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Publications (10 of 46) Show all publications
Van Pelt, W., Pohjola, V., Pettersson, R., Marchenko, S., Kohler, J., Luks, B., . . . Reijmer, C. (2019). A long-term dataset of climatic mass balance, snow conditions, and runoff in Svalbard (1957–2018). The Cryosphere, 13, 2259-2280
Open this publication in new window or tab >>A long-term dataset of climatic mass balance, snow conditions, and runoff in Svalbard (1957–2018)
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2019 (English)In: The Cryosphere, ISSN 1994-0416, E-ISSN 1994-0424, Vol. 13, p. 2259-2280Article in journal (Refereed) Published
Abstract [en]

The climate in Svalbard is undergoing amplified change compared to the global mean. This has major implications for runoff from glaciers and seasonal snow on land. We use a coupled energy balance–subsurface model, forced with downscaled regional climate model fields, and apply it to both glacier-covered and land areas in Svalbard. This generates a long-term (1957–2018) distributed dataset of climatic mass balance (CMB) for the glaciers, snow conditions, and runoff with a 1 km×1 km spatial and 3-hourly temporal resolution. Observational data including stake measurements, automatic weather station data, and subsurface data across Svalbard are used for model calibration and validation. We find a weakly positive mean net CMB (+0.09 m w.e. a−1) over the simulation period, which only fractionally compensates for mass loss through calving. Pronounced warming and a small precipitation increase lead to a spatial-mean negative net CMB trend (−0.06 m w.e. a−1 decade−1), and an increase in the equilibrium line altitude (ELA) by 17 m decade−1, with the largest changes in southern and central Svalbard. The retreating ELA in turn causes firn air volume to decrease by 4 % decade−1, which in combination with winter warming induces a substantial reduction of refreezing in both glacier-covered and land areas (average −4 % decade−1). A combination of increased melt and reduced refreezing causes glacier runoff (average 34.3 Gt a−1) to double over the simulation period, while discharge from land (average 10.6 Gt a−1) remains nearly unchanged. As a result, the relative contribution of land runoff to total runoff drops from 30 % to 20 % during 1957–2018. Seasonal snow on land and in glacier ablation zones is found to arrive later in autumn (+1.4 d decade−1), while no significant changes occurred on the date of snow disappearance in spring–summer. Altogether, the output of the simulation provides an extensive dataset that may be of use in a wide range of applications ranging from runoff modelling to ecosystem studies.

National Category
Physical Geography
Identifiers
urn:nbn:se:uu:diva-392819 (URN)10.5194/tc-13-2259-2019 (DOI)000484163900001 ()
Funder
Swedish Research Council, VR 3903The Research Council of Norway, 2018_00010
Available from: 2019-09-10 Created: 2019-09-10 Last updated: 2019-10-17Bibliographically approved
Marchenko, S., Cheng, G., Lötstedt, P., Pohjola, V., Pettersson, R., van Pelt, W. & Reijmer, C. (2019). Thermal conductivity of firn at Lomonosovfonna, Svalbard, derived from subsurface temperature measurements. The Cryosphere, 13, 1843-1859
Open this publication in new window or tab >>Thermal conductivity of firn at Lomonosovfonna, Svalbard, derived from subsurface temperature measurements
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2019 (English)In: The Cryosphere, ISSN 1994-0416, E-ISSN 1994-0424, Vol. 13, p. 1843-1859Article in journal (Refereed) Published
National Category
Physical Geography
Identifiers
urn:nbn:se:uu:diva-334156 (URN)10.5194/tc-13-1843-2019 (DOI)000474653300002 ()
Available from: 2019-07-09 Created: 2017-11-21 Last updated: 2019-09-01Bibliographically approved
Levy, J. S., Fountain, A. G., Obryk, M. K., Telling, J., Glennie, C., Pettersson, R., . . . Van Horn, D. (2018). Decadal topographic change in the McMurdo Dry Valleys of Antarctica: Thermokarst subsidence, glacier thinning, and transfer of water storage from the cryosphere to the hydrosphere. Geomorphology, 323, 80-97
Open this publication in new window or tab >>Decadal topographic change in the McMurdo Dry Valleys of Antarctica: Thermokarst subsidence, glacier thinning, and transfer of water storage from the cryosphere to the hydrosphere
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2018 (English)In: Geomorphology, ISSN 0169-555X, E-ISSN 1872-695X, Vol. 323, p. 80-97Article in journal (Refereed) Published
Abstract [en]

Recent local-scale observations of glaciers, streams, and soil surfaces in the McMurdo Dry Valleys of Antarctica (MDV) have documented evidence for rapid ice loss, glacial thinning, and ground surface subsidence associated with melting of ground ice. To evaluate the extent, magnitude, and location of decadal-scale landscape change in the MDV, we collected airborne lidar elevation data in 2014-2015 and compared these data to a 2001-2002 airborne lidar campaign. This regional assessment of elevation change spans the recent acceleration of warming and melting observed by long-term meteorological and ecosystem response experiments, allowing us to assess the response of MDV surfaces to warming and potential thawing feedbacks. We find that locations of thermokarst subsidence are strongly associated with the presence of excess ground ice and with proximity to surface or shallow subsurface (active layer) water. Subsidence occurs across soil types and landforms, in low-lying, low-slope areas with impeded drainage and also high on steep valley walls. Glacier thinning is widespread and is associated with the growth of fine-scale roughness. Pond levels are rising in most closed-basin lakes in the MDV, across all microclimate zones. These observations highlight the continued importance of insolation-driven melting in the MDV. The regional melt pattern is consistent with an overall transition of water storage from the local cryosphere (glaciers, permafrost) to the hydrosphere (dosed basin lakes and ponds as well as the Ross Sea). We interpret this regional melting pattern to reflect a transition to Arctic and alpine-style, hydrologically mediated permafrost and glacial melt.

Keywords
Antarctic, Permafrost, Glaciers, Lidar
National Category
Physical Geography
Identifiers
urn:nbn:se:uu:diva-371033 (URN)10.1016/j.geomorph.2018.09.012 (DOI)000449897200007 ()
Available from: 2019-01-07 Created: 2019-01-07 Last updated: 2019-01-07Bibliographically approved
Van Pelt, W. J. .., Pohjola, V. A., Pettersson, R., Ehwald, L. E., Reijmer, C. H., Boot, W. & Jakobs, C. L. (2018). Dynamic response of a High Arctic glacier to melt and runoff variations. Geophysical Research Letters, 45(10), 4917-4926
Open this publication in new window or tab >>Dynamic response of a High Arctic glacier to melt and runoff variations
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2018 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 45, no 10, p. 4917-4926Article in journal (Refereed) Published
Abstract [en]

The dynamic response of High Arctic glaciers to increased runoff in a warming climateremains poorly understood. We analyze a 10-year record of continuous velocity data collected atmultiple sites on Nordenskiöldbreen, Svalbard, and study the connec tion between ice flow andrunoff within and between seasons. During the melt season, the sensitivit y of ice motion to runoffat sites in the ablation and lower accumulation zone drops by a fac tor of 3 when cumulative runoff exceedsa local threshold, which is likely associated with a transition from inefficient (distributed) to efficient(channelized) drainage. Average summer (June–August) velocities are found to increase with summerablation, while subsequent fall (September–November) velocities decrease. Spring (March–May)velocities are largely insensitive to summer ablation, which suggests a short-lived impact of summermelt on ice flow during the cold season. The net impact of summer ablation on annual velocities is foundto be insignificant.

Keywords
glacier dynamics, runoff, velocity, climate change, High Arctic
National Category
Physical Geography
Identifiers
urn:nbn:se:uu:diva-350228 (URN)10.1029/2018GL077252 (DOI)000435262000043 ()
Funder
Swedish Research CouncilSwedish Polar Research Secretariat
Available from: 2018-05-08 Created: 2018-05-08 Last updated: 2019-06-27Bibliographically approved
Ruskeeniemi, T., Engstrom, J., Lehtimaki, J., Vanhala, H., Korhonen, K., Kontula, A., . . . Pettersson, R. (2018). Subglacial permafrost evidencing re-advance of the Greenland Ice Sheet over frozen ground. Quaternary Science Reviews, 199, 174-187
Open this publication in new window or tab >>Subglacial permafrost evidencing re-advance of the Greenland Ice Sheet over frozen ground
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2018 (English)In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 199, p. 174-187Article in journal (Refereed) Published
Abstract [en]

Greenland Ice Sheet (GrIS) covers an area of 1.7 million km(2). It has been an important source of climate information and the air temperature history of Greenland is well known. However, the thermal history and temperature conditions of the Greenland bedrock are poorly known. There are only few records on the temperature of the proglacial bedrock and no records on bedrock temperature underneath the ice sheet. The Greenland Analogue Project (GAP) recently investigated hydrological, hydrogeological and geochemical processes in Kangerlussuaq, West Greenland. Because permafrost has a major hydrological impact in Arctic regions, the cryogenic structure of the bedrock was an important research topic. From previous studies it was already known that Kangerlussuaq is located within the zone of continuous permafrost. Temperature profiling in a new research borehole, extending horizontally 30 m underneath the ice sheet, revealed that permafrost is 350 m deep at the ice margin. This result raised the question how far the permafrost extends under the ice sheet? In order to investigate the thermal properties, we made a series of electromagnetic (EM) soundings at the ice margin area - on proglacial area and on the ice sheet - and detected, that subglacial permafrost extends at least 2 km from the ice margin to inland. We also observed a patchy unfrozen sediment layer between the ice and the frozen bedrock. Possible existence of subglacial sediments and their role in ice dynamics has been debated in many recent papers. Our successful campaign shows that geophysics can be used for bedrock investigations through thick ice, which is known to be challenging for electromagnetic methods. Our results provide the first direct evidence supporting the proposed Holocene ice re-advance over frozen ground, and contribute to the discussion on the rapid climate changes in past, to the future of the ice sheet under warming climate and hydrogeology at the ice margin.

Keywords
Greenland ice sheet, Deglaciation, Permafrost, Electromagnetics, Cryogenic structure, Crystalline bedrock, Holocene
National Category
Physical Geography
Identifiers
urn:nbn:se:uu:diva-370008 (URN)10.1016/j.quascirev.2018.09.002 (DOI)000448493900013 ()
Available from: 2019-01-07 Created: 2019-01-07 Last updated: 2019-01-07Bibliographically approved
Lindbäck, K., Kohler, J., Pettersson, R., Nuth, C., Langley, K., Messerli, A., . . . Brandt, O. (2018). Subglacial topography, ice thickness, and bathymetry of Kongsfjorden, northwestern Svalbard. Earth System Science Data, 10(4), 1769-1781
Open this publication in new window or tab >>Subglacial topography, ice thickness, and bathymetry of Kongsfjorden, northwestern Svalbard
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2018 (English)In: Earth System Science Data, ISSN 1866-3508, E-ISSN 1866-3516, Vol. 10, no 4, p. 1769-1781Article in journal (Refereed) Published
Abstract [en]

Svalbard tidewater glaciers are retreating, which will affect fjord circulation and ecosystems when glacier fronts become land-terminating. Knowledge of the subglacial topography and bathymetry under retreating glaciers is important to modelling future scenarios of fjord circulation and glacier dynamics. We present high-resolution (150m gridded) digital elevation models of subglacial topography, ice thickness, and ice surface elevation of five tidewater glaciers in Kongsfjorden (1100 km(2)), northwestern Spitsbergen, based on similar to 1700 km airborne and ground-based ice-penetrating radar profiles. The digital elevation models (DEMs) cover the tidewater glaciers Blomstrandbreen, Conwaybreen, Kongsbreen, Kronebreen, and Kongsvegen and are merged with bathymetric and land DEMs for the non-glaciated areas. The large-scale subglacial topography of the study area is characterized by a series of troughs and highs. The minimum subglacial elevation is 180m above sea level (a.s.l.), the maximum subglacial elevation is 1400m a.s.l., and the maximum ice thickness is 740m. Three of the glaciers, Kongsbreen, Kronebreen, and Kongsvegen, have the potential to retreat by similar to 10 km before they become land-terminating. The compiled data set covers one of the most studied regions in Svalbard and is valuable for future studies of glacier dynamics, geology, hydrology, and fjord circulation.

Place, publisher, year, edition, pages
COPERNICUS GESELLSCHAFT MBH, 2018
National Category
Physical Geography
Identifiers
urn:nbn:se:uu:diva-367386 (URN)10.5194/essd-10-1769-2018 (DOI)000446324600001 ()
Funder
The Research Council of Norway, 243808EU, European Research Council, 320816The European Space Agency (ESA), 4000109873/14/I-NB
Available from: 2018-12-04 Created: 2018-12-04 Last updated: 2018-12-04Bibliographically approved
Fuerst, J. J., Navarro, F., Gillet-Chaulet, F., Huss, M., Moholdt, G., Fettweis, X., . . . Braun, M. H. (2018). The Ice-Free Topography of Svalbard. Geophysical Research Letters, 45(21), 11760-11769
Open this publication in new window or tab >>The Ice-Free Topography of Svalbard
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2018 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 45, no 21, p. 11760-11769Article in journal (Refereed) Published
Abstract [en]

We present a first version of the Svalbard ice-free topography (SVIFT1.0) using a mass conserving approach for mapping glacier ice thickness. SVIFT1.0 is informed by more than 1 million point measurements, totalling more than 8,700 km of thickness profiles. SVIFT1.0 is publicly available and represents the geometric state around the year 2010. Our estimate for the total ice volume is 6,199 km(3), equivalent to 1.5-cm sea level rise. The thickness map suggests that 13% of the glacierized area is grounded below sea level. A complementary map of error estimates comprises uncertainties in the thickness surveys as well as in other input variables. Aggregated error estimates are used to define a likely ice-volume range of 5,200-7,300 km(3). The ice front thickness of marine-terminating glaciers is a key quantity for ice loss attribution because it controls the potential ice discharge by iceberg calving into the ocean. We find a mean ice front thickness of 135 m for the archipelago (likely range 123-158 m). Plain Language Summary Svalbard is an archipelago in the Arctic, north of Norway, which is comparable in size to the New York metropolitan area. Roughly half of it is covered by glacier ice. Yet to this day, the ice volume stored in the many glaciers on Svalbard is not well known. Many attempts have been made to infer a total volume estimate, but results differ substantially. This surprises because of the long research activity in this area. A large record of more than 1 million thickness measurements exists, making Svalbard an ideal study area for the application of a state-of-the-art mapping approach for glacier ice thickness. The mapping approach computes an ice volume that will raise global sea level by more than half an inch if instantaneously melted. If spread over the metropolitan area, New York would be buried beneath a 100-m ice cover. The asset of this approach is that it provides not only a thickness map for each glacier on the archipelago but also an error map that defines the likely local thickness range. Finally, we provide the first well-informed estimate of the ice front thickness of all marine-terminating glaciers that loose icebergs to the ocean. The archipelago-wide mean ice front cliff is 135 m.

National Category
Physical Geography
Identifiers
urn:nbn:se:uu:diva-372714 (URN)10.1029/2018GL079734 (DOI)000451832600028 ()
Funder
German Research Foundation (DFG), FU1032/1-1
Available from: 2019-01-08 Created: 2019-01-08 Last updated: 2019-01-08Bibliographically approved
Sevestre, H., Benn, D. I., Luckman, A., Nuth, C., Kohler, J., Lindback, K. & Pettersson, R. (2018). Tidewater Glacier Surges Initiated at the Terminus. Journal of Geophysical Research - Earth Surface, 123(5), 1035-1051
Open this publication in new window or tab >>Tidewater Glacier Surges Initiated at the Terminus
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2018 (English)In: Journal of Geophysical Research - Earth Surface, ISSN 2169-9003, E-ISSN 2169-9011, Vol. 123, no 5, p. 1035-1051Article in journal (Refereed) Published
Abstract [en]

There have been numerous reports that surges of tidewater glaciers in Svalbard were initiated at the terminus and propagated up-glacier, in contrast with downglacier-propagating surges of land-terminating glaciers. Most of these surges were poorly documented, and the cause of this behavior was unknown. We present detailed data on the recent surges of two tidewater glaciers, Aavatsmarkbreen and Wahlenbergbreen, in Svalbard. High-resolution time series of glacier velocities and evolution of crevasse patterns show that both surges propagated up-glacier in abrupt steps. Prior to the surges, both glaciers underwent retreat and steepening, and in the case of Aavatsmarkbreen, we demonstrate that this was accompanied by a large increase in driving stress in the terminal zone. The surges developed in response to two distinct processes. (1) During the late quiescent phase, internal thermodynamic processes and/or retreat from a pinning point caused acceleration of the glacier front, leading to the development of terminal crevasse fields. (2) Crevasses allowed surface meltwater and rainwater to access the bed, causing flow acceleration and development of new crevasses up-glacier. Upward migration of the surge coincided with stepwise expansion of the crevasse field. Geometric changes near the terminus of these glaciers appear to have led to greater strain heating, water production, and storage at the glacier bed. Water routing via crevasses likely plays an important role in the evolution of surges. The distinction between internally triggered surges and externally triggered speedups may not be straightforward. The behavior of these glaciers can be understood in terms of the enthalpy cycle model.

Place, publisher, year, edition, pages
AMER GEOPHYSICAL UNION, 2018
Keywords
glaciers, surges, tidewater, Svalbard, remote sensing, dynamics
National Category
Physical Geography
Identifiers
urn:nbn:se:uu:diva-358100 (URN)10.1029/2017JF004358 (DOI)000435277100011 ()
Funder
EU, European Research Council, 320816
Available from: 2018-08-24 Created: 2018-08-24 Last updated: 2018-08-24Bibliographically approved
Marchenko, S., Pohjola, V. A., Pettersson, R., van Pelt, W. J. J., Vega, C. P., Machguth, H., . . . Isaksson, E. (2017). A plot-scale study of firn stratigraphy at Lomonosovfonna, Svalbard, using ice cores, borehole video and GPR surveys in 2012–14. Journal of Glaciology, 63(237), 67-78
Open this publication in new window or tab >>A plot-scale study of firn stratigraphy at Lomonosovfonna, Svalbard, using ice cores, borehole video and GPR surveys in 2012–14
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2017 (English)In: Journal of Glaciology, ISSN 0022-1430, E-ISSN 1727-5652, Vol. 63, no 237, p. 67-78Article in journal (Refereed) Published
Abstract [en]

Spatial heterogeneity of snow and firn properties on glaciers introduces uncertainty in interpretation of point and profile observations and complicates modelling of meltwater percolation and runoff. Here we present a study of the temporal and spatial dynamics of firn density and stratigraphy at the plot-scale (approximate to 10 m x 10 m x 10 m) repeated annually during 2012-14 at the Lomonosovfonna ice-field, Svalbard. Results from cores, video inspections in boreholes and radar grid surveys are compared. Ice layers 0.1-50 cm thick comprised approximate to 8% of the borehole length. Most of them are 1-3 cm thick and could not be traced between boreholes separated by 3 m. Large lateral variability of firn structure affects representativeness of observations in single holes and calls for repeated studies in multiple points to derive a representative stratigraphy signal. Radar reflections are poorly correlated with ice layers in individual boreholes. However, the match between the high amplitude peaks in the grid-averaged radar signal and horizons of preferential ice layer formation revealed by averaging the video surveys over multiple boreholes is higher. These horizons are interpreted as buried firn layers previously exposed to melt-freeze or wind-driven densification and several of them are consistently recovered throughout three field campaigns.

Keywords
borehole video, firn core, radar, stratigraphy
National Category
Physical Geography Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-308681 (URN)10.1017/jog.2016.118 (DOI)000394435300006 ()
Funder
Swedish Research Council, 621-2014-3735
Available from: 2016-11-29 Created: 2016-11-29 Last updated: 2018-01-13Bibliographically approved
Fuerst, J. J., Gillet-Chaulet, F., Benham, T. J., Dowdeswell, J. A., Grabiec, M., Navarro, F., . . . Braun, M. (2017). Application of a two-step approach for mapping ice thickness to various glacier types on Svalbard. The Cryosphere, 11(5), 2003-2032
Open this publication in new window or tab >>Application of a two-step approach for mapping ice thickness to various glacier types on Svalbard
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2017 (English)In: The Cryosphere, ISSN 1994-0416, E-ISSN 1994-0424, Vol. 11, no 5, p. 2003-2032Article in journal (Refereed) Published
Abstract [en]

The basal topography is largely unknown beneath most glaciers and ice caps, and many attempts have been made to estimate a thickness field from other more accessible information at the surface. Here, we present a two-step reconstruction approach for ice thickness that solves mass conservation over single or several connected drainage basins. The approach is applied to a variety of test geometries with abundant thickness measurements including marine-and landterminating glaciers as well as a 2400 km(2) ice cap on Svalbard. The input requirements are kept to a minimum for the first step. In this step, a geometrically controlled, non-local flux solution is converted into thickness values relying on the shallow ice approximation (SIA). In a second step, the thickness field is updated along fast-flowing glacier trunks on the basis of velocity observations. Both steps account for available thickness measurements. Each thickness field is presented together with an error-estimate map based on a formal propagation of input uncertainties. These error estimates point out that the thickness field is least constrained near ice divides or in other stagnant areas. Withholding a share of the thickness measurements, error estimates tend to overestimate mismatch values in a median sense. We also have to accept an aggregate uncertainty of at least 25% in the reconstructed thickness field for glaciers with very sparse or no observations. For Vestfonna ice cap (VIC), a previous ice volume estimate based on the same measurement record as used here has to be corrected upward by 22 %. We also find that a 13% area fraction of the ice cap is in fact grounded below sea level. The former 5% estimate from a direct measurement interpolation exceeds an aggregate maximum range of 6-23% as inferred from the error estimates here.

National Category
Geology Physical Geography
Identifiers
urn:nbn:se:uu:diva-334921 (URN)10.5194/tc-11-2003-2017 (DOI)000409059700001 ()
Funder
German Research Foundation (DFG), FU1032/1-1; 1158; BR2105/9-1EU, FP7, Seventh Framework Programme, 226375EU, European Research Council, 320816
Available from: 2017-11-29 Created: 2017-11-29 Last updated: 2018-01-13Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-6961-0128

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