Driftwood in Svalbard as an Indicator of Sea Ice Conditions

ABSTRACT

The amount and type of driftwood logs on raised beaches in Svalbard probably indicate variations in sea ice conditions through time in the Arctic Ocean. This idea is based on the fact that wood floating in water has a limited buoyancy. The maximum period of buoyancy for coniferous wood (Picea/spruce, Larix/larch, Pinus/pine) is between 10 and 17 months: for broadleaves (Betula/birch, Salix/willow, Populus/aspen) from 6 to 10 months. The buoyancy depends on many circumstances but foremost on the properties and basic density of wood when the drift starts.

Two dominant drift features are evident in the Arctic Ocean. The Pacific Gyral has a clockwise circulation in the Beaufort Sea. There are large variations in the rate of drift of this circulation, but the average speed is probably 700–800 km/year. The Transpolar Drift Stream runs from the Siberian coast to Svalbard and north Greenland and the average drift rate 600 km/year may be close to the actual net speed of an ice floe or a log of driftwood.

The passage from the Siberian coast to the Svalbard area takes, roughly, five years. A trunk with the best possible buoyancy sinks after a third of that time. However, because of rafting on or in the sea ice, driftwood logs land on the islands of Svalbard. Most of the wood on the eastern islands of the archipelago is coniferous wood of Siberian origin. There are at least two easily noticeable zones on the shores with raised beaches where the amount of driftwood is small. These zones probably represent climatic conditions with periods of “long summers”; a high percentage of open water and a northerly position of the ice limit.