Ice ridge keel geometry and shape derived from one year of upward looking sonar data in the Fram Strait

Ekeberg, Ole-Christian; Høyland, Knut V.; Hansen, Edmond

doi:10.1016/j.coldregions.2014.10.003

Cited by 17 publications

(13 citation statements)

References 33 publications

(59 reference statements)

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“…Ekeberg et al . [] identified individual ridges deeper than 5 m in the same ice thickness data set from Fram Strait over these years, and found that both the number of ridges and their mean keel draft was significantly reduced over the period. The cause of this short‐term change in the ridged volume of sea ice in Fram Strait is not obvious.…”

Section: Resultsmentioning

confidence: 99%

Variability in categories of Arctic sea ice in Fram Strait

et al. 2014

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An attempt to quantify the temporal variability in the volume composition of Arctic sea ice is presented. Categories of sea ice in the Transpolar Drift in Fram Strait are derived from monthly ice thickness distributions obtained by moored sonars . The inflection points on each side of the old ice modal peak are used to separate modal ice from ice which is thinner and thicker than ice in the modal range. The volume composition is then quantified through the relative amount of ice belonging to each of the three categories thin, modal, and thick ice in the monthly ice thickness distributions. The trend of thin ice was estimated to be negative at 28.8% per decade (relative to the long-term mean), which was compensated for by increasing trends in modal and thick ice of 7.9% and 4.7% per decade, respectively. A 7-8 year cycle is apparent in the thin and thick ice records, which may explain a loss of deformed ice since 2007. We also quantify how the categories contribute to the mean ice thickness over time. Thick (predominantly deformed) ice dominates the mean ice thickness, constituting on average 66% of the total mean. Following the loss of deformed ice since 2007, the contribution of thick ice to the mean decreased from 75% to 52% at the end of the record. Thin deformed ice did not contribute to this reduction; it was pressure ridges thicker than 5 m that were lost and hence caused the decrease in mean ice thickness.

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Section: Resultsmentioning

confidence: 99%

Variability in categories of Arctic sea ice in Fram Strait

et al. 2014

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“…Arctic ridges are somewhat more well-studied, with Tucker III and Govoni (1981) finding a square-root relationship between block size and above-water (sail) height, and Timco and Burden (1997) finding a linear relationship between sail height and keel depth but no relationship between sail height and level ice thickness. Ekeberg et al (2015) found that first-year (Arctic) ridge keels are better characterized by a trapezoid than a triangle, and Petty et al (2016) found that ice thickness could be predicted (with considerable error) from metrics taken from lidar-derived topography of deformed ice. These results may or may not hold for Antarctic ridges.…”

Section: A1 List Of Metrics For the Segments Inmentioning

confidence: 99%

Morphological approaches to understanding Antarctic Sea ice thickness

Mei¹

2020

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“…The deepest keel draft observed is 35 m, with estimated 100-year return period drafts up to 41 m [2]. The mean keel draft is typically 7.3 m [3].…”

Section: Introductionmentioning

confidence: 99%

Post-simulations of Ice Basin Tests of a Moored Structure in Broken Ice - Challenges and Solutions

et al. 2015

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Interaction between a moored structure and drifting broken ice is a complex process. To document the expected structure response, ice basin tests of the interaction are common practice. The outcomes of ice basin tests need to be carefully analyzed before extrapolation to expected full-scale target responses. The preferred strategy is to use numerical simulations to correct the measurements. The numerical model needs to be qualified by successful post-simulations of the achieved ice basin interactions.Post-simulations of interactions between drifting broken ice and a moored floating structure are of high complexity. The response of both the structure and the ice field needs to be replicated. This requires a good modeling of the ice field properties that matter (such as the floe size distributions and concentrations) and the boundary conditions affecting the interactions (such as the effect of the ice basin walls).Statoil's SIBIS numerical model is used to post-simulate ice basin tests of the moored Cat-I drillship. The present paper discusses the challenges with such post-simulations and presents the philosophy chosen for achieving successful postsimulations. BackgroundThere is a limited experience with design and operation of moored structures in ice infested waters. Per today, the screening, feasibility or detailed design phases of such concept rely greatly on ice basin tests. This is inline with ISO 19906 (2010) normative requirements which states: "Appropriately scaled physical models and mathematical models may also be used to determine the response of structures to ice actions, in combination with current, wind and wave actions".The outcome of ice basin tests has to be interpreted and corrected to be exploited in the design process. Different correction methods can be applied, and the use of empirical formulations is a common practice (see e.g. Tatinclaux, 1988). The interaction between a moored structure and drifting ice is a complex process, as changes in the action will affect the structure response and vice-versa. It can be challenging to only use empirical formulations to correct the measurements due to the complex interdependency between the ice action and the structure response. The preferred strategy to correct ice basin measurements is thus to combine ice basin tests with numerical modeling (see also Jensen et al., 2011, Bonnemaire et al., 2014:1. Simulate numerically the ice basin tests, under achieved conditions, 2. Compare measurements and simulation outcome and qualify the numerical model for the considered interactions, 3. Use the qualified numerical model to simulate the response of the structure to the relevant ice interactions, under target conditions. This methodology results in a correction of the ice basin outcome for the effect of all deviations in the achieved conditions under testing. In addition, the numerical model is qualified and can be used further for simulating additional similar interactions.This procedure applied to moored floating structures in drifting ice is presented and d...

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Ice ridge keel geometry and shape derived from one year of upward looking sonar data in the Fram Strait

Cited by 17 publications

References 33 publications

Variability in categories of Arctic sea ice in Fram Strait

Variability in categories of Arctic sea ice in Fram Strait

Morphological approaches to understanding Antarctic Sea ice thickness

Post-simulations of Ice Basin Tests of a Moored Structure in Broken Ice - Challenges and Solutions

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