830 



POUNDER 



[sect. 7 



TEMPERATURE (°C) 



Fig. 1. Strength conditions of sea-ice for various temperature and salinity ranges. (After 

 Assur, 1958.) 



The variations in strength with temperature are striking and far from hnear. 

 Abrupt increases in strength have been observed at temperatures of about 

 — 8°C and — 23°C. These are respectively the temperatures at which 

 Na2S04- IOH2O and NaCl -21120 start to precipitate from brine. Figs. 1 and 2 

 show some theoretical curves taken from Assur (1958). They indicate the 

 enormous range in tensile strength possible. The relative strength scale on 

 the left applies at temperatures above — 8.2*^0, that on the right for lower 

 temperatures. This scale change is introduced because even small amounts of 



-20 -30 



TEMPERATURE CO 



Fig. 2. Relative tensile strength of sea-ice as a function of temperature and salinity. 

 (After Assur, 1958.) 



