holmes, Felicity A., et al.
(author)
-
Relating ocean temperatures to frontal ablation rates at Svalbard tidewater glaciers : Insights from glacier proximal datasets
- 2019
-
In: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 9
-
Journal article (peer-reviewed)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.
|
|
