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Author: Matti Leppäranta Publisher: ISBN: Category : Dynamics Languages : en Pages : 212
Book Description
Modeling studies were carried through with three types of ice rheologies: free drift, linear viscosity, and plasticity. It is suggested that ice thickness variations may be important to the dispersion of ice edge and lead to e.g. clustering of ice floes. Analytic linear viscous solutions show that variable ice strength rather than variable forcing is likely to produce sharp changes in ice velocity near the ice edge. Steady state ideal plastic solutions give a constant ice flow under constant forcing in the MIZ. In general, ice interaction has a rectifying effect on the flow pattern. Ice kinematics measurements were made with the Del Norte microwave trisponder system in MIZEX-83 Greenland Sea experiment. Differential ice motion was measured with four stations on the ice in the scale of 5 km at three-minute intervals. On several occasions, a rapid slip occurred in measured distances. Ice velocity fluctuations were typically of the order of 1 cm/s and large deformation rates a few per cent per hour. Various spectra of differential ice drift showed a moderate inertial peak and a red noise character at higher frequencies, up to about half-hour period. The maximum rate of shear was about twice as large as divergence from 12-h to about 2-h period.
Author: Matti Leppäranta Publisher: ISBN: Category : Dynamics Languages : en Pages : 212
Book Description
Modeling studies were carried through with three types of ice rheologies: free drift, linear viscosity, and plasticity. It is suggested that ice thickness variations may be important to the dispersion of ice edge and lead to e.g. clustering of ice floes. Analytic linear viscous solutions show that variable ice strength rather than variable forcing is likely to produce sharp changes in ice velocity near the ice edge. Steady state ideal plastic solutions give a constant ice flow under constant forcing in the MIZ. In general, ice interaction has a rectifying effect on the flow pattern. Ice kinematics measurements were made with the Del Norte microwave trisponder system in MIZEX-83 Greenland Sea experiment. Differential ice motion was measured with four stations on the ice in the scale of 5 km at three-minute intervals. On several occasions, a rapid slip occurred in measured distances. Ice velocity fluctuations were typically of the order of 1 cm/s and large deformation rates a few per cent per hour. Various spectra of differential ice drift showed a moderate inertial peak and a red noise character at higher frequencies, up to about half-hour period. The maximum rate of shear was about twice as large as divergence from 12-h to about 2-h period.
Author: Matti Lepparanta Publisher: ISBN: Category : Languages : en Pages : 9
Book Description
The report consists of an initial analysis of the ice kinematics field data from MIZEX-83 Greenland Sea Study. The data set consists of distance measurements accurate to 1-2 metres between Del Norte units at five sites, with one site being the ship. The data set represents a unique set of measurements of the deformation field of a series of interacting floes.
Author: Jean-Pierre Auclair Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
The Marginal Ice Zone (MIZ) is a highly dynamic region between the open ocean and the inner ice pack. The ice over this region is subjected to waves, introducing new forces but also changing the ice from a cohesive material to a mobile collection of floes. Until recently, the challenges posed by in-situ ice measurements in the MIZ prevented a detailed characterization of changes in the ice cover. The rapidly changing conditions over short distances have also prevented detailed numerical simulations. Recent developments in observational and computational capabilities allow further investigations of the physical processes for ice formation and wave-ice interactions in the MIZ. Many features of the MIZ remain to be explained and quantified, particularly rapid ice movement near the ice edge and ice thickening under wave pressure. In order to investigate these and support future field and numerical studies, a model of the MIZ is developed with a new numerical method better suited for high resolution. Simulations of waves causing ice compaction and the ice edge jet are then performed to detail the expected impacts of waves on sea ice. The potential of numerical improvements in sea ice models to obtain greater efficiency and accuracy at high resolutions is successfully demonstrated. The addition of the wave radiative stress allows the generation of realistic thickness profiles, provided that the sea ice strength is modified to represent the difference between pack ice and thinner ice. With the same modifications, obliquely incident waves on the ice edge produced an ice edge jet with a range of characteristics depending on wave parameters and modeled interactions. The magnitude of wave attenuation in sea ice and the ice strength are found to be very important factors in the simulations. Consideration of wave effects on ice thickness and drift speed are also shown to have potential to increase both open water and ice formation.
Author: Sirpa Häkkinen Publisher: ISBN: Category : Ocean-atmosphere interaction Languages : en Pages : 124
Book Description
This study is aimed at the modelling of mesoscale processes such as up/downwelling and ice edge eddies in the marginal ice zones. A 2-dimensional coupled ice-ocean model is used for the study. The ice model is coupled to the reduced gravity ocean model (f-plane) through interfacial stresses. The constitutive equations of the sea ice are formulated on the basis of the Reiner-Rivlin theory. The internal ice stresses are important only at high ice concentrations (90-100%), otherwise the ice motion is essentially free drift, where the air-ice stress is balanced by the ice-water stress. The model was tested by studying the upwelling dynamics. Winds parallel to the ice edge with the ice on the right produce upwelling because the air-ice momentum flux is much greater than air-ocean momentum flux, and thus the Ekman transport is bigger under the ice than in the open water. The upwelling simulation was extended to include temporally varying forcing, which was chosen to vary sinusoidally with 4 day period. This forcing resembles successive cyclone passings. In the model with thin oceanic upper layer, ice bands were formed. The up/downwelling signals do not disappear in wind reversals because of nonlinear advection. This leads to convergences and divergences in oceanic and ice velocities which manifest themselves as ice banding. At least one wind reversal is needed to produce one ice band.
Author: Norbert Untersteiner Publisher: Springer ISBN: 1489953523 Category : Science Languages : en Pages : 1197
Book Description
Based on the proceedings of the NATO Advanced Study Institute on Air-Sea-Ice Interaction held September 28-October 10, 1981 in Acquafredda di maratea, Italy. Intent is to present the topic of sea ice in the broad and interdisciplinary context of atmospheric and oceanographic science.
Author: Matti Leppäranta Publisher: Springer Science & Business Media ISBN: 9783540408819 Category : Science Languages : en Pages : 308
Book Description
The author presents in The Drift of Sea Ice the fundamental laws of sea ice drift which come from the material properties of sea ice and the basic laws of mechanics. The resulting system of equations is analysed for the general properties of sea ice drift, the free drift model and analytical models for ice drift in the presence of internal friction, and the construction of numerical ice drift models is detailed. The science of sea ice drift through its 100-year history to the present day is explained. The text includes the geophysical theory, observations from field programs, and mathematical models. Topics covered include the science of sea ice drift, forecasting drift velocity based on volume, size and shape, sea ice ridging and remote sensing, modelling of the ice conditions, and finally the role of sea ice drift in research fields in ice-covered seas, oceanography, marine ecology and engineering.
Author: Matti Leppäranta
Author: Matti Leppäranta
Author: Matti Lepparanta
Author: Jean-Pierre Auclair
Author: Sirpa Häkkinen
Author: Harvey Ernest Jordan
Author: 
Author: Norbert Untersteiner
Author: Matti Leppäranta
Author: 
Author: Edmond Hansen