Preprints
https://doi.org/10.5194/tc-2022-232
https://doi.org/10.5194/tc-2022-232
 
05 Dec 2022
05 Dec 2022
Status: this preprint is currently under review for the journal TC.

A field study on ice melting and breakup in a boreal lake, Pääjärvi, in Finland

Yaodan Zhang1,2, Marta Fregona3, John Loehr2, Joonatan Ala-Könni4, Shuang Song5,6, Matti Leppäranta2, and Zhijun Li1 Yaodan Zhang et al.
  • 1State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian, China
  • 2Lammi Biological Station, University of Helsinki, Finland
  • 3Department of Civil, Environmental and Mechanical Engineering, University of Trento, Italy
  • 4Institute of Atmospheric and Earth Sciences, University of Helsinki, Helsinki, Finland
  • 5Water Conservancy and Civil Engineering College, Inner-Mongolia Agricultural University, Hohhot, China
  • 6College of Water Conservancy, Shenyang Agricultural University, Shenyang, China

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 relatively little is known about its details. In the present work, ice monitoring was based on foot, hydrocopter, and boat to get a full time-series of the evolution of ice structure and geochemical properties through the melting period. The field observations were made in Lake Pääjärvi during the ice decay periods in 2018 and 2022. In 2022, the maximum thickness of ice was 55 cm with 60 % snow-ice, and based on the data and heat budget analysis, the ice melted by 33 cm from the surface and 22 cm from the bottom while porosity increased to 40–50 % at breakup. In 2018, the snow-ice layer was small and bottom and internal melting dominated during the decay. Due to global warming, the ice breakup date became earlier. 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) in ice was 11.4±5.79 S cm–1, one order of magnitude lower than in the lake water, and ice pH was 6.44±0.28, lower by 0.4 than in water. pH and EC of ice and lake water decreased along the ice decay except slight increases in ice due to flushing by lake water. Chlorophyll a was less than 0.5 g L–1 in porous ice, approximately one-third of that in the lake water. These results are important for further development of numerical models and understanding the process of ice decay with consequences to lake ecology and to safety of ice cover for human activities.

Yaodan Zhang et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2022-232', Anonymous Referee #1, 09 Jan 2023
  • RC2: 'Comment on tc-2022-232', Anonymous Referee #2, 09 Jan 2023

Yaodan Zhang et al.

Yaodan Zhang et al.

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Short summary
There are few detailed studies during ice decay period primarily because in situ observations during decay stages face enormous challenges due to safety issues. In the present work, ice monitoring was based on foot, hydrocopter and boat to get a full time-series of the evolution of ice structure and geochemical properties. We argue that the rapid changes in physical and geochemical properties of ice have an important influence on regional climate and the ecological environment under ice.