The Superior minus Erie ice peak date gap had no clear linear trend in 1973-2026

We tested change in the recorded annual ice peak date gap between Lake Superior and Lake Erie. We used a fixed NOAA GLERL table with 54 winters in 1973-2026. The mean gap was 16.36 days. Its conditional 95% five-year block interval was 11.64 to 21.46 days. The linear gap trend was 0.07 days per decade, with an interval of -3.17 to 3.27. Later-period estimates and seven-day date bins also gave intervals that include zero. A daily-chart-era check had only 16 winters and wide uncertainty. The general order of lake peaks is known; this study gives an updated pairwise trend test and aggregate evidence. It does not establish constant timing or a physical cause. Chart frequency changes, unknown peak tie rules, one lake pair and block-model assumptions limit inference. Raw data and annual extracts remain external. The package contains code, source hashes, aggregate results, parameter draws, an independent audit and a figure.

Great Lakes · ice peak timing · Lake Superior · Lake Erie · null result · block bootstrap