Study On The Physical And Mechanical Engineering Parameters Of Sea Ice During Melt Season For Arctic Passage

The global warming has accelerated the melt of Arctic sea ice in summer,which makes it possible to sail through the Arctic Ocean.The related engineering problems of Arctic navigation are attracting more and more attention,and reasonable design of ice resistance of polar ships is one of these key issues.Sea ice shows different physical and mechanical properties due to melt,thus,obtaining accurate physical and mechanical engineering parameters of Arctic sea ice during melt season becomes the constraint of design ice resistance of polar ships.Based on the observation of sea ice thickness,concentration and physical parameters and uniaxial compressive strength test conducted during Chinese Arctic expeditions combined with kinetic friction coefficient test of sea ice conducted in Bohai Sea,this paper studied the physical and mechanical parameters of Arctic sea ice during melt season which are needed to calculate ice resistance.Both Arctic sea ice thickness and concentration increases with increasing latitude dring melt season,and the sea ice thickness in Chukchi Sea,Beaufort Sea,and the central sea of the Arctic Ocean conformes to nomal distribution approximately.Based on the sea ice concentration obtained,the data from passive microwave remote sensing was verified.The melt pond affects the accuracy of the sea ice concentration from passive microwave remote sensing during melt season,and with the increase of the melt pond,passive microwave remote sensing underestimates the sea ice concentration.During melt season in 2008?2016,Arctic sea ice temperature was-2.7?-0.3?;sea ice salinity was 0.4‰?3.0‰;sea ice density was 601.6?903.2 kg/m3;sea ice brine volume fraction was 21.7‰?259.3‰;sea ice air volume fraction was 34.4‰?380.3‰.All of these parameters showed no obvious spatial variation in Chukchi Sea,Beaufort Sea,and the central sea of the Arctic Ocean,while ice temperature and brine volume fraction increased annually during 2008?2016.Besides,the result of ice crystal structure showed that most Arctic sea ice are dominated by thermodynamic growth.The uniaxial compressive strength of Arctic sea ice in the vertical direction during melt season first increases and then decreases with the increase of strain rate,while decreases with the increase of porosity.Based on strain rate and porosity an equation is established to estimate the uniaxial compressive strength of Arctic sea ice during melt season.With the equation the strength of an ice sheet can be calculated using its porosity profile.The maximum uniaxial compressive strength in vertical direction of Arcitc ice sheets during melt season in 2010?2016 was 2.07?3.83 MPa.The in-situ similar test of the kineitc friction coefficient of sea ice was conducted based on the movement direction relative to ice surface and the corresponding velocities of polar ship during ice navigation.The results showed that the kinetic friction coefficient of sea ice is independent of the motion direction while increases with the increase of velocity.Besides,air temperature and normal stress also affect the kinetic friction coefficient of sea ice.The theoretical models of ice friction were verified using test data,and it was found that velocity-state constitutive model can be used to estimate the sea ice kinetic friction coefficient.The study areas in this paper are the Chukchi Sea,Beaufort Sea and the Central sea area of the Arctic Ocean,which are parts of the Arctic Passage.In order to provide scientific basis for the design ice resistance of polar ships in Arctic summer navigation,the suggested values of the physical and mechanical parameters of sea ice required for ice resistance calculation of polar ships in the above sea areas during melt season are given.