CRYOMET - Bridging models for the terrestrial cryosphere and the atmosphere (avsluttet)

• Biskaborn, Boris K.; Smith, Sharon L.; Noetzli, Jeannette; Matthes, Heidrun; Vieira, Gonçalo & Streletskiy, Dmitry A. [Vis alle 48 forfattere av denne artikkelen] (2019). Permafrost is warming at a global scale. Nature Communications. 10. doi: 10.1038/s41467-018-08240-4. Fulltekst i vitenarkiv Vis sammendrag

  Permafrost warming has the potential to amplify global climate change, because when frozen sediments thaw it unlocks soil organic carbon. Yet to date, no globally consistent assessment of permafrost temperature change has been compiled. Here we use a global data set of permafrost temperature time series from the Global Terrestrial Network for Permafrost to evaluate temperature change across permafrost regions for the period since the International Polar Year (2007–2009). During the reference decade between 2007 and 2016, ground temperature near the depth of zero annual amplitude in the continuous permafrost zone increased by 0.39 ± 0.15 °C. Over the same period, discontinuous permafrost warmed by 0.20 ± 0.10 °C. Permafrost in mountains warmed by 0.19 ± 0.05 °C and in Antarctica by 0.37 ± 0.10 °C. Globally, permafrost temperature increased by 0.29 ± 0.12 °C. The observed trend follows the Arctic amplification of air temperature increase in the Northern Hemisphere. In the discontinuous zone, however, ground warming occurred due to increased snow thickness while air temperature remained statistically unchanged.

• Aas, Kjetil Schanke; Gisnås, Kjersti; Westermann, Sebastian & Berntsen, Terje Koren (2017). A Tiling Approach to Represent Subgrid Snow Variability in Coupled Land Surface–Atmosphere Models. Journal of Hydrometeorology. ISSN 1525-755X. 18(1), s. 49–63. doi: 10.1175/JHM-D-16-0026.1. Fulltekst i vitenarkiv Vis sammendrag

  A mosaic approach to represent subgrid snow variation in a coupled atmosphere–land surface model (WRF–Noah) is introduced and tested. Solid precipitation is scaled in 10 subgrid tiles based on precalculated snow distributions, giving a consistent, explicit representation of variable snow cover and snow depth on subgrid scales. The method is tested in the Weather Research and Forecasting (WRF) Model for southern Norway at 3-km grid spacing, using the subgrid tiling for areas above the tree line. At a validation site in Finse, the modeled transition time from full snow cover to snow-free ground is increased from a few days with the default snow cover fraction formulation to more than 2 months with the tiling approach, which agrees with in situ observations from both digital camera images and surface temperature loggers. This in turn reduces a cold bias at this site by more than 2°C during the first half of July, with the noontime bias reduced from −5° to −1°C. The improved representation of subgrid snow variation also reduces a cold bias found in the reference simulation on regional scales by up to 0.8°C and increases surface energy fluxes (in particular the latent heat flux), and it resulted in up to 50% increase in monthly (June) precipitation in some of the most affected areas. By simulating individual soil properties for each tile, this approach also accounts for a number of secondary effects of uneven snow distribution resulting in different energy and moisture fluxes in different tiles also after the snow has disappeared. This research was originally published in Journal of Hydrometeorology. © 2017 American Meteorological Society

• Gisnås, Kjersti; Etzelmüller, Bernd; Lussana, Cristian; Hjort, Jan; Sannel, Britta & Isaksen, Ketil [Vis alle 11 forfattere av denne artikkelen] (2017). Permafrost Map for Norway, Sweden and Finland. Permafrost and Periglacial Processes. ISSN 1045-6740. 28(2), s. 359–378. doi: 10.1002/ppp.1922. Fulltekst i vitenarkiv
• Aas, Kjetil Schanke; Dunse, Thorben; Collier, E.; Schuler, Thomas; Berntsen, Terje Koren & Kohler, Jack [Vis alle 7 forfattere av denne artikkelen] (2015). Simulating the climatic mass balance of Svalbard glaciers from 2003 to 2013 with a high-resolution coupled atmosphere-glacier model. The Cryosphere Discussions. 9, s. 5775–5815. doi: 10.5194/tcd-9-5775-2015. Fulltekst i vitenarkiv Vis sammendrag

  In this study we simulate the climatic mass bal- ance of Svalbard glaciers with a coupled atmosphere–glacier model with 3 km grid spacing, from September 2003 to September 2013. We find a mean specific net mass bal- ance of − 257 mm w.e. yr − 1 , corresponding to a mean annual mass loss of about 8.7 Gt, with large interannual variabil- ity. Our results are compared with a comprehensive set of mass balance, meteorological, and satellite measurements. Model temperature biases of 0.19 and − 1.9 ◦ C are found at two glacier automatic weather station sites. Simulated cli- matic mass balance is mostly within about 100 mm w.e. yr − 1 of stake measurements, and simulated winter accumulation at the Austfonna ice cap shows mean absolute errors of 47 and 67 mm w.e. yr − 1 when compared to radar-derived values for the selected years 2004 and 2006. Comparison of mod- eled surface height changes from 2003 to 2008, and satel- lite altimetry reveals good agreement in both mean values and regional differences. The largest deviations from obser- vations are found for winter accumulation at Hansbreen (up to around 1000 mm w.e. yr − 1 ), a site where sub-grid topog- raphy and wind redistribution of snow are important factors. Comparison with simulations using 9 km grid spacing reveal considerable differences on regional and local scales. In addi- tion, 3 km grid spacing allows for a much more detailed com- parison with observations than what is possible with 9 km grid spacing. Further decreasing the grid spacing to 1 km appears to be less significant, although in general precipita- tion amounts increase with resolution. Altogether, the model compares well with observations and offers possibilities for studying glacier climatic mass balance on Svalbard both his- torically as well as based on climate projections.

• Aas, Kjetil Schanke; Berntsen, Terje Koren; Boike, Julia; Etzelmuller, Bernd; Kristjansson, Jon Egill & Maturilli, Marion [Vis alle 9 forfattere av denne artikkelen] (2015). A comparison between simulated and observed surface energy balance at the Svalbard Archipelago. Journal of Applied Meteorology and Climatology. ISSN 1558-8424. 54(5), s. 1102–1119. doi: 10.1175/JAMC-D-14-0080.1. Fulltekst i vitenarkiv
• Dunse, Thorben; Schellenberger, Thomas; Hagen, Jon Ove Methlie; Kääb, Andreas; Schuler, Thomas & Reijmer, CH (2014). Destabilisation of an Arctic ice cap triggered by a hydro-thermodynamic feedback to summer-melt. The Cryosphere Discussions. 8, s. 2685–2719. doi: 10.5194/tcd-8-2685-2014. Fulltekst i vitenarkiv Vis sammendrag

  Mass loss from glaciers and ice sheets currently accounts for two-thirds of the observed global sea-level rise and has accelerated since the 1990s, coincident with strong atmospheric warming in the Polar Regions. Here we present continuous GPS measurements and satellite synthetic aperture radar based velocity maps from the Austfonna ice cap, Svalbard, that demonstrate strong links between surface-melt and multiannual ice-flow acceleration. We identify a hydro-thermodynamic feedback that successively mobilizes stagnant ice regions, initially frozen to their bed, thereby facilitating fast basal motion over an expanding area. By autumn 2012, successive destabilization of the marine terminus escalated in a surge of the ice cap's largest drainage basin, Basin-3. The resulting iceberg discharge of 4.2 ± 1.6 Gt a−1 over the period April 2012 to May 2013 triples the calving loss from the entire ice cap. After accounting for the terminus advance, the related sea-level rise contribution of 7.2 ± 2.6 Gt a−1 matches the recent annual ice-mass loss from the entire Svalbard archipelago. Our study highlights the importance of dynamic glacier wastage and illuminates mechanisms that may trigger a sustained increase in dynamic glacier wastage or the disintegration of ice-sheets in response to climate warming, which is acknowledged but not quantified in global projections of sea-level rise.

• Gisnås, Kjersti; Westermann, Sebastian; Schuler, Thomas; Litherland, Tobias; Isaksen, Ketil & Boike, Julia [Vis alle 7 forfattere av denne artikkelen] (2014). A statistical approach to represent small-scale variability of permafrost temperatures due to snow cover. The Cryosphere Discussions. 8, s. 509–536. doi: 10.5194/tcd-8-509-2014. Fulltekst i vitenarkiv Vis sammendrag

  In permafrost environments exposed to strong winds, drifting snow can create a small-scale pattern of strongly variable snow heights, which has profound implications for the thermal regime of the ground. Arrays of 26 to more than 100 temperature loggers were installed to record the distribution of ground surface temperatures within three study areas across a climatic gradient from continuous to sporadic permafrost in Norway. A variability of the mean annual ground surface temperature of up to 6°C was documented within areas of 0.5 km2. The observed variation can, to a large degree, be explained by variation in snow height. Permafrost models, employing averages of snow height for grid cells of, e.g., 1 km2, are not capable of representing such sub-grid variability. We propose a statistical representation of the sub-grid variability of ground surface temperatures and demonstrate that a simple equilibrium permafrost model can reproduce the temperature distribution within a grid cell based on the distribution of snow heights.

• Gisnås, Kjersti; Westermann, Sebastian; Schuler, Thomas; Litherland, Tobias; Isaksen, Ketil & Boike, Julia [Vis alle 7 forfattere av denne artikkelen] (2014). A statistical approach to represent small-scale variability of permafrost temperatures due to snow cover. The Cryosphere. ISSN 1994-0416. 8, s. 2063–2074. doi: 10.5194/tc-8-2063-2014. Fulltekst i vitenarkiv
• Farbrot, Herman; Isaksen, Ketil; Etzelmuller, Bernd & Gisnås, Kjersti (2013). Ground Thermal Regime and Permafrost Distribution under a Changing Climate in Northern Norway. Permafrost and Periglacial Processes. ISSN 1045-6740. 24(1), s. 20–38. doi: 10.1002/ppp.1763. Fulltekst i vitenarkiv
• Østby, Torbjørn; Schuler, Thomas; Hagen, Jon Ove Methlie; Hock, Regine & Reijmer, Carleen (2013). Parameter uncertainty, refreezing and surface energy balance modelling at Austfonna ice cap, Svalbard, 2004-2008. Annals of Glaciology. ISSN 0260-3055. 54(63), s. 229–240. doi: 10.3189/2013AoG63A280. Fulltekst i vitenarkiv Vis sammendrag

  We apply a physically based coupled surface energy balance and snowpack model to a site close to the equilibrium line on Austfonna ice cap, Svalbard, over the 2004–08 melt seasons, to explain contributions to the energy available for melting and to quantify the significance of refreezing. The model is forced using in situ meteorological measurements and precipitation downscaled from ERA- Interim reanalysis. Applying a Monte Carlo approach to determine the tunable parameters of the model, we estimate the uncertainty related to the choice of parameter values. Multiple criteria are evaluated to identify well-performing parameter combinations, evaluating the model performance with respect to longwave outgoing radiation, snow and ice temperatures and surface displacement. On average, over the investigated melt seasons (1 June to 15 September) net radiation and sensible heat contributed 90 ± 2% and 10 ± 2%, respectively, to the mean energy available for melting snow and ice. The energy consumed by subsurface heat exchange reduced runoff by 15 ± 2% in 2004 and 49 ± 3% in 2008. Refreezing of meltwater and rain was estimated to be 0.37 ± 0.04 mw.e.a –1 on average over the five seasons, which represents a considerable reduction of mass loss during summer. Our findings suggest that refreezing potentially exerts a decisive control on glacier mass balance in persistently snow- or firn-covered areas.

• Westermann, Sebastian; Schuler, Thomas; Gisnås, Kjersti & Etzelmuller, Bernd (2013). Transient thermal modeling of permafrost conditions in Southern Norway. The Cryosphere. ISSN 1994-0416. 7(2), s. 719–739. doi: 10.5194/tc-7-719-2013. Fulltekst i vitenarkiv Vis sammendrag

  Thermal modeling is a powerful tool to infer the temperature regime of the ground in permafrost areas. We present a transient permafrost model, CryoGrid 2, that calculates ground temperatures according to conductive heat transfer in the soil and in the snowpack. CryoGrid 2 is forced by operational air temperature and snow-depth products for potential permafrost areas in Southern Norway for the period 1958 to 2009 at 1 km2 spatial resolution. In total, an area of about 80 000 km2 is covered. The model results are validated against borehole temperatures, permafrost probability maps from "bottom temperature of snow" measurements and inventories of landforms indicative of permafrost occurrence. The validation demonstrates that CryoGrid 2 can reproduce the observed lower permafrost limit to within 100 m at all validation sites, while the agreement between simulated and measured borehole temperatures is within 1 K for most sites. The number of grid cells with simulated permafrost does not change significantly between the 1960s and 1990s. In the 2000s, a significant reduction of about 40% of the area with average 2 m ground temperatures below 0 °C is found, which mostly corresponds to degrading permafrost with still negative temperatures in deeper ground layers. The thermal conductivity of the snow is the largest source of uncertainty in CryoGrid 2, strongly affecting the simulated permafrost area. Finally, the prospects of employing CryoGrid 2 as an operational soil-temperature product for Norway are discussed.

• Hawley, Robert L.; Brandt, Ola; Dunse, Thorben; Hagen, Jon Ove Methlie; Helm, Veit & Kohler, Jack [Vis alle 9 forfattere av denne artikkelen] (2013). Using airborne Ku-band altimeter waveforms to investigate winter accumulation and glacier facies on Austfonna, Svalbard. Journal of Glaciology. ISSN 0022-1430. 59(217), s. 893–899. doi: 10.3189/2013JoG13J051. Fulltekst i vitenarkiv
• Gisnås, Kjersti; Etzelmuller, Bernd; Farbrot, Herman; Schuler, Thomas & Westermann, Sebastian (2013). CryoGRID 1.0: Permafrost Distribution in Norway estimated by a Spatial Numerical Model. Permafrost and Periglacial Processes. ISSN 1045-6740. 24(1), s. 2–19. doi: 10.1002/ppp.1765. Fulltekst i vitenarkiv
• Langer, Moritz; Westermann, Sebastian; Heikenfeld, Max; Dorn, Wolfgang & Boike, Julia (2013). Satellite-based modeling of permafrost temperatures in a tundra lowland landscape. Remote Sensing of Environment. ISSN 0034-4257. 135, s. 12–24. doi: 10.1016/j.rse.2013.03.011. Fulltekst i vitenarkiv
• Etzelmuller, Bernd (2013). Recent Advances in Mountain Permafrost Research. Permafrost and Periglacial Processes. ISSN 1045-6740. 24(2), s. 99–107. doi: 10.1002/ppp.1772. Fulltekst i vitenarkiv

Se alle arbeider i NVA

• Gisnås, Kjersti; Westermann, Sebastian; Schuler, Thomas & Etzelmuller, Bernd (2014). Towards Inclusion of Sub-grid Variability of Snow in Distributed Permafrost Models. Fulltekst i vitenarkiv
• Gisnås, Kjersti; Westermann, Sebastian; Etzelmuller, Bernd; Schuler, Thomas; Isaksen, Ketil & Litherland, Tobias [Vis alle 7 forfattere av denne artikkelen] (2014). A probabilistic approach to represent small-scale variability of permafrost temperatures due to snow cover. Fulltekst i vitenarkiv
• Gisnås, Kjersti; Etzelmuller, Bernd; Christiansen, Hanne H; Elberling, Bo; Engström, Jonas & Hjort, Jan [Vis alle 10 forfattere av denne artikkelen] (2014). A First Nordic Permafrost Map for Norway, Sweden and Finland. Fulltekst i vitenarkiv
• Aas, Kjetil Schanke; Dunse, Thorben; Collier, Emily; Schuler, Thomas; Kohler, Jack & Berntsen, Terje Koren (2014). Simulating the Climatic Mass Balance of Svalbard Glaciers from 2003 to 2014 Using a Coupled Atmosphere and Climatic Mass-Balance Model. Fulltekst i vitenarkiv
• Aas, Kjetil Schanke; Berntsen, Terje Koren; Boike, Julia; Etzelmuller, Bernd; Kristjansson, Jon Egill & Schuler, Thomas [Vis alle 8 forfattere av denne artikkelen] (2013). Observed and simulated surface energy budget at Ny-Ålesund, Svalbard. Fulltekst i vitenarkiv
• Aas, Kjetil Schanke; Berntsen, Terje Koren; Boike, Julia; Etzelmuller, Bernd; Kristjansson, Jon Egill & Schuler, Thomas [Vis alle 8 forfattere av denne artikkelen] (2013). Observert og simulert bakke-energibalanse på Svalbard. Fulltekst i vitenarkiv
• Aas, Kjetil Schanke; Berntsen, Terje Koren; Boike, Julia; Etzelmuller, Bernd; Kristjansson, Jon Egill & Schuler, Thomas [Vis alle 8 forfattere av denne artikkelen] (2013). Observed and simulated SEB at Ny-Ålesund, Svalbard. Fulltekst i vitenarkiv
• Østby, Torbjørn; Schuler, Thomas & Westermann, Sebastian (2013). Quality assessment of MODIS land surface temperatures over an Arctic ice cap,Svalbard. Fulltekst i vitenarkiv
• Østby, Torbjørn; Schuler, Thomas & Westermann, Sebastian (2013). Quality assessment of MODIS land surface temperatures over an Arctic ice cap. Fulltekst i vitenarkiv
• Dunse, Thorben; Schuler, Thomas; Hagen, Jon Ove Methlie & Eiken, Trond (2013). Ground-based monitoring of snowcover, firn area and glacier facies of Austfonna, Svalbard, to validate and improve PolarWRF climate simulations. Fulltekst i vitenarkiv
• Westermann, Sebastian; Langer, Moritz; Heikenfeld, Max & Boike, Julia (2013). CryoGrid 3 – a new flexible tool for permafrost modeling. Fulltekst i vitenarkiv
• Westermann, Sebastian; Berntsen, Terje; Etzelmuller, Bernd; Gisnås, Kjersti; Hagen, Jon Ove Methlie & Kristjansson, Jon Egill [Vis alle 8 forfattere av denne artikkelen] (2013). The CryoMet project - combining deterministic and probabilistic downscaling to model snow depth over a wide range of scales. Fulltekst i vitenarkiv
• Schuler, Dagrun Vikhamar; Schuler, Thomas; Morin, Samuel; Lafayasse, M. & Boike, Julia (2013). Using the land surface model SURFEX/ISBA-Crocus to simulate ground temperatures in Ny Ålesund, Svalbard. Fulltekst i vitenarkiv
• Litherland, Tobias; Gisnås, Kjersti & Schuler, Thomas (2013). HIGH- RESOLUTION SNOW DISTRIBUTION MODELLING IN ALPINE NORWAY. Fulltekst i vitenarkiv
• Schuler, Thomas; Dunse, Thorben; Eiken, Trond & Hagen, Jon Ove Methlie (2013). Considering orographic enhancement to downscale precipitation: resolving the accumulation asymmetry and deriving a 55 year accumulation history of Austfonna, Svalbard. Fulltekst i vitenarkiv
• Etzelmuller, Bernd; Christiansen, H.H.; Gisnås, Kjersti; Isaksen, Ketil; Schuler, Thomas & Westermann, Sebastian (2013). GROUND THERMAL REGIME AND ACTIVE LAYER THICKNESS MONITORING AND MODELLING IN THE NORDIC AREA. Fulltekst i vitenarkiv
• Etzelmuller, Bernd; Westermann, Sebastian; Berntsen, Terje Koren; Gisnås, Kjersti; Hagen, Jon Ove Methlie & Kristjansson, Jon Egill [Vis alle 10 forfattere av denne artikkelen] (2013). Bridging models for the terrestrial cryosphere and the atmosphere - The CryoMET project. Fulltekst i vitenarkiv
• Gisnås, Kjersti; Westermann, Sebastian; Etzelmuller, Bernd & Schuler, Thomas (2013). From Snow Depth Distribution to Small-Scale Variability of Soil Temperatures. Fulltekst i vitenarkiv
• Aas, Kjetil Schanke; Berntsen, Terje Koren; Westermann, Sebastian & Etzelmuller, Bernd (2012). Observations and plans for simulations of surface energy balance on Svalbard, Norway. Fulltekst i vitenarkiv
• Østby, Torbjørn; Schuler, Thomas; Hagen, Jon Ove Methlie; Hock, Regine & Reijmer, Carleen (2012). The role of subsurface heat exchange: energy partitioning at Austfonna ice cap, Svalbard, over 2004-2008. Fulltekst i vitenarkiv
• Østby, Torbjørn; Schuler, Thomas & Westermann, Sebastian (2012). Quality assessment of MODIS land surface temperatures over an Arctic ice cap. Fulltekst i vitenarkiv
• Østby, Torbjørn & Dunse, Thorben (2012). Glaciological research on Svalbard. Fulltekst i vitenarkiv
• Gisnås, Kjersti; Westermann, Sebastian; Hipp, Tobias Florian; Etzelmuller, Bernd & Schuler, Thomas (2012). From Snow Depth Distribution to Small-Scale Variability of Soil Temperatures –a Probabilistic View on Permafrost in Norway. Fulltekst i vitenarkiv
• Westermann, Sebastian; Gisnås, Kjersti; Schuler, Thomas & Etzelmuller, Bernd (2012). Towards operational permafrost monitoring in Norway. Fulltekst i vitenarkiv
• Westermann, Sebastian; Lilleøren, Karianne Staalesen; Schuler, Thomas; Gisnås, Kjersti & Etzelmuller, Bernd (2012). Towards operational permafrost modelling for Norway. Fulltekst i vitenarkiv
• Westermann, Sebastian; Berntsen, Terje Koren; Etzelmuller, Bernd; Gisnås, Kjersti; Hagen, Jon Ove Methlie & Kristjansson, Jon Egill [Vis alle 8 forfattere av denne artikkelen] (2012). The CryoMET project – combining deterministic and probabilistic downscaling to model snow depth over a wide range of scales. Fulltekst i vitenarkiv

Se alle arbeider i NVA