Geometry, morphology and physical properties of ice ridges during the transition period from first-year to second-year in the GoNorth Expedition 2023

The GoNorth expedition was carried out in July - August 2023 in northern Fram Strait. The geometry, morphology and physical properties of four ridges were investigated during three ice stations by drilling cross-sections with salinity and temperature measurements of the water column and ice-coring. Snow thickness and weather conditions were recorded. The first ice station was located furthest north, and the ridge was fully consolidated with a keel temperature of -2 °C. On the second ice station, the ice was rotten. Here, two ice ridges were investigated: one had a small sail and curious macropore structure with a large void close to the bottom and smaller voids in the top part as well as in the surface zone of surrounding level ice. The second one and the ridge on the third station both had a sail-to-keel ratio of 1/4 and differently sized voids inside. In general, keel depth ranged from 3.5 m to 4.0 m and sail height from 0.3 m to 1.0 m. Mean density and salinity of ridge samples were 900 kg/m³ and 2.1 ppt, respectively. The average constant temperature in the keel was -1.8 °C. Salinity of level ice from station 1 and 2 were similar at 1,6 and 1,7 ppt, respectively.