Jökull - 01.12.1993, Blaðsíða 31

BUOYANCY OF DRIFTWOOD IN CONNECTION
WITH THE ORIGIN OF THE DRIFTICE
As noted, wood has a limited buoyancy or ability
to float on water. It becomes water saturated and
sooner or later sinks. In connection with log drifting
and water storage of timber in the lumber industry, the
buoyancy of wood has been studied (Nylinder, 1961;
Edlund, 1966). Haggblom (1982) summarized these
results, taking into account factors like removal of
the bark, which reduces the buoyancy of a trunk, and
the salinity of oceanic water that could improve the
buoyancy (Table 5). A major rule for coniferous trees
is that buoyancy decreases with decreased volume.
This means that the smaller the driftwood is the shorter
the tirne it can stay afloat in water (Hággblom, 1982).
Because of the relatively short buoyancy time of
the driftwood (Table 5), much shorter than it takes for
the wood to reach the islands in the North Atlantic,
it is obvious, as mentioned by rnany authors that the
drift ice of the Arctic Ocean is the main factor in
transporting the wood. When the driftwood reaches
the ocean, normally during river breakups, it floats on
open water for probably a couple of months until it
becomes frozen into the pack ice.
Vowinckel (1963) estimated that the drift ice of
the East Greenland Current had its main origin in the
Arctic Ocean, and that only a small amount of ice is
formed south of 80°N.
From the origin of the driftwood it must be con-
cluded that some of the drift ice reaching the coasts
°f Iceland has the "same" origin as the driftwood, i.e.
Siberian coast and the Barents Sea.
CONCLUSION
The driftwood deposited on today’s coasts of
Iceland mainly consists of coniferous trees of Rus-
sian/Siberian origin. Pinus and Picea components
dominate the logs that have come loose during tim-
ber floating on the Russian/Siberian rivers draining
>nto the Arctic Ocean, while the majority of the Larix
wood has a natural origin (root system intact).
The wood has been transported with currents from
the Arctic Ocean through the Fram Strait between
Greenland and Svalbard, south along the east cost of
Type of wood Maximum period of buoyancy
Picea 17 months
Pinus 10 months
Larix 10 months
Betula 6 months
Populus 10 months
Salix 10 months
Table 5. The buoyancy of wood (modified from
Haggblom 1982). —Aœtlaðurflottími rekaviðar.
Greenland to Iceland. The relatively short buoyancy
time of the driftwood indicates that the wood must
have been frozen in and transported by the drift ice.
This implies further that driftwood and drift ice have
the same origin, the Barents and Siberian seas. When
the ice approaches the coasts of Iceland it melts and
the imbedded wood is released and floats in open wa-
ter. Some of the wood is then transported by currents
clockwise around Iceland until it is washed ashore.
Dendrochronological analyses on the youngest
dated driftwood show that it may take less than six
years for the Arctic driftwood to reach Iceland and,
correspondingly drift ice takes the same time.
American driftwood has so far not been identi-
fied in the Icelandic driftwood collections although it
is present in collections from East Greenland. This
suggests that the western part of the East Greenland
Current carries driftwood and drift ice of a partly dif-
ferent origin than the eastern part of the same current.
A further conclusion of the present study is that, if
a pollution accident should occur in the Arctic Basin
the waste will be transported in the same direction
as the driftwood. This is especially relevant to the
possible initiation of oil prospecting in the Barents
sea. Some driftwoodon the coasts of Iceland has been
transported frorn the White Sea region via the Barents
Sea. An accident in the Barents Sea could possibly
affect the Icelandic waters.
JÖKULL, No. 43, 1993 29