Searching for the Shipwrecks
What the Ice Can Tell Us (CIS)
Data from the Canadian Ice Service: Parks Canada underwater archaeologist working collaboratively with CIS to determine what their research can tell us.
By Tom Zagon, Canadian Ice Service
Canadian Ice Service
Modern icebreakers rely heavily on information obtained from remote sensing satellites for planning routes through the ice and making navigational decisions. The ice charts produced by the Canadian Ice Service are crucial for navigation in ice covered waters and up-to-date ice information is regularly delivered to the bridges of icebreakers in near-real time through satellite communications. It is daunting to think that vessels like HMS Erebus and HMS Terror had none of the benefits provided by today's satellite technology that are often taken for granted.
While the satellite imagery collected over the Canadian Arctic over last few decades has certainly had an operational benefit, it has also created a valuable archive that can be used to analyze the historical ice conditions over any given region. Ice conditions do vary from year to year, but this variability manifests itself within a well defined range and many ice features reoccur in the same location on an annual basis. Sea ice is dynamic, but numerous studies have shown that it does not behave in a random fashion.
A detailed examination of historical satellite imagery is being used to support the current search effort for HMS Erebus and HMS Terror. The imagery can be used to provide a more complete understanding of the ice environment in the region where the vessels ran into trouble. For example, by examining the ice conditions in the early autumn of different years, it is possible to identify the most likely scenario that led to the vessels becoming beset in 1846. More importantly, the imagery makes it is possible to ascertain the general drift patterns that occur in the region and identify crucial aspects of the progression of winter freeze-up and spring break-up. This can help determine the direction the ships might have drifted after they were abandoned in April 1848 off the northwest shore of King William Island.
Most of what is known about the subsequent sinking of the vessels is derived from historical evidence. Unfortunately some of that evidence is unclear and at times even contradictory. It is hoped that the use of historical satellite imagery will be able to resolve some of this uncertainty by assigning probabilities to the different scenarios and locations under consideration. When used in conjunction with archaeological evidence and invaluable Inuit oral history testimony, the satellite imagery of ice patterns becomes an important addition to help solve the Franklin puzzle.
These two images show the break-up and clearing in eastern Queen Maud Gulf in July of 2010. The area of fast ice, shown on the image from July 14, has fractured by July 18.
Satellite sensor: MODIS
July 14, 2010, O'Reilly Island
July 18, 2010, O'Reilly Island