On the decay of first-year ice ridges: Measurements and evolution of rubble macroporosity, ridge drilling resistance and consolidated layer strength

Ervik, Åse; Høyland, Knut V.; Shestov, Aleksey; Nord, Torodd Skjerve

doi:10.1016/j.coldregions.2018.03.024

Cited by 16 publications

(8 citation statements)

References 32 publications

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“…) but in good agreement with the values presented byErvik et al (2018). Present results showed variation of the sail macroporosity between 0 and 30% and values from less than 1% up to 51% in the case of keels.…”

supporting

confidence: 92%

Morphology, internal structure and formation of ice ridges in the sea around Svalbard

Bonath

Petrich

Sand

et al. 2018

Cold Regions Science and Technology

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The results from 3 years of comprehensive field investigations on first-year ice ridges in the Arctic are presented in this paper. The scopes of these investigations were to fill existing knowledge gaps on ice ridges, gain understanding on ridge characteristics and study internal properties of ice. The ability of developing reliable simulations and load predictions for ridge-structure interactions is the final principal purpose, but beyond the scope of this paper. The presented data comprise ridge geometry, ice block dimensions from ridge sails, ice structure in the ridge and values on the ridge porosity and the degree of consolidation. The total ridge thickness conformed to other ridges studied in the same regions. The consolidated layer thickness was on average 2-3 times the level ice thickness. Minimum 33% and in average 90% of the ridge keel area was consolidated. The distribution of ice block sizes and block shapes within a ridge appears to be predictable. A new approach for deriving a possible ridging scenario and ridge age is presented. Different steps of the ridge building process were identified, which are in good agreement with earlier simulated ridging events. After formation of very thin lead ice between two floes deformation occurs through rafting and ridging until closure of the lead. Subsequently the adjacent level ice floe fractures proceeding ridge formation until ridging forces exceed driving forces. A time span of 10 days could be assessed for a possible ridge formation date, estimating the ridge age of the studied ridge located east of Edgeøya at 78° N to be 7 to 8 weeks.

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supporting

confidence: 92%

Morphology, internal structure and formation of ice ridges in the sea around Svalbard

Bonath

Petrich

Sand

et al. 2018

Cold Regions Science and Technology

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“…From literary sources it is known that averaged porosity of the unconsolidated portion of the keel can vary from 0.2 (Strub-Klein and Sudom 2012;Ervik et al 2018) to 0.3 (Beketsky and Truskov 1995;Høyland 2007), reaching in some cases up to 0.5 (Bonath et al 2018). As can be seen from the graphs in Figs.…”

Section: Kharitonov Ice Ridges In Landfast Ice Of Shokal'skogo Straitmentioning

confidence: 89%

Ice ridges in landfast ice of Shokal'skogo Strait

Kharitonov

2019

GES

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Three first-year ice ridges have been examined with respect to geometry and morphology in landfast ice of Shokal'skogo Strait (Severnaya Zemlya Archipelago) in May 2018. Two of the studied ice ridges were located on the edge of the ridged field and were part of it, because their keels extended for a long distance deep into this field. Ice ridges characteristics are discussed in the paper. These studies were conducted using hot water thermal drilling with computer recording of the penetration rate. Boreholes were drilled along the cross-section of the ridge crest at 0.25 m intervals. Cross-sectional profiles of ice ridges are illustrated. The maximal sail height varied from 2.9 up to 3.2 m, the maximal keel depth varied from 8.5 up to 9.6 m. The average keel depth to sail height ratio varied from 2.8 to 3.3, and the thickness of the consolidated layer was 2.5-3.5 m. The porosity of the non-consolidated part of the keel was about 23-27%. The distributions of porosity versus depth for all ice ridges are presented.

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“…coastal regions, because Hopkins (1998) and Amundrud et al (2004) pointed out that ridges in the central Arctic rarely reach the maximum thickness as the critical stresses do often not last long enough to complete the ridge building process. (Ervik et al, 2018;Høyland, 2007). If we assume that the fraction of 86 % of deformed ice in all observations had a porosity of 11-22 % the mean modeled thickness would increase by 0.1-0.3 m to 1.8-2 m.…”

Section: Magnitude Of Deformation Shapes Itdmentioning

confidence: 98%

Linking sea ice deformation to ice thickness redistribution using high-resolution satellite and airborne observations

Albedyll

Haas

Dierking

2020

Preprint

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Abstract. An unusual, large polynya opened and then closed by freezing and convergence north of the coast of Greenland in late winter 2018. The closing corresponded to a natural, but well-constrained, full-scale ice deformation experiment. We have observed the closing of and deformation within the polynya with satellite synthetic-aperture radar (SAR) imagery, and measured the accumulated effects of dynamic and thermodynamic ice growth 5 with an airborne electromagnetic (AEM) ice thickness survey one month after the closing began. During that time strong ice convergence decreased the area of the former polynya by a factor of 2.5. The AEM survey showed mean and modal thicknesses of the one-month old ice of 1.96 ± 1.5 m and 0.95 m, respectively.We show that this is in close agreement with the modeled thermodynamic growth and with the dynamic thickening expected from the polynya area decrease during that time. In addition,we found characteristic differences in the shapes of ice thickness distributions in different regions of the closing polynya. These closely corresponded to different deformation histories of the surveyed ice that were derived from the high-resolution SAR imagery by drift tracking along Lagrangian backward trajectories. Results show a linear proportionality between convergence and thickness change that agrees well with ice thickness redistribution theory. In addition, the e-folding of the tails of the different ice thickness distributions is proportional to the magnitude of the total deformation experienced by the ice. Lastly, we developed a simple volume-conserving model to derive dynamic ice thickness change from high-resolution SAR deformation tracking. The model has a spatial resolution of 1.4 km and reconstructs thickness profiles in reasonable agreement with the AEM observations. The computed ice thickness distribution resembles main characteristics like mode, e-folding, and width of the observed distribution. This demonstrates that high-resolution SAR deformation observations are capable of producing realistic ice thickness distributions. The MYI surrounding the polynya had a mean and modal total thickness (snow + ice) of 2.1 ± 1.4 m and 2.0 m, respectively. The similar first- and multi-year ice mean thicknesses elude to the large amount of deformation experienced by the closing polynya.

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On the decay of first-year ice ridges: Measurements and evolution of rubble macroporosity, ridge drilling resistance and consolidated layer strength

Cited by 16 publications

References 32 publications

Morphology, internal structure and formation of ice ridges in the sea around Svalbard

Morphology, internal structure and formation of ice ridges in the sea around Svalbard

Ice ridges in landfast ice of Shokal'skogo Strait

Linking sea ice deformation to ice thickness redistribution using high-resolution satellite and airborne observations

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