Glossary_2

RUSSIAN GLOSSARY OF SEA ICE TERMINOLOGY

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Glossary Terms: A-D, I, J-R, S-Z

E

EASIEST WAY OF ICE NAVIGATION. The vessel route through a region of ice chosen in order to obtain the most favorable overall combination of ice sheet properties (thickness, compactness, hummockness, degree of destruction of the ice, etc.).

ECONOMIC EFFECT OF ICE FORECAST. The estimate of consumer usefulness and economic reasonability of using an ice forecast to implement production functions in economic industries that depend on ice conditions.

EDDY MOTION OF ICE. A motion of ice where the ice floes perform translation motions and simultaneously rotate around a temporarily fixed point.

ANTICYCLONIC MOTION OF ICE. A clockwise eddy motion of the ice, e.g. the anticyclonic circular motion of ice in the Arctic basin (according to data on ice drifts averaged over an observation period of several years, one year or one season). Note that when Arctic Basin data is averaged over a shorter time period, other motion preferences may be indicated.

CYCLONIC MOTION OF ICE. A counterclockwise eddy motion of the ice.

EDGE OF SHORE ICE. A line separating an immobile ice sheet (shore ice, landfast ice) from open water or moving pack ice ( Photographs 11 and 53).

EFFECTIVENESS OF ICE FORECAST. The ratio of the effect of its use to the total amount of charges for all forecasting stages.

ELASTIC MODULI OF ICE. Elastic moduli are parameters that characterize the elastic properties of ice.

Under conditions of small deformations, the most general relationship between the components of stress sxx, syy, ... sxy and the components of strain exx, eyy, exy are presented in the form of six linear equations of the type

sxx = c11 exx + c12 eyy + c13ezz + c14eyz + c15ezx + c16exy

where sxx is a so-called normal stress which is directed along the x axis, eyz is the relative shear, (i.e., the change in the value of the right angle of elementary parallelepiped in a plane yz), etc. The coefficients c11, c12,.... are elasticity moduli or the constants of rigidity and have dimensions of stress, i.e. are expressed in terms of units of force divided by units of area.

For hexagonal crystals there are only five independent moduli of elasticity known as the rigidity constants. These parameters, (c11, c12, c13, c33, c44), appear as coefficients in the equation relating the components of the stress tensor to the components of the strain tensor.

The physical meaning of the elasticity moduli can be understood by considering the main types of stressed ice states – uniaxial normal stress, shear deformation, and triaxial compression. The relation between stress and the corresponding strain is in each case presented in the form of a simple formula where stress is the product of the corresponding strain and the elasticity modulus.

ELEMENTS OF MACRORELIEF OF AN ICE SHEET (COVER) SURFACE. Comparatively stable aggregates of large structural unevenness as observed on the surfaces of sheets of sea ice or on the ice cover as a whole. Typical sizes fluctuate from a few meters to several tens of meters.

ENSEMBLES (SETS) OF ICE COVER ELEMENTS. Groups of ice floes of different shapes and sizes which either partially or completely cover the surface of a water body

EQUILIBRIUM ICE THICKNESS. The thickness of old drift ice. Ideally the thickness at which the winter’s growth is completely compensated by the summer’s melting and evaporation. In arctic regions, the equilibrium ice thickness is on the average equal to 3 m, but occasionally may reach 5-6m.

ERROR OF LONG-TERM ICE FORECASTS WITH TIMELINESS UP TO 2 MONTHS. The error that does not exceed ± 0.674 s.

ERROR OF LONG-TERM ICE FORECASTS WITH TIMELINESS FROM 2 TO 6 MONTHS. The error that does not exceed ± 0.8 s.

ERROR OF SUPER-LONG-TERM FORECASTS. The error that does not exceed the average quadratic error of a forecast event.

Here Ui is the parameter value or the ice sheet indicator arranged in multi-year observation rows, Up is the calculated value of the forecast parameter or indicator, d is the deviation of calculated values from the actual ones d = (Ui - Up), n is the number in a multi-year row, and m is the number of degrees of freedom (for a linear regression equation m = 2).

ESTIMATE OF ICE FORECAST QUALITY. The defining of their accuracy, reliability, justifiability, and efficiency.

EVOLUTION OF AN ICE SHEET (COVER). Gradual changes (trends) in the properties and components of an ice sheet (cover) with time ( Figure 2).

F

FABRIC DIAGRAM OF CRYSTAL AXIS ORIENTATIONS. A diagram that shows the results of measurements of the C-axes orientations of crystals as usually observed in a thin section.

FAST ICE. Sea ice which is attached to the shore (Photographs 11 and 53) or to grounded ice features such as shamuhka ( Photograph 54) or icebergs. Although fast ice may move up and down with the tides and may undergo small lateral movements, when considered on a larger scale it is essentially fixed in place. It may form in situ or be comprised of ice of any age that has drifted into its present location before becoming incorporated in the fast ice. Fast ice widths can vary from a few meters to 100s of kilometers.

FAST ICE BORDER. The line separating shore ice from drifting ice (Photographs 11 and 53).

FAST ICE FORMATION. Fast ice formation occurs along the coasts of continents, archipelagos, and islands and also around old stranded sea ice masses and icebergs on shoals.

The formation of fast ice can be described in terms of four dates: the date of the first off-shore ice occurrence (the day when a stable ice sheet appears along the coast with the width of the strip of less than 200 m); the date of the first fast ice formation (the day when the fast ice is more than 200 m wide and formed along the coastal line); the date of stable fast ice formation ( the day when the stable ice sheet is more than 200 m wide and formed near the coast or other immobile objects such as stamukhi); the date of the final fast ice formation (the day when a stagnant ice sheet has formed over the whole surface of the water area of interest and has existed there for either a period of over one month or during the entire winter period until break-up).

FIRN. Firn is infiltrated as well as recrystallized medium to coarse-grained snow. It typically has densities in the range of 450 to 800 kg/m3 and represents a transition stage between snow and ice of infiltration origin.

"FLOAT" OSCILLATIONS OF ICE. The vertical movement of ice as a whole. The oscillation period depends on the ice thickness.

FLOE. A continuous, connected, relatively flat area of drifting ice with horizontal dimensions ranging from 20 m to dozens of kilometers and vertical dimensions ranging from several centimeters to several meters. Floes are usually classified according to horizontal extent as follows:

> Small: 20-100 m across

> Medium: 100-500 m across

> Big: 500-2000 m across

> Vast: 2-10 km across

> Giant: over 10 km across

FLOODED ICE. A part of an ice sheet that is covered with a water layer that has formed either due to the melting of snow and ice on its surface, the inflow of water onto the ice from the shore, or the depression of the ice surface below sea level by factors such as snow loading or non-isostatic forces.

FLUCTUATIONS OF ICE DRIFT. Deviations of ice drift parameters from their average values caused by a variety of factors

FOAM ICE. A frozen aqueous foam usually resulting from layer-by-layer freezing of a foamed cold water solution containing a dispersion of surface-active substances.

FORECASTING OF ICE EVENTS AND PROCESSES. The scientific and research process aimed at understanding the physical basis of mechanisms occurring in ice events and processes that define the limit of their predictability, the development of forecast procedures, and their formalism.

FORECASTING PREREQUISITES. The possibility of resolving forecast tasks defined by specific features of an ice event or process, the level of its study, information support, timeliness, and the method of forecast.

Forecasting timeliness. The time defined by the predictability of the process, i.e. the possibility to receive a forecast of required accuracy under existing conditions.

Event study level. The knowledge of factors that directly or indirectly influence the process or event, as well as the availability of the reason/consequence linking the events of different levels in the past, present, and future.

PREDICTABILITY LIMIT. The maximum possible timeliness of a forecast defined by the studied mechanisms of processes linking the ice sheet with meteorological, hydrological, and heliogeophysical processes.

Forecast timeliness. The time period between the submission of the forecast and the start of the time for which it was developed.

FORECASTING STAGES. The consequence of performing certain operations that define the scientific and research process of developing ice forecasts and that include the setting of targets, the selection and compiling of a system of predictors, the development of a constructive forecast model, the development of a specific forecast procedure, and a verification of the forecast.

Setting of forecasting tasks. A forecasting stage that includes the analysis of properties and specific features of ice events and processes, as well as the selection of a suite of indicators that are believed to have significant predictive capabilities concerning the particular problem at hand, the selection of the order with which to use this information, and the setting of forecast timeliness.

Preforecast analysis. A forecasting stage that includes the selection of potential predictors on the basis of theoretical ideas concerning mechanisms and reasonable links in the interaction between physical events and the forecasting process, information support of predictors and the predictant, and the existence of reasonable time shifts between predictors and the predictant when retrospective material is used.

Development of constructive forecasting model. A forecasting stage that includes the establishment of mathematical correlations (probability-statistical and thermohydrodynamic). It transfers into a forecast model upon completion of the final optimization of model parameters and the finalization of the model structure.

FORELL BANDING. A thin straight ribbing relating to the location of the edges of the basal plates that can be seen on the surface of some ice crystals. Forell banding is particularly visible under conditions of either ice sublimation or limited melting with the immediate evaporation of the thawed water.

FRACTURE IN AN ICE COVER. see Rasvodije (Russ.).

FREEZING OF WATER. The transition of water from the liquid to the solid state caused by the crystallization process.

FREEZING OF A WATER BODY. The formation of a continuous layer of ice on the surface of a water body.

The external evidence of this process is the covering of the water body with a continuous layer of primary ice. The process is characterized by two dates: the day when the first complete freezing occurs (i.e., the day when observations performed under conditions of full visibility show that the area of the water body was covered by a continuous layer of primary ice for the first time in the given year) and the day when the final freezing occurs (the day when observations conducted under conditions of full visibility show that the area of the water body remained covered with a continuous layer of ice for a period of time no shorter than one month).

FRESH SNOW SHEET. A loose, relatively even snow sheet formed from newly-fallen (newly-precipitated) snow.

FROST STEAM or FROST SMOKE. The formation of fog over cracks, channels, leads and air holes resulting from cold air with temperatures below 0°C passing over open water ( Photograph 29).

G

GLADE. A large area of up to 30 km wide, of open or scattered ice formed at the border between the fast ice or the shore or an ice shelf and the drift ice due to a sustained offshore wind (off-fast-ice glade, offshore glade). .

GLAZE (GLAZED ICE). Ice of an atmospheric or hydrospheric origin that covers the surface of an object and consists of rain drops or light spray spattered onto objects from waves ( Photograph 44). Depending on the salinity of the water and the formation mechanism (spray, water spattered by waves) one can distinguish between fresh-water, salty, and sea glaze, and also between wind, wave, slush and drift glaze. Various combinations of the above glaze types are also possible.

GLEN’S FLOW LAW FOR ICE. A power law useful in describing the creep of ice given by

where A depends on the ice temperature, the impurity content, and the crystal orientation as well as other possible factors and n is an exponent varying from 1.5 to 4.2 as the stress changes from 0.1 to 1.5 MPa. It is common to assume n = 3 as a mean value. The temperature dependence of the parameter A is usually expressed in terms of the Arrhenius equation

where Qcreep is the activation energy for creep, T is the ice temperature, R is Boltzmann’s constant and is independent of temperature.

GOUGING OF THE SEAFLOOR BY HUMMOCKY FORMATIONS. The plowing up of the seafloor by the underwater parts of hummocks, ridges and stranded ice masses (Photographs 30 and 31). The depth of the resulting furrows may in extreme cases reach 10 m. In English this process has also been referred to as scoring and scouring.

GRADIENT OF ICE DRIFT SPEED. The change in the ice drift speed per unit distance in a specified direction.

GRANULAR HOARFROST (RIME). Fresh-water ice of atmospheric origin formed from water droplets such as fog ( Photograph 26). It forms on the surfaces of objects.

GROUP VELOCITY OF WAVES IN AN ICE SHEET (VELOCITY OF THE WAVE FRONT). A parameter which characterizes the velocity of non-harmonic (i.e. non-sinusoidal) waves in ice. For a period of time during which the envelope shape of the wave disturbance remains the same with the required accuracy, one may introduce the propagation velocity of the envelope that characterizes the velocity of elastic impulse perturbations in the medium. In a floating ice sheet, its value may be less (normal dispersion) or more (anomalous dispersion) than the phase velocity.

GROWLER. An accumulation of ice blocks, debris and/or an iceberg fragment that extends less than 1 m above the sea surface and normally occupies an area of roughly 20 m2. Growlers can be quite hazardous to shipping as they commonly are not visible on radar and are particularly difficult to sight during storms.

H

HAZARDOUS ICE PHENOMENA. Ice phenomena which may cause damage to facilities located in areas affected by the phenomena.

One should take necessary measures to prevent this damage. Dangerous ice phenomena include events such as the unusually early formation of ice, piling of ice, partial breaking off of shore ice, and the icing of ship superstructures, etc.

EXTREMELY DANGEROUS ICE PHENOMENA. Ice phenomena which, because of their intensity, time of occurrence, duration and affected area may cause considerable damage to objects in affected areas. In case the objects cannot be evacuated, nor protected and if safety precautions are not followed, this type of phenomena may present a real danger to human life.

A sudden increase in the ice drift rate and intensive ice compression along a navigation route ( Photograph 32) are some types of this phenomena.

It should be noted that the critical values of indexes of hazardous and extremely dangerous ice phenomena have yet to be established.

HEAT CAPACITY OF ICE. An important material property required in the investigation of changes in ice temperature as related to changes in the temperature of the environment. The heat capacity of ice gives the quantity of heat needed to increase the temperature of a unit mass of ice by 1°K. The heat capacity of freshwater ice [2.12 kJ/(kg °K) at 0°C] decreases with a decrease in temperature and trends toward zero at 0°K.

HILL. See ice hill

HILLY PATTERN OF MULTIYEAR ICE. The ratio of the area of hilly ice to the total surface area of multiyear ice on which the hills are located. Expressed in points.

HUMMOCK. A separate pile of pieces and fragments of ice on the upper surface of an ice sheet formed due to the compression of ice fields at their contact points ( Photographs 33).

HUMMOCK BARRIER. A large ridge formed by a line of hummocks in the shore fast ice ( Photograph 59). The underwater part of a hummock barrier is partially grounded, thus assisting in stabilizing the shore fast ice.

HUMMOCK BELT. A row of parallel hummock barriers formed as the result of multiple and prolonged compressive hummocking events. Hummock belts are mainly located at the external edge of the fast ice ( Photograph 59). They also occur in straits and drift divide regions.

HUMMOCKNESS OF ICE. A measure for evaluating hummocky ice defined by the ratio of the hummocky ice area to the entire area of the zone where the estimate of the degree of ice coverage by hummocks is being performed. It is expressed on a 5 point scale.

RIDGE HUMMOCKNESS. An ordered ice hummockness in the form of uniformly distributed hummock ridges on the ice sheet surface. It is estimated in accordance with the number of hummock ridges per unit length of the observation zone which should be oriented perpendicular to the direction of the hummock ridges.

NON-UNIFORM HUMMOCKNESS. Chaotically distributed hummocks and their ridges occurring on the surface of an ice sheet ( Photograph 34). It is estimated in the same manner as the general hummockness (in points).

HUMMOCK RIDGE. A extended, chain-like piling of ice fragments on the upper surface of an ice sheet formed due to compression of ice fields along their line of contact. The elements of a hummock ridge include:

HUMMOCK RIDGE HEIGHT. See morphometric characteristics of ice sheet relief; hummock height.

HUMMOCK RIDGE CREST. The topmost part of a hummock ridge ( Figure 15).

HUMMOCK RIDGE FOOT. An imaginary line separating the hummock ridge slope from the surrounding level (non-deformed) surface.

HUMMOCK RIDGE SLOPE. The side walls of hummocks, the lengths of which are measured from the edge to the foot.

ANGLE OF SLOPE. The angle between the hummock ridge slope and the horizontal plane of the ice sheet (the upper surface of level ice).

WIDTH OF HUMMOCK CHAIN. The distance between two slopes measured on the ice surface near the ridge foot.

HYDROGENIC OR CONGELATION ICE (WATER ICE). Hydrogenic ice forms as the result of water freezing. Such ice is analogous to magmatic rocks. It occurs in various shapes and is extremely wide spread in nature.

HYDROLOCATION IMAGE OF AN ICE COVER. Normally, a black-and-white image on a paper chart or on an electronic monitor which has been obtained through the use of a narrow scanning beam produced by a hydrolocation station (sonar). The antenna of the station is installed on an object that moves: 1) horizontally under the ice sheet at a specified depth (upward-looking side-scan sonar image, Figure 6) or vertically while at a fixed horizontal location (circular scanning sonar). These images allows one to make assessments of the 3 dimensional roughness of the lower surface of an ice sheet thereby determining areas of uneven, level and continuous ice.

HYDROMETEOROLOGICAL SUPPORT. The complex of works performed by Rosgidromet organizations aimed at timely and completely providing economic organizations with hydrometeorological materials obtained using standard techniques and in accordance with approved schedules.

HYDROMETEOROLOGICAL INFORMATION TYPES

PRIMARY INFORMATION. Data obtained through observations at stations, during expeditions, and from laboratory research. This type of data characterizes hydrometeorological and ice conditions in the area under study at the moment of the observation and serves as a basis for practical decisions concerning sea ice operations. Such data is also used in scientific research and in developing new calculation and forecasting methods.

REVIEW AND ANALYTICAL INFORMATION. Information of this type is obtained through the generalization of primary information and by conducting analytical calculations to characterize the spatial distribution of the ice and the associated hydrometeorological characteristics at given moment of time or for a specified period of time. Such information usually contains at least one of a set of factors that should be considered in the process of determining optimum routes for navigating vessels through ice.

REGULATORY AND REFERENCE INFORMATION. This type of information is obtained through the statistical processing of primary and analytical information and characterizes climatic and statistical hydrometeorological conditions within a given water area and the dynamics of their change. Such information is commonly used as a part of feasibility studies undertaken in connection with large-scale economic projects.

FORECASTING INFORMATION. Forecasting (prognostic) information is obtained by calculations and forecasts and gives scientifically substantiated characteristics of expected phenomena and processes. It also contains recommendations for dealing with conditions that are likely to take place in the future.

NAVIGATIONAL RECOMMENDATIONS. Recommendations from operational units concerning optimum ice navigation routes, coastal station supply timetables, periods when icebreakers will lead during the transit and periods and routings for led vessels not designed for ice navigation.

STORM WARNING. A timely warning of dangerous and extremely dangerous natural phenomena allowing economic and operational organizations to take preventive measures against possible damage resulting from storm wind intensification, unfavorable changes in the wind direction, rapidly worsening ice conditions, sharp rises or falls of water level, and any other hazardous factors not foreseen by the original ice forecast.

HYDRO-THERMODYNAMICS OF ICE. A branch of hydrology and of ice science which studies the laws governing changes in the thermal state of ice, water currents, and water bodies in the presence of ice formation and melting. The main aim of research in the field of ice thermodynamics is to establish the laws governing the processes of ice formation, evolution and destruction as determined by changes in climatic conditions.

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Glossary Terms: A-D, I, J-R, S-Z