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Abstract. The flexural strength of ice surfaces bonded by freezing, termedfreeze bond, was studied by performing four-point bending tests of bondedfreshwater S2 columnar-grained ice samples in the laboratory. The sampleswere prepared by milling the surfaces of two ice pieces, wetting two of thesurfaces with water of varying salinity, bringing these surfaces together,and then letting them freeze under a compressive stress of about 4 kPa. Thesalinity of the water used for wetting the surfaces to generate the bondvaried from 0 to 35 ppt (parts per thousand). Freezing occurred in air under temperatures varyingfrom −25 to −3 ∘C over periods that varied from 0.5 to∼ 100 h. Results show that an increase in bond salinity ortemperature leads to a decrease in bond strength. The trend for the bondstrength as a function of salinity is similar to that presented in Timco andO'Brien (1994) for saline ice. No freezing occurs at −3 ∘C oncethe salinity of the water used to generate the bond exceeds ∼ 25 ppt. The strength of the saline ice bonds levels off (i.e., saturates)within 6–12 h of freezing; bonds formed from freshwater reach strengthsthat are comparable or higher than that of the parent material in less than0.5 h. 

Abstract The structural integrity of the arctic sea ice cover is under threat owing largely to the combination of thinning and larger waves. Another contributor may be thermal cracking. In concentrating stress, thermal cracks may weaken the cover. Of interest, therefore, is the strength of thermally damaged ice. To that end, new experiments were performed on sea ice and on lab‐grown saline and salt‐free ice that had been cracked by thermal shocking. As expected, the cracks weakened the materials in accord with fracture mechanics. However, within tens to hundreds of seconds of shocking, the strength recovered completely, for the ice had healed. Healing is attributed to thermally activated sintering related to surface diffusion, assisted possibly by the formation of a quasi‐liquid layer on crack faces. Whether behavior on the small scale is indicative of behavior on the large scale remains to be determined.