Jökull - 01.12.1990, Síða 112

DEPTH SAMPLE CORE3
Figure 6. Cores no. 3-9, showing the core coverage of the integrated samples and the locations of ice lenses in
the cores. The ice lenses are shown by the hatched lines but the length of each core step is shown by the solid
lines. The 1986-1987 precipitation layer is shaded. The numbers at the end of each core represent the integrated
length of the core and the log of the depth of the hole in cm. — Línurit fyrir kjarna 3-9. Orvarnar sýna hvar
heildarsýnin (Tafla 1) eru tekin úr kjörnunum. Þverlínur eru dregnar í kjarnana við hvern borunaráfanga.
Brotalínurnar sýna hvar íslinsur eru í snjónum. Snjórinn frá 1986-1987 er skyggður.
cause the original ratio is preserved. Mg2+ is released
preferential to Cl~, but K+ sits behind in the snow
compared to Cl_ and the same is probably true for
Ca2+ and SCC2-. None of the samples from Vatna-
jökull has calcium and sulfate concentration (Fig. 8)
as high as the average ”excess calcium and sulfate“
in Icelandic precipitation (Figs. le and lf). Thus ”the
excess“ calcium and sulfate in the original precipita-
tion on Vatnajökull (Fig. 8) must be less than the
average one for Iceland as shown in Figs. le and
f, where it equals to 0.389 and 1.22 ppm for calcium
and sulfate, respectively. This indicates that the aver-
age ”excess“ concentration in Icelandic precipitation
(Figs. le and lf), partly attributedto pollution, is not
constant but variable and some of it might be caused
by local pollution.
The relative mobility of the ions during the partial
melting of snow can be studied further by looking at
the downcore changes in the ion to chloride ratios for
core 2 (Fig. 9). The core is partially melted down to
about 190 cm depth and the lower part represented by
the 1986-1987 precipitation layer underwent partial
108 JÖKULL, No. 40, 1990