Jökull - 01.12.1984, Blaðsíða 66

Fig. 9. Annual average acidities exceeding
approx. 3.5 pequiv. H+/kg of ice in the Camp
Century acid record. This figure is a revised
version of Fig. 3 in Hammer et al. (1980). Note,
that the revised figure is not comprehensive (see
text for explanation). The values for the 4400
B.C. and 6230 B.C. eruptions represent average
values over more than 1 year.
Mynd 9. Árlegt meðaltal sýrumagns sem nær yfir
3.5 míkró jafngildi H+lkg íss í ískjarnanum frá
Camp Century.
Chemical analysis of the high acidity segments of
the cores should be standard procedure and
correlation between cores must be undertaken.
What about tephra, or to be more specific,
what about fine grained tephra? Can the erup-
tions be “fingerprinted” by searching for fine
ash-tephra in the ice? If this becomes possible,
ice core information would be more naturally
linked to the many case studies offered by the
science of volcanology. In Antarctic ice cores
visible tephra layers have been traced back to
specific Antarctic volcanoes, but “fingerprint”
studies based on the chemical composition of the
acids are much more problematic.
The ice core segments of high acidity do indi-
cate, where in the core it may be profitable to
search for fine grained tephra or/and determine
the chemical composition of the acid. A first step
could be to analyze an ice segment identified by
the acid fallout from a well known eruption e.g.
Tambora 1815. However, the lack of large ash
particles in the ice segment will imply a rather
time consuming analysis and the findings may be
difficult to interpret.
It will probably take some time before the
analysis of chemical composition both of the
acids and individual solid particles can compete
with the fast and easy acidity method, but in the
meantime it is worthwhile to explore the
potentiality of the acidity method.
SOME FINAL REMARKS
This article has naturally been concentrated on
Icelandic eruptions. Only a few eruptions have
been mentioned, but among them are some of
the most impressive eruptions during the Holo-
cene. The Lakagígar eruption played an essential
role in relating acidity records from ice cores to
volcanic records, but the works of Sigurður Thor-
arinsson and the inspiration I received from him
were of equal importance. Therefore, I dedicate
this paper to the Memory of Sigurdur Thorarins-
son.
Note added in proof:
Recent evidence proves the high acidity layer
in 1360 to be caused by strong percolation, i.e. it
is not a volcanic signal.
REFERENCES
Clausen, H.B. (personal communication, 1982).
Dansgaard, W. 1964: Stable isotopes in precipita-
tion. Tellus 16: 436-468.
Fisher, D.A. (personal communication, 1982).
Froggatt, P.C. 1981: Did Taupo’s eruption
enhance European sunsets? Nature 293: 491.
Gow, A.J. and T. Williamson 1971: Volcanic ash
in the Antarctic Ice Sheet and its possible
climatic implications. Earth Planet. Sci. Lett.
13: 210-218.
Hammer C.U. 1977: Past volcanism revealed by
Greenland Ice Sheet impurities. Nature, 270:
482-486.
64 JÖKULL 34. ÁR