Widespread loss of safe lake ice access in response to a warming climate

RESEARCH ARTICLE Widespread loss of safe lake ice access in response to a warming climate Joshua CulpepperID1*, Lei Huang2,3, R. Iestyn Woolway4, Sapna Sharma5 1 Department of Biology, York University, Toronto, ON, Canada, 2 College of Resource Environment and Tourism, Capital Normal University, Beijing, China, 3 Institute for Basic Science, Center for Climate Physics, Busan, South Korea, 4 School of Ocean Sciences, Bangor University, Bangor, United Kingdom, 5 Department of Biology, York University, Toronto, ON, Canada * joshua.abel.culpepper@gmail.com Abstract Millions of people rely on lake ice for safe winter recreation. Warming air temperatures impact the phenology (timing of formation and breakup) and quality (ratio of black to white ice) of lake ice cover, both critical components of ice safety. Later formation and earlier breakup of lake ice lead to overall shorter periods of use. However, greater proportions of white ice may further inhibit safe ice use owing to its lower weight-bearing capacity. As ice cover duration decreases and ice quality changes in a warming world, the period of safe ice use will similarly diminish. We use a large ensemble modeling approach to predict ice safety throughout the winter period in the Northern Hemisphere. We used the Community Earth System Model Version 2 Large Ensemble (CESM2-LE) to calculate the period when ice first appears until it is of sufficient thickness for safe use, which depends on the ratio of black to white ice. We conducted this analysis for 2,379 to 2,829 ~1˚ by 1˚ grid cells throughout the

Northern Hemisphere. We focus on the period between ice formation (� 2 cm) to a safe thickness for general human use (i.e., �10, �15, or �20 cm, depending on the ratio of black to white ice). We find that the transition period from unsafe to safe ice cover is growing lon- ger, while the total duration of safe ice cover is getting shorter. The transition period of unsafe ice increases by 5.0 ± 3.7 days in a 4˚C warmer world, assuming 100% black ice. Diminished ice quality further limits safe ice conditions. The unsafe transition period increases by an average of 19.8 ± 8.9 days and 8.8 ± 6.6 days for the ice formation and breakup periods, respectively in a 4˚C warmer world assuming 100% white ice conditions. We show that although many lakes are forecasted to freeze, they will be unsafe to use for an average of 5 to 29 fewer days in a 4˚C warmer world for 100% black and 100% white ice ratios, respectively. This wide range indicates that ice quality has a strong influence on ice safety. This work highlights the need to understand both lake ice phenology and quality to better assess safe lake ice use during the formation and melt periods. 1. Introduction Anthropogenic climate change is causing rapid loss of lake ice in the Northern Hemisphere, driven largely by rising air temperatures [1]. Studies have illustrated that the timing of ice-on PLOS ONE PLOS ONE | https://doi.org/10.1371/journal.pone.0313994 December 11, 2024 1 / 19 a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: Culpepper J, Huang L, Woolway RI,

Sharma S (2024) Widespread loss of safe lake ice access in response to a warming climate. PLoS ONE 19(12): e0313994. https://doi.org/10.1371/ journal.pone.0313994 Editor: Sher Muhammad, ICIMOD: International Centre for Integrated Mountain Development, NEPAL Received: May 10, 2024 Accepted: October 27, 2024 Published: December 11, 2024 Peer Review History: PLOS recognizes the benefits of transparency in the peer review process; therefore, we enable the publication of all of the content of peer review and author responses alongside final, published articles. The editorial history of this article is available here: https://doi.org/10.1371/journal.pone.0313994 Copyright: © 2024 Culpepper et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: Data from the CESM2 Large Ensemble Community Project are publicly available at: https://www.cesm.ucar.edu/ projects/community-projects/LENS2/ data-sets.