Abstract. New systematic experiments reveal that the flexural
strength of saline S2 columnar-grained ice loaded normal to the columns can
be increased upon cyclic loading by about a factor of 1.5. The experiments
were conducted using reversed cyclic loading over ranges of frequencies from
0.1 to 0.6 Hz and at a temperature of −10 ∘C on saline ice
of two salinities: 3.0 ± 0.9 and 5.9 ± 0.6 ‰.
Acoustic emission hit rate during cycling increases with an increase in
stress amplitude of cycling. Flexural strength of saline ice of 3.0 ± 0.9 ‰ salinity appears to increase linearly with
increasing stress amplitude, similar to the behavior of laboratory-grown
freshwater ice (Murdza et al., 2020b) and to the behavior
of lake ice (Murdza et al., 2021). The flexural strength of saline ice of
5.9 ± 0.6 ‰ depends on the vertical location of the
sample within the thickness of an ice puck; i.e., the strength of the upper
layers, which have a lower brine content, was found to be as high as 3
times that of lower layers. The fatigue life of saline ice is erratic.
Cyclic strengthening is attributed to the development of an internal back
stress that opposes the applied stress and possibly originates from
dislocation pileups.