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publication. CONCLUSIONS In this study, we quantitatively analyzed draft and bottom unevenness of sea ice. The purpose was to acquire inputs or boundary conditions needed to forecast the spread of oil spilled under sea ice, as well as for estimating ice loads acting when sea ice interacts with a structure. The results are as follows: • The collected observation data (distance vs. draft) were analyzed by discrete wavelet transform (for distance – wave number analysis) and by locally stationary AR model. The results indicate that non-stationary characteristics may need to be considered, depending on the scale concerned. The average power (variance of draft depth) differs along distance axis (for each section), but the spectrum characteristics are similar. The normalized spectrum is roughly the same for each section considered locally stationary. • From the results obtained in 1) above, we described the estimation method of a typical normalized spectrum. This also suggests that the complicated sea ice draft profile or bottom unevenness that is non-Gaussian and has non-stationary characteristics can be represented using only the typical normalized spectrum and variance (standard deviation) of sea ice draft. Also, thereby, we can easily simulate an ice draft profile and bottom unevenness using them. • We found that significant amplitude of bottom unevenness elevation were roughly proportional to standard deviation of sea ice draft (its ratio: 3.6), which means we could describe the bottom unevenness elevation of sea ice intuitively and visually using the standard deviation. We will continue to collect sea ice draft data, and especially, we need to get more information about distribution and range of the variance that indirectly reflects non-stationary characteristics of the sea ice draft. We also have to collect information on cross-sectional shapes from various angles and spatial profile. REFERENCES Belliveau, D.J., Budgen, G.L. and Melrose, S.G.K. Measurement of sea ice motion using bottom mounted Acoustic Doppler Current Profilers. Sea Technology (1989). Birch, R., Fissel, D., Melling, H., Vaudrey, K., Schaudt, K., Heideman, J. and Lamb, W. Ice Profiling Sonar. Sea Technology-Arcticle on Sahalin Ice Project (1999). SakikawA, M., Yamamoto, Y., and Honma, D. Underside Profile of Sea Ice on the Okhotsk Coast. In Proceedings of the 17th International Symposium on Okhotsk Sea & Sea Ice, Mombetsu, Japan (2002) 163–167. Yamamoto, Y., Sakikawa, M., Honma, D. and Kioka, S. Underside profile and drift characteristics of sea ice on the Japanese Coast of Okhotsk Sea, Proc. of the 16th International Symposium on Ice, Dunedin, New Zealand (2002) Vol. II, 399-406. Yamamoto, Y., Kioka, S., Sakikawa, M., Honma, D. Sea Ice Draft Profile on Okhotsk Sea Coast of Hokkaido, Proc. of the 13th International Offshore and Polar Engineering Conference (ISOPE), Honolulu, USA (2003) Vol. I, 439-444. 198
17th International Symposium on Ice Saint Petersburg, Russia, 21 - 25 June 2004 International Association of Hydraulic Engineering and Research AN ORIENTED THICKNESS DISTRIBUTION FOR SEA ICE Max D. Coon 1 , Gerald S. Knoke 2 , Douglas C. Echert 3 , and Robert S. Pritchard 4 ABSTRACT This paper describes the kinematics and ice-thickness redistribution of pack ice while accounting for lead and ridge orientations. The pack ice deformations are described in terms of velocity discontinuities rather than invariants, allowing direct interpretation of open-water production and ridging. This description of pack ice allows an oriented icethickness distribution to account for the growth and ridging of ice in refrozen leads. Results of simple model calculations for ice-thickness redistribution appear reasonable. Results for kinematics indicate that most of the apparent scatter in isotropic calculations of open-water production can be explained by accounting for lead orientation. INTRODUCTION In polar regions, the sea-ice cover acts as a barrier between the atmosphere and the ocean, curtailing the transfer of thermal and mechanical energy as well as curtailing mass transport. The large-scale motion of the pack ice creates a small amount of open water, in the form of leads. In the Arctic winter and spring, leads are linear features often several hundred kilometers long. As these leads close and shear, rafted ice, pressure ridges, shear ridges, and rubble are created along these same linear features. SAR ice motion products show active leads as linear slip-lines in the pack ice (Stern et al., 1995). For convenience, all of these linear features will be referred to as leads. In this paper, the term ‘lead’ indicates a lead system that has a direction. An ice dynamics model that assumes isotropy in the ice cover can adequately characterize an ice cover in the absence of leads, e.g., summer/autumn ice with multi-year floes surrounded on all sides by open water or thin ice. However, once a lead forms, the ice becomes anisotropic and is best described by a model that accounts for this property. Careful modeling of leads in sea ice is important not only because leads provide the opportunity for the heat exchange necessary for ice production, but also because the re- 1 NorthWest Research Associates, Inc., Bellevue, WA, USA 2 Energy International, Inc., Bellevue, WA, USA 3 Skip Echert Web Associates, Renton, WA, USA 4 IceCasting Inc., San Rafael, CA, USA 199
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Page 3 and 4: 3 3 2 2 n = ⎜ ⎛ n + ⎟ ⎞ ice
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Page 37 and 38: open-water width; t i = initial ice
Page 39 and 40: Similarly, the governing equations
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Page 59 and 60: Fig.1. Radar ice images: R0000920 a
Page 61 and 62: application of PIV, the comparison
Page 63 and 64: OBSERVATIONS We set up five observa
Page 65 and 66: Variations of snow depth and sea-ic
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Page 79 and 80: Equations and Boundary Conditions
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The ice jam release simulation last
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17th International Symposium on Ice
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(1982), where temperatures 20 cm be
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255
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changes in hyporheic flow may affec
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growth processes is quite interesti
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Fig.3. Temperature variations at th
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During the snowfall and subsequent
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Fig. 7. Relation of oxygen and hydr
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the experiment seems to be shorter
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changes in sea ice concentration in
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10 Point for Point Concentrations 1
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NASA Team - Video Mean 10 67-70: NM
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There can also be cases where a sno
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FIELD TEST OF FLEXURAL STRENGTH Tes
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The ratio of elastic modulus to fle
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Shape and installation of the FICS
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conspicuous and the currents beneat
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For the Bb/BL=0.71 model, tip vorti
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are found. The pixels within this s
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Experiment Table 1. Summarized resu
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CONCLUSION From the results of thes
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The ice run in the region of the sp
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Table 2. Time to pass the distance
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Free surface drawdown above upstrea
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а) x/H 3.6 3.2 2.8 2.4 2 1.6 1.2 0
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Table. Approximate values of free s
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where I is a down gradient, B is st
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THE MEASURING SYSTEM MT Uikku is a
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Near the shore where the ice was th
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The ship had to use full power for
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of Bothnia. She got stuck in ice 5
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the position of ice edge, defined a
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As the ice cover rafts and thickens
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Fig. 5 The Clarkson wave tank We ap
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Thermometer Temperature Change with
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The wave attenuates with respect to
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REFERENCES Ackley, S.F., H.H. Shen,
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ICE CONDITIONS ON RESERVOIRS The ic
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Weakened ice Tunnel Dam Fig 1. Exam
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River ice differs in crack structur
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Fig.8. Lower ice surface Fig.9. The
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finer spatial resolution of the 85G
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Several polynyas (note that unless
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a) b) c) Fig. 4: Charts of the surf
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ubble might have to be cleared befo
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Table 2. Suggested loading window c
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tankers. If loading windows should
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pollutant propagation in tidal ice
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THE 1-D ICE JAM MODEL Model of inte
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group roughness in the Manning form
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Figure 3a corresponds to an initial
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