A probabilistic description of pressure ridge width, spacing, and keel depth for the Chukchi and Beaufort seas based on IPS and ADCP observations

16 seasons of under-ice measurements, from both the Beaufort and Chukchi seas, were processed and pressure ridge keel features were identified. A starting threshold value of 6m was justified by statistical goodness-of-fit results and used to identify keels from the under-ice measurements. Statistics for keel depth, keel width, keel slope, and keel spacing were determined and compared to other sources. It was shown that the Exponential, Gamma and Weibull Distributions all fit depth data well; with the three-parameter Weibull Distribution being the better fit. Keel width and slope were studied by comparing the most common modal keel width, for each 1m increment of keel depth, and comparing the results to other sources. A presumed keel slope, for an idelaized triangular keel, of 33.7 degrees for the Western Beaufort and 32.5 degrees for the Chukchi seas did not compare well with field measurements from some sources but did compare favorably with published results from models of ridge formation. The disparity could have significant implications when designing offshore structures in ice-covered waters. The best fit found for keel spacing was the Lognormal Distribution, which is consistent with other studies. Parameters for the distributions considered in the paper are provided along with rudimentary statistics for the parameters studied.

Automated summary

This study analyzed under-ice measurements from the Beaufort and Chukchi seas over 16 seasons to identify pressure ridge keel features. Statistical analysis determined the parameters of keel depth, width, slope, and spacing, with different distributions showing varying degrees of fit. The findings have implications for designing offshore structures in ice-covered waters.