Abstract
Relationship between ship speed along the Northern Sea Route and sea ice condition is analyzed by implementing Ice Index. Ship speed is detected by satellite AIS. Ice Index along the actual ship track is calculated from sea ice concentration and thickness, which is derived from the data assimilation system TOPAZ4. The ships sailed independently until Ice Index decreases to be 15, then they sailed under ice-breaker assistance. Navigable speed reached 10~12knots under icebreaker assistance until the Ice Index decrease to -10, then it tends to decrease with decrease of Ice Index.
