Jökull - 01.12.1993, Page 28

Figure 7. Location of master tree-ring chronologies
from the White Sea region. Numbers refer to Table 2.
— Staðsetning grunngilda frá svæðinu umhverfis
Hvíta Haf. Númer vísa til töflu 2.
be synchronised internally, giving a mean curve (Ice-
land 3 in Tables 2 and 3) which was dated to 1948
for the last tree ring via Pinus master chronologies
from the White Sea region, this time centred around
Murmansk (Table 2a; Figures 7 and 9).
Thirteen Picea samples from sites B and C could
also be synchronised and seven of them were used for
a mean curve (Iceland 4 in Table 3). This Picea mean
curve could be dated via Picea master chronologies
from the White Sea region, with the end year of 1982
(Table 2b; Figure 7 and 10).
From Greenland, one mean curve made out of two
Pinus samples (Greenland 1 in Table 3) and one made
out of three Picea samples (Greenland 2) (Figure 1 ;D)
could also be dated by chronologies from the White
Sea region (Table 2; Figure 7).
Eggertsson (1994a) dated two Picea samples from
Scoresby Sund via chronologies from the North Amer-
ica. One with chronologies from the Mackenzie delta
in Canada, and one with chronologies from the Yukon
river drainage area in Alaska. American driftwood
has, however, not been detected so far in the re-
cent driftwood collections from Iceland or Svalbard
(Bartholin and Hjort, 1987; Eggertsson 1994b).
THE LARIX DRIFTWOOD
Dendrochronological analysis of the Larix drift-
wood samples is difficult due to problems with missing
tree-rings and irregular tree-ring growth often caused
by outbreaks of the larch bud moth (Schweingruber,
1988). Most of the Larixdriftwoodhas the root system
preserved (78%), indicating that itbegan itsjourney to
Iceland via natural processes, probably eroded from a
river bank.
Seven of the sampled logs gave relatively high in-
ternal correlations and could be used to form a mean
curve (Iceland 5 in Table 3), yet, that curve was not
datable with the available chronologies from Rus-
sia/Siberia. However, in the mountainous permafrost
areas east of the Lena river (Figure 2) erosion by rivers
is large and Larix is the dominating tree genus of the
area (Hustich, 1966). Therefore it is assumed, as sug-
gested by Samset (1991), that most of the Larix drift-
wood found on Iceland originates from these areas and
possibly also from farther east, from the drainages of
Indigirka and Kolyma (Figure 2). Unfortunately, no
tree-ring chronologies are available for comparison.
DISCUSSION
Of the 53 Picea samples collected in Iceland 13
(24%) could be absolutely dated with Picea master
chronologies from the White Sea region (Figure 2)
and out of the 232 Pinus samples collected, 12 (5%)
could be dated with Pinus chronologies from the same
area. Figure 11 shows the distribution of the ages of
the outermost tree-ring for each of the datable logs
from the White Sea area and Table 3 lists the dated
driftwood mean curves from this study. The youngest
of the outermost tree-ring on a Picea log collected
in Strandir (Figure 1;B) in August 1988 was 1982,
indicating that it may take less than six years for a
log to drift from the White Sea region to the coasts of
Iceland.
The drift route of the samples originating in the
White Sea region can be pictured as follows: rivers
26 JÖKULL, No. 43, 1993