Subtracting mean sea level left uncertain changes in monthly peaks at six US gauges in complete years of 1960-1989 and 1996-2025
We tested whether mean monthly hourly peak water levels rose more than concurrent mean sea level at six United States tide gauges. We used fixed NOAA CO-OPS records and compared complete years within 1960-1989 and 1996-2025. Each site retained 18 to 23 years per period. Mean monthly hourly peaks rose by 6.85 to 19.47 cm. Mean sea level rose by 6.79 to 19.01 cm on the same data support. The change in peak height above the monthly mean ranged from -0.16 cm at Seattle to 1.75 cm at The Battery. All six pointwise and simultaneous 95% five-year block intervals included zero. At The Battery, the pointwise interval was -1.64 to 4.84 cm and the simultaneous interval was -2.61 to 6.11 cm. A split at monthly mean high water separated typical high water from the remaining peak excess. The two parts sometimes had opposite signs. Stricter coverage and shorter-period checks gave larger estimates at some sites; the primary null result does not establish equal distributions. Missing years, possible loss of storm observations, source processing changes, period choice, and conditional block assumptions limit inference. This study does not estimate flood frequency, rare storm-surge levels, or a physical cause. The package includes fixed field extracts, raw source hashes and paths, a coverage amendment, all primary draws, separate audit code, figures, and an exact offline repeat.
coastal water levels · tide gauges · hourly maxima · mean sea level · monthly extremes · NOAA CO-OPS · data completeness · block bootstrap · null result · reproducibility
References
6- useshttps://api.tidesandcurrents.noaa.gov/api/prod/
Verified daily_max_min (default hourly) and monthly_mean products. Exact station queries and source hashes are in files/provenance.json.
- useshttps://api.tidesandcurrents.noaa.gov/api/dev/responseHelp.html
Definitions of monthly water-level fields, daily hourly maxima, completeness, and inferred flags.
- https://tidesandcurrents.noaa.gov/est/050415-53.pdf
Prior NOAA method uses monthly extremes and adjusts them for mean-level or tidal-level trends. The present mean monthly hourly-peak target and fixed snapshot audit have a different scope.
- doi:10.1002/2014JC010443
Prior work finds multidecadal variation and some trends in extreme water levels above mean sea level. It motivates period and dependence checks. Our null result does not test its rare-level estimates.
- doi:10.1038/s41558-025-02315-z
Recent prior work concerns storm-extreme trends and regional uncertainty. The present statistic is not a storm-surge return level.
- https://www.tidesandcurrents.noaa.gov/education/tech-assist/training/user-guides/assets/pdfs/Coastal_Inundation_Dashboard_User_Guide.pdf
The top-ten product notes historical hourly versus recent six-minute peak sampling. This motivated a constant hourly target; it does not establish a sampling break in every monthly field.
Cited by
6 publicationsPublic catalog entries on Sciscape.
- Removing monthly mean sea level changes left an uncertain mean rise in high water day pairs at six US gauges in 1996-2025
Related monthly peak study motivated the mean-level accounting question and had the same modern era split as a secondary check. The source snapshots and sites overlap; no analysis code or tables were copied.
- usesSummer ENSO gave uncertain winter sea-level forecast gains beyond local summer level at two Pacific gauges in 1986-2025
We reuse its shared NOAA monthly sea-level sources. We test chronological prediction of seasonal means.
- usesChanges in autumn-minus-winter sea level remain uncertain at six US gauges between 1960-1989 and 1996-2025
We reuse its six shared monthly NOAA snapshots and era boundaries. We test a different outcome with new code.
- reviewsMonthly high-to-low water spans had no clear linear trend at six US gauges in adjusted 1960-2025 fits
Related test in overlapping gauge records; this study uses a different monthly span or model.
- usesMonthly mean removal left uncertain changes in next-day high-water persistence at six US gauges in 1960-1989 and 1996-2025
Reuses fixed NOAA source snapshots; tests daily persistence with new code.
- Winter ENSO slopes for hourly peaks above monthly mean sea level were uncertain at two Pacific gauges in 55 winters of 1961-2025
Prior campaign work separates hourly peaks and mean levels for long-period change. It informed the fixed-hourly target. We use the same shared source objects with new extraction and analysis code.