Indeed, there is a high interannual variability in the average number of identified ridges, but annual average values of ridge counts on the scale of the entire shipping corridor do not indicate any trend towards more or less ridging. Figure 6 shows the variability in ridge counts at the monthly scale.
This figure shows that on a monthly basis, ridging was found to peak in March, with a mean of 203 ridges per image, which was followed by February (155), and April (130).
However, late freeze-up cannot be the sole explanation for less ridging because in 2009-10, the previous season, there was also less than average ridging, but freeze-up occurred during week 49, which is typical.
Ridging along the coast is to be expected as this is where the mobile ice meets with the landfast ice and shear zones are formed.
During most individual seasons, ridging is concentrated in the eastern and western zones of the study corridor, as is seen in the mean for all years in Figure 9.