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Applying strict clean room techniques and sector field ICP-MS, a total of 567 ice and snow samples from Devon Ice Cap, Arctic Canada, have been analysed for silver (Ag) and thallium (Tl), providing a continuous record of atmospher...
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Applying strict clean room techniques and sector field ICP-MS, a total of 567 ice and snow samples from Devon Ice Cap, Arctic Canada, have been analysed for silver (Ag) and thallium (Tl), providing a continuous record of atmospheric deposition of both elements for the past ～16,000 yr. Concentrations of Ag and Tl ranged from 0.02 to 5.84 pg/g and from 0.03 to 3.40 pg/g, respectively. The natural Tl/Sc background ratio established with ice samples dating between 10,590 and 15,010 yr BP, amounted to 0.11 ±0.03 which is in good agreement with the corresponding value of 0.107 reported for the Upper Continental Crust (UCC). The Ag/Sc background ratio in ice (0.09 ±0.06), in turn, is much more variable and ～10-times higher than UCC values. The high temporal resolution provided by 45 samples from the 5 m snow pit representing the period AD 1994 to 2004, revealed the greatest elemental concentrations as well as accumulation rates during the winter months when air masses reach the Arctic predominantly from Eurasia. The greatest Sc concentrations, however, are also found during winter months which clearly reflect strong seasonal variations in atmospheric dust inputs. Enrichment factors calculated for both elements (Ag, Tl) using Sc show contrasting behaviours, with the maximum EF for Tl (up to 48) during summer when air masses arriving to the Arctic are predominantly from North America, probably reflecting coal burning, base metal mining and smelting. The greatest enrichments of Ag (up to 17), on the other hand, tend generally to be found in winter, although some enrichment maxima corresponding to summer months are also seen. While modern Ag EF are comparable to those corresponding to ancient (back to ca. 3 k yr) anthropogenic activities, modern Tl EF clearly exceed the impact of Medieval, Roman and Greek/Phoenician civilization. Accumulation rates during the past decade have been variable (mean 36 and 130 ng/m~2/yr for Ag and Tl, respectively), but the trend is clearly in decline. Based on the best estimate of natural inputs, more than 80% of the Ag and 90% of the Tl supplied to the Arctic today (AD 1994-2004) are derived from anthropogenic sources.
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A Joint Finnish Industry Project in 1983-87 measured cone ice loads by installing an instrumented cone around the Kemi-I lighthouse in the Gulf of Bothnia. A Canadian University/Joint Industry Project has been conducting cone ice ...
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A Joint Finnish Industry Project in 1983-87 measured cone ice loads by installing an instrumented cone around the Kemi-I lighthouse in the Gulf of Bothnia. A Canadian University/Joint Industry Project has been conducting cone ice load measurements since 1997 on two instrumented piers of the Confederation Bridge, in the Southern Gulf of St Lawrence. The diameters of the cones at the waterline are 10 and 14 m respectively. Ice conditions are more severe at Kemi-I but ice movement is faster and ridge encounters more frequent at Confederation Bridge. However, all types of first year ice features have been encountered at both locations. The cone ice load measurements and observations indicate that ice failure patterns and broken floe clearing mechanisms are, in general, similar. Comparisons with reference to ice thickness, temperature, and velocity, are made on: rubble formation, rubble surcharge height, rubble jamming, pressure ridge failure modes, dynamic effects, and measured and predicted ice loads. The results pave the way for a better understanding of ice failure against cones and cone ice load design.
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Ice on wind turbine blades reduces efficiency and causes financial loss to energy companies. Thus, it is important to know the possible risk of icing already in the planning phase of a wind park. This paper presents a new Finnish ...
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Ice on wind turbine blades reduces efficiency and causes financial loss to energy companies. Thus, it is important to know the possible risk of icing already in the planning phase of a wind park. This paper presents a new Finnish Icing Atlas and the methodology behind it and is prepared by applying the mesoscale numerical weather prediction model AROME with 2.5 km horizontal resolution and an ice growth model based on ISO 12494. The same meteorological dataset is used as was used in the Finnish Wind Atlas (published in 2009), and thus is fully compatible with and comparable with existing climatological wind resource estimations. Representation of the selected time period is evaluated from an icing point of view. Comparing reanalysed temperature and humidity datasets for both the past 20 years and the wind atlas period, we conclude that the used time period represents large-scale atmospheric conditions favourable for icing. We perform a series of sensitivity tests to evaluate how sensitive this ice model is to input from the weather model. The new atlas presents climatological distributions of active and passive icing periods and wind power production loss in map form for three different heights (50, 100 and 200 m) over all of Finland. The results show that the risk for active icing is much greater in coastal areas, while the risk of passive icing is larger inland. (C) 2016 The Authors. Wind Energy Published by John Wiley & Sons Ltd.
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On the basis of the results of small-scale and medium-scale indentation tests and full-scale measurements of ice forces, a methodology to estimate crushing ice forces is presented. The main point to note is that the effective pres...
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On the basis of the results of small-scale and medium-scale indentation tests and full-scale measurements of ice forces, a methodology to estimate crushing ice forces is presented. The main point to note is that the effective pressure depends on the relative indentation speed, which in turn depends on the speed of a moving ice floe and the compliance of a structure. An increase in indentation speed leads to a change in failure mode from ductile to brittle, resulting in decreased effective pressure, and vice versa. The ice forces also depend on the temperature of the ice, because its strength and brittleness increase with decreasing temperature. The two codes for bridge piers and offshore structures are valid for brittle crushing of ice at high indentation speeds, and the recommended design effective pressure from these two codes is the same for wide structures (or large contact area) but differs for narrow structures (or small contact area).
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Ice is an effective and economical means of supporting loads for construction and resource extraction. The
main requirement is to have continuous ice of sufficient thickness to support the intended loadings. Ice has
been used to...
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Ice is an effective and economical means of supporting loads for construction and resource extraction. The
main requirement is to have continuous ice of sufficient thickness to support the intended loadings. Ice has
been used to support heavy loads, both mobile and stationary and long-term loads such as oil and gas drilling
rigs. It has been used to support the installation of offshore pipelines and related facilities. The paper
describes the various uses of ice as a load-bearing medium and presents methods for determining required
thicknesses.
The bending of floating ice under applied load causes flexural stress to be imposed on the ice cross section.
Because ice is weak in tension, the critical stress is the maximum tensile stress at the bottom of the ice
directly under the load. The paper presents standard methods of calculating the maximum, extreme fibre
stress for different types of loads and presents an allowable stress for safe use of the ice as a load-bearing
medium. This allowable stress is also instrumental in ensuring that long term, creep deformation does not
result in submergence of the ice surface. The paper presents a method of estimating long-term deflection and
also presents a method of assessing the effects of dynamic or moving loads.
Grounded ice roads require sufficient thickness to spread applied wheel loads and avoid overstressing of the
tundra or seabed. A method of assessing the support provided by widely differing subgrade conditions is
presented.
Construction methods and techniques for ice roads and structures, including the best types of equipment to
use, are presented, with photographs. Issues such as snow removal vs. flooding of thick snow are discussed.
Durability of the road surface and surface repairs is outlined.
During the construction phase of ice structures, the quality control (QC) tasks verify material quantity and
material quality as required by the design. An outline of considerations for this task is presented. Failures and
anecdotal information related to the design, construction and use of ice roads and structures are presented,
with illustrative photographs.
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Earlier research highlighted severe detrimental effects related to aircraft performance due to ice crystal icing. As part of current research impact of glaciated icing cloud on heated substrates is investigated. To that end, a ser...
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Earlier research highlighted severe detrimental effects related to aircraft performance due to ice crystal icing. As part of current research impact of glaciated icing cloud on heated substrates is investigated. To that end, a series of experiments were carried out at the icing wind tunnel of Technische Universitt Braunschweig to investigate the physics of ice crystal accretion on heated substrates for various operating conditions. Dedicated transparent and metallic heatable substrates were designed for macro and microscopic investigation of ice accretion from a qualitative visualization and heat transfer physics perspective. In addition to that numerical simulations were performed at ONERA. Qualitative observations from dedicated experiments on ice accretion initiation phase resulted in advancement of numerical model to accurately capture the different stages leading up to ice accretion as well as the necessary conditions for growth of slushy and glaciated ice layers. Furthermore, a dedicated test matrix was defined to explicitly study the influence of dominant parameters such as flow velocity, heat flux, wet bulb temperature and ice water content on ice accretion process. The experiments showcased a strong influence of increasing flow velocity and ice water content yielding shorter duration required to accrete an ice layer on a heat-able substrate. Further experimental investigation reflected that upon increasing the heating power of the test article the icing cloud had to overcome a larger temperature gradient resulting in longer duration required for accretion. It was found that on one hand, the test run with negative wet bulb temperature required a heating source from the substrate as the necessary condition for ice accretion resulting in glaciated ice layers. On the other hand, for positive wet bulb temperature cases natural melting of ice layer was sufficient to induce ice accretion generating slushy ice layers and the heating source from the substrate had little to no influence on the overall ice accretion growth. Numerical simulations were also performed for same conditions and were able to correctly capture the trends and orders of magnitude in comparison with experimental results. The experimental findings presented in this paper lead to development of an accretion solver based on enthalpy approach which considers accretion process as a homogeneous mixture of crystals and liquid water and not by a mere superposition of ice layer and liquid water film. The findings helped calibrate, validate and advance the numerical model for ice crystal icing and found to be more representative of accretion process than unsteady triple layer approach. The findings ensure better predictive capability resulting in improved flight safety and performance criterion.
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Experimental adhesion force measurements were conducted on accumulated ice on the leading edge of a scaled wind turbine blade in both glaze and rime icing regimes. An apparatus was first designed for specifically measuring the adh...
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Experimental adhesion force measurements were conducted on accumulated ice on the leading edge of a scaled wind turbine blade in both glaze and rime icing regimes. An apparatus was first designed for specifically measuring the adhesion force of ice on a curved surface at climatic temperature where a vertical force was applied to the mounted structure in the test apparatus. Adhesion force measurements were measured and adhesion pressure calculated for plain and ice-mitigated test specimens. Results are presented for the increase in force of ice adhesion over a curved surface area in proportion to degree centigrade decrease in temperature.
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This paper presents a study of the flow of ice in wedge-shaped converging channels. Such flows are encountered in the relatively constricted waters of the Canadian Arctic Archipelago. Ridging, lead opening patterns, development of...
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This paper presents a study of the flow of ice in wedge-shaped converging channels. Such flows are encountered in the relatively constricted waters of the Canadian Arctic Archipelago. Ridging, lead opening patterns, development of a high-pressure area, and arch formation are some of the processes which take place during ice flow through converging channels. An idealized geometry and steady wind forcing were used in the testing. The results give ice cover velocity, distribution of stresses, ice thickness, area coverage and ridging. Some of the conditions leading to arch formation at the constricted exit of the channel are explored.
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Abstract Sea-ice pore microstructure constrains ice transport properties, affecting fluid flow relevant to oil-in-ice transport and biogeochemical processes. Motivated by a lack of pore microstructural data, in particular for gran...
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Abstract Sea-ice pore microstructure constrains ice transport properties, affecting fluid flow relevant to oil-in-ice transport and biogeochemical processes. Motivated by a lack of pore microstructural data, in particular for granular ice and across the seasonal cycle, throat size, tortuosity, connectivity, and other microstructural variables were derived from X-ray computed tomography for brine-filled pores in seasonal landfast ice off northern Alaska. Data were obtained for granular and columnar ice during the ice growth, transition, and melt season. While granular ice exhibits a more heterogeneous pore space than columnar ice, pore and throat size distributions are comparable. The greater tortuosity of pores in granular (1.2 < τg < 1.7) compared to columnar ice (1.0 < τc < 1.1) compounded with a less interconnected pore space translates into lower permeability for granular ice during the growth season for a given porosity. The microstructural data explain findings of granular ice hindering vertical oil-in-ice transport during ice growth and transition stage. With granular ice more frequent in the changing Arctic, data from studies such as this are needed to inform improved modeling of porosity-permeability relationships.
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There is probably no more important characteristic of river and lake ice than the thickness. This paper consists of three parts: In Part I the thickening of ice via conduction is analyzed and tested against an extensive data set a...
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There is probably no more important characteristic of river and lake ice than the thickness. This paper consists of three parts: In Part I the thickening of ice via conduction is analyzed and tested against an extensive data set assembled by Bilello (1961-1996) that included weekly measurements of ice thickness and snow on the ice for a number of sites in Alaska and Canada. It is shown that the largest variations from year to year at a given site are associated with the thickness of the snow on the ice, and secondarily by variations in the coldness of the winter period of thickening. If no snow ice forms, quite good agreement with a simple thickening algorithm is achieved. This leads to Part II where the formation of snow ice is analyzed but the analysis is constrained by the fact that sometimes, even though the weight of the snow is enough to submerge the solid ice cover, there seems to be no snow ice formation. Differences between the formation of snow ice on river and lake ice covers are examined. For river ice covers, the water from below cannot always find a path to the top of the ice cover. Finally, in Part III the thinning of river ice covers is analyzed using a simple algorithm based on solar radiation calculations and sensible and latent heat transfers from the air to the ice. Good agreement is obtained with the extensive data set of Bilello (1980). Implications for practical calculations of thickness are discussed.
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