A first continuous three-year temperature record from the dimictic arctic–alpine Lake Tarfala, northern Sweden

ABSTRACT

Arctic lakes are exposed to warming during increasingly longer ice-free periods and, if located in glaciated areas, to increased inflow of meltwater and sediments. However, direct monitoring of how such lakes respond to changing environmental conditions is challenging not only because of their remoteness but also because of the scarcity of present and previously observed lake states. At the glacier-proximal Lake Tarfala in the Kebnekaise Mountains, northern Sweden, temperatures throughout the water column at its deepest part (50 m) were acquired between 2016 and 2019. This three-year record shows that Lake Tarfala is dimictic and is overturning during spring and fall, respectively. Timing, duration, and intensity of mixing processes, as well as of summer and winter stratification, vary between years. Glacial meltwater may play an important role regarding not only mixing processes but also cooling of the lake. Attribution of external environmental factors to (changes in) lake mixing processes and thermal states remains challenging owing to for example, timing of ice-on and ice-off but also reflection and absorption of light, both known to play a decisive role for lake mixing processes, are not (yet) monitored in situ at Lake Tarfala.

KEYWORDS:

• Lake
• vertical mixing
• Arctic
• Tarfala
• water temperature

Acknowledgments

We thank T. Bergelv, T. Bergström, P. Hancke, T. Karlin, E. Kirchner, L. Kirchner, and E. Strandell Erstorp for support in the field. We are grateful to the editor and two reviewers (Jeffery Stone and anonymous) whose valuable constructive feedback helped improve the article considerably.

Author contributions

NK, JK, and GR designed the original study and conducted fieldwork in the initial phase of the project. AG and MH continued the fieldwork. NK, AG, KW, JW, FS, and AK designed the continuation of the measuring campaign in Lake Tarfala focusing on the near-surface water layer. NK analyzed all data sets, supported by PE for the TRS-AWS data analysis. NK drafted the article. All authors contributed to the interpretation of the data and results and the writing of the article.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability

The lake water temperature data are available from the Bolin Centre Database at https://doi.org/10.17043/kirchner-2020 and via the SITES data portal at data.fieldsites.se/portal.

Supplementary material

Supplemental material for this article can be accessed on the publisher’s website.

Additional information

Funding

This work was supported by the Swedish Infrastructure for Ecosystem Sciences (SITES Waters), The Göran Gustafsson Foundation for nature and environment in Lappland, The Bolin Centre for Climate Research at Stockholm University, the Centre for Naval Architecture at KTH Royal Institute of Technology, and Arctic Avenue (a spearhead research project between the University of Helsinki and Stockholm University).