Surface ablation model evaluation on a drifting ice island in the Canadian Arctic

Crawford, Anna; Mueller, Derek; Humphreys, Elyn; Carrières, Tom; Tran, Hang

doi:10.1016/j.coldregions.2014.11.011

Cited by 16 publications

(21 citation statements)

References 44 publications

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“…A value of 6.4 mm w.e.·°C À1 ·day À1 was assigned to the DDF parameter (Crawford et al, 2015). PDDs were calculated using hourly 2-m air temperature data from the CGRF data set (Smith et al, 2014).…”

Section: Meltwater Dispersalmentioning

confidence: 99%

The Aftermath of Petermann Glacier Calving Events (2008–2012): Ice Island Size Distributions and Meltwater Dispersal

et al. 2018

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Three large calving events occurred at Petermann Glacier in northwest Greenland between 2008 and 2012 that generated ice islands (large tabular icebergs) that ranged from ~30 to 300 km2 in areal extent. Ice islands are known to deteriorate, via fracture and melt, during their drift through regional water bodies where they pose a potential risk to offshore resource extraction operations and disperse freshwater from the Greenland Ice Sheet. This study presents the first analysis of the deterioration occurring across the flux of ice islands that travel between Nares Strait and the North Atlantic after Petermann Glacier calving events. The evolution of Petermann ice island size distributions was evaluated, and the spatial dispersal of meltwater was quantified, through analyses that utilized the newly developed Canadian Ice Island Drift, Deterioration and Detection Database. Size‐frequency distributions remained relatively consistent, both spatially and temporally, and were well fit by power law models with slopes of approximately −1.7. This suggested that fracture was an important process by which the Petermann ice islands deteriorated, regardless of elapsed time or distance from the glacier. Ice island meltwater fluxes into the Baffin Island and Labrador currents were not large enough to slow down the Atlantic Meridional Overturning Circulation by weakening deep‐water convection in the Labrador Sea. However, augmented meltwater input was calculated within Petermann Fjord (2.0 mSv) and in the vicinity of grounding locations (0.4 mSv). Further research is necessary to better understand how this freshwater alters fjord circulation and influences the composition of local ocean waters.

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Section: Meltwater Dispersalmentioning

confidence: 99%

The Aftermath of Petermann Glacier Calving Events (2008–2012): Ice Island Size Distributions and Meltwater Dispersal

et al. 2018

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“…The chronic lowering of the surface from radiation and turbulent heat fluxes [16], which affects the vertical dimension, is also possible to detect with these surveying techniques. However, the influence of buoyancy on freeboard height would need to be considered when reporting deterioration magnitudes.…”

Section: Detection Thresholds and Monitoring Iceberg Deterioration Prmentioning

confidence: 99%

“…Chronic sidewall recession caused by radiation and forced convection is much harder to detect. Assuming a rate of 0.3 m day −1 [16,66] is representative, deterioration from this process could be reliably measured if employing dual-frequency GPS receivers within 8 days with TLS surveying or 1.3 days with SfM processing of aerial photography. Figure 9.…”

Section: Detection Thresholds and Monitoring Iceberg Deterioration Prmentioning

confidence: 99%

“…Unfortunately, the calibration and validation of both iceberg and ice island deterioration models has been restrained by a paucity of in-situ data sets that accurately capture both the morphological change and corresponding environmental data required [14,15]. This is largely due to logistical, financial, and safety issues that accompany surveying these subjects in remote locations [16,17]. In addition, one must overcome the technical challenges associated with surveying a The two surveying methods are evaluated with consecutive, triplicate surveys over which time (<70 min) we assume that no appreciable deterioration (i.e., from melting or calving) has occurred.…”

Section: Introductionmentioning

confidence: 99%

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Surveying Drifting Icebergs and Ice Islands: Deterioration Detection and Mass Estimation with Aerial Photogrammetry and Laser Scanning

2018

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Icebergs and ice islands (large, tabular icebergs) are challenging targets to survey due to their size, mobility, remote locations, and potentially difficult environmental conditions. Here, we assess the precision and utility of aerial photography surveying with structure-from-motion multi-view stereo photogrammetry processing (SfM) and vessel-based terrestrial laser scanning (TLS) for iceberg deterioration detection and mass estimation. For both techniques, we determine the minimum amount of change required to reliably resolve iceberg deterioration, the deterioration detection threshold (DDT), using triplicate surveys of two iceberg survey targets. We also calculate their relative uncertainties for iceberg mass estimation. The quality of deployed Global Positioning System (GPS) units that were used for drift correction and scale assignment was a major determinant of point cloud precision. When dual-frequency GPS receivers were deployed, DDT values of 2.5 and 0.40 m were calculated for the TLS and SfM point clouds, respectively. In contrast, values of 6.6 and 3.4 m were calculated when tracking beacons with lower-quality GPS were used. The SfM dataset was also more precise when used for iceberg mass estimation, and we recommend further development of this technique for iceberg-related end-uses.

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“…It is necessary to systematically conduct field operations to collect deterioration data for analysis, further develop remote sensing monitoring techniques and improve drift and deterioration models. Recent calving events at the Petermann Glacier in northwest Greenland have provided numerous study subjects that have been used to examine ice island deterioration in eastern Canadian waters (Forrest et al, 2012;Halliday et al, 2012;Wagner et al, 2014;Crawford et al, 2015Crawford et al, , 2016Stern et al, 2015). However, the current compilation of ice island deterioration research in this region exhibits the following three shortcomings: no long term field dataset of ice island thinning has been collected, a framework for quantifying the error associated with field deterioration assessment has not been developed and the ice island flux through eastern Canadian waters after relatively large Petermann Glacier calving events has not been comprehensively monitored and analyzed.…”

Section: Ice Islands In a Changing Climate And Research Justificationmentioning

confidence: 99%

Ice island deterioration

Crawford¹

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Ice islands are large, tabular icebergs that calve from ice shelves and floating ice tongues. Their drift and deterioration is of concern to offshore industry and influences the dispersal of freshwater from Earth's major ice sheets. However, the analysis and modelling of ice island deterioration is constrained by a lack of systematic studies using field and remotely sensed data. The aim of this thesis is to improve our understanding of ice island deterioration through the use and development of novel techniques and datasets. It uses complementary field and remotely sensed datasets in three studies that individually focus on vertical deterioration (i.e., thinning), small-scale areal deterioration (e.g., wave erosion), and large-scale areal deterioration (i.e., fracture). The study subjects are ice islands in eastern Canadian waters that calved from the Petermann Glacier of northwest Greenland between 2008 and 2012. The vertical deterioration of a grounded Petermann ice island (PII) was quantified with stationary ice penetrating radar (IPR), mobile IPR and ablation stake data measurements collected over three field campaigns. Derived basal ablation was used to calibrate a basal ablation model, which was applied in a separate study to quantify the spatial distribution of meltwater from the drift and deterioration of hundreds of PIIs. This study used the Canadian Ice Island Drift, Deterioration and Detection Database, which was generated through the analysis of thousands of RADARSAT-2 synthetic aperture radar scenes. The database was also used to evaluate the fit of statistical distributions to the size-frequency distributions of PIIs. The results indicate that fracture remained an influential deterioration process over the monitoring period. A third study found that deterioration on the order of 40 cm could be detected under optimal conditions with aerial photogrammetry with structure-from-motion processing and that this technique was superior to laser scanning. iii This thesis presents new insights into ice island deterioration processes. It also documents new techniques for measuring deterioration and contributes pertinent information to two major ice island research themes (i.e., hazards and freshwater vectors). Finally, many results and future research directions are applicable to ice island research conducted in both Polar Regions on planet Earth. The time that I have spent as a graduate student researching big, diminishing blocks of ice has been an incredible experience due to a wide support network. Derek Mueller's supervision was paramount, as was his encouragement, understanding and enthusiasm for innovation. I thank Gregory Crocker and Doug King for providing strategic and analytical guidance from the time of my comprehensive exam to thesis submission. I also greatly appreciate the thoughtful review of my thesis by Douglas MacAyeal (University of Chicago) and Shawn Kenney (Carleton University). It has been exciting to watch the Water and Ice Research Lab (WIRL) grow over my seven years in the Department of...

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Surface ablation model evaluation on a drifting ice island in the Canadian Arctic

Cited by 16 publications

References 44 publications

The Aftermath of Petermann Glacier Calving Events (2008–2012): Ice Island Size Distributions and Meltwater Dispersal

The Aftermath of Petermann Glacier Calving Events (2008–2012): Ice Island Size Distributions and Meltwater Dispersal

Surveying Drifting Icebergs and Ice Islands: Deterioration Detection and Mass Estimation with Aerial Photogrammetry and Laser Scanning

Ice island deterioration

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