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Sea‐level rise is leading to increasingly frequent coastal floods globally. Recent research shows that changes in tidal properties and storm surge magnitudes can further exacerbate sea‐level rise‐related increases in flood frequencies. However, such non‐stationarity in tide and storm surge statistics are largely neglected in existing coastal flood projection methodologies. Here we develop a framework to explore the effect that different realizations of various sources of uncertainty have on projections of coastal flood frequencies, including changes in tidal range and storminess. Our projection methodology captures how observed flood rates depend on how storm surges coincide with tidal extremes. We show that higher flood rates and earlier emergence of chronic flooding are associated with larger sea‐level rise rates, lower flood thresholds, and increases in tidal range and skew surge magnitudes. Smaller sea‐level rise rates, higher flood thresholds and decreases in sea level variability lead to commensurately lower flood rates. Percentagewise, changes in tidal amplitudes generally have a much larger impact on flood frequencies than equivalent percentagewise changes in storm surge magnitudes. We explore several implications of these findings. Firstly, understanding future local changes in storm surges and tides is required to fully quantify future flood hazards. Secondly, existing hazard assessments may underestimate future flood rates as changes in tides are not considered. Finally, identifying the flood frequencies and severities relevant to local coastal managers is imperative to develop useable and policy‐relevant projections for decisionmakers. Plain Language Summary: It is not just increases in mean sea level that cause coastal floods to become more frequent. Tidal range is the typical difference between the daily high and daily low tides that arise due to the gravity of the moon and sun acting on the Earth and how the resultant water level changes interact with coastlines. Many studies have shown that past changes in tidal range have led to observed changes in flood frequency that could not be explained by sea‐level rise. Despite tidal ranges being expected to change in future, the implications of this for future flood frequencies has never been systematically assessed. We develop a new projection methodology that can consider such changes in flood risk. Our method also allows us to assess how much of an effect the way that weather and ocean patterns coincide with high tides influence how often flooding occurs. We show that for the considered Australian locations, future changes in tidal amplitude are generally expected to have a greater effect on future coastal flood rates than comparable changes in weather and ocean patterns. Understanding and accounting for potential future tidal range changes is important when formulating sea‐level rise adaptation plans. Key Points: We develop a new coastal flood projection method that considers how tides and storm surges coincide, better replicating observationsThe method facilitates the first ever Australian national assessment of how flood rates may respond to future changes in tidal range and skew surgesPercentagewise, changes in tidal range generally have a much larger impact on flood frequencies than equivalent changes in storm surge [ABSTRACT FROM AUTHOR]

Coastal water level measurements represent one of the earliest geophysical measurements and allow an assessment of historical sea level rise and trends in tides, river flow and storm surge. However, recovery and digitization of archival tidal records have been much less widespread and systematic than, for example meteorological records. In this contribution, we discuss data rescue efforts and lessons learned in France, the United States and the United Kingdom, countries with early and extensive tide gauge networks by the mid‐19th century. We highlight the importance of (a) cataloguing the historical gauge records, as a first step towards locating them; (b) locating data in archives, and then recovering and saving data by any means necessary, including photographs and scanning; (c) obtaining metadata, including both quantitative survey records, gauge checks and clock data, but also qualitative records such as gauge notes, letters and reports; and (d) quantitative statistical analysis of data and datum quality, using both standard data‐entry checks but also tools that leverage the unique predictability of tide measurements. Methods for digitizing original analogue records are also discussed, including semi‐automatic, computer‐based methods of digitizing tidal charts (marigrams). Although the current best practice is described, future improvements are desirable and needed to make the more than estimated 10,000 station years of unused, undigitized records available to the scientific community. [ABSTRACT FROM AUTHOR]

This paper describes a major update to the quasi‐global, higher‐frequency sea‐level dataset known as GESLA (Global Extreme Sea Level Analysis). Versions 1 (released 2009) and 2 (released 2016) of the dataset have been used in many published studies, across a wide range of oceanographic and coastal engineering‐related investigations concerned with evaluating tides, storm surges, extreme sea levels, and other related processes. The third version of the dataset (released 2021), presented here, contains double the number of years of data, and nearly four times the number of records, compared to Version 2. The dataset consists of records obtained from multiple sources around the world. This paper describes the assembly of the dataset, its processing, and its format, and outlines potential future improvements. [ABSTRACT FROM AUTHOR]

The January 15, 2022, Tonga eruption provides a rare opportunity to understand global tsunami impacts of explosive volcanism, including 'air-shock" tsunamis induced by Lamb waves travelling in the atmosphere, and to evaluate future hazards. The propagation of the air-shock and oceanic tsunami components were analyzed using globally distributed 1-min measurements of air pressure and water level (tide gauges and deep-water buoys). Oceanic tsunamis (up to 1.7 m) propagated primarily throughout the Pacific, but air-shock tsunamis arrived first and traveled globally, producing water-level perturbations in the Indian Ocean, the Mediterranean, and the Caribbean. The air-shock induced water level response of most Pacific Rim gauges was amplified, likely related to bathymetric processes. The air-shock repeatedly boosted tsunami wave energy as it circled the planet several times. In some locations, the air-shock was amplified as much as 35X relative to inverse barometer by Proudman resonance and topographic effects. Thus, a large volcanic air-shock (10–30 mb) could cause a 3.5–10 m near-field tsunami that would occur in advance of (usually) larger oceanic tsunami waves, posing an additional hazard to local populations. Present tsunami warning systems do not consider this threat. [ABSTRACT FROM AUTHOR]

Using archival research methods, we found and combined data from multiple sources to produce a unique, 140 year record of daily water temperature (Tw) in the lower Willamette River, Oregon (1881–1890, 1941–present). Additional daily weather and river flow records from the 1850s onwards are used to develop and validate a statistical regression model of Tw for 1850–2020. The model simulates the time-lagged response of Tw to air temperature and river flow, and is calibrated for three distinct time periods: the late 19th, mid 20th, and early 21st centuries. Results show that Tw has trended upwards at ~1.1 °C /century since the mid-19th century, with the largest shift in January/February (1.3 °C /century) and the smallest in May/June (~ 0.8 °C /century). The duration that the river exceeds the ecologically important threshold of 20 °C has increased by ~20 days since the 1800s, to ~60 d yr-1. Moreover, cold water days below 2 °C have virtually disappeared, and the river no longer freezes. Since ~1900, changes are primarily correlated with increases in air temperature (Tw increase of 0.81 ±0.25 °C) but also occur due to increased reservoir capacity, altered land use and river morphology, and other anthropogenic changes (0.34 ±0.12 °C). Managed release of water influences Tw seasonally, with an average reduction of 0.27 °C and 0.56 °C estimated for August and September. System changes have decreased daily variability (σ) by 0.44 °C, increased thermal memory, and reduced interannual variability. These system changes fundamentally alter the response of Tw to climate change, posing additional stressors on fauna. [ABSTRACT FROM AUTHOR]