geologia: Tide

Evidence: 100 • authority: 72

Tides are the periodic rise and fall of sea level resulting from the differential gravitational forces exerted primarily by the Moon and the Sun, combined with inertial effects associated with the Earth–Moon system’s orbital motion and the Earth's rotation. While these astronomical forcings generate the fundamental tidal potential, actual observed tides are strongly modified by terrestrial factors, including the geometry of ocean basins, continental boundaries, bathymetry, the coriolis effect, frictional dissipation within shallow seas and the tidal resonance of coastlines. Tides vary on timescales ranging from hours to years due to a number of factors, which determine the lunitidal interva…

Evidence: 55 • authority: 88

Quality Control of Redundant Water Level Gauges in South Korea River Gauging Stations. In South Korea, river stage gauging stations operate redundant water level gauges to mitigate instrument malfunctions and anomalous measurements. Currently, redundant gauges are installed at over 60% of gauging stations, reflecting their widespread implementation; however, their quality management and practical utilization remain limited. In many cases, installation and operational conditions are not fully accounted for in observed water levels, leading to significant discrepancies between primary and redundant gauges. These discrepancies may arise from river characteristics, artificial configuration erro…

Evidence: 55 • authority: 88

Reprocessed height time series of GPS stations at tide gauges. Abstract. Precise weekly positions of 403 Global Positioning System (GPS) stations located worldwide are obtained by reprocessing GPS data of these stations at the time span from 4 January 1998 until 29 December 2007. The used processing algorithm and models as well as the solution and results obtained are presented. Vertical velocities of GPS stations having tracking history longer than 2.5 yr are computed and compared with the estimates from the colocated tide gauges and other GPS solutions. Examples of typical behavior of station height changes are given and interpreted. The derived time series and vertical motions of continu…

Evidence: 55 • authority: 92

Relative sea level projections constrained by historical trends at tide gauge sites.. Assessing the impacts of future relative sea level rise requires projections consistent with historical observations. However, existing projections often do not align with past data, complicating adaptation planning, impact assessments, and communication. We present a spatial Bayesian model that generates local projections at tide gauge sites from historical records. The model integrates tide gauges, GPS, and satellite altimetry with past and future constraints on mountain glaciers, polar ice sheets, thermal expansion, ocean circulation, land water storage, and glacial history. By separating unforced ocean…

Evidence: 48 • authority: 80

Preliminary Differences in Mean Water Level Between Tide Gauges Along the South American Pacific Coast

Evidence: 48 • authority: 72

A tide gauge is a device for measuring the change in instantaneous sea level, including periodic tides and long-term sea level rise, relative to a vertical datum. It is also known as a mareograph, marigraph, and sea-level recorder. When applied to freshwater continental water bodies, the instrument may also be called a limnimeter. Stream gauges may record water level, discharge, or both. In general, a water level sensor may be used in arbitrary bodies, such as reservoirs or a tank.

Evidence: 48 • authority: 92

Estimating tidal constituents in shallow waters from satellite altimetry using a 2D hydrodynamic model with nonlinear tide-surge interactions.. Tidal models that incorporate satellite altimeter data have historically shown discrepancies in accuracy between shallow and deep marine environments. A recent study suggests that these differences may partly stem from neglecting the nonlinear tide-surge interactions in tidal analyses. In this study, we introduce a novel method for estimating tidal constituents from satellite altimeter data in shallow waters, leveraging a 2D hydrodynamic model that accounts for these nonlinear interactions. This approach substantially reduces the variance of unaccou…

Evidence: 48 • authority: 92

Reconstructing hourly coastal total sea levels and assessing current and future extreme sea levels threats to the Coast of China.. Climate-driven sea level rise (SLR) will intensify extreme sea level (ESL) events along China's coast. This study reconstructs continuous hourly total sea level (TSL) by incorporating SLA, tide, storm surge, and wave components, addressing the sparse coverage of tide gauges and their often overlooked extreme events (waves). Using a peak-over-threshold method (thresholds optimised between the 97.00-99.99th percentiles) and a 3-day declustering interval, extreme samples were fitted with generalised Pareto distributions via maximum likelihood estimation. Present-da…

Evidence: 48 • authority: 72

A harmful algal bloom (HAB), or excessive algae growth, sometimes called a red tide in marine environments, is an algal bloom that causes negative impacts to other organisms by production of natural algae-produced toxins, water deoxygenation, mechanical damage to other organisms, or by other means. HABs are sometimes defined as only those algal blooms that produce toxins, and sometimes as any algal bloom that can result in severely lower oxygen levels in natural waters, killing organisms in marine or fresh waters. Blooms can last from a few days to many months. After the bloom dies, the microbes that decompose the dead algae use up more of the oxygen, generating a "dead zone" which can caus…

Evidence: 41 • authority: 72

Rising sea levels pose a major threat to Venice, Italy. Known for its old structures, layers of history, and unique ties to the water, Venice faces increasing risks of major flooding and damage due to both rising sea levels and subsidence. Studies show a range of future projections for sea-level rise in Venice, with the likely outcome by 2100 being a rise of 21–52 cm. Low elevation, proximity to the Venice lagoon, and the city's series of canals make it particularly vulnerable to sea level changes. Flooding is a frequent and damaging disruption that poses threats to cultural heritage, biodiversity, public health, and tourism. Venetians have implemented measures to mitigate these changes, su…

Evidence: 41 • authority: 92

Observing the tidal pulse of rivers from wide-swath satellite altimetry.. The characteristic tides of coastal rivers influence the distribution of estuarine and wetland habitats 1 , the extent of fresh drinking water 2 , carbon and nitrogen cycles 3,4 , and sediment export to the ocean 5 . Despite the importance of riverine tides, their range is generally unknown over most of the world's rivers because the propagation of tidal waves in channels is complex, gauging stations are scarce and conventional nadir altimetry 6 has historically been too sparse for use in rivers. Here we use data from the recently launched Surface Water and Ocean Topography (SWOT) satellite to quantify tidal dynamics…

Evidence: 41 • authority: 72

The annual cycle of sea level height (or seasonal cycle or annual harmonic) describes the variation of sea level that occurs with a period of one year. Historically, analysis of the annual cycle has been limited by locations with tide gauge records, i.e., coastlines and some islands in the deep ocean, and by sparse records in the Southern Hemisphere. Since 1992, satellite-based altimeters have provided near global coverage of sea level variability, allowing for a more thorough understanding of the annual cycle both in the deep ocean and in coastal margins.