**6. Permafrost erosion models**

Several assumptions were made for estimating the amount of eroded soil during the one year period:


As the average erosion rate in Varandey area was 2.7 m/year between 2005 and 2007 [11], based on these assumptions, the amount of eroded soil could be estimated.

The assumption that all melted material is being removed by a storm surge at the end of each "season" means that a new frozen soil layer is now exposed to heat and melting processes. A melted soil layer that stays intact could create an insulation layer that prevents heat penetration and decreases the melting processes, so the overall melted and eroded soil amount would be much smaller. For example, a single storm surge that hits the shore at the end of fall would hardly influence the erosion rate.

An erosion rate sensitivity analysis was made to assess and better understand the effect of the number of storms in a year on the total erosion rate. Three different

**Figure 4.** *The effect of number of storms on the total erosion as a function of time [10].*

**Figure 5.** *Total erosion as a function of number of storm surges [10].*

cases of storm surge were examined: the period between May and September was divided into sub-periods. It was then assumed that a storm surge hits the shore at the end of each sub-period and erodes all melted material.

As can be seen in **Figure 4**, the results correspond to the expectations—the erosion rate is increased as the number of storms rises. This result is further detailed in **Figure 5**, which shows the total erosion as number of storms/storm surges.
