Finnur Pálsson

University of Iceland

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Helgi Björnsson

University of Iceland

107

Eyjólfur Magnússon

University of Iceland

Guðfinna Ađalgeirsdóttir

University of Iceland

Tómas Jøhannesson

Icelandic Meteorological Office

M. T. Guðmundsson

University of Iceland

Sverrir Guðmundsson

University of Iceland

Joaquín M. C. Belart

University of Iceland

ÉB

Étienne Berthier

Laboratoire d’Études en Géophysique et Océanographie Spatiales

ÞH

Þórdís Högnadóttir

University of Iceland

ÞÞ

Þorsteinn Þorsteinsson

Icelandic Meteorological Office

Cooperative Institutions

University of Iceland

115

National Oceanic and Atmospheric Administration

Centre National de la Recherche Scientifique

University of Colorado Boulder

Goddard Space Flight Center

Cooperative Institute for Research in Environmental Sciences

Icelandic Meteorological Office

Jet Propulsion Laboratory

Institut de Recherche pour le Développement

University of Washington

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Geodetic mass balance record with rigorous uncertainty estimates deduced from aerial photographs and lidar data – Case study from Drangajökull ice cap, NW Iceland

The cryosphere (2016)

Eyjólfur Magnússon Joaquín M. C. Belart Finnur Pálsson Hálfdán Ágústsson P. Crochet

Abstract. In this paper we describe how recent high-resolution digital elevation models (DEMs) can be used to extract glacier surface DEMs from old aerial photographs and to evaluate the uncertainty of the mass balance record derived from the DEMs. We present a case study for Drangajökull ice cap, NW Iceland. This ice cap covered an area of 144 km2 when it was surveyed with airborne lidar in 2011. Aerial photographs spanning all or most of the ice cap are available from survey flights in 1946, 1960, 1975, 1985, 1994 and 2005. All ground control points used to constrain the orientation of the aerial photographs were obtained from the high-resolution lidar DEM. The lidar DEM was also used to estimate errors of the extracted photogrammetric DEMs in ice- and snow-free areas, at nunataks and outside the glacier margin. The derived errors of each DEM were used to constrain a spherical semivariogram model, which along with the derived errors in ice- and snow-free areas were used as inputs into 1000 sequential Gaussian simulations (SGSims). The simulations were used to estimate the possible bias in the entire glaciated part of the DEM and the 95 % confidence level of this bias. This results in bias correction varying in magnitude between 0.03 m (in 1975) and 1.66 m (in 1946) and uncertainty values between ±0.21 m (in 2005) and ±1.58 m (in 1946). Error estimation methods based on more simple proxies would typically yield 2–4 times larger error estimates. The aerial photographs used were acquired between late June and early October. An additional seasonal bias correction was therefore estimated using a degree-day model to obtain the volume change between the start of 2 glaciological years (1 October). This correction was largest for the 1960 DEM, corresponding to an average elevation change of −3.5 m or approx. three-quarters of the volume change between the 1960 and the 1975 DEMs. The total uncertainty of the derived mass balance record is dominated by uncertainty in the volume changes caused by uncertainties of the SGSim bias correction, the seasonal bias correction and the interpolation of glacier surface where data are lacking. The record shows a glacier-wide mass balance rate of Ḃ = −0.26 ± 0.04 m w.e. a−1 for the entire study period (1946–2011). We observe significant decadal variability including periods of mass gain, peaking in 1985–1994 with Ḃ = 0.27 ± 0.11 m w.e. a−1. There is a striking difference when Ḃ is calculated separately for the western and eastern halves of Drangajökull, with a reduction of eastern part on average ∼ 3 times faster than the western part. Our study emphasizes the need for applying rigorous geostatistical methods for obtaining uncertainty estimates of geodetic mass balance, the importance of seasonal corrections of DEMs from glaciers with high mass turnover and the risk of extrapolating mass balance record from one glacier to another even over short distances.

Elevation (ballistics)

Aerial Survey

10.5194/tc-10-159-2016

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Citations (62)

Modeling of surface energy balance for Icelandic glaciers using remote-sensing albedo

The cryosphere (2023)

Andri Gunnarsson Sigurður M. Garðarsson Finnur Pálsson

Abstract. During the melt season, absorbed solar energy, modulated at the surface by albedo, is one of the main governing factors controlling surface melt variability for glaciers in Iceland. An energy balance model was applied with the possibility of utilizing spatiotemporal Moderate Resolution Imaging Spectroradiometer (MODIS) satellite-derived daily surface albedo driven by high-resolution climate forcing data to reconstruct the surface energy balance (SEB) for all Icelandic glaciers for the period 2000–2021. The SEB was reconstructed from April through September for 2000–2021 at a daily time step with a 500 m spatial resolution. Validation was performed using observations from various glaciers spanning distinct locations and elevations with good visual and statistical agreement. The results show that spatiotemporal patterns for the melt season have high annual and interannual variability for Icelandic glaciers. The variability was influenced by high climate variability, deposition of light-absorbing particles (LAPs) from volcanic eruptions and dust hotspots in pro-glacial areas close to the glaciers. Impacts of LAPs can lead to significant melt enhancement due to lowering of albedo and increased short-wave radiative energy forced at the surface. Large impacts on the SEB were observed for years with high LAP deposits, such as the volcanic eruption years of 2004, 2010 and 2011 and the sand- and dust-rich year of 2019. The impacts of volcanic eruptions and other LAP events were estimated using historical mean albedo under the same climatology forcing to provide estimations of melt energy enhancements. The impact of LAPs was often significant even though the glaciers were far away from the eruption location. On average, the melt enhancements due to LAPs were ∼27 % in 2010, ∼16 % in 2011 and ∼14 % in 2019 for Vatnajökull, Hofsjökull and Langjökull.

Albedo (alchemy)

Glacier mass balance

Forcing (mathematics)

10.5194/tc-17-3955-2023

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The August 2020 jökulhlaup from a marginal lake at Langjökull, W-Iceland: Course of events, discharge and volume estimates, future monitoring

Þorsteinn Thorsteinsson Kristjana G. Eythórsdóttir Esther Hlíðar Jensen Ingibjörg S. Jónsdóttir Finnur Pálsson

J&#246;kulhlaups from marginal and subglacial lakes are a considerable hazard in Iceland and the rapid retreat of glaciers and ice caps is leading to hydrological changes in many locations at or near the glaciers. This calls for careful monitoring of glaciers and proglacial areas.On August 17 2020, increased discharge was observed in Hv&#237;t&#225;, a glacial river originating in the ice cap Langj&#246;kull. Sediment-laden j&#246;kulhlaup waters filled a narrow gorge of the river near the farm and tourist resort H&#250;safell and dead salmon were found strewn over fields 30&#8211;40 km downstream.Reconnaissance trips, overflights and satellite image studies revealed the following course of events:A marginal glacial lake (current size: 1.3 km2) started forming at 890 m elevation at the western margin of Langj&#246;kull after the turn of the century. Sentinel-2 satellite images indicate that subglacial outflow from the lake had started in the morning of August 17. The exact path of the 2 km long subglacial water course can be inferred from a Landsat-8 image taken on November 11 2020. The image shows a narrow surface depression resulting from lowering of the glacier surface when the subglacial tunnel carrying the water was formed. The ice thickness averages 70 m along the flowpath.Emerging from beneath the ice cap, the water flowed 13 km through the Svart&#225; river canyon, eroding sediment from the river bed and canyon walls. Fresh colouring and sediment deposition was observed on sandur plains where Svart&#225; joins the Geit&#225; and Hv&#237;t&#225; rivers.Observations of the j&#246;kulhlaup (water level and flow velocity) as it passed beneath a bridge near H&#250;safell help constrain discharge levels and flood volume at a location 18 km from the outlet at Langj&#246;kull. In addition, real-time data on Hv&#237;t&#225; river water level are available from the Klj&#225;foss hydrometric station 35 km further downstream, discharge started rising from a background value of 90 m3/s on August 17 at 16:00. The flood peaked there at 260 m3/s at 01:45 in the early morning of August 18 and had subsided again at noon on that day.Using imagery from the Sentinel-2 satellites the area of the marginal lake is estimated to have diminished from 1.29 km2 to 0.46 km2 during the j&#246;kulhlaup. A lowering of 4 m has been determined from aerial imagery and the total volume released was 3.4 million m3 according to preliminary estimates. We estimate an average flow velocity of 3&#177;1 m/s for the entire distance from the outlet at the glacier to Klj&#225;foss.The glacier margin in the region has retreated by 500-1000 m and thinned by 3 m/a in the period 2004-2019 leading to the formation of the proglacial lake. Flooding events occurring in 2014 and 2017 have now been detected in hydrometric and remote sensing data. The lake is likely to become larger when retreat continues and further thinning of the ice may lead to more frequent j&#246;kulhlaups in coming years. Plans to monitor the lake level and install early warning systems will be outlined in the presentation.

Outflow

10.5194/egusphere-egu21-13666

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Afkomu- og hraðamælingar á Langjökli jökulárið 2019-2019

Finnur Pálsson Andri Gunnarsson Hlynur Skagfjörð Pálsson Sveinbjörn Steinþórsson Jarðvísindastofnun Háskólans

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Veður og orka : loftslagsbreytingar og áhrif þeirra á vatnafar og orkuframleiðslu

P. Crochet Tómas Jøhannesson Guðfinna Ađalgeirsdóttir Helgi Björnsson Elías B. Elíasson

Utdrattur ur skýrslunni : Effect of climate change on hydrology and hydro-resources in Iceland. Ath. sama skýrslunumer baeði a islenskri og enskri utgafu.

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A hydrogeological conceptual model of aquifers in catchments headed by temperate glaciers

Aude Vincent Clémence Daigre Ophélie Fischer Guðfinna Ađalgeirsdóttir Sophie Violette

Abstract. Achieving understanding and quantification of unknown aquifer systems in glacial context is crucial to forecast the evolution under climate change of water resources and of potential floods and landslides hazards. We focus on four south-eastern outlet glaciers of the main Icelandic icecap, Vatnajökull. New data are being acquired in the field to characterise groundwater dynamics. From this we propose a hydrogeological conceptual model: two distinct aquifers and their hydraulic conductivities are identified. A comprehensive water balance at the scale of the watershed has been obtained. Recharge to the aquifers is 4 times higher under the glaciers than on the plain, and we demonstrate the glacial melt recharge impact on the groundwater dynamic.

10.5194/egusphere-2022-1442

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Area, volume and mass changes of southeast Vatnajökull ice cap, Iceland, from the Little Ice Age maximum in the late 19th century to 2010

Hrafnhildur Hannesdóttir Helgi Björnsson Finnur Pálsson Guðfinna Ađalgeirsdóttir Sverrir Guðmundsson

Abstract. Area and volume changes and the average geodetic mass balance of the non-surging outlet glaciers of southeast Vatnajökull ice cap, Iceland, during different time periods between ~1890 and 2010, are derived from a multi-temporal glacier inventory. A series of digital elevation models (DEMs) (∼1890, 1904, 1936, 1945, 1989, 2002, 2010) have been compiled from glacial geomorphological features, historical photographs, maps, aerial images, DGPS measurements and a LiDAR survey. Given the mapped bedrock topography we estimate relative volume changes since the end of the Little Ice Age (LIA) ~1890. The variable dynamic response of the outlets, assumed to have experienced similar climate forcing, is related to their different hypsometry, bedrock topography, and the presence of proglacial lakes. In the post-LIA period the glacierized area decreased by 164 km2 and the glaciers had lost 10–30% of their ~1890 area by 2010. The glacier surface lowered by 150–270 m near the terminus and the outlet glaciers collectively lost 60 ± 8 km3 of ice, which is equivalent to 0.154 ± 0.02 mm of sea level rise. The relative volume loss of individual glaciers was in the range of 15–50%, corresponding to a geodetic mass balance between −0.70 and −0.32 m w.e. a−1. The rate of mass loss was most negative in the period 2002–2010, on average −1.34 ± 0.12 m w.e. a−1, which lists among the most negative mass balance values recorded worldwide in the early 21st century. From the data set of volume and area of the outlets, spanning the 120 years post-LIA period, we evaluate the parameters of a volume-area power law scaling relationship.

Glacier morphology

Glacier mass balance

Bedrock

Elevation (ballistics)

Ice caps

10.5194/tcd-8-4681-2014

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The Arctic

Bulletin of the American Meteorological Society (2024)

Matthew L. Druckenmiller Richard Thoman Twila Moon Liss M. Andreassen Thomas J. Ballinger

10.1175/bams-d-24-0101.1

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Array seismologic insights into Skaftá jökulhlaups (GLOFs), Iceland, 2014-2016.

Thoralf Dietrich Eva P. S. Eibl Finnur Pálsson Eyjólfur Magnússon Wolfgang Schwanghart

GLOFs, glacier lake outburst floods – or by their local type name jökulhlaups – sometimes travel and propagate subglacially. Usually, these subglacial floods can be observed only indirectly using records of the related glacier’s surface deformation derived from GNSS and InSAR techniques. However, these floods can also be monitored by the seismic signals they generate: Flood noise by turbulent water or carried sediments, ice quakes, and others. At Iceland’s Vatnajökull glacier, floods from the Skaftá cauldrons travel more than 40km below the ice before feeding into the Skaftá river. To study the propagation and the physics of the jökulhlaups, temporal seismic arrays were installed close to the glacier terminus, i.e., west and southwest of Vatnajökull between 2014 and 2016. To locate the generated tremor along the flood propagation path, we used two seismic methods: frequency-wavenumber-analysis (fk-analysis) and match field processing (MFP). In previous works, we were able to track the subglacial propagation of the flood tremors seismically for four GLOF events occurring between 2014 and 2016. For the discharge-highest flood occuring in October 2015 we were also able to identify seismic signals related to the rising water level downstream at rapids outside of the glacier. These findings can be directly related to hydrometric and GNSS observations, measured outside and on the glacier respectively. We find that the tremor can be related to the vertical deformation of the glacier after the flood front’s passing: an important insight allowing to reconstruct the glacier’s deformation seismically. Our results highlight the potential of seismic methods for monitoring subglacial floods, especially in combination with GNSS and hydrometric observations. We emphasize that such multi-method approaches can improve the understanding and quantification of flood characteristics such as their volume, origin, propagation and timing which are critical to effectively provide early warning of subglacial floods.

10.5194/egusphere-egu24-12879

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Sensitivity of Glacier Runoff to Winter Snow Thickness Investigated for Vatnajökull Ice Cap, Iceland, Using Numerical Models and Observations

Atmosphere (2018)

Louise Steffensen Schmidt Peter L. Langen Guðfinna Ađalgeirsdóttir Finnur Pálsson Sverrir Guðmundsson

Several simulations of the surface climate and energy balance of Vatnajökull ice cap, Iceland, are used to estimate the glacier runoff for the period 1980–2015 and the sensitivity of runoff to the spring conditions (e.g., snow thickness). The simulations are calculated using the snow pack scheme from the regional climate model HIRHAM5, forced with incoming mass and energy fluxes from the numerical weather prediction model HARMONIE-AROME. The modeled runoff is compared to available observations from two outlet glaciers to assess the quality of the simulations. To test the sensitivity of the runoff to spring conditions, simulations are repeated for the spring conditions of each of the years 1980–2015, followed by the weather of all summers in the same period. We find that for the whole ice cap, the variability in runoff as a function of varying spring conditions was on average 31% of the variability due to changing summer weather. However, some outlet glaciers are very sensitive to the amount of snow in the spring, as e.g., the variation in runoff from Brúarjökull due to changing spring conditions was on average 50% of the variability due to varying summer weather.

Glacier mass balance

10.3390/atmos9110450

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Citations (18)