Jökull - 01.01.2001, Side 68

Þorvaldur Þórðarson and Stephen Self
Figure 2. Occurrence and first appearance of the Laki haze elsewhere in the northern Hemisphere (outside Eu-
rope). Filled symbols indicate observation locations and dates mark the first occurrence of the Laki haze at
those sites. Open symbols mark sites (Alaska and Norway) where the occurrence of the Laki haze is inferred
from tree-ring growth data. Information on the occurrence of the Laki haze in North America and Alaska is
obtained from Demarée et al. (1998) and Jacoby et al. (1999). – Dagsetningar þegar Skaftáreldamóðan sást
fyrst yfir tilteknum stöðum á Norðurhveli, utan Evrópu.
and southern Europe it was first noticed between 16
and 19 June (Figure 1) and the early haze was de-
scribed as being “spread in a vast space, relatively
thin, and transparent.” Between 22–24 June the in-
tensity of the haze increased greatly over western and
central Europe, as shown by meteorological reports
from weather stations operated under the auspices of
the Mannheim Meteorological Society. At the same
time as the haze was first noticed in England, it was
also recorded in the higher regions of the French and
Swiss Alps, the Nordic countries, and eastern Europe.
By 26 June almost all of Europe was covered by thick
dry fog (Figure 1). The haze spread much further and
the available data indicates that the sulfuric aerosol
plumes from Laki covered the northern Hemisphere
from the latitude of 35


N all the way to the North
Pole (Figure 2).
In the first week (i.e. 8–15 June) the Laki erup-
tion featured three vigorous explosive phases produc-
ing eruption columns that carried ash and gases to
altitudes of 10–12 km, including 40 megatons of
SO  (Thordarson and Self, 1993; Thordarson et al.,
1996). Consequently, the bulk of this material was in-
jected into the polar jet stream, which dominates the
atmospheric circulation over Iceland at the tropopause
level (between 8–11 km altitude; Jónsson, 1990), and
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