Consolidation of first-year sea ice ridges

[1] Measurements of spatial and temporal temperature development, geometry morphology, and physical properties in three first-year sea ice ridges at Spitsbergen and in the Gulf of Bothnia have been performed. The corresponding thickness and the physical properties of the surrounding level ice were also measured. The thickness of the consolidated layer was examined through drilling and temperature measurements: the temperatures gave a ratio of the thickness of the consolidated layer to the level ice thickness from 1.39 to 1.61, whereas the drillings indicated a ratio of 1.68-1.85. The measured consolidated layer appeared to be 28% thicker when based on drillings in comparison to temperature. Thus the result depended on the method of investigation; the drillings included a partly consolidated layer. However, the measured growth of the consolidated layer did not depend on the method of investigation. The scatter of the physical properties in the consolidated layer was higher than that of the level ice. The consistency of the unconsolidated rubble differed markedly at the two sites. It was soft and slushy at Spitsbergen and harder in the Gulf of Bothnia. Three possible explanations for these differences are discussed: surrounding currents, different keel shapes, and difference in salinity.