Svalbard Sea Ice And European Whaling In The 18thC
By Paul Homewood
Map showing maximum (April) sea ice extension in the Atlantic sector of the Arctic (Norwegian Polar Institute 2000). The map is based on a database on sea ice extension in the area shown during the past 400 years, to a high degree based on written records found in ships logbooks.
In my post the other day, Long Term Perspectives For Arctic Sea Ice, I included the above chart from the Norwegian Polar Institute, showing ice extents in the Barents Sea. The caption states that these are maximum/April extents. This is confirmed in the original report from the Institute:
on page 7:
There is, however, some doubt about the dating of the 1769 line. According to a paper by Isasksson et al in 2004, the 1769 sea ice edge is actually for August, and not April.
The mystery, however, deepens, as another paper, At the rainbow’s end: high productivity fuelled by winter upwelling along an Arctic shelf, by Petersen et al, states in the Abstract:
Herein we document findings from a unique scientific expedition north of Svalbard in the middle of the polar night in January 2012, where we observed an ice edge north of 82°N coupled with pronounced upwelling. The area north of Svalbard has probably been ice-covered during winter in the period from approximately 1790 until the 1980s, a period during which heavy ice conditions have prevailed in the Barents Sea and Svalbard waters. However, recent winters have been characterized by midwinter open water conditions on the shelf, concomitant with northeasterly along-shelf winds in January 2012. The resulting northward Ekman transport resulted in a strong upwelling of Atlantic Water along the shelf. We suggest that a reduction in sea ice and the upwelling of nutrient-rich waters seen in the winter of 2012 created conditions similar to those that occurred during the peak of the European whaling period (1690–1790) and that this combination of physical features was in fact the driving force behind the high primary and secondary production of diatoms and Calanus spp., which sustained the large historical stocks of bowhead whales (Balaena mysticetus) in Arctic waters near Spitsbergen.
Whalers Bay, as mentioned by Isaakson, lies at 81N, so this basically the same area that appears to have been ice free in winter between 1690 and 1790. This would therefore appear to confirm the Polar Institute’s version of events.
There is no doubt anyway that this was an unusually warm interlude, particularly in the middle of the Little Ice Age, which was the reason for the inclusion of 1769 on the Polar Institute’s map. Isaakson confirms this with their chart of sea ice edge:
Note that the edge of the summer sea ice was even further north than recently in the early 18thC. (Bear in mind that the paper was written in 2002, but summer ice extent near Svalbard has changed little since then).
It is also worth a look at the graph below from the Petersen paper:
Graph A shows the position of summer sea ice edge, and again we find some years in the early 18thC at similar latitudes as recently.
Also Petersen states:
European whaling commenced in the early 1600 s and was initially focused on the Spitsbergen bowhead whale stock (Fig. 1). The peak of the Spitsbergen whaling period, between 1680 and 1790, coincided with an era during which the minimum (August–September) ice edge was north of 80N for extended periods, a situation similar to that observed during the last 15 years (Fig. 2). The subsequent near extinction of these whales coincided with a period of rapid expansion of the autumn ice edge from around 1790, when the border of the minimum sea-ice cover expanded some 500 km southwards to around 76N within a few years (Fig. 2). The Spitsbergen bowhead stock has been estimated to have numbered as many as 100,000 individuals before whaling started (Reeves 1980; Allen and Keay 2006). By the end of the whaling period, around 1800, the Spitsbergen bowhead population had been hunted to near extinction (Woodby and Botkin 1993). The species was very attractive for early whalers; bowheads were valued both for their baleen and for the oil content of their huge blubber deposits, which was used both for human consumption and for lamp oil. The oil was so valuable that Amsterdam ship owners sent their whaling ships northwards into hostile arctic waters northwest of Svalbard for over 100 years.
Regardless of the 1769 dating issue, it is evident that there have been very large swings in sea ice extent during the last 300 years.
Finally, I should point out the eruption of the Icelandic Laki volcano in 1783 was one of the key factors in the colder climate that arrived at that time.
- Norwegian Polar Institute