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Amplitude, Greenwich phase lag, and dimensionless ad- mittance for the M 2 group at Port Orford, Oregon.
Source publication
Seasonal variability of the M2 ocean tide
can be detected at many ports, perhaps most.
Examination of the cluster of tidal constituents residing within
the M2 tidal group can shed light on the physical mechanisms
underlying seasonality. In the broadest terms these are astronomical, frictional–advective interactions, and climate processes; some indu...
Contexts in source publication
Context 1
... time series at Port Orford, Oregon, is one of the better examples. Tidal constants estimated from 26 years of data 2 are listed in Table 2. The magnitudes of tidal admittances |Z| are all consistent within error limits, all phases are close, and the compound MSK 2 is very small. ...Context 2
... note that the amplitude vertical axis spans only 1 cm, so in fact the amplitude agreement is also quite good, with all data implying very little amplitude modulation. The small differences in amplitude curves occur because the estimated admittances in Table 2 are not identical, simply due to unavoidable estimation error. ...Citations
... Thus, the fatigue corrosion of icebreaker steel occurs commonly in this region. The polar tide is hindered by the presence of crushed ice, which reduces the impact of this phenomenon on the corrosion of polar steel materials in the icebreaking area [113][114][115][116]. ...
The desire to explore the natural resources and geopolitical patterns of the North and South Poles has significantly increased the interest of experts and researchers in the development and utilization of the polar regions. In this article, we comprehensively analyzed the current state of the development of polar low-temperature steel around the world. We highlighted the challenges that must be addressed in the ongoing development efforts and summarized the expected future trends in this field. The main theme of this article involves the challenges encountered in polar environments primarily caused by the low-temperature toughness and seawater corrosion of marine steel.
... Ray 75 (2022) proposes several physical mechanisms underlying the seasonality of the M2 tide group: climate induced variations such as those found by Müller et al. (2014), astronomical changes due to the Sun's third body perturbations of the lunar orbit, which are small, and compound tides such as the MSK2 tide. Ray (2022) used long duration O(10 yrs) data sets taken from St. Malo (France), Chittagong (Bangladesh), and Port Orford (Oregon), which allowed the high resolution spectral analysis necessary for such a study. Our study cannot capture the small frequency differences in the M2 tidal group, and we 80 shall refer to them as the same constituent. ...
... As proposed previously, the seasonal variation of tides can result from several reasons. Müller et al. (2014) argued that stronger stratification leads to less loss of 450 energy from the barotropic tide to turbulence and mixing, and Ray (2022) proposed that compound tides with frequencies very near the vicinity of the M2 tide as well as astronomical modulations of the Sun's third body perturbations of the lunar orbit play a role in the observed seasonality of the M2 tide alongside climate processes. ...
Currents and pressure records from the DeepLev mooring station (Eastern Levantine Basin) are analyzed to identify the dominant tidal constituents and their seasonal and depth variability. Harmonic and spectral analysis on seasonal segments of currents and pressure reveal attributes of the tidal regime in the Eastern Levantine Basin: (1) Dominant semidiurnal sea-level variability; (2) seasonal variation of semidiurnal and diurnal tides found in both currents and pressure datasets; and (3) significant diurnal currents with weak semidiurnal currents in all seasons. The most dominant tidal constituent found from the pressure dataset is the M2 (12.4 h). Results from pressure datasets generally agree with previous models and observations of semidiurnal tides, while the diurnal tides are larger than previously reported by 8-9 cm in the winter and 1-2 cm in the summer. The surface current variability differs from the one reported before in the Eastern Levantine Basin, with M2 magnitudes weaker by 1 cm, while the diurnal tides (K1, O1) are 1-2 cm larger. Seasonal segments showed seasonal differences in the local tidal regime’s amplitudes, with the K1 (7 cm difference between winter and fall) and S2 (4 cm difference between summer and fall) the most pronounced. We analyzed the M2 and S2 tides using surface drifters near DeepLev at different dataset lengths while considering the time constraints needed to resolve the tides adequately. The longer the dataset, the higher the resolution of the tidal analysis and the lower the amplitude leakages from nearby frequencies resulting in weaker tidal currents.
... Of particular interest is the inclusion of the MA2 and MB2 constituents which can reach relatively large amplitudes in certain regions both globally and within the region of interest (Ray 2022). To the best of our knowledge, these tides are not available in any global empirical ocean tidal atlases that could be used in this region, at least none that are publicly available, which motivated their incorporation into the EOT-NECS developments and, eventually, within DCSM-FM. ...
With the continued rise in global mean sea level, operational predictions of tidal height and total water levels have become crucial for accurate estimations and understanding of sea level processes. The Dutch Continental Shelf Model in Delft3D Flexible Mesh (DCSM-FM) is developed at Deltares to operationally estimate the total water levels to help trigger early warning systems to mitigate against these extreme events. In this study, a regional version of the Empirical Ocean Tide model for the Northwest European Continental Sea (EOT-NECS) is developed with the aim to apply better tidal forcing along the boundary of the regional DCSM-FM. EOT-NECS is developed at DGFI-TUM by using 30 years of multi-mission along-track satellite altimetry to derive tidal constituents which are estimated both empirically and semi-empirically. Compared to the global model, EOT20, EOT-NECS showed a reduction in the root-square-sum error for the eight major tidal constituents of 0.68 cm compared to in situ tide gauges. When applying constituents from EOT-NECS at the boundaries of DCSM-FM, an overall improvement of 0.29 cm was seen in the root-mean-square error of tidal height estimations made by DCSM-FM, with some regions exceeding a 1 cm improvement. Furthermore, of the fourteen constituents tested, eleven showed a reduction of RMS when included at the boundary of DCSM-FM from EOT-NECS. The results demonstrate the importance of using the appropriate tide model(s) as boundary forcings, and in this study, the use of EOT-NECS has a positive impact on the total water level estimations made in the northwest European continental seas.
... The M 2 barotropic tide group contains a few tidal constituents centering around M 2 , and their superposition causes seasonal variability of the M 2 tide group (Ray, 2022, table 1 therein). Some studies report that the seasonal variation of internal tides is closely correlated to the barotropic tidal forcing (Liu et al., 2015). ...
... Note that some ocean regions demonstrate strong seasonal variation of the barotropic tide (Bij de Vaate et al., 2021;Müller et al., 2014). Ray (2022) points out that both tide and internal tide can be modulated by climate processes such as ocean stratification, ice cover, and river discharge. In addition, incoming internal tides from the western North Pacific are weak; therefore, their influence is not examined in this study (Ubelmann et al., 2022;Zaron, 2019;Zhao, 2021). ...
Satellite altimetry sea surface height (SSH) measurements from 1993 to 2017 are used to investigate the seasonal variability of mode‐1 M2 internal tides from the Luzon Strait. The 25 years of SSH data are divided into four seasonal subsets, from which four seasonal internal tide models are constructed following the same mapping procedure. Climatological seasonal hydrography in the World Ocean Atlas 2013 is used to calculate two seasonally variable parameters required in the mapping procedure: Wavelength and the transfer function from the SSH amplitude to depth‐integrated energy flux. The M2 internal tides from the Luzon Strait are extracted using propagation direction determined in plane wave analysis. The satellite results show that the westward and eastward M2 internal tides both demonstrate significant seasonal variation. The westward and eastward internal tides seesaw seasonally: The westward internal tides strengthen (weaken) in summer and fall (winter and spring); while the eastward internal tides strengthen (weaken) in winter and spring (summer and fall). We suggest that the seasonal seesaw is mainly determined by ocean stratification and the Kuroshio Current; however, further studies are needed to quantify their relative contributions.
... Egbert and Ray (2000) indicated that deep sea mixing needs~2TW energy to maintain deep-water circulation and at least 1TW energy is provided by baroclinic tides. As a result of seasonal changes in ocean environment (such as river flow, ocean stratification and sea ice), tides and tidal currents display significant seasonal variations which have been explored in the global ocean (Corkan, 1934;Foreman et al., 1995;Kang et al., 2002;St-Laurent et al., 2008;Kagan and Sofina, 2010;Georgas, 2012;Müller, 2012;Devlin et al., 2018;Wang et al., 2020;Du and Yu, 2021;Ray, 2022). ...
Exact knowledge on the seasonal variations of main tidal constituents is beneficial for improving tidal prediction. The semi-annual cycles in K1 and S2 tides are abnormally exaggerated by astronomical P1 and K2 tides, which interferes with our understanding on tidal seasonality. The widely-used tidal inference method in previous studies cannot fully separate astronomical P1 and K2 tides from seasonal P1 and K2 tides due to inaccurate inference relationship. In this study, on the basis of the ‘credo of smoothness’ which indicates that tidal admittances are smooth functions of tidal frequencies, we develop a novel but simple method to address this intractable issue and applied this method to explore the seasonality of tidal currents observed in the deep Timor Passage at the depth of 1800m. We find that the timing and range of seasonal modulations of M2, S2, K1, and O1 tides are distinct. Annual variations in tidal currents are much stronger than semi-annual variations in tidal currents. The annual and semi-annual ranges of M2 tide can reach 2.69 cm/s and 1.51 cm/s, which are largest among main constituents. Although the annual range of K1 tide is only 1.85 cm/s, considering the relatively small amplitude of time-averaged K1 tide (2.87cm/s), K1 the most affected tide by the annual cycle. The seasonal cycles of semi-diurnal tides (M2 and S2) are basically synchronous while those of diurnal tides (K1 and O1) are generally out-of-phase. As a general method, the proposed method can be widely applied to other sea areas to explore local tidal seasonality.
Classical harmonic analysis (CHA) model needs ~180-day hourly sea level observations to simultaneously resolve eight major constituents based on the Rayleigh criterion. To fully resolve eight major tides from short-term records, CHA model usually infers unresolved constituents with the help of inference relationships from nearby long-term tide gauges. Our previous study developed a modified harmonic analysis model using the credo of smoothness (i.e., MHACS) which can achieve this without inference relationships. Via introducing the inherent natural links between major tides, MHACS breaks the restrictions of the Rayleigh criterion and requires only ~9-day hourly records to resolve eight major tides. However, when data length is shorter than 9 days, the results of MHACS become problematic due to over-fitting. In this study, we introduce ridge regression to replace ordinary least squares (OLS) in the MHACS. Practical experiments on short-term hourly tide gauge records and satellite altimeter observations indicate that ridge regression can effectively eliminate meaningless mathematical artifacts obtained by OLS. The minimum length of records for MHACS to resolve eight major tides dramatically decreases from ~210 hours to ~75 hours as a result of using ridge regression. It is also found that ridge regression can notably reduce the uncertainties of tidal estimates from MHACS. Moreover, other modified harmonic analysis models such as NS_TIDE designed for river tides also suffer from over-fitting which can be solved by ridge regression in a similar way.
In operational flood forecast systems, the effect of sea ice is typically neglected or parameterized solely in terms of ice concentration. In this study, an efficient way of adding ice effects to the global total water level prediction systems, via the ice–ocean stress, is described and evaluated. The approach features a novel, consistent representation of the tidal relative ice–ocean velocities, based on a transfer function derived from ice and ocean tidal ellipses given by an external ice–ocean model. The approach and its impact are demonstrated over four ice seasons in the Northern Hemisphere, using in situ observations and model predictions. We show that adding ice effects helps the model reproduce most of the observed seasonal modulations in tides (up to 40 % in amplitude and 50∘ in phase for M2) in the Arctic and Hudson Bay. The dominant driving mechanism for the seasonal modulations is shown to be the under-ice friction, acting in areas of shallow water (less than 100 m) and its accompanied large shifts in the amphidromes (up to 125 km). Important contributions from baroclinicity and tide–surge interaction due to ice–ocean stress are also found in the Arctic. Both mechanisms generally reinforce the seasonal modulations induced by the under-ice friction. In forecast systems that neglect or rely on simple ice concentration parameterizations, storm surges tend to be overestimated. With the inclusion of ice–ocean stress, surfaces stresses are significantly reduced (up to 100 % in landfast ice areas). Over the four ice seasons covered by this study, corrections up to 1.0 m to the overestimation of surges are achieved. Remaining limitations regarding the overestimated amphidrome shifts and insufficient ice break-up during large storms are discussed. Finally, the anticipated trend of increasing risk of coastal flooding in the Arctic, associated with decreasing ice and its profound impact on tides and storm surges, is briefly discussed.
Understanding seasonal tidal changes is vital for accurate tidal prediction which is essential for numerous practical purposes, such as flood warning and navigation. It is common knowledge that main constituents show significant seasonal modulations in the global ocean due to non-astronomical factors such as river discharge, sea ice and ocean stratification. Less known, and less studied, is the seasonal variability of shallow water constituents. In this paper, we revisit the abnormally large semi-annual modulation of shallow water constituents at Lamu indicated by a previous study. We find that large semi-annual modulations of shallow water tides at Lamu are mostly not physical, but artifacts induced by unresolved nearby nonlinear shallow water tides due to short length of records. We also propose a novel method based on the ‘credo of smoothness’ to extract real semi-annual modulations of shallow water tides. Tidal harmonic analysis and other widely-used time series methods are generally frequency-depend, which means that they can only extract the amplitude and phase of one specific tidal frequency, but cannot distinguish different origins of a tidal constituent. It is suggested that care must be taken to ensure the obtained tidal amplitude/phase series are really reflecting tidal changes and are not artifacts of frequency-depend methods.
