scholarly journals Surface roughness over the northern half of the Greenland Ice Sheet from airborne laser altimetry

2009 ◽  
Vol 114 (F1) ◽  
Author(s):  
C. J. van der Veen ◽  
Y. Ahn ◽  
B. M. Csatho ◽  
E. Mosley-Thompson ◽  
W. B. Krabill
Keyword(s):  
Surface Roughness ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Laser Altimetry ◽  
Airborne Laser ◽  
Northern Half

scholarly journals Surface roughness on the Greenland Ice Sheet from airborne laser altimetry

1998 ◽  
Vol 25 (20) ◽  
pp. 3887-3890 ◽  
Author(s):  
C. J. van der Veen ◽  
W. B. Krabill ◽  
B. M. Csatho ◽  
J. F. Bolzan
Keyword(s):  
Surface Roughness ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Laser Altimetry ◽  
Airborne Laser

Accuracy of airborne laser altimetry over the Greenland ice sheet

1995 ◽  
Vol 16 (7) ◽  
pp. 1211-1222 ◽  
Author(s):  
W. B. Krabill ◽  
R. H. Thomas ◽  
C. F. Martin ◽  
R. N. Swift ◽  
E. B. Frederick
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Laser Altimetry ◽  
Airborne Laser

Changes in Northwest Greenland Ice Sheet Elevation and Mass

2021 ◽  
Author(s):  
Inès Otosaka ◽  
Andrew Shepherd ◽  
Andreas Groh
Keyword(s):  
Mass Balance ◽  
Spatial Scales ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Mass Change ◽  
Elevation Change ◽  
Laser Altimetry ◽  
Mass Budget ◽  
Airborne Laser ◽  
The Impact

<p>About a third of Greenland’s total ice losses come from the Northwest sector, a sector that includes a large number of marine-terminating outlet glaciers, which have all experienced widespread retreat triggered by ocean-induced melting. Here, we derive changes in surface elevation, volume and mass in the Northwest sector of the Greenland Ice Sheet using a decade of CryoSat-2 observations. We find an average elevation change rate of 18.7 ± 0.4 cm/yr, with rapid thinning at the ice sheet margins at a rate of 42.7 ± 0.9 cm/yr. We compare our CryoSat-2 rates of elevation change to airborne laser altimetry data from Operation IceBridge. Overall, there is a good agreement between the two datasets with a mean difference of 6.5 ± 0.5 cm/yr and standard deviation of 31.1 cm/yr. We further compute volume change, which we convert to mass change by testing three alternate density models and we find that the northwest sector has lost 386 ± 3.7 Gt of ice between July 2010 and July 2019. We compare our mass balance estimate to independent estimates from gravimetry and the mass budget method across different spatial scales. First, we compare the different estimates by splitting the sector into two and four regions. While our altimetry estimate is the least negative across all regions, the gravimetry and mass budget estimates alternate in recording the largest ice losses. We further compare mass changes derived from altimetry and the mass budget method in each of the 74 individual glacier basins of the Northwest sector. We find a high correlation of 0.81 between rates of mass change from altimetry and the mass budget method, with the highest differences recorded in Steenstrup-Dietrichson and Kjer Gletscher basins. Our comparisons show that the spatial pattern of the differences between mass balance estimates is complex, suggesting that discrepancies between techniques do not solely originate from one single region or technique. Finally, we explore several factors that could potentially bias our altimetry mass balance estimation, by investigating differences between satellite radar and airborne laser altimetry, the dependency on grid spatial resolution and the impact of using different density models.</p>

Airborne laser altimetry mapping of the Greenland ice sheet

2002 ◽  
Vol 34 (3-4) ◽  
pp. 391-403 ◽  
Author(s):  
W Abdalati ◽  
W Krabill ◽  
E Frederick ◽  
S Manizade ◽  
C Martin ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Laser Altimetry ◽  
Airborne Laser

scholarly journals Interannual changes of the floating ice shelf of Petermann Gletscher, North Greenland, from 2000 to 2012

2014 ◽  
Vol 60 (221) ◽  
pp. 489-499 ◽  
Author(s):  
Andreas Münchow ◽  
Laurie Padman ◽  
Helen A. Fricker
Keyword(s):  
Mass Loss ◽  
Three Dimensional ◽  
Greenland Ice Sheet ◽  
Altimeter Data ◽  
Ice Shelf ◽  
Laser Altimetry ◽  
Laser Altimeter ◽  
Airborne Laser ◽  
Tracking Surface ◽  
Basal Melting

AbstractPetermann Gletscher, northwest Greenland, drains 4% of the Greenland ice sheet into Nares Strait. Its floating ice shelf retreated from 81 to 48 km in length during two large calving events in 2010 and 2012. We document changes in the three-dimensional ice-shelf structure from 2000 to 2012, using repeated tracks of airborne laser altimetry and ice radio-echo sounding, ICESat laser altimetry and MODIS visible imagery. The recent ice-shelf velocity, measured by tracking surface features between flights in 2010 and 2011, is ~1.25 km a−1, ~15–30% faster than estimates made before 2010. The steady- state along-flow ice divergence represents 6.3 Gta−1 mass loss through basal melting (~5Gta−1) and surface melting and sublimation (~1.0Gta−1). Airborne laser altimeter data reveal thinning, both along a thin central channel and on the thicker ambient ice shelf. From 2007 to 2010 the ice shelf thinned by ~5 m a−1, which represents a non-steady mass loss of ~4.1 Gta−1. We suggest that thinning in the basal channels structurally weakened the ice shelf and may have played a role in the recent calving events.

scholarly journals Time-evolving mass loss of the Greenland ice sheet from satellite altimetry

2014 ◽  
Vol 8 (1) ◽  
pp. 1057-1093
Author(s):  
R. T. W. L. Hurkmans ◽  
J. L. Bamber ◽  
C. H. Davis ◽  
I. R. Joughin ◽  
K. S. Khvorostovsky ◽  
...  
Keyword(s):  
Mass Loss ◽  
Satellite Altimetry ◽  
Climate Model ◽  
Regional Climate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Laser Altimetry ◽  
Radar Altimetry ◽  
Appropriate Treatment ◽  
Satellite Radar

Abstract. Mass changes of the Greenland ice sheet may be estimated by the Input Output Method (IOM), satellite gravimetry, or via surface elevation change rates (dH / dt). Whereas the first two have been shown to agree well in reconstructing mass changes over the last decade, there are few decadal estimates from satellite altimetry and none that provide a time evolving trend that can be readily compared with the other methods. Here, we interpolate radar and laser altimetry data between 1995 and 2009 in both space and time to reconstruct the evolving volume changes. A firn densification model forced by the output of a regional climate model is used to convert volume to mass. We consider and investigate the potential sources of error in our reconstruction of mass trends, including geophysical biases in the altimetry, and the resulting mass change rates are compared to other published estimates. We find that mass changes are dominated by SMB until about 2001, when mass loss rapidly accelerates. The onset of this acceleration is somewhat later, and less gradual, compared to the IOM. Our time averaged mass changes agree well with recently published estimates based on gravimetry, IOM, laser altimetry, and with radar altimetry when merged with airborne data over outlet glaciers. We demonstrate, that with appropriate treatment, satellite radar altimetry can provide reliable estimates of mass trends for the Greenland ice sheet. With the inclusion of data from CryoSat II, this provides the possibility of producing a continuous time series of regional mass trends from 1992 onward.

scholarly journals Laser altimetry reveals complex pattern of Greenland Ice Sheet dynamics

2014 ◽  
Vol 111 (52) ◽  
pp. 18478-18483 ◽  
Author(s):  
Beata M. Csatho ◽  
Anton F. Schenk ◽  
Cornelis J. van der Veen ◽  
Gregory Babonis ◽  
Kyle Duncan ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Complex Pattern ◽  
Laser Altimetry ◽  
Ice Sheet Dynamics

Contribution of turbulent heat fluxes to surface ablation on the Greenland ice sheet.

2020 ◽  
Author(s):  
Maurice Van Tiggelen ◽  
Paul Smeets ◽  
Carleen Reijmer ◽  
Brice Noël ◽  
Jakob Steiner ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Turbulent Fluxes ◽  
Heat Fluxes ◽  
Model Parameters ◽  
Turbulent Heat ◽  
Surface Ablation ◽  
Turbulent Heat Fluxes

<p>Over ice sheets and glaciers, the turbulent heat fluxes are, next to the radiative fluxes, the second largest source of energy driving the ablation. In general, most (climate) models use a bulk turbulence parametrization for the estimation of these energy fluxes. Recent work suggest that the turbulent heat fluxes might be greatly underestimated by such models. Unfortunately, only a few direct and long-term observations of turbulent fluxes are available over ice sheets to evaluate their inclusion in models. </p><p>In this study, we developed a vertical propeller eddy-covariance method to continuously monitor the sensible heat fluxes over the Greenland ice sheet (GrIS). We quantify its contribution to surface ablation using three years of data from the K-transect, located in the western ablation area of the GrIS. The direct flux measurements are also compared to those from several bulk turbulence models, and to a high-resolution regional climate model (RACMO2), in order to quantify modelling uncertainty.</p><p>The differences between observations and models highlight the need for upgrading the bulk turbulence parameterizations and especially the model parameters, such as the surface roughness lengths. We also find that during short but extreme warm events, the turbulent heat fluxes become the largest source for surface ablation. Typical for such intense events on the K-transect are fast changes in wind direction, which cause changes in the surface roughness parameters due to the anisotropic feature of the ice hummocks. These parameters are critical for modelling the turbulent fluxes in bulk parameterizations, but are often variable and unknown. We conclude with drone topography measurements to better constrain the surface roughness locally, and discuss methods to improve the modelling of turbulent surface fluxes on the whole GrIS.</p>

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