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Abstract High‐tide flooding—minor, disruptive coastal inundation—is expected to become more frequent as sea levels rise. However, quantifying just how quickly high‐tide flooding rates are changing, and whether some places experience more high‐tide flooding than others, is challenging. To quantify trends in high‐tide flooding from tide‐gauge observations, flood thresholds—elevations above which flooding begins—must be specified. Past studies of high‐tide flooding in the United States have used different data sets and approaches for specifying flood thresholds, only some of which directly relate to coastal impacts, which has lead to sometimes conflicting and ambiguous results. Here we present a novel method for quantifying, with uncertainty, high‐tide flooding thresholds along the United States coast based on sparsely available impact‐based flood thresholds. We use those newly modeled thresholds to make an updated assessment of changes in high‐tide flooding across the United States over the past few decades. From 1990–2000 to 2010–2020, high‐tide flooding rates almost certainly (probability ) increased along the United States East Coast, Gulf Coast, California, and Pacific Islands, while they very likely decreased along Alaska during that time; significant changes in high‐tide flooding rates between the two decades were not detected in Oregon, Washington, and the Caribbean. Averaging spatially, we find that high‐tide flooding rates probably more than doubled nationally between 1990–2000 and 2010–2020. Our approach lays a foundation for future studies to more accurately model high‐tide flood thresholds and trends along the global coastline. 

This repository contains hourly Shelfbreak jet transport (Sv) derived from the three central moorings of the OOI Coastal Pioneer Array (https://ooinet.oceanobservatories.org/).  Transport is computed from east velocity component (u, in m/s), which is then depth integrated from 15 until 115m. The depth integrated velocity (m2/s) is transformed in transport considering a jet width of 40 km, and then converted into Sv (by dividing by 10^6 factor). Thus, to convert the transport time series back to m2/s, the time series must be divided by 4.10^10. Tides were removed from the velocity component, with Utide harmonic estimation, using the 68 standard tidal coefficients, except for the Semi-annual and Annual components (Sa and SSa). First column: date (datetime format, year-month-day hour:min:second)Second column: Qy (jet transport, in Sv)   accompanying paper: Camargo, C. M. L., Piecuch, C. G., & Raubenheimer, B. (2024). From Shelfbreak to Shoreline: Coastal sea level and local ocean dynamics in the northwest Atlantic. Geophysical Research Letters, 51, e2024GL109583. https://doi.org/10.1029/2024GL109583 

Abstract. Identifying the causes for historical sea-level changes in coastal tide-gauge records is important for constraining oceanographic, geologic, and climatic processes. The Río de la Plata estuary in South America features the longest tide-gauge records in the South Atlantic. Despite the relevance of these data for large-scale circulation and climate studies, the mechanisms underlying relative sea-level changes in this region during the past century have not been firmly established. I study annual data from tide gauges in the Río de la Plata and stream gauges along the Río Paraná and Río Uruguay to establish relationships between river streamflow and sea level over 1931–2014. Regression analysis suggests that streamflow explains 59 %±17 % of the total sea-level variance at Buenos Aires, Argentina, and 28 %±21 % at Montevideo, Uruguay (95 % confidence intervals). A long-term streamflow increase effected sea-level trends of 0.71±0.35 mm yr−1 at Buenos Aires and 0.48±0.38 mm yr−1 at Montevideo. More generally, sea level at Buenos Aires and Montevideo respectively rises by (7.3±1.8)×10-6 m and (4.7±2.6)×10-6 m per 1 m3 s−1 streamflow increase. These observational results are consistent with simple theories for the coastal sea-level response to streamflow forcing, suggesting a causal relationship between streamflow and sea level mediated by ocean dynamics. Findings advance understanding of local, regional, and global sea-level changes; clarify sea-level physics; inform future projections of coastal sea level and the interpretation of satellite data and proxy reconstructions; and highlight future research directions. Specifically, local and regional river effects should be accounted for in basin-scale and global mean sea-level budgets as well as reconstructions based on sparse tide-gauge records. 

Reconstructions of Common Era sea level are informative of relationships between sea level and natural climate variability, and the uniqueness of modern sea-level rise1. Kench et al.2 recently reconstructed Common Era sea level in the Maldives, Indian Ocean, using corals, and reported periods of 150–500 years when sea level fell and rose at average rates of 2.7–4.3 mm yr−1, which they attributed to ocean cooling and warming inferred from reconstructions of sea-surface temperature (SST) and radiative forcing (Fig. 2 of ref. 2). We challenge their interpretation, using principles of sea-level physics to argue that pre-industrial radiative forcing and SST changes were insufficient to cause thermosteric sea-level (TSL) trends as large as reported for the Maldives2. Our results support the paradigm that modern rates and magnitudes of sea-level rise due to climate change are unprecedented during the Common Era3,4. 

Abstract Tide gauges provide a rich, long‐term, record of the amplitude and spatiotemporal structure of interannual to multidecadal coastal sea‐level variability, including that related to North American east coast sea level “hotspots.” Here, using wavelet analyses, we find evidence for multidecadal epochs of enhanced decadal (10–15 year period) sea‐level variability at almost all long (70 years) east coast tide gauge records. Within this frequency band, large‐scale spatial covariance is time‐dependent; notably, coastal sectors north and south of Cape Hatteras exhibit multidecadal epochs of coherence (1960–1990) and incoherence (1990‐present). Results suggest that previous interpretations of along coast covariance, and its underlying physical drivers, are clouded by time‐dependence and frequency‐dependence. Although further work is required to clarify the mechanisms driving sea‐level variability in this frequency band, we highlight potential associations with the North Atlantic sea surface temperature tripole and Atlantic Multidecadal Variability. 

Abstract Monthly observations are used to study the relationship between the Atlantic meridional overturning circulation (AMOC) at 26° N and sea level (ζ) on the New England coast (northeastern United States) over nonseasonal timescales during 2004–2017. Variability inζis anticorrelated with AMOC on intraseasonal and interannual timescales. This anticorrelation reflects the stronger underlying antiphase relationship between ageostrophic Ekman‐related AMOC transports due to local zonal winds across 26° N andζchanges arising from local wind and pressure forcing along the coast. These distinct local atmospheric variations across 26° N and along coastal New England are temporally correlated with one another on account of large‐scale atmospheric teleconnection patterns. Geostrophic AMOC contributions from the Gulf Stream through the Florida Straits and upper‐mid‐ocean transport across the basin are together uncorrelated withζ. This interpretation contrasts with past studies that understoodζand AMOC as being in geostrophic balance with one another.