| The global climate has been changing rapidly over the past few decades, resulting in a rapid decline in Arctic sea ice extent and thickness, while an increasing trend of the Antarctic sea ice extent. The predicted results have suggested that a summer ice-free Arctic Ocean would be likely before 2050. With the rapid changes of the Arctic sea ice, the Northern Sea Route has opened up as a possible avenue of trade for containerized products between Asia and Europe, and sea ice becomes clearly the main factor contributing to the safety of navigation of ships in the Arctic Ocean. Thus, the spatial distribution of sea ice and the mechanical properties of sea ice are important for ships and ice-resistant structures. This study was carried out on the spatial and temporal distributions of sea ice in Polar Routes, characterization of sea ice kinematic in the Arctic and the physical, mechanical properties of sea ice.Firstly, by analyzing the data measured by ASSIST/ASPeCt and the data sets of sea ice spatial and temporal distributions, sea ice thickness and concentration measured by remote sensors, the distribution and change trend of sea ice concentration, floe ice size, melt-pond coverage and ice thickness in the three marginal seas of the Arctic Ocean (East Siberian Sea, Kara Sea and Laptev Sea) on the Northeast Passage, the Beaufort Sea on the Northwest Passage, the Fram Strait, the central Arctic Ocean (in north of 85°N) on the Polar Passage, and the Prydz Bay in the Antarctica are analyzed and discussed in detailed. The results are the follows, (1) the floe sizes were mostly smaller than 500 m in the East Siberian Sea and Laptev Sea in July. The distribution of melt-pond coverage was in a range of 10 to 40%, and the ridge coverage was in a range of 5 to 40%. (2) The sea ice concentration increased with increasing latitude and was generally less than 50% in south of 72°N, and the average thickness was 126.4 cm in the region of ice concentration greater than 80% in the summer during 2006?2015 in Beaufort Sea. (3) The floe sizes were mostly smaller than 100 m, and sea ice thickness mainly laid in a range of 150 to 200 cm in the summer during 2012?2015 in Fram Strait. (4) The summer sea ice concentrations were generally greater than 90%, and ice thickness was greater than 200 cm in the central Arctic Ocean. The study also indicated that the ice thickness had a linear decrease of 47.7 cm/decade in north of 87°N, and 56.7 cm/decade in north of 89°N in summer during 1979?2015. (5) The floe sizes were mostly smaller than 20 m, and sea ice thickness was mainly in a range of 20 to 150 cm and the average thickness was 83.3 cm in the summer in Prydz Bay.Secondly, using six ice-tethered buoys deployed in 2012, we analyzed the sea ice motion in the central Arctic Ocean and Fram Strait. The results showed that, (1) the accuracy of ice velocity is related to the calculated time interval. With the increasing calculated time interval, the accuracy of ice velocity is reduced. (2) The ice drift velocities were unevenly in time and space in the Arctic Basin. The ice velocities were generally less than 0.4 m/s before drifted into the Fram Strait, and increased significantly after drifted into the Fram Strait. Meanwhile, the ice velocities changed with the seasons, we find out that a maximum occurred in October and a minimum occurred in April. (3) The amplitudes of sea ice velocities showed a non-symmetric inertial oscillation at all the six buoys. And the inertial oscillations were evidenced by a strong peak observed at the frequency of about -2 cycle/day. (4) Sea ice moved with a speed of about 1.4% of the wind speed and about 30°to the right of the wind direction.Thirdly, we analyzed in detail the internal structure and physical properties of the Arctic floe ice and the Antarctic fast ice in summer. The results are as follows:(1) the Arctic floe ice usually consists of the granular ice, the columnar ice and the transition layer, the Antarctic fastice, however, includes the granular ice, the columnar ice and the platelet ice. (2) Summer sea ice temperature was generally higher than-2.0?. The Arctic floe ice temperature was in the range of-0.5? to-1.5?, and the Antarctic fast ice temperature varied between-0.6? to-1.8?. (3) The Arctic floe ice density was in the range of 0.58 g/cm3 to 0.93 g/cm3, while the Antarctic fast ice density, however, was in the range of 0.88 g/cm3 to 0.92 g/cm3. The Arctic floe ice density increased linearly with increasing per unit normalized depth, with a gradient of 0.176 g/cm3. (4) The Arctic floe ice salinity was generally lower than 4.2%o, and the salinity increased linearly with increasing per unit normalized depth with a gradient of 3.22%o. The Antarctic fast ice salinity also increased with depth, the salinity approached 0.45%o at the top, 8.05%o at the bottom. (5) The gas content of Arctic floe ice decreased linearly with per unit normalized depth with a gradient of 200%o, and the brine content increased linearly with per unit normalized depth with a gradient of 89%o. The porosity of Arctic floe ice was in the range of 120%o to 400%o, and the porosity decreased linearly with per unit normalized depth with a gradient of 123%o. The porosity of Antarctic fast ice was varied from 140‰ to 250‰.Fourthly, the quasi-in situ uniaxial compressive tests were carried out to determine the uniaxial compressive strength of the summer Arctic floe ice and the Antarctic fast ice in summer. Meanwhile, the fractal dimension of the fragment length and the viscoelastic properties of the Antarctic fast ice under the Maxwell model were studied. The findings are as follows:(1) the uniaxial compressive strength depends on several parameters such as physical indices (porosity and density) of the ice, the loading rate (stress rate), and the temperature. We established the relationship between the influence factors and the uniaxial compressive strength, and found that the uniaxial compressive strength decreased with increasing temperature. (2) The fractal dimension of the fragment length decreased with the increase of strain rate. Additionally, the fractal dimension of the fragment length increased with decreasing tested temperature. (3) By describing the uniaxial compression behavior of sea ice with the Maxwell model, we calculated the viscosity coefficient and elastic modulus of sea ice when sea ice was tested under multi- stage loading and cyclic loading that based on the Maxwell model, and obtained the range of 19?207 GP a·s for viscosity coefficient and 0.17 to 0.50 GPa for elastic modulus. |
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