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| Titel |
Changes of hydrology and carbon cycling in a mid-latitude lake from Late Glacial to Anthropocene: model-data comparison for Lake Gosciaz, Central Poland |
| VerfasserIn |
M. Klisch, K. Rozanski, P. Wachniew |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250020580
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| Zusammenfassung |
| Lake sediments are considered among the most valuable archives of climatic and
environmental changes on continents. Studies aimed at reconstruction of continental
climates based on lake sediments are usually of interdisciplinary character, comprising
physicochemical, biological and isotopic tools. To utilize fully the potential of lacustrine
sediments as environmental archives, a deeper understanding of hydrology and carbon
cycling in lakes under contrasting climatic conditions is required.
Lake Gosciaz is situated in central Poland (5235’N, 1921’E, 64.3 m a.s.l.) in the
Vistula river valley. It is the largest in a group of four lakes which were formed during
the final stages of the last glaciation, on the outskirts of retreating Fennoscandian
ice sheet. Laminated sediments of Lake Gosciaz have been a subject of extensive
interdisciplinary investigations aimed at reconstructing environmental and climatic changes
in central Europe during late Glacial and Holocene. Also process studies aimed at
better understanding of carbon cycling in the present-day lake have been carried
out.
The presented study was focussed on long-term changes of δ18O of lake water and δ13C
of authigenic calcite preserved in sediments of Lake Gosciaz. The available isotope records
span entire history of the lake, from Younger Dryas till recent times. Changes of δ18O of
aquatic cellulose have been used to derive information on past evolution of 18O isotope
composition of lake water, while δ13C of authigenic calcite gave insights into variations in
carbon cycling in the system. Quantitative mass-balance models describing both hydrology
and carbon cycling in the lake were constructed and used to evaluate past changes in the
system.
The water balance of Lake Gosciaz varied dramatically in the past. It evolved from fast,
through-flow lake during Younger Dryas, characterized by the total inflow to evaporation
ratio (I/E) in the order of 30-35, through evaporation-dominated system during early
Holocene (I/E ≈ 3-4), back to relatively fast, groundwater controlled lake at present (I/E =
10). In addition, in order to fit the reconstructed changes of δ18O of lake water, some changes
of the relative humidity need to be postulated (reduction in the order of 5 to 10%
across the YD/PB boundary, and subsequent increase to the present-day value of ca.
85%).
The modeling of carbon cycling in the lake revealed that δ13C of authigenic calcite is
controlled mainly through flux of dissolved inorganic carbon entering the lake with inflowing
waters. The remaining two processes which influence carbon isotope composition of total
dissolved inorganic carbon pool and δ13C of authigenic calcite are related to photosynthesis
and respiration of organic matter, both produced in the lake and transported from the
catchment. Satisfactory agreement between measured and simulated δ13C values of
authigenic calcite could be reached by appropriate adjustment of these three factors. The
strong link between lakes’ hydrology and carbon isotope signature of authigenic
calcite observed in the studied system was not recognized earlier in the literature. |
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