Fróðskaparrit - 01.01.1998, Blaðsíða 154

160
HOLOCENE CLIMATIC VARIABILITY IN THE NORTH ATLANTIC REGION
AS SHOWN BY PEAT BOG RECORDS
Climatic inferences
The evidence for environmental changes in
the Holocene as reconstructed from mire
records suggests periods when climatic
conditions became wetter, and/or cooler.
Occasionally, times of drier climate have
been inferred, although this is thought dif-
ficult due to the habit of mires to grow
above the water table even in constant con-
ditions. The climates of the peat areas of
north-west Europe are greatly influenced
by air flowing from the Atlantic, and by the
tracking of low-pressure systems, with as-
sociated rain-bringing fronts across the
continent’s western seaboard. By exploit-
ing the north-south ‘transect’ of peat de-
posits, it should be possible to infer where,
and when, the influence of moist maritime
air has been greater, and less, over the late
Holocene period. This has been attempteđ
to a limited extent by Magny (1982), who
suggested that the broad sub-divisions of
the Holocene could be explained by the
changing influence of Atlantic-derived air
masses. Thus wetter conditions in the north
of the region may be associated with drier
climates in the south, as depression tracks
move north, or indeed the pattern may be
more complex.
Peat, climate and the Faroe Islands
The climatic parameters suitable for peat
growth are present throughout much of the
Faroe Islands, namely an annual moisture
surplus and consistent precipitation, cou-
pled with low rates of evaporation. The peat
cover has been extensively exploited for
fuel however, with most valley and plateau
mires having a long history of peat eutting.
Despite this, Persson (1968) described up-
wards of 2m of peat at several sites, includ-
ing Klovinmyren (Vágar) where 2.8m of
peat, dated at 6,505 (100 BP) at the base,
was described. The peat sites thought most
suited to palaeoclimatic reconstructions are
watershedding, ombrotrophic areas. Much
of the plateaux areas above 250m are high-
ly eroded, although thin peat covers and
isolated pockets of deeper peat can be
found. There are three distinct advantages
of the Faroe Islands for studies of peat-
based palaeoclimatology. First, the loca-
tion, in the centre of the North Atlantic,
close to the atmospheric and oceanic polar
fronts, provides great potential in under-
standing the possible mechanisms of
Holocene climatic change. Second, Pers-
son (1968) demonstrated the existence of
several tephra layers which can be used for
precise dating and correlation (Blackford,
1997). The principle advantage, however, is
the apparent absence of humans and large
land animals until early medieval times.
For the majority of the Holocene period,
then, the disturbing influence of people can
be discounted.
Conclusions - a testable
working hypothesis
There remain a series of problems with
peat-based palaeoclimatic reconstruction
that need to be solved. However, even with-
in the constraints of these limitations, it has
been shown that certain key dates do keep
recurring in different studies and from dif-
ferent areas. There is also evidence of peri-
odicity in peat bog data, but as yet this has
not been shown to be consistent. Further-