Overview of The dangers of warming winter lakes
This NPR Shortwave episode (host Emily Kwong; reporter Burley McCoy) examines how warming winters are changing lake ice—threatening recreational traditions, increasing safety risks on the ice, and jeopardizing lifelines for some communities. Reporting from Madison, Wisconsin (Frozen Assets festival, lake rescue training) is interwoven with expert commentary and data about shifting ice patterns, drowning risk, and long-term projections.
Key points / main takeaways
- Black ice (clear, formed from lake water freezing downward) is strongest and generally safe to walk on at about 4 inches thickness; white ice (snow/slush refreeze) is weaker and less predictable.
- Climate variability—“winter weirding” of big cold snaps interspersed with warm spells—is making ice formation less stable, causing more freeze–thaw cycles and dangerously variable ice.
- Between 1991 and 2017 there were >4,000 fatal drownings through ice across 10 countries; about 50% of those drownings are correlated with winter air temperature (Sapna Sharma, York University).
- Projections: depending on greenhouse gas emissions, lake ice cover could shrink by 10–28 days by century’s end; around 5,700 lakes may become permanently ice-free this century under some scenarios.
- Thinner/false ice harms culture and recreation (ice fishing, festivals, winter roads) and increases demand for rescues. Training and rescue teams are adapting, but outcomes are not always positive—cold-water immersion can kill within minutes.
Reporting highlights
- Frozen Assets (Madison, Lake Mendota): annual winter festival featuring skating, hockey, curling, kites, and large gatherings on ice. Some recent years have forced the festival to move to shore because ice formed too late or was unsafe.
- Lake rescue training (Madison Fire Department Lake Rescue Team): training performed near a river inflow (always-open water area) using immersion “Gumby” suits and a rescue sled anchored to shore. Demonstrated how ice cracks, ice shelves (solid ice with water and refrozen ice on top), and shifting ice create rescue challenges.
- A real rescue example: a person fell through an ice shelf that looked passable; drone footage showed rescuers breaking up underfoot ice; the victim survived after about 25 minutes in the water—an outcome that could easily have been fatal.
Science & data summarized
- Ice types: black (clear, strong) vs. white (opaque, airy, weaker). Mixed ice layers and white ice complicate safety judgments.
- Drownings and temperature link: warmer, variable winter temps increase weak ice events and drownings; about half of recorded ice drownings tied to air-temperature patterns.
- Climate projections: shorter ice seasons, later freeze and earlier melt, and many lakes possibly becoming permanently ice-free—affecting ecosystems, recreation, and communities dependent on winter ice (including remote Indigenous communities that use winter ice roads).
Risks and cultural/environmental impacts
- Immediate safety: more unstable ice increases the chance of people falling through, cold shock, incapacitation, and drowning. False-shelving and layered ice are especially hazardous at night.
- Community & cultural loss: festivals, everyday winter practices (skating, ice fishing), and social cohesion around frozen lakes are at risk.
- Practical impacts: winter ice roads used by remote communities for supplies and social access may be compromised, with serious logistical consequences.
Notable quotes and figures
- “Black ice … is strongest. It’s safe for a person to walk on when there is four inches of black ice.” — Hilary Dugan (lake scientist)
- “We’ve documented over 4,000 fatal drownings through ice” (1991–2017, 10 countries) and “50% of those drownings are related to air temperature.” — Sapna Sharma (global change biologist)
- Projection: “You might expect 10 to 28 days less ice cover by the end of the century… about 5,700 lakes may permanently become ice-free within this century.”
Practical recommendations / action items
- Never assume ice is safe—know the type (black vs. white), local conditions, and recent weather (freeze–thaw cycles increase risk).
- Minimum guideline: about 4 inches of solid black ice for a person—but local conditions vary; white ice requires much more caution.
- Avoid areas with flowing water, inlets/outlets, cracks, or visible slush; these are common weak spots.
- If you go onto ice: carry ice picks, wear a flotation device, go with others, and have a rope or rescue plan on shore.
- Support local rescue teams and public education on ice safety; heed local advisories and festival decisions to move off-ice when conditions are poor.
- For larger-scale action: engage with climate mitigation and adaptation measures—protecting winter ice is linked to reducing greenhouse gas emissions and local resilience planning.
Where to find more
- The episode offers photos and follow-up reporting (show notes) and promises another Shortwave episode on changing lake ice next week. Credits: reporter Burley McCoy; host Emily Kwong; local experts James Tai (Clean Lakes Alliance), Justin Tooze (Madison firefighter), Hilary Dugan (lake scientist), Sapna Sharma (global change biologist).