TopoToolbox: A set of Matlab functions for topographic analysis

Schwanghart, Wolfgang; Kuhn, N. J.

doi:10.1016/j.envsoft.2009.12.002

Cited by 329 publications

(239 citation statements)

References 37 publications

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“…The main components of the model, which has been applied in a previous version to the Croker Bay catchment of the Devon Ice Cap (Clason et al, 2012), comprise: (1) a degree-day model for meltwater generation; (2) an algorithm for routing meltwater across the ice surface (Schwanghart and Kuhn, 2010) and storing meltwater within supraglacial lakes; and (3) a model for calculating penetration depths of water-filled crevasses, after van der Veen (2007). The model, which is run here with a spatial resolution of 500 m and a temporal resolution of 1 day, is the first predictive (rather than prescriptive) model for moulin formation and the transfer of meltwater to the ice-bed interface applied to the Greenland ice sheet.…”

Section: Methodsmentioning

confidence: 99%

“…A single-flow direction algorithm was applied to route available surface meltwater across the ice surface based on surface elevation (Schwanghart and Kuhn, 2010;Schwanghart and Scherler, 2014), where the amount of meltwater in each cell weighted downstream flow accumulation. The 100 m Palmer et al (2011) DEM was resampled to the standard model spatial resolution of 500 m. We did not define a threshold for discrete stream formation due to the spatial resolution of the DEM; instead meltwater was distributed across the ice surface by flow accumulation only.…”

Section: Meltwater Routing and Accumulation In Supraglacial Lakesmentioning

confidence: 99%

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Modelling the transfer of supraglacial meltwater to the bed of Leverett Glacier, Southwest Greenland

et al. 2015

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Abstract. Meltwater delivered to the bed of the GreenlandIce Sheet is a driver of variable ice-motion through changes in effective pressure and enhanced basal lubrication. Ice surface velocities have been shown to respond rapidly both to meltwater production at the surface and to drainage of supraglacial lakes, suggesting efficient transfer of meltwater from the supraglacial to subglacial hydrological systems. Although considerable effort is currently being directed towards improved modelling of the controlling surface and basal processes, modelling the temporal and spatial evolution of the transfer of melt to the bed has received less attention. Here we present the results of spatially distributed modelling for prediction of moulins and lake drainages on the Leverett Glacier in Southwest Greenland. The model is run for the 2009 and 2010 ablation seasons, and for future increased melt scenarios. The temporal pattern of modelled lake drainages are qualitatively comparable with those documented from analyses of repeat satellite imagery. The modelled timings and locations of delivery of meltwater to the bed also match well with observed temporal and spatial patterns of ice surface speed-ups. This is particularly true for the lower catchment ( < 1000 m a.s.l.) where both the model and observations indicate that the development of moulins is the main mechanism for the transfer of surface meltwater to the bed. At higher elevations (e.g. 1250-1500 m a.s.l.) the development and drainage of supraglacial lakes becomes increasingly important. At these higher elevations, the delay between modelled melt generation and subsequent delivery of melt to the bed matches the observed delay between the peak air temperatures and subsequent velocity speed-ups, while the instantaneous transfer of melt to the bed in a control simulation does not. Although both moulins and lake drainages are predicted to increase in number for future warmer climate scenarios, the lake drainages play an increasingly important role in both expanding the area over which melt accesses the bed and in enabling a greater proportion of surface melt to reach the bed.

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Section: Methodsmentioning

confidence: 99%

Section: Meltwater Routing and Accumulation In Supraglacial Lakesmentioning

confidence: 99%

Modelling the transfer of supraglacial meltwater to the bed of Leverett Glacier, Southwest Greenland

et al. 2015

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“…We therefore employ only a D8 flow routing algorithm here as it is coupled with sink preservation tools in ArcHydro ('Fill Sinks' tool Flow routing was carried out using the ArcHydro toolbox in ArcGIS 10.3.1 [43], which allows for sink preservation during sink filling and flow routing using a standard D8 flow routing algorithm [50]. A multi-directional flow (MDF) routing algorithm was also tested using the MATLAB based TopoToolbox [51]. Similar to findings by Karlstrom and Yang (2016) [10], channel networks delineated with MDF were similar to those delineated with D8.…”

Section: Channel Network Extractionmentioning

confidence: 99%

Flow Routing for Delineating Supraglacial Meltwater Channel Networks

et al. 2016

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Abstract:Growing interest in supraglacial channels, coupled with the increasing availability of high-resolution remotely sensed imagery of glacier surfaces, motivates the development and testing of new approaches to delineating surface meltwater channels. We utilized a high-resolution (2 m) digital elevation model of parts of the western margin of the Greenland Ice Sheet (GrIS) and retention of visually identified sinks (i.e., moulins) to investigate the ability of a standard D8 flow routing algorithm to delineate supraglacial channels. We compared these delineated channels to manually digitized channels and to channels extracted from multispectral imagery. We delineated GrIS supraglacial channel networks in six high-elevation (above 1000 m) and one low-elevation (below 1000 m) catchments during and shortly after peak melt (July and August 2012), and investigated the effect of contributing area threshold on flow routing performance. We found that, although flow routing is sensitive to data quality and moulin identification, it can identify 75% to 99% of channels observed with multispectral analysis, as well as low-order, high-density channels (up to 15.7 km/km 2 with a 0.01 km 2 contributing area threshold) in greater detail than multispectral methods. Additionally, we found that flow routing can delineate supraglacial channel networks on rough ice surfaces with widespread crevassing. Our results suggest that supraglacial channel density is sufficiently high during peak melt that low contributing area thresholds can be employed with little risk of overestimating the channel network extent.

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“…Bed profiles were then fit with a linear regression model to establish retrograde or seaward sloping beds. To estimate drainage catchment areas and the percentage of each catchment below present sea level for each study glacier, surface drainage catchments were delineated using the GIMP surface DEM and topographic analysis functions within TopoToolbox in MATLAB (Schwanghart and Kuhn, 2010). First, all sinks in the DEM were filled and the resultant DEM was used calculate flow direction and flow accumulation.…”

Section: Fjord Width Ice Surface and Basal Topographymentioning

confidence: 99%

“…Surface air temperature data were acquired from the Danish Meteorological Institute (Vinther et al, 2006 ) are shown between 1993 and 2015 derived from the multi-year mosaic dataset (Joughin et al, 2010), acquired 5 from the National Snow and Ice Data Centre. Glacier drainage catchments (black outlines) were calculated using the surface DEM from the IceBridge Bed Machine dataset (Morlighem et al, 2015), and hydrological analysis using the TopoToolbox in Matlab (Schwanghart and Kuhn, 2010). …”

Section: Data Availabilitymentioning

confidence: 99%

Dynamic changes in outlet glaciers in northern Greenland from 1948 to 2015

Hill¹,

Carr²,

Stokes³

et al. 2018

Preprint

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The Greenland Ice Sheet (GrIS) is losing mass in response to recent climatic and oceanic warming. Since the mid-1990s, marine-terminating outlet glaciers across the GrIS have retreated, accelerated and thinned, but recent changes in northern 10Greenland have been comparatively understudied. Consequently, the dynamic response (i.e. changes in surface elevation and velocity) of these outlet glaciers to changes at their termini, particularly calving from floating ice tongues, remains unknown.Here we use satellite imagery and historical maps to produce an unprecedented 68-year record of terminus change across 18 major outlet glaciers and combine this with previously published surface elevation and velocity datasets. Overall, recent (1995Overall, recent ( -2015 retreat rates were higher than at any time in the previous 47 years, but change-point analysis reveals three categories of 15 frontal position change: (i) minimal change followed by steady and continuous retreat, (ii) minimal change followed by a switch to a period of short-lived rapid retreat, (iii) glaciers that underwent cycles of advance and retreat. Furthermore, these categories appear to be linked to the terminus type, with those in category (i) having grounded termini and those in category (ii) characterised by floating ice tongues. We interpret glaciers in category (iii) as surge-type. Glacier geometry (e.g. fjord width and basal topography) is also an important influence on the dynamic re-adjustment of glaciers to changes at their termini. 20Taken together, the loss of several ice tongues and the recent acceleration in the retreat of numerous marine-terminating glaciers suggests northern Greenland is undergoing rapid change and could soon impact on some large catchments that have capacity to contribute an important component to sea level rise.

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TopoToolbox: A set of Matlab functions for topographic analysis

Cited by 329 publications

References 37 publications

Modelling the transfer of supraglacial meltwater to the bed of Leverett Glacier, Southwest Greenland

Modelling the transfer of supraglacial meltwater to the bed of Leverett Glacier, Southwest Greenland

Flow Routing for Delineating Supraglacial Meltwater Channel Networks

Dynamic changes in outlet glaciers in northern Greenland from 1948 to 2015

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