Jökull - 01.12.1993, Blaðsíða 18

Figure 1. Surface currents
in Icelandic waters and sam-
pling sites for driftwood.
A: Reykjanes, B: Strandir,
C: Langanes, D: Scoresby
Sund. Current pattern from
Stefánsson (1961 and 1962).
— Yfirborðsstraumar í haf-
inu við Island og sýnatöku-
staðir rekaviðs.
ocean to the coasts of Iceland and Greenland. The
driftwood originates in the boreal forest regions sur-
rounding the Arctic. Rivers which drain the forested
areas carry driftwood into the Arctic Ocean. Most of
the wood, caught in drifting ice and transported by the
oceanic currents, probably sinks but some is eventu-
ally deposited along the shores of the Arctic. The aim
of this paper is to describe how the dendrochronologi-
cal method (tree-ring dating) can be applied to identify
the origin and age of driftwood, and to suggest how
this method can give information on the pattern and
velocity of the sea ice drift. Most of the driftwood
samples were collected from the shores of Iceland,
and a small number from the Scoresby Sund area on
the east coast of Greenland (Figure 1).
ARCTICICE COVER CIRCULATION
The main factors governing ice cover circulation in
the Arctic Basin are a gyre in the Beaufort Sea and the
Transpolar Current. The Transpolar Current carries
ice from the Arctic Ocean across the North Pole and
down along the east coast of Greenland (Figure 2).
The estimated transportation time for the sea ice to
drift from the Laptev Sea, outside the north coast of
Siberia, to the Fram strait is estimated as two to three
years (Vinje, 1982).
Because of the circulating character of the Beau-
fort Sea gyre it is possible for the ice to stay in the gyre
and circulate for many years (Koerner, 1973), as can
the driftwood. Some of the thickest multi-year ice is
found in this region (Hibler, 1989). Ice stations in the
Arctic have been found to drift at an average rate of
about 6 km/day, althoughthe driftrate varies from day
to day and from year to year. One-day drifts of over 20
km have been observed (Thorndike and Colony, 1980).
The ice station data are not sufficient to give detailed
information of the temporal and spatial variation of
ice drift. More recent measurements, available since
1966 and using satellite navigation equipment (Vinje,
1982) and laser surveying equipment, have supplied a
more complete description of the temporal and spatial
variation in ice drift (Thorndike and Colony, 1980).
Two main factors influence the ice drift, the wind
and the currents. The steady currents play the most
significant role when studying long term ice drift (Hi-
bler, 1989).
16 JÖKULL,No. 43, 1993