Preprints
https://doi.org/10.5194/tc-2020-374
https://doi.org/10.5194/tc-2020-374

  22 Jan 2021

22 Jan 2021

Review status: this preprint is currently under review for the journal TC.

Geographic variation and temporal trends in ice phenology in Norwegian lakes over a century

Jan Henning L’Abée-Lund1, Leif Asbjørn Vøllestad2, John Edward Brittain1,3, Ånund Sigurd Kvambekk1, and Tord Solvang1 Jan Henning L’Abée-Lund et al.
  • 1Norwegian Water Resources and Energy Directorate, Box 5091 Majorstuen, N-0301 Oslo, Norway
  • 2Centre for Ecological and Evolutionary Synthesis, University of Oslo, Box 1066 Blindern, N-0316 Oslo, Norway
  • 3Natural History Museum, University of Oslo, Box 1072 Blindern, N-0316 Oslo, Norway

Abstract. Long-term observations of ice phenology in lakes are ideal for studying climatic variation in time and space. We used a large set of observations from 1890 to 2020 of the timing of freeze-up and break-up, and the length of ice-free season, for 101 Norwegian lakes to elucidate variation in ice phenology across time and space. The dataset of Norwegian lakes is unusual, covering considerable variation in altitude (4–1401 m a.s.l.) and climate (from oceanic to continental) within a substantial latitudinal and longitudinal gradient (58.2–69.9° N; 4.9–30.2° E).

The average date of ice break-up occurred later in spring with increasing altitude, latitude and longitude. The average date of freeze-up and the length of the ice-free period decreased significantly with altitude and longitude. No correlation with distance from the ocean was detected, although the geographical gradients were related to regional climate due to adiabatic processes (altitude), solar radian (latitude) and the degree of continentality (longitude). There was a significant lake area effect as small lakes froze-up earlier due to less volume. There was also a significant trend that lakes were completely frozen over later in the autumn in recent years. After accounting for the effect of long-term trends in the large-scale NAO index, a significant but weak trend over time for earlier ice break-up was detected.

An analysis of different time periods revealed significant and accelerating trends for earlier break-up, later freeze-up and completely frozen lakes after 1991. Moreover, the trend for a longer ice-free period also accelerated during this period, although not significant.

An understanding of the relationship between ice phenology and geographical parameters is a prerequisite for predicting the potential future consequences of climate change on ice phenology. Changes in ice phenology will have consequences for the behaviour and life cycle dynamics of the aquatic biota.

Jan Henning L’Abée-Lund et al.

Status: open (until 19 Mar 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2020-374', Andrew Newton, 22 Feb 2021 reply
    • AC1: 'Reply on RC1', Jan Henning L'Abée-Lund, 23 Feb 2021 reply
  • RC2: 'Comment on tc-2020-374', Anonymous Referee #2, 01 Mar 2021 reply
    • AC2: 'Reply on RC2', Jan Henning L'Abée-Lund, 02 Mar 2021 reply

Jan Henning L’Abée-Lund et al.

Jan Henning L’Abée-Lund et al.

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Short summary
Observations from 1890 to 2020 of ice phenology for 101 Norwegian lakes were used to detect variation in ice phenology. The average date of ice break-up occurred later in spring with increasing altitude, latitude and longitude. The average date of freeze-up and the length of the ice-free period decreased with altitude and longitude. Lakes were completely frozen later recently later in autumn. A significant trend for earlier break-up, later freeze-up and completely frozen lakes after 1991.