AIDJEX Bulletin #40 - Polar Science Center - University of Washington

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Although we have not studied in this work the magnitude of the discontinuities, there is information available elsewhere on this topic. The system of partial differential equations governing model response has been transformed into a system of ordinary differential equations with derivatives occurring only along characteristic curves. This analysis has been completed for two somewhat different modifications to the rigid-plastic AIDSEX model: (1) advection is neglected, and (2) the flow rule is modified to be non-normal to the yield surface. We have as yet been unable to analyze the AlDJEX model when advection is considered and a normal flow rule is assunled. The characteristic directions at each location depend on the stress or stretching states. The existence and orientation of the characteristic curves are independent of advection, air stress, water drag, Coriolis force, sea surface tilt, and yield strength gradients, except as the terms affect the stress state. Variations in stress along the stress characteristics, however, is affected by these terms. Along velocity characteristic curves there can be no stretching. Although this property does not provide a physical explanation for a correspondence between leads and characteristics, neither does it provide evidence that no such relationship exists. Inongoing work we intend to study directly whether or not there is a correlation between lead patterns and the stretching tensor. Preliminary work suggests that during unfaxial opening, leads form orthogonally to the direction of maximum opening. This result, however, is easily anticipated. We have not yet found any correlation in other stretching states. If such a correlation between lead orientations and characteristics can be found, we intend to apply the theory to use satellite imagery to compare with characteristic directions calculated in two-dimensional simulations of sea ice dynamics. This will provide a simple indication of direction of principal stress. as well as ratio of shearing to dilating 0. Since we feel that leads would be more likely to be generated along lines of velocity discontinuities than along stress characteristics. it is perhaps more direct to express characteristic directions in terms of b-he stretching tensor rather than the stress state. We have 148
and this relationship is given in terms of measurable quantities. From these two directions both'y and 0 may be inferred, leaving only the magnitude of the stretching undetermined. It isanticipated that the characteristic equations will also be useful for understanding flow of ice through restricted channels and other basic problems that have not yet been addressed adequately. ACKNOWLEDGMENTS We thank Max D, Coon, John F. Nye, and Roger Colony for helpful discussions on plasticity and characteristic analysis. They have helped us to avoid many of the pitfalls that we might have encountered. This work was supported by the National Science Foundation Grant OPP71-09031 to the University of Washington for the Arctic Sea Ice Study. REFERENCES Colony, R. 1975. The simulation of sea ice dynamics. In Proceedings, Third Internutima2 Conference on Port and Ocean Enginee2.ing Under Arctic Conditions, vol. 1, pp. 469-486, Institute of Marine Science, Univ. of Alaska, Fairbanks. Coon, M. D., and R. S. Pritchard. 1974. Application of an elastic-plastic model of arctic pack ice. In The Coast and SheZf of the Beaufort Sea . (ed. J. C. Reed and J. E. Sater), pp. 173-193, Arctic Institute of North America, Arlington, Va, Coon, M. D., G. A. Maykut, R. S. Pritchard, D. A. Rothrock, and A. S. Thomdike. 1974. Modeling the pack ice as an elastic-plastic material. AIDJEX BuZZetin, 24, 1-106. Coon, M. D., R. Colony, R. S. Pritchard, and D. A. Rothrock. 1976. Calculations to test a pack ice model. In NwneKcaZ Methods in Geomechanics (ed. C. S. Desai), vol. 2, pp. 1210-1227, American Society of Civil Engineers, New York. Coon, M. D., R. T. Hall, and R. S. Pritchard. 1977. Prediction of arctic ice conditions for operations. In ProceecXngs, Ninth Offshore TechnoZogy Conference, vol. 4, pp. 307-314, Houston, Texas. 149
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DATA BUOYS AIDJEX BULLETIN No. 40 J
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NOTE TO FRIENDS, AND BYSTANDERS . .
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SUMMARY OF TECHNICAL DEVELOPMENTS I
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milestones, kept the vendor working
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The scene during deployment of HF-N
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The initial AIDJEX scientific plan
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poizr-orbiting satellite, which is
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t@ the spacecraft during each orbit
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BUOY NAHE COMMUN. COMMANDS FIXES TA
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L( 0 I 2 3 4 3 Radial error, kilome
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The buoy will be subjected to tempe
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nics occupy about 12 feet of the 17
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Ill -- - KEY AIUJEX WIN WW AEBa 0 4
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event that a melt pond should form
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chute supplied by Paranetics Inc. i
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6'" IqORGANIC LITHIUM BP.TTEI?Y IMP
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OM (AD RAMS) UREMEN~ \ AIRDROP N m
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provides a grid from which geostrop
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words; a four-bit air temperature w
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PERFORMANCE OF MET/OCEAN BUOYS IN A
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Sensor samples were taken every thr
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strengths are known, were used with
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the ice (causing reduced shear). An
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(McPhee, Mangum, and Martin) , TABL
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70°N 75'N n 3 P 17OOW (D Y 170°W
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12OOW * U Station 25. Xeasurements
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(McPhee , Mangum, and Martin) 2701
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(McPhee, Mangum, and Martin) a 0 a
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"i BUOY 4 I 43 360- 309- 257 206 15
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a30gl 251 I 60 511 r 43 BUOY 4 I
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n 4, (McPhee, Mangum, and Martin) 8
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(McPhee, Mangum, and Martin) 33 W c
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. '-,..I.. . B A R R O W W I N D S
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:
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I 25 23 t h--:!li[ NCI PiHCEl4l 22
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.5 .4 .3 0 A R 2 R 0 W J - 0 B U -
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9 1.5 1.0 c 8 w .5 R 930 $ 565 1000
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Clock corrections were applied rout
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Q) u o z z i 4- 4- Z + + z f n 9 Ef
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TABLE 1 DIFFERENCES IN DAILY TEMPER
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Laboratory calibration of the ADRAM
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3.20- - 1 t W o? 2 3.051 ...:-.;..
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POSITION MEASUREMENTS OF AIDJEX MAN
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some redundancy. Four points were u
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75.5 75.: - E75.1 LLI % y75.c - 1 1
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The translocation principle removes
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POSITION ACCURACY To evaluate the q
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TABLE 1 STAND-ALONE ACCURACY 68th P
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Az i mu t h s When both receivers a
Page 100 and 101: DATA PROCESSING Following the field
Page 102 and 103: model ice motion in the statistical
Page 104 and 105: FREC 1 INCY / DOPPLER / FREQUENCY /
Page 106 and 107: 35 30 25 v) > 0 2 20 LL 0 r= E m 15
Page 108 and 109: An example of a large-scale buoy ar
Page 110 and 111: observations are needed in remote a
Page 112 and 113: useful for determining how various
Page 114 and 115: as well as velocity fields, we must
Page 116 and 117: Since small changes in the yield su
Page 118 and 119: The transformation of the system of
Page 120 and 121: e able to judge how well such a mod
Page 122 and 123: then the flow rule becomes Q = +A -
Page 124 and 125: [-B' -F Finally, we eliminate Carte
Page 126 and 127: differential equation. 2. Discontin
Page 128 and 129: Substituting (36) and (37) into (34
Page 130 and 131: arbitrarily assign the values of 1
Page 132 and 133: The special case when advection can
Page 134 and 135: TABLE 1 STRETCHING, STRESS, ASP CHA
Page 136 and 137: ate of deformation, we have normali
Page 138 and 139: CHARACTERISTIC EQUATIONS The ordina
Page 140 and 141: One way to circumvent the problems
Page 142 and 143: The equations governing solutions a
Page 144 and 145: It is readily seen that when body f
Page 146 and 147: which may be substituted into equat
Page 148 and 149: a the stress derivative dCldS remai
Page 152 and 153: Courant, R., and D. Hilbert. 1962.
Page 154 and 155: A RESEARCH PLAN TO TEST THE AIDJEX
Page 156 and 157: the barges managed to reach their d
Page 158 and 159: APPROACH A baseline simulation 0-f
Page 160 and 161: SENSITIVITY OF ICE RESPONSE TO DIFF
Page 162 and 163: Since free drift of ice is computed
Page 164 and 165: and what is observed becomes less i
Page 166 and 167: stresses appear to be relatively un
Page 168 and 169: ehavior is directly related to accu
Page 170 and 171: TABLE 1 COMPARISON OF ESTIMATED ERR
Page 172 and 173: a) Base line b) 24-hour prediction
Page 174 and 175: \ / a) Base line b) 24- hour predi
Page 176 and 177: a) Base line b) 24- hour predi ct i
Page 180 and 181: \ / a) Base line b) 24-hour predict
Page 182 and 183: .. a) Base line b) 24- hour predict
Page 184 and 185: J2 a) Base line b) 24-hour predicti
Page 186 and 187: ) 24-hour prediction c) 36-hour pre
Page 190 and 191: 8 Figure 17. AIDJEX surface pressur
Page 192 and 193: APPENDIX 1 AIDJEX DATA FILES 1. Pos
Page 194 and 195: 9A. Surface-1 eve1 ai r pressure (d
Page 196 and 197: 19. Surface pressure (Val i dated)
Page 198 and 199: APPENDIX 2 AIDJEX DATA TRANSFERRED
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I -7-71327GEO A Cards (continued) 7
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B Cards (continued) 201
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AIDJEX Bulletin #40 - Polar Science Center - University of Washington

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