Draft Preliminary Analysis of Sea Ice Characteristics in Relation to Lost Franklin Vessels (2013)

Conclusions

There are a number of conclusions that can be drawn from the satellite image record. First, a probable reason for the besetment of Erebus and Terror was most likely caused by a strong north westerly wind that trapped the vessels against King William Island. Secondly, while the general direction of the drift in Victoria Strait is in a southerly direction, it also shows that there exists a marked difference between the eastern and western halves of the strait; most of the ice is flushed south through the western half while the eastern half moves at a much slower pace. The vessels were trapped in the eastern half.

The imagery also shows that, most of the time, ice in the eastern half of Victoria Strait is flushed south through Alexandra Strait. This is evidenced by the presence of shear lines running in the direction of Alexandra Strait. This would indicate that there would be a higher probability that the vessels were drawn towards Alexandra Strait from the point of abandonment.

There is a lower probability that they would have passed to the west of the Royal Geographical Society Islands. If that was the case they would have been delivered to the southern shores of Queen Maud Gulf. The probability of finding the vessels also decreases further eastward into Erebus Bay since that ice tends to form in-situ. Shearing occurs between the mobile ice moving through Alexandra Strait and the fast ice surrounding the Royal Geographical Society Islands. Shearing also occurs between this mobile ice stream and the fast ice formed in Erebus Bay. If the assumption is that a vessel sank due to hull failure from ice pressure, these shear lines might represent a good target for survey lines.

There are other possible outcomes that cannot be excluded although their probability seems low. The currents in eastern Victoria Strait are very weak; therefore much would have depended on the break-up and clearing sequence followed during the summer of 1848, after the vessels were abandoned.

Satellite imagery shows that in the summer months the ice moves mostly in response to wind direction. This means that it can be moved in an east-west direction across Victoria Strait and it can also be pushed north. However, these examples come from years when the Strait was filled with first-year ice and therefore might not make for useful analogue conditions. We know that the vessels were abandoned in multi-year since the ice did not clear for two winters. The evidence seems to indicate that ice motion in response to wind forcing is constrained in years when Victoria Strait is filled with high ice concentrations of multi-year ice during the summer months.