Estimation of the uniaxial compressive strength of Arctic sea ice during melt season

A series of uniaxial compressive tests using ice cores collected in the Arctic Ocean was conducted in the cold laboratory on board R/V Xuelong during the summers of 2012 and 2014. A total of 130 ice samples were tested at temperatures ranging from -9 degrees C to -3 degrees C at strain rates ranging from 10(-7) s(-1) to 10(-2) s(-1) with the loading direction along the core axis. The uniaxial compressive strength of sea ice depends mainly on two parameters: sea ice porosity and strain rate during the test. Arctic sea ice presented characteristics of weak porosity effect and low transition strain rate. The effect of strain rate on the uniaxial compressive strength could be parameterized using a piecewise function for ductile, transition and brittle regimes. A power-law relationship was found between the uniaxial compressive strength of ice samples and their porosity. These relationships made it feasible to estimate the natural uniaxial compressive strength of ice as a function of in-situ porosity and strain rate. The results derived from the ice samples were extended to large-scale strength of ice sheets based on their porosity profiles determined using field measurements of ice physical properties. The strength of Arctic ice sheets in the summers of 2012 and 2014 was far less than previous estimates, probably because of accelerated interior ice melt caused by Arctic warming.