Surface heights and crevasse morphologies of surging and fast-moving glaciers from ICESat-2 laser altimeter data - Application of the density-dimension algorithm (DDA-ice) and evaluation using airborne altimeter and Planet SkySat data

Herzfeld, U. C.; Trantow, T.; Lawson, Matthew; Hans, Jacob; Medley, G.

doi:10.1016/j.srs.2020.100013

Cited by 28 publications

(85 citation statements)

References 30 publications

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“…3 and 4. Fortunately, information smaller than the footprint diameter can be extracted from the ATL03 product, as shown by Herzfeld et al (2020), in which a density-dimension algorithm is used that facilitates surface height determination at the 0.7 m nominal along-tack resolution. In the following part we describe a method to produce a 1 m resolution alongtrack surface height estimation from the ATL03 raw photons signal.…”

Section: Icesat-2 Laser Altimetermentioning

confidence: 99%

Mapping the aerodynamic roughness of the Greenland Ice Sheet surface using ICESat-2: evaluation over the K-transect

et al. 2021

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Abstract. The aerodynamic roughness of heat, moisture, and momentum of a natural surface are important parameters in atmospheric models, as they co-determine the intensity of turbulent transfer between the atmosphere and the surface. Unfortunately this parameter is often poorly known, especially in remote areas where neither high-resolution elevation models nor eddy-covariance measurements are available. In this study we adapt a bulk drag partitioning model to estimate the aerodynamic roughness length (z0m) such that it can be applied to 1D (i.e. unidirectional) elevation profiles, typically measured by laser altimeters. We apply the model to a rough ice surface on the K-transect (west Greenland Ice Sheet) using UAV photogrammetry, and we evaluate the modelled roughness against in situ eddy-covariance observations. We then present a method to estimate the topography at 1 m horizontal resolution using the ICESat-2 satellite laser altimeter, and we demonstrate the high precision of the satellite elevation profiles against UAV photogrammetry. The currently available satellite profiles are used to map the aerodynamic roughness during different time periods along the K-transect, that is compared to an extensive dataset of in situ observations. We find a considerable spatio-temporal variability in z0m, ranging between 10−4 m for a smooth snow surface and 10−1 m for rough crevassed areas, which confirms the need to incorporate a variable aerodynamic roughness in atmospheric models over ice sheets.

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Section: Icesat-2 Laser Altimetermentioning

confidence: 99%

Mapping the aerodynamic roughness of the Greenland Ice Sheet surface using ICESat-2: evaluation over the K-transect

et al. 2021

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“…Investigation of the performance of the six ICESat-2 beams in comparison to the ICESat beam through intra-beam crossovers within a timespan of less than 30 days showed that ICESat crossover errors are higher and increase by a factor of 2.5 over a range of cross track slopes, while ICESat-2 beams comparably perform with lower overall error values [11]. Additionally, a new "density-dimension algorithm" transforms ATLAS acquisitions to ice height retrievals with a spacing of 0.7 m and automatically adopts measurements to variable background conditions [60]. This enables the determination of detailed surface characteristics, such as those on heavily crevassed, rapidly accelerating surge-type glaciers [60].…”

Section: Crossover Technique Performancementioning

confidence: 99%

“…Additionally, a new "density-dimension algorithm" transforms ATLAS acquisitions to ice height retrievals with a spacing of 0.7 m and automatically adopts measurements to variable background conditions [60]. This enables the determination of detailed surface characteristics, such as those on heavily crevassed, rapidly accelerating surge-type glaciers [60]. Technological and methodological improvements, such as those are expected to produce highly accurate elevation change measurements in further crossover attempts by including ICESat-2 data, even in complex terrain.…”

Section: Crossover Technique Performancementioning

confidence: 99%

Increased Ice Thinning over Svalbard Measured by ICESat/ICESat-2 Laser Altimetry

2021

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A decade-long pronounced increase in temperatures in the Arctic, especially in the Barents Sea region, resulted in a global warming hotspot over Svalbard. Associated changes in the cryosphere are the consequence and lead to a demand for monitoring of the glacier changes. This study uses spaceborne laser altimetry data from the ICESat and ICESat-2 missions to obtain ice elevation and mass change rates between 2003–2008 and 2019. Elevation changes are derived at orbit crossover locations throughout the study area, and regional volume and mass changes are estimated using a hypsometric approach. A Svalbard-wide annual elevation change rate of −0.30 ± 0.15 m yr−1 was found, which corresponds to a mass loss rate of −12.40 ± 4.28 Gt yr−1. Compared to the ICESat period (2003–2009), thinning has increased over most regions, including the highest negative rates along the west coast and areas bordering the Barents Sea. The overall negative regime is expected to be linked to Arctic warming in the last decades and associated changes in glacier climatic mass balance. Further, observed increased thinning rates and pronounced changes at the eastern side of Svalbard since the ICESat period are found to correlate with atmospheric and oceanic warming in the respective regions.

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“…Fortunately, information smaller than the footprint diameter can be extracted from the ATL03 product, as shown by Herzfeld et al (2020). In the following part we describe a method to produce a 1 m resolution along-track surface height estimation from the ATL03 raw photons signal.…”

Section: Icesat-2 Laser Altimetermentioning

confidence: 99%

Comment on tc-2020-378

2021

View full text Add to dashboard Cite

The aerodynamic roughness of heat, moisture and momentum of a natural surface is an important parameter in atmospheric models, as it co-determines the intensity of turbulent transfer between the atmosphere and the surface. Unfortunately this parameter is often poorly known, especially in remote areas where neither high-resolution elevation models nor eddy-covariance measurements are available. In this study we adapt a bulk drag partitioning model to estimate the aerodynamic roughness length (z 0m) such that it can be applied to 1D (i.e. unidirectional) elevation profiles, typically measured by laser altimeters. We apply the model to a rough ice surface on the K-transect (western Greenland ice sheet) using UAV photogrammetry, and evaluate the modelled roughness against in situ eddy-covariance observations. We then present a method to estimate the topography at 1 m horizontal resolution using the ICESat-2 satellite laser altimeter, and demonstrate the high precision of the satellite elevation profiles against UAV photogrammetry. The currently available satellite profiles are used to map the aerodynamic roughness during different time periods along the K-transect, that is compared to an extensive dataset of in situ observations. We find a considerable spatio-temporal variability in z 0m , ranging between 10 −4 m for a smooth snow surface over 10 −1 m for rough crevassed areas, which confirms the need to incorporate a variable aerodynamic roughness in atmospheric models over ice sheets.

show abstract

Surface heights and crevasse morphologies of surging and fast-moving glaciers from ICESat-2 laser altimeter data - Application of the density-dimension algorithm (DDA-ice) and evaluation using airborne altimeter and Planet SkySat data

Cited by 28 publications

References 30 publications

Mapping the aerodynamic roughness of the Greenland Ice Sheet surface using ICESat-2: evaluation over the K-transect

Mapping the aerodynamic roughness of the Greenland Ice Sheet surface using ICESat-2: evaluation over the K-transect

Increased Ice Thinning over Svalbard Measured by ICESat/ICESat-2 Laser Altimetry

Comment on tc-2020-378

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