the Expedition ARKTIS-XIX/4 of the research vessel POLARSTERN ...

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The low amounts of solubles in the water column are documented in the low values
of the conductivity, ranging in all investigated lakes below 50 µS/cm (Tab. 6.1-1).
These extremely low amounts can be traced back to the inflow of solubles depleted
melt water in during spring and summer. However, it also indicates that the influence
of spray, also in lakes located at low altitudes, as for example in Loon Lake on
Geographical Society Ø, is restricted.
The low amounts of solubles and, particularly, the lack of fine suspended clastic and
organic matter in the water column leads to a relatively high visibility, ranging in the
studied lakes on Store Koldewey and Geographical Society Ø between 3.0 and 8.1 m
(Tab. 6.1-1). Thus it confirms the oligotrophic to ultra-oligotrophic state of the lakes.
6.2 Palaeolimnological work
Bernd Wagner
The study of lake sediments is a common tool to reconstruct the regional
environmental and climatic history. In East and Northeast Greenland, lake sediments
were used for palaeolimnological work for the last two and a half decades (e.g.,
Funder 1978, Björck & Persson 1981, Björck et al. 1994a, Bennike & Funder 1997).
At the beginning of these studies, pollen were most important for the reconstruction
of the palaeoenvironments. However, a delay due to the long immigration paths of
plants to East and Northeast Greenland and dating problems caused several
uncertainties in reconstructing the onset and the duration of environmental changes
(Björck et al. 1994b). During the past decade, the dating techniques, particularly in
radiocarbon dating, became more precise, and studies on lake sediments became
more and more multi-proxy studies, including sedimentological, geochemical, and
biological methods (e.g., Cremer et al. 2001a, Wagner & Melles 2001). Thus, a better
knowledge about regional environmental history meanwhile exists. Nevertheless,
compared to other, more accessible regions, the data basis for the high arctic regions
is still poor, and much work needs to be done to better understand the period of
deglaciation and the postglacial climatic and environmental changes.
For this purpose c. 55 m of sediment cores were recovered from 7 lakes on Store
Koldewey, and c. 20 m from a lake on the outer Geographical Society Ø,
respectively. A complete list of the sediment cores is given in Tab. 6.2-1. The
sediment cores will be investigated with chronological (radiocarbon dating),
sedimentological (grain-size analyses, XRD), biological (diatoms, pollen,
macrofossils, chironomids, bacterial activity and bacteria assemblages), and
biogeochemical (carbon, nitrogen, sulphur, biogenic opal, methane) methods.
The sediment cores were recovered using three different coring systems from a small
and a bigger floating platform. A gravity corer (UWITEC Corp., Austria) was used to
obtain undisturbed surface sediments of up to c. 85 cm length. The corer is equipped
with a PVC liner of 60 or 120 cm in length and 6 cm in diameter. The penetration
depth can be controlled by the falling distance during the coring process and the
number of weights used. A successful coring process is indicated by horizontally
laying surface sediments in the liner and by undisturbed water super standing on top
of them.