A field study on ice melting and breakup in a boreal lake, Pääjärvi, in Finland
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Published:2023-05-12
Issue:5
Volume:17
Page:2045-2058
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ISSN:1994-0424
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Container-title:The Cryosphere
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language:en
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Short-container-title:The Cryosphere
Author:
Zhang Yaodan,Fregona Marta,Loehr John,Ala-Könni Joonatan,Song Shuang,Leppäranta Matti,Li Zhijun
Abstract
Abstract. Lake ice melting and breakup form a fast, nonlinear process with
important mechanical, chemical, and biological consequences. The process is
difficult to study in the field due to safety issues, and therefore only
little is known about its details. In the present work, the field data were
collected on foot, by hydrocopter, and by boat for a full time series of the
evolution of ice thickness, structure, and geochemistry through the melting
period. The observations were made in lake Pääjärvi in 2018
(pilot study) and 2022. In 2022, the maximum thickness of ice was 55 cm with
60 % snow ice, and in 40 d the ice melted by 33 cm from the surface
and 22 cm from the bottom while the porosity increased from less than 5 %
to 40 %–50 % at breakup. In 2018, the snow-ice layer was thin, and bottom
and internal melting dominated the ice decay. The mean melting rates were
1.31 cm d−1 in 2022 and 1.55 cm d−1 in 2018. In 2022 the
electrical conductivity (EC) of ice was 11.4 ± 5.79 µS cm−1, which is
1 order of magnitude lower than in the lake water, and ice pH was 6.44 ± 0.28, which is lower by 0.4 than in water. The pH and EC of ice and water
decreased during the ice decay except for slight increases in ice due to
flushing by lake water. Chlorophyll a was less than 0.5 µg L−1 in
porous ice, approximately one-third of that in the lake water. The results
are important for understanding the process of ice decay with consequences
for lake ecology, further development of numerical lake ice models, and
modeling the safety of ice cover and ice loads.
Funder
National Key Research and Development Program of China National Natural Science Foundation of China Academy of Finland
Publisher
Copernicus GmbH
Subject
Earth-Surface Processes,Water Science and Technology
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