The 2010-2022 sea-level surge at 10 US Gulf coast tide gauges did not continue in 2023-2026; surge, acceleration and rate-return forecasts were too high

From 2010 to 2022, relative sea level at US Gulf and Southeast coast tide gauges rose by more than 10 mm per year. We tested five forecasts that were possible at the end of 2022 against NOAA CO-OPS monthly means for January 2023 to September 2026 (45 months) at 36 long-record US gauges. For the mean of 10 Gulf gauges (1980-2009 rate 4.0 mm/yr; 2010-2022 rate 11.9 mm/yr), the 2023-2026 level was 66 mm below a continued 2010-2022 line (p < 0.001), 50 mm below a 1980-2022 quadratic (p = 0.006-0.014) and 52 mm below a forecast that keeps the end-2022 level with the old rate (p = 0.002). Each p-value comes from 2,000 synthetic records made from that model plus block-bootstrapped residual noise. Holding the 2021-2022 mean level gave the smallest error at all 10 Gulf gauges. All 10 gauges were 32-115 mm below the continued-surge forecast. The excess over the 1980-2009 line fell from 85 mm (2019-2022) to 47 mm (2023-2026), mostly in 2025. These Gulf rejections held for issue dates from 2021 to 2024 and fit starts from 1970 to 1990. On the Southeast Atlantic coast (6 gauges), the level also stayed near the 2021-2022 level, but no forecast was clearly rejected (continued surge p = 0.10). Mid-Atlantic and Northeast gauges were above all forecasts. Offshore 0-700 m thermosteric height (NCEI) with a fixed one-to-one coefficient explained about 20-40% of the 2010-2022 excess. It did not explain the stop, because Gulf of Mexico thermosteric height continued to increase in 2023-2026. Limitations: only 45 test months with correlated gauges, no land-motion, pressure or wind corrections, and the result cannot separate a pause from a new long-term rate.

sea level · tide gauges · Gulf of Mexico · sea-level acceleration · out-of-sample forecast · thermosteric sea level · internal variability · NOAA CO-OPS · US Southeast coast