scholarly journals On elevation models as input for mass-balance calculations of the Greenland ice sheet

1996 ◽  
Vol 23 ◽  
pp. 181-186 ◽  
Author(s):  
R. S. W. van de Wal ◽  
S. Ekholm
Keyword(s):  
Marginal Zone ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Balance Model ◽  
Data Sets ◽  
Differential Gps ◽  
Data Set ◽  
Radio Echo Sounding ◽  
The Difference ◽  
Elevation Model

In this paper the elevation model for the Greenland ice sheet based upon radio-echo-sounding flights of the Technical University of Denmark (TUD) (Letréguilly and others, 1991) are compared with the satellite-altimetry model (Tscherning and others, 1993) improved with airborne-laser and radar altimetry (IA model). Although the general hypsometry of both data sets is rather similar, differences seem to be large at individual points along the ice margin. Over the entire ice sheet, the difference between the IA model and the TUD model is 33 m with a root-mean-square error of 112 m. Differential GPS measurements collected in the ice-marginal zone near Søndre Strømfjord show that the IA model is more accurate than the TUD model. The latter data set underestimates the elevation by approximately 150 m in the ice-marginal zone near Søndre Strømfjord. Calculation of the ablation with an energy-balance model and with a degree-day model points to a 20% decrease in the ablation if the IA model is used. Not only does this show the sensitivity of ablation calculations to the orographic input but it also indicates that the ablation calculated by the models used nowadays is relatively overestimated.

scholarly journals On elevation models as input for mass-balance calculations of the Greenland ice sheet

1996 ◽  
Vol 23 ◽  
pp. 181-186 ◽  
Author(s):  
R. S. W. van de Wal ◽  
S. Ekholm
Keyword(s):  
Marginal Zone ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Balance Model ◽  
Data Sets ◽  
Differential Gps ◽  
Data Set ◽  
Radio Echo Sounding ◽  
The Difference ◽  
Elevation Model

In this paper the elevation model for the Greenland ice sheet based upon radio-echo-sounding flights of the Technical University of Denmark (TUD) (Letréguilly and others, 1991) are compared with the satellite-altimetry model (Tscherning and others, 1993) improved with airborne-laser and radar altimetry (IA model). Although the general hypsometry of both data sets is rather similar, differences seem to be large at individual points along the ice margin. Over the entire ice sheet, the difference between the IA model and the TUD model is 33 m with a root-mean-square error of 112 m. Differential GPS measurements collected in the ice-marginal zone near Søndre Strømfjord show that the IA model is more accurate than the TUD model. The latter data set underestimates the elevation by approximately 150 m in the ice-marginal zone near Søndre Strømfjord.Calculation of the ablation with an energy-balance model and with a degree-day model points to a 20% decrease in the ablation if the IA model is used. Not only does this show the sensitivity of ablation calculations to the orographic input but it also indicates that the ablation calculated by the models used nowadays is relatively overestimated.

scholarly journals A daily, 1 km resolution data set of downscaled Greenland ice sheet surface mass balance (1958–2015)

2016 ◽  
Vol 10 (5) ◽  
pp. 2361-2377 ◽  
Author(s):  
Brice Noël ◽  
Willem Jan van de Berg ◽  
Horst Machguth ◽  
Stef Lhermitte ◽  
Ian Howat ◽  
...  
Keyword(s):  
Mass Balance ◽  
Climate Model ◽  
Regional Climate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Surface Mass Balance ◽  
Data Set ◽  
Surface Mass ◽  
Ice Caps ◽  
Elevation Model

Abstract. This study presents a data set of daily, 1 km resolution Greenland ice sheet (GrIS) surface mass balance (SMB) covering the period 1958–2015. Applying corrections for elevation, bare ice albedo and accumulation bias, the high-resolution product is statistically downscaled from the native daily output of the polar regional climate model RACMO2.3 at 11 km. The data set includes all individual SMB components projected to a down-sampled version of the Greenland Ice Mapping Project (GIMP) digital elevation model and ice mask. The 1 km mask better resolves narrow ablation zones, valley glaciers, fjords and disconnected ice caps. Relative to the 11 km product, the more detailed representation of isolated glaciated areas leads to increased precipitation over the southeastern GrIS. In addition, the downscaled product shows a significant increase in runoff owing to better resolved low-lying marginal glaciated regions. The combined corrections for elevation and bare ice albedo markedly improve model agreement with a newly compiled data set of ablation measurements.

scholarly journals Isochronous information in a Greenland ice sheet radio echo sounding data set

2014 ◽  
Vol 41 (5) ◽  
pp. 1593-1599 ◽  
Author(s):  
Louise C. Sime ◽  
Nanna B. Karlsson ◽  
John D. Paden ◽  
S. Prasad Gogineni
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Data Set ◽  
Radio Echo Sounding ◽  
Echo Sounding

scholarly journals Analysis of the Surface Mass Balance for Deglacial Climate Simulations

2020 ◽  
Author(s):  
Marie-Luise Kapsch ◽  
Uwe Mikolajewicz ◽  
Florian Andreas Ziemen ◽  
Christian B. Rodehacke ◽  
Clemens Schannwell
Keyword(s):  
Mass Balance ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Meridional Overturning Circulation ◽  
Balance Model ◽  
Surface Mass Balance ◽  
Equilibrium Line Altitude ◽  
Data Set ◽  
Surface Mass ◽  
Climate Conditions

Abstract. Most studies analyzing changes in the surface mass balance (SMB) of the Greenland ice sheet are limited to the last century, due to the availability of observations and the computational limitations of regional climate modeling. Using transient simulations with a comprehensive Earth System Model (ESM) we extend previous research and study changes in the SMB and equilibrium line altitude (ELA) for deglacial climate conditions. An energy balance model (EBM) is used to downscale atmospheric processes. It determines the SMB on higher spatial resolution and allows to resolve SMB variations due to topographic gradients not resolved by the ESM. An evaluation for historical climate conditions (1980–2010) shows that derived SMBs compare well with SMBs from regional modeling. Throughout the deglaciation changes in insolation dominate the Greenland SMB: 1) The increase in insolation and associated warming early in the deglaciation result in an ELA and SMB increase. The SMB increase is caused by compensating effects of melt and accumulation, as a warmer atmosphere precipitates more. After 13 ka before present (BP) melt begins to dominate and the SMB decreases. 2) The decline in insolation after 9 ka BP leads to an increasing SMB and decreasing ELA. Superimposed on these long-term changes are episodes of significant SMB/ELA decreases, related to slowdowns of the Atlantic Meridional Overturning Circulation (AMOC) that lead to cooling over most of the Northern Hemisphere. To study associated changes in the ice sheet geometry, the SMB data set is made available to the ice sheet modeling community.

scholarly journals A complete glacier inventory of the Antarctic Peninsula based on Landsat 7 images from 2000 to 2002 and other preexisting data sets

2017 ◽  
Vol 9 (1) ◽  
pp. 115-131 ◽  
Author(s):  
Jacqueline Huber ◽  
Alison J. Cook ◽  
Frank Paul ◽  
Michael Zemp
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Antarctic Peninsula ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Data Sets ◽  
Rock Outcrops ◽  
Data Set ◽  
Glacier Inventory ◽  
The Antarctic

Abstract. The glaciers on the Antarctic Peninsula (AP) potentially make a large contribution to sea level rise. However, this contribution has been difficult to estimate since no complete glacier inventory (outlines, attributes, separation from the ice sheet) is available. This work fills the gap and presents a new glacier inventory of the AP north of 70° S, based on digitally combining preexisting data sets with geographic information system (GIS) techniques. Rock outcrops have been removed from the glacier basin outlines of Cook et al. (2014) by intersection with the latest layer of the Antarctic Digital Database (Burton-Johnson et al., 2016). Glacier-specific topographic parameters (e.g., mean elevation, slope and aspect) as well as hypsometry have been calculated from the DEM of Cook et al. (2012). We also assigned connectivity levels to all glaciers following the concept by Rastner et al. (2012). Moreover, the bedrock data set of Huss and Farinotti (2014) enabled us to add ice thickness and volume for each glacier. The new inventory is available from the Global Land Ice Measurements from Space (GLIMS) database (doi:10.7265/N5V98602) and consists of 1589 glaciers covering an area of 95 273 km2, slightly more than the 89 720 km2 covered by glaciers surrounding the Greenland Ice Sheet. Hence, compared to the preexisting data set of Cook et al. (2014), this data set covers a smaller area and one glacier less due to the intersection with the rock outcrop data set. The total estimated ice volume is 34 590 km3, of which one-third is below sea level. The hypsometric curve has a bimodal shape due to the unique topography of the AP, which consists mainly of ice caps with outlet glaciers. Most of the glacierized area is located at 200–500 m a.s.l., with a secondary maximum at 1500–1900 m. Approximately 63 % of the area is drained by marine-terminating glaciers, and ice-shelf tributary glaciers cover 35 % of the area. This combination indicates a high sensitivity of the glaciers to climate change for several reasons: (1) only slightly rising equilibrium-line altitudes would expose huge additional areas to ablation, (2) rising ocean temperatures increase melting of marine terminating glaciers, and (3) ice shelves have a buttressing effect on their feeding glaciers and their collapse would alter glacier dynamics and strongly enhance ice loss (Rott et al., 2011). The new inventory should facilitate modeling of the related effects using approaches tailored to glaciers for a more accurate determination of their future evolution and contribution to sea level rise.

scholarly journals High-resolution ice thickness and bed topography of a land-terminating section of the Greenland Ice Sheet

2014 ◽  
Vol 6 (2) ◽  
pp. 331-338 ◽  
Author(s):  
K. Lindbäck ◽  
R. Pettersson ◽  
S. H. Doyle ◽  
C. Helanow ◽  
P. Jansson ◽  
...  
Keyword(s):  
Sea Level ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Airborne Radar ◽  
Ice Thickness ◽  
Data Sets ◽  
Equilibrium Line Altitude ◽  
Data Set ◽  
Bed Topography ◽  
Ice Sheet Dynamics

Abstract. We present ice thickness and bed topography maps with a high spatial resolution (250–500 m) of a land-terminating section of the Greenland Ice Sheet derived from ground-based and airborne radar surveys. The data have a total area of ~12 000 km2 and cover the whole ablation area of the outlet glaciers of Isunnguata Sermia, Russell, Leverett, Ørkendalen and Isorlersuup up to the long-term mass balance equilibrium line altitude at ~1600 m above sea level. The bed topography shows highly variable subglacial trough systems, and the trough of Isunnguata Sermia Glacier is overdeepened and reaches an elevation of ~500 m below sea level. The ice surface is smooth and only reflects the bedrock topography in a subtle way, resulting in a highly variable ice thickness. The southern part of our study area consists of higher bed elevations compared to the northern part. The compiled data sets of ground-based and airborne radar surveys cover one of the most studied regions of the Greenland Ice Sheet and can be valuable for detailed studies of ice sheet dynamics and hydrology. The combined data set is freely available at doi:10.1594/pangaea.830314.

scholarly journals Simulating the growth of supra-glacial lakes at the western margin of the Greenland ice sheet

2012 ◽  
Vol 6 (2) ◽  
pp. 1307-1336
Author(s):  
A. A. Leeson ◽  
A. Shepherd ◽  
S. Palmer ◽  
A. Sundal ◽  
X. Fettweis
Keyword(s):  
Climate Model ◽  
Regional Climate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Porous Space ◽  
Glacial Lakes ◽  
Western Margin ◽  
The Difference ◽  
Using Data ◽  
Elevation Model

Abstract. We present a method of modelling the growth of supra-glacial lakes at the western margin of the Greenland ice sheet, based on routeing runoff estimated by a Regional Climate Model (RCM) across a digital elevation model (DEM) of the ice sheet surface. Using data acquired during the 2003 melt season, we demonstrate that the model is 18 times more likely to correctly predict the presence or absence of lakes identified in MODIS satellite imagery within an elevation range of 1000 to 1600 metres above sea level (m.a.s.l.) than it is to make incorrect predictions. Our model does not, however, simulate processes leading to lake stagnation or decay, such as refreezing or drainage – a process which affects approximately 17% of lakes in our study area (Selmes et al., 2011). This likely explains much of why our model over-predicts cumulative area by 32% although other factors including uncertainty in the DEM and in the MODIS derived observations used for validation contribute to this error. Simulated lake filling tends to lead observations by approximately 5 days which could be related to a filling period required to saturate cracks, crevasses and other porous space within the ice. We find that the maximum modelled lake covered ice sheet area is 6% and suggest that this is a topographic limitation for this sector. We can take this as an upper bound; given the absence of drainage in the model. In 2003, the difference between RCM estimates of runoff and the maximum volume of water simulated to be stored in lakes was 12.49 km3. This can be taken as a measure of potential water available for lubrication and is calculated to be 1.86 m3 per square metre of ice. This study has proved a good first step towards capturing the variability of supra-glacial lake evolution with a numerical model; we are optimistic that the model will develop further into a useful tool for use in analysing the behaviour of supra-glacial lakes on the Greenland ice sheet in the present day and beyond.

scholarly journals Response of the Energy Balance on the Margin of the Greenland Ice Sheet to Temperature Changes

1990 ◽  
Vol 36 (123) ◽  
pp. 217-221 ◽  
Author(s):  
Roger J. Braithwaite ◽  
Ole B. Olesen
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Air Temperature ◽  
Sensible Heat Flux ◽  
Ice Sheet ◽  
Temperature Response ◽  
Greenland Ice Sheet ◽  
Energy Balance Model ◽  
Balance Model ◽  
Sensible Heat

AbstractDaily ice ablation on two outlet glaciers from the Greenland ice sheet, Nordbogletscher (1979–83) and Qamanârssûp sermia (1980–86), is related to air temperature by a linear regression equation. Analysis of this ablation-temperature equation with the help of a simple energy-balance model shows that sensible-heat flux has the greatest temperature response and accounts for about one-half of the temperature response of ablation. Net radiation accounts for about one-quarter of the temperature response of ablation, and latent-heat flux and errors account for the remainder. The temperature response of sensible-heat flux at QQamanârssûp sermia is greater than at Nordbogletscher mainly due to higher average wind speeds. The association of high winds with high temperatures during Föhn events further increases sensible-heat flux. The energy-balance model shows that ablation from a snow surface is only about half that from an ice surface at the same air temperature.

scholarly journals A new bedrock and surface elevation dataset for modelling the Greenland ice sheet

2003 ◽  
Vol 37 ◽  
pp. 351-356 ◽  
Author(s):  
Jonathan L. Bamber ◽  
Duncan J. Baldwin ◽  
S. Prasad Gogineni
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Detailed Comparison ◽  
Radar Data ◽  
The Arctic ◽  
Small Scale ◽  
Surface Model ◽  
Rock Outcrops ◽  
Bed Topography ◽  
Elevation Model

AbstractA new digital elevation model of the surface of the Greenland ice sheet and surrounding rock outcrops has been produced from a comprehensive suite of satellite and airborne remote-sensing and cartographic datasets. The surface model has been regridded to a resolution of 5 km, and combined with a new ice-thickness grid derived from ice-penetrating radar data collected in the 1970s and 1990s. A further dataset, the International Bathymetric Chart of the Arctic Ocean, was used to extend the bed elevations to include the continental shelf. The new bed topography was compared with a previous version used for ice-sheet modelling. Near the margins of the ice sheet and, in particular, in the vicinity of small-scale features associated with outlet glaciers and rapid ice motion, significant differences were noted. This was highlighted by a detailed comparison of the bed topography around the northeast Greenland ice stream.

scholarly journals Greenland ice velocity maps from the PROMICE project

2021 ◽  
Vol 13 (7) ◽  
pp. 3491-3512
Author(s):  
Anne Solgaard ◽  
Anders Kusk ◽  
John Peter Merryman Boncori ◽  
Jørgen Dall ◽  
Kenneth D. Mankoff ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Radar Data ◽  
Temporal Consistency ◽  
Gps Measurements ◽  
High Accumulation ◽  
Synthetic Aperture Radar Data ◽  
Spatial Coverage ◽  
Ice Velocity ◽  
The Difference

Abstract. We present the Programme for Monitoring of the Greenland Ice Sheet (PROMICE) Ice Velocity product (https://doi.org/10.22008/promice/data/sentinel1icevelocity/greenlandicesheet, Solgaard and Kusk, 2021), which is a time series of Greenland Ice Sheet ice velocity mosaics spanning September 2016 through to the present. The product is based on Sentinel-1 synthetic aperture radar data and has a 500 m grid spacing. A new mosaic is available every 12 d and spans two consecutive Sentinel-1 cycles (24 d). The product is made available within ∼ 10 d of the last acquisition and includes all possible 6 and 12 d pairs within the two Sentinel-1A cycles. We describe our operational processing chain from data selection, mosaicking, and error estimation to final outlier removal. The product is validated against in situ GPS measurements. We find that the standard deviation of the difference between satellite- and GPS-derived velocities (and bias) is 20 m yr−1 (−3 m yr−1) and 27 m yr−1 (−2 m yr−1) for the components in an eastern and northern direction, respectively. Over stable ground the values are 8 m yr−1 (0.1 m yr−1) and 12 m yr−1 (−0.6 m yr−1) in an eastern and northern direction, respectively. This is within the expected values; however, we expect that the GPS measurements carry a considerable part of this uncertainty. We investigate variations in coverage from both a temporal and spatial perspective. The best spatial coverage is achieved in winter due to the comprehensive data coverage by Sentinel-1 and high coherence, while summer mosaics have the lowest coverage due to widespread melt. The southeast Greenland Ice Sheet margin, along with other areas of high accumulation and melt, often has gaps in the ice velocity mosaics. The spatial comprehensiveness and temporal consistency make the product ideal both for monitoring and for studying ice-sheet-wide and glacier-specific ice discharge and dynamics of glaciers on seasonal scales.

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