scholarly journals Surface currents in the Porsanger fjord in northern Norway

2016 ◽  
Vol 37 (3) ◽  
pp. 337-360 ◽  
Author(s):  
Malgorzata Stramska ◽  
Andrzej Jankowski ◽  
Agata Cieszyńska
Keyword(s):  
Sea Level ◽  
Barents Sea ◽  
Surface Current ◽  
Current Data ◽  
Tidal Range ◽  
Surface Currents ◽  
Tidal Component ◽  
Level Data ◽  
Sea Level Oscillations ◽  
Tidal Constituents

Abstract We describe surface currents in the Porsanger fjord (Porsangerfjorden) located in the European Arctic in the vicinity of the Barents Sea. Our analysis is based on surface current data collected in the summer of 2014 using High Frequency (WERA, Helzel Messtechnik GmbH) radar system. One of our objectives was to separate out the tidal from the nontidal components of the currents and to determine the most important tidal constituents. Tides in the Porsanger fjord are substantial, with tidal range on the order of about 3 m. Tidal analysis attributes to tides about 99% of variance in sea level time series recorded in Honningsvaag. The most important tidal component in sea level data is the M2 component, with amplitude of ~90 cm. The S2 and N2 constituents (amplitude of ~20 cm) also play a significant role in the semidiurnal sea level oscillations. The most important diurnal component is K1 with amplitude of about 8 cm. The most important tidal component in analyzed surface currents records is the M2 component. The second most important component is the S2. Our results indicate that in contrast to sea level, only about 10-30% of variance in surface currents can be attributed to tidal currents. This means that about 70-90% of variance is due to wind-induced and geostrophic currents.

On the flushing of Port Phillip Bay: an application of HF ocean radar

1999 ◽  
Vol 50 (6) ◽  
pp. 483 ◽  
Author(s):  
A. Prytz ◽  
M. L. Heron
Keyword(s):  
Numerical Models ◽  
Surface Current ◽  
Coastal Ocean ◽  
Current Data ◽  
Surface Currents ◽  
Tidal Forcing ◽  
Residual Currents ◽  
Tidal Component ◽  
The Matrix ◽  
Ocean Radar

HF ocean radar can produce maps of surface current in coastal ocean and estuarine waters by providing coverage in both the space and time dimensions. The deployment of COSRAD in Port Phillip Bay for two successive five-day periods provided hourly values of surface currents over the topographically complex area at the south end of the bay. Analysis of the current data provided tidal ellipses for the validation of numerical models, with resultant residual currents of the order of 0·05 m s–1. The repeated hourly maps were the basis for producing Lagrangian tracks; most tracks resulted in trapped paths which remained for long periods of time in the matrix of channels and sand-banks. A ‘tidal run’ technique was developed to calculate the length of Lagrangian tracks over one phase (ebb or flood) of the main tidal component. All tidal runs were about equal to, or shorter than, the length of the relevant channel; this indicates that tidal forcing is not effective in flushing the bay. In contrast, the observed residual currents can be an effective flushing agent if they persist for three days or longer. It is suggested that phenomena on the scale of meteorological to seasonal forcing are the effective flushing agents for Port Phillip Bay.

scholarly journals Spectral Analysis of Satellite Altimeter and Tide Gauge Data around the Northern Australian Coast

2020 ◽  
Vol 12 (1) ◽  
pp. 161 ◽  
Author(s):  
Zahra Gharineiat ◽  
Xiaoli Deng
Keyword(s):  
Time Series ◽  
Sea Level ◽  
High Frequency ◽  
Tide Gauge ◽  
Tidal Range ◽  
Tide Gauges ◽  
The North ◽  
Power Spectral ◽  
Level Data ◽  
Tidal Constituents

The north of Australia is known for its complex tidal system, where the highest astronomical tides (HATs) reach 12 m. This paper investigates the tidal behaviour in this region by developing spectral climatology for tide gauge and altimetry data. Power spectral density analysis is applied to detect the magnitude of ocean tides in 20 years of sea-level data from multimission satellite altimeters and tide gauges. The spectra of altimetry sea level anomaly (SLA) time series have their strongest peaks centred at approximately 2.11, 5.88, and 7.99 cycles per year (cpy), corresponding to the diurnal and semidiurnal tidal constituents K1, M2, and O1, respectively. Closer to the coastline, the spectra peak at high-frequency overtide and shallow-water constituents such as M4, MK4, and MK3. There have been many large, high-frequency spectral peaks near the coastline, indicating the difficulty of predicting tidal signals by coastal altimetry. Similar to altimetry observations, there are dominant semidiurnal and diurnal tidal peaks in tide gauge SLA time series accompanying a number of overtides. The semidiurnal and diurnal peaks are mostly higher on the northwest coast of Australia compared with the north and northeast coast. The results from both altimetry and tide gauges indicate that tidal range increases with increasing continental shelf.

Water circulation and shelf waves in the northern Great Barrier Reef lagoon

1981 ◽  
Vol 32 (5) ◽  
pp. 721 ◽  
Author(s):  
E Wolanski ◽  
B Ruddick
Keyword(s):  
Great Barrier Reef ◽  
Sea Level ◽  
Low Frequency ◽  
Current Data ◽  
Barrier Reef ◽  
Sea Levels ◽  
The North ◽  
Level Data ◽  
Shelf Wave ◽  
Salinity Water

Currents and sea levels were measured at a number of locations in the Great Barrier Reef (GBR) lagoon from about 10 to 13� S., during the period October-December 1979. A strong non-tidal, low-frequency modulation of all sea-level and current data was found. The currents nearshore were driven northward by the wind, and then at least partially blocked by the dense network of reefs to the north of 10� s. The water then flowed southward in deeper water adjacent to the reef, driven by a longshore pressure gradient. The low- frequency sea-level data, though not the current records, showed northward phase propagation at speeds characteristic of a first-mode shelf wave trapped in the lagoon between the shore and the reef. Data are presented revealing the intrusion of low-salinity water, through Bligh Entrance, in the GBR lagoon, as a result of river discharges in the Gulf of Papua. It is suggested that low-frequency longshore currents may periodically flush these river plumes from the GBR lagoon and enhance interaction between reefs. In the Coral Sea in front of reef passages, the large horizontal velocities may result in forces upwelling by selective withdrawal and jet entrainment.

scholarly journals Modeling the Nonlinearity of Sea Level Oscillations in the Malaysian Coastal Areas Using Machine Learning Algorithms

2019 ◽  
Vol 11 (17) ◽  
pp. 4643
Author(s):  
Vivien Lai ◽  
Ali Najah Ahmed ◽  
M.A. Malek ◽  
Haitham Abdulmohsin Afan ◽  
Rusul Khaleel Ibrahim ◽  
...  
Keyword(s):  
Sea Level ◽  
Peninsular Malaysia ◽  
Machine Learning Algorithms ◽  
Support Vector ◽  
Mean Sea Level ◽  
Sea Levels ◽  
Tuning Parameters ◽  
Level Data ◽  
Input Dataset ◽  
Sea Level Oscillations

The estimation of an increase in sea level with sufficient warning time is important in low-lying regions, especially in the east coast of Peninsular Malaysia (ECPM). This study primarily aims to investigate the validity and effectiveness of the support vector machine (SVM) and genetic programming (GP) models for predicting the monthly mean sea level variations and comparing their prediction accuracies in terms of the model performances. The input dataset was obtained from Kerteh, Tioman Island, and Tanjung Sedili in Malaysia from January 2007 to December 2017 to predict the sea levels for five different time periods (1, 5, 10, 20, and 40 years). Further, the SVM and GP models are subjected to preprocessing to obtain optimal performance. The tuning parameters are generalized for the optimal input designs (SVM2 and GP2), and the results denote that SVM2 outperforms GP with R of 0.81 and 0.86 during the training and testing periods, respectively, at the study locations. However, GP can provide values of 0.71 and 0.79 for training and testing, respectively, at the study locations. The results show precise predictions of the monthly mean sea level, denoting the promising potential of the used models for performing sea level data analysis.

Meteotsunami research in the Strait of Georgia: Critical observational contributions from a student school network on Vancouver Island

2020 ◽  
Author(s):  
Alexander Rabinovich ◽  
Jadranka Šepić ◽  
Richard Thomson
Keyword(s):  
Sea Level ◽  
Vancouver Island ◽  
Small Scale ◽  
Tide Gauges ◽  
Strait Of Georgia ◽  
Level Data ◽  
Atmospheric Disturbances ◽  
Sea Level Oscillations ◽  
School Network ◽  
The Persian Gulf

<p>Meteorological tsunamis are frequently destructive tsunami-like waves generated by small-scale atmospheric disturbances. Several devastating events occurred recently in various regions of the world oceans, including the Balearic Islands, Sicily, the Adriatic and Black seas, the Great Lakes, the west coast of South Korea, the Netherlands and the Persian Gulf. Although this phenomenon has been actively studied for more than 25 years, the exact mechanism (or mechanisms) responsible for producing these extreme events remains a puzzle. One of the major problems making it difficult to determine the physical process generating meteotsunamis is the absence of a network of simultaneously working precise tide gauges and microbarographs in the affected region. A unique set of high-resolution atmospheric data from the meteorological “school network” of 132 school stations became available for 2008-2019 for the area of southern Vancouver Island and nearby Gulf Islands located in the Strait of Georgia. These data, combined with 1-min sea level data from Canadian Hydrographic Service (CHS) and USA National Oceanic and Atmospheric Administration (NOAA) tide gauges, has enabled us to examine both the spatial and temporal features of mesoscale atmospheric disturbances and coincident properties of the associated sea level oscillations. The data analyses, supported by a series of numerical experiments, has made it possible to reconstruct observed events and to determine the specific atmospheric parameters producing the strongest sea level response in the southern part of the Strait of Georgia. These experiments have helped us to recognize the most effective (and hence, most hazardous) directions and speeds of propagating atmospheric disturbances and to identify “hot spots” along the coast that are under the highest risk of large meteotsunamis.</p>

scholarly journals Features of Seasonal Sea Level Oscillations in the Russian Arctic Seas

Oceanology ◽  
2021 ◽  
Author(s):  
I. P. Medvedev
Keyword(s):  
Sea Level ◽  
Barents Sea ◽  
Extreme Values ◽  
Mean Amplitude ◽  
Arctic Seas ◽  
Lena River ◽  
Sharp Maximum ◽  
Sea Level Oscillations ◽  
The Mean ◽  
Seasonal Oscillations

Abstract Based on the analysis of long series of monthly mean sea level values from the database of the PSMSL and ESIMO portals, we obtained estimates of the mean and extreme amplitudes of seasonal oscillations. The mean amplitude of annual sea level oscillations in the White Sea is 7 cm, in the Barents Sea is 9–10 cm, in the Kara Sea, is 8–9 cm, in the Laptev Sea, is 10–11 cm, in the East Siberian and Chukchi seas is 13–14 cm. In the estuarine areas of seas, the amplitude of annual oscillations increases, and the semiannual, third-annual, and quarter-annual components appear in the sea level spectra. They are formed due to the asymmetry of the seasonal sea level variation with a sharp maximum during the flood period in June. Interannual changes in the amplitude of seasonal oscillations were identified and estimates of their extreme values were obtained. In some years, the amplitude of seasonal oscillations reaches 50 cm in the Yenisei Gulf and Gulf of Ob, 60 cm near the mouth of the Lena River, and 75 cm at the mouth of the Olenek River.

scholarly journals Prediction of geostrophic currents using big weather data archive and neural networks for the Aegean Sea

2019 ◽  
Vol 9 (1) ◽  
pp. 10-20
Author(s):  
Timur İnan ◽  
Ahmet Fevzi BABA
Keyword(s):  
Neural Network ◽  
Surface Current ◽  
Aegean Sea ◽  
Current Data ◽  
Sea Surface ◽  
Weather Data ◽  
Time Of Arrival ◽  
Surface Currents ◽  
Data Archive ◽  
Wave Direction

Prediction of sea and weather environment variables like wind speed, wind direction, wave height, wave direction, sea surface current direction and magnitude has always been an important subject in marine engineering as they effect on ship speed and effect the time of arrival to destination point as well. In this study, we propose a neural network that can predict the latitudinal and longitudinal components of sea surface currents in the Aegean Sea. The system can predict the sea surface currents components using the wind components which are gathered from the INMARSAT weather report system. The neural network is trained using the historical data which is gathered from UCAR historical weather database and historical surface current data which is gathered from IFREMER database. Keywords: Sea surface current, weather report, prediction, neural network, big data archive.

Comparison of predictions of a numerical model and observations of tides in Bass Strait

1985 ◽  
Vol 36 (6) ◽  
pp. 737 ◽  
Author(s):  
CB Fandry ◽  
GD Hubbert ◽  
PC McIntosh
Keyword(s):  
Numerical Model ◽  
Sea Level ◽  
Travelling Waves ◽  
Phase Lag ◽  
Tidal Amplitude ◽  
Tidal Constituent ◽  
Tidal Waves ◽  
Level Data ◽  
Grid Points ◽  
Tidal Constituents

A depth-averaged numerical model is used to describe the tidal regime in Bass Strait. Tidal constants corresponding to the four major tidal constituents (M2, S2, O1 and K1) are calculated at the grid points of the model, and co-amplitude and co-phase contours drawn for each of the constituents. At 17 locations in Bass Strait, the computed tidal constants are in excellent agreement with those obtained from flow and sea-level data. The dominant tidal constituent is found to be the semi-diurnal, M2, tide, which is predicted by the model with an accuracy of 10% in sea-level amplitude and 10� in phase. The M2 tide in Bass Strait is generated by two oppositely travelling waves, one entering the eastern end and another entering the western end with a phase lag of about 3 h. Some amplification of these waves occurs as they move from the deep water into the much shallower continental shelf waters of the Strait, and their superposition causes a large tidal amplitude (up to 1.2 m) to occur in central Bass Strait. The other three constituents are much weaker than the M2 constituent, and are driven by tidal waves entering from the western end. They propagate eastwards, emerging at the eastern end with little change in amplitude throughout the Strait.

scholarly journals A survey of strong high-frequency sea level oscillations along the US East Coast between 2006 and 2011

2013 ◽  
Vol 13 (2) ◽  
pp. 473-482 ◽  
Author(s):  
S. Pasquet ◽  
I. Vilibić ◽  
J. Šepić
Keyword(s):  
Sea Level ◽  
High Frequency ◽  
East Coast ◽  
Level Data ◽  
The Us ◽  
Sea Level Oscillations ◽  
Wave Heights ◽  
Generation Mechanisms ◽  
Future Work ◽  
Us East Coast

Abstract. A systematic survey of high-frequency sea level oscillations (<6 h) measured between 2006 and 2011 along the US East Coast is performed. Raw 1-min resolution sea level data is used. After performing a data quality check, the nine most intense events, with maximum recorded wave heights ranging from 40 to 100 cm, are identified. Focusing on three of these events enables us to recognize two different generation mechanisms: (i) topographically-trapped edge waves which are found to be a significant contributor to the strongest observed oscillations, and (ii) standing waves, which occur over enclosed shallow waters and may result in significant wave heights of up to 100 cm. A reproduction of the observed oscillations is a part of a future work, which will include an assessment of a generating force in the atmosphere, allowing for a better prevention of potential flooding along the US East Coast.

scholarly journals The Influence of Fetch on the Response of Surface Currents to Wind Studied by HF Ocean Surface Radar

2008 ◽  
Vol 38 (5) ◽  
pp. 1107-1121 ◽  
Author(s):  
Yadan Mao ◽  
Malcolm L. Heron
Keyword(s):  
Wind Speed ◽  
Momentum Transfer ◽  
Surface Current ◽  
Ocean Surface ◽  
Growth Function ◽  
Current Data ◽  
Hf Radar ◽  
Stokes Drift ◽  
Surface Currents ◽  
Sea State

Abstract The momentum transfer from wind to sea generates surface currents through both the wind shear stress and the Stokes drift induced by waves. This paper addresses issues in the interpretation of HF radar measurements of surface currents and momentum transfer from air to sea. Surface current data over a 30-day period from HF ocean surface radar are used to study the response of surface currents to wind. Two periods of relatively constant wind are identified—one for the short-fetch condition and the other for the long-fetch condition. Results suggest that the ratio of surface current speed to wind speed is larger under the long-fetch condition, while the angle between the surface current vector and wind vector is larger under the short-fetch condition. Data analysis shows that the Stokes drift dominates the surface currents under the long-fetch condition when the sea state is more mature, while the Stokes drifts and Ekman-type currents play almost equally important roles in the total currents under the short-fetch condition. The ratios of Stokes drift to wind speed under these two fetch conditions are shown to agree well with results derived from the empirical wave growth function. These results suggest that fetch, and therefore sea state, significantly influences the total response of surface current to wind in both the magnitude and direction by variations in the significance of Stokes drift. Furthermore, this work provides observational evidence that surface currents measured by HF radar include Stokes drift. It demonstrates the potential of HF radar in addressing the issue of momentum transfer from air to sea under various environmental conditions.

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