Please use this identifier to cite or link to this item:
|Title:||Thickness and roughness variations of arctic multiyear sea ice|
|Authors:||National Science Foundation (U.S.)|
Ackley, Stephen F.
Hibler, William D.
Kugzruk, F. K.
Weeks, W. F.
Ice thickness models
|Publisher:||Cold Regions Research and Engineering Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||CRREL report ; 76-18.|
Abstract: Three surface elevation and ice thickness profiles obtained during the 1972 Arctic Ice Dynamics Joint Experiment Pilot Study on a multiyear ice floe were analyzed to obtain relationships between the surface elevation, thickness and physical properties of the ice. It was found that for ice freeboards from 0.10 m to 1.05 m above sea level a linear relationship between the ice density and the freeboard could be postulated. The equation for the regression line is ρ = -194𝘧' + 974 kg/m^3, where ρ is the ice density and 𝘧' is the ice freeboard plus snow depth in ice equivalent at the point in question. This statistical relationship is consistent with the observed physical properties, which indicate that as the ice freeboard increases, the ice salinity decreases and the higher freeboard or thicker ice therefore decreases in density. Using this variable density with freeboard relationship, a model was constructed to predict the ice thickness, given the ice freeboard and snow depth alone. This prediction is desirable, since the snow depth and freeboard are relatively easy to obtain, whereas the ice thickness can usually be obtained only by drilling through the ice. The model was compared with two other models, one assuming constant ice density (independent of freeboard) and the other using smoothing filters for predicting the ice thickness. It was found that the variable density prediction model gave the best approximation to the observed ice thickness, with a standard error between the measured and predicted value of about 0.4 m, compared with errors from 50 to 100% higher for the other two models. The model was also compared with data on multiyear ice from two other investigations in different regions and was found to give error estimates similar to the error of the data set on which the model was based. It is therefore concluded that the model can be useful to estimate multiyear ice thicknesses from surface elevation information obtained either by ground-based techniques or by aerial methods such as laser profilometry or stereo aerial photogrammetry. The effect of the variable density on estimates of the stress induced in the ice sheet by isostatic imbalance loading was examined and the results are presented in an appendix. Consideration of this property led to the conclusion that stresses from sources other than isostatic imbalance must account for 75% or more of the bending stresses necessary to induce cracking in multiyear ice.
|Appears in Collections:||CRREL Report|
Files in This Item:
|CRREL Report 76-18 revised.pdf||2.24 MB||Adobe PDF|