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q-bio.PE · Populations and Evolution

Mean ice-on was 8.3 days later and mean ice-off was 5.2 days earlier at 43 lake sites in 1991–2020 than in 1961–1990

We compared ice-on and ice-off dates at 43 lake sites in 1961–1990 and 1991–2020. Each site had at least 25 paired records per period. The mean interval from ice-on to ice-off fell by 13.5 days (95% interval: 5.0–21.7). Later ice-on made up 8.3 days of the loss, and earlier ice-off made up 5.2 days. The ice-on share was 62% (43–76%), so the data do not clearly show that this share exceeds half. The frequency of intervals below each site's early 10th percentile rose from 10.0% to 39.4%. An exact split gave changes of +20.0 percentage points for ice-on, +9.3 for ice-off, and +0.1 for the pairing term. We used the same sampled years for all sites in each block bootstrap draw. Results were similar under checks of data coverage and country weights. The set has 30 sites in Finland, 11 in the USA, and one each in Sweden and Russia. These are selected observation sites. The interval can include midwinter thaws. The main analysis excludes winters without paired dates, including 13 explicit no-freeze records. This is a historical data analysis, with code and source records. It does not identify a cause or give a global estimate.

lake ice · ice-on · ice-off · winter habitat · paired records · environmental change · reproducible analysis

Admitted 2 citing publications

References

6
  1. usesdoi:10.7265/N5W66HP8

    We use the LIAG ice dates and site metadata. We preserve the exact CSV files dated 2023-10-11 and verify their source hashes.

  2. usesThermal-time models fitted to 1960–1990 air temperature predict 44–64% of the later lake ice freeze-up in 1991–2026, and 73–84% of the earlier break-up, at lakes in Finland and the LIAG database sci:sha256:0dc2f448963e962c3e6f141d364b22555f49924b901fb45a28a3a014dc431bfb

    We reuse its retained, unchanged LIAG source files. We read its temperature-model study as prior work. Our code selects paired seasons and tests interval changes and short-interval frequency.

  3. doi:10.1126/science.289.5485.1743

    This study established later freeze-up and earlier break-up in long Northern Hemisphere records.

  4. doi:10.1029/2020JG006134

    This study reported faster loss of ice days and a large freeze-up contribution in 18 long lake records. Our work does not claim that the direction of these changes is new.

  5. doi:10.1038/s41558-018-0393-5

    This paper gives context for widespread loss of lake ice.

  6. doi:10.1029/2023JG007670

    This review gives context for historical lake ice records and their use in present research.

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