Analysis Of Sea Level Changes Research Articles

Development and Validation of an Instrument for Wave Height Measurement with Encoder Sensors and Accelerometer

Ocean waves play a significant role in coastal dynamics and the management of coastal development activities. However, there are limited instruments to measure the wave height, particularly in developing countries. This study introduces a novel instrument design for simple and cost-effective wave height measurement. The proposed instrument combines a Hall-effect sensor and an accelerometer to capture the rise and fall of a buoy in response to wave movements. The Hall-effect sensor as a rotary encoder detects the rotation of the buoy while the accelerometer measures the tilt of the instrument caused by ocean waves. The instrument is constructed using PVC pipes and incorporates long-range (LoRa) communication technology for real-time monitoring. Experimental tests were conducted at a study site in Banyuwangi Regency, Indonesia, where the performance of the instrument was compared with an ultrasonic sensor-based instrument. The results validate the effectiveness of the proposed instrument design for wave height measurement. The collected data were transmitted via the LoRa communication system, enabling convenient monitoring and analysis of sea-level changes. The valuable contribution of the instrument to the field stems from its precision in measuring the wave height, adaptability to diverse conditions, and potential applicability in shallow waters.

Analysis of Sea Level Changes in Eastern Taiwan Coast—Case of Yilan Area

This study considers the impact of extreme climates on most of the world’s land and seas, which may cause the average sea level to rise due to global climate change. Affected by the rise of sea level, it will change the distribution characteristics of sea tides, waves and currents. When the distribution of tides, waves and currents in the sea area changes, it may cause changes in the overall environmental characteristics of the estuary and coastal areas, and further affects the function of coastal protection facilities. This study takes the sea area of Yilan as an example, and analyzes the problem of sea level rise in the three-in-one climate change (including sea level rise, typhoon and heavy rain). For the analysis of sea level rise, this study calculates tide level data in three ways, the first is simple moving average (SMA), then there are empirical mode decomposition (EMD) and ensemble empirical mode decomposition (EEMD) in the hilbert-huang transform (HHT) for sea level rise analysis. The use of ensemble empirical mode decomposition (EEMD) is because when modal confusion occurs in empirical mode decomposition (EMD), the occurrence of modal confusion can be reduced by adding the decomposed signal to the white noise sequence. Comparing the analysis results of the three respectively, the result obtained by using simple moving average (SMA) is the smallest (2.78 mm/yr), and the result obtained by using ensemble empirical mode decomposition (EEMD) calculation is the largest (4.11mm/yr). By analyzing the results obtained, it can be provided for assessing future hydrological and environmental changes based on climate change conditions.

How climate change affected on water level in Ha Long coastal area in the period 1974–2020: results from the mann-kendall test and sen’s slope estimate

The impact of climate change on sea level has attracted much attention from scientists worldwide. The analysis of sea-level change at global and regional scales is based on altimetry and/or tide gauge data. The main objective’s study relied on statistical tests to highlight the significant long-term changes in sea level in Ha Long coastal area through the 47 years (1974–2020) historical tide gauge record of the Bai Chay station. The average water level in this area was 207.9 cm, which tended to be higher in recent years, especially from 2006 to the present (above 210 cm). Moreover, sea level trends were carried out separately for the whole period (1974–2020) and the last 19 years (2002–2020) by the Mann-Kendall test and Sen’s slope estimator. The results showed a significant sea-level rise (SLR) trend with a 95–100% confidence level. The average annual rates of sea-level were 3.14 mm/year and 5.83 mm/year in 1974–2020 and 2002–2020, respectively, indicating an SLR of about 14.76 cm over 47 years and significant acceleration in SLR recently (11.01 cm over the last 19 years).

Simulation and Analysis of Sea-Level Change from Tide Gauge Station by Using Artificial Neural Network Models

Sea level change is one of the most certain results of global warming. Sea level change would increase erosion in coastal areas, result in intrusion into water supplies, inundate coastal marshes and other important habitats, and make the coastal property more vulnerable to erosion and flooding. This situation coincides with the massive socio-economic development of the coastal city areas. The coastal areas of the East Coast of Peninsular Malaysia are vulnerable to sea-level change, flooding, and extreme erosion events. The monthly Mean Sea Level (MSL) change was simulated by using two Artificial Neural Network (ANN) models, Feed Forward- Neural Network (FF-NN) and Nonlinear Autoregressive Exogenous- Neural Network (NARX-NN) models. Both models did well in recreating sea levels and their fluctuating patterns, according to the data. The NARX-NN model with architecture (5-6-1) and four lag options, on the other hand, got the greatest results. The findings of the model's mean sea level rise simulation show that Kuala Terengganu would have a growing and upward trend of roughly 25.34 mm/year. This paper shows that the eastern coast of Malaysia is highly vulnerable to sea-level rise and therefore, requires sustainable adaptation policies and plans to manage the potential impacts. It recommends that various policies, which enable areas to be occupied for longer before the eventual retreat, could be adapted to accommodate vulnerable settlements on the eastern coast of Malaysia.

Analysis of the Temporal and Spatial Changes of Sea Level in Korean Coastal Zone

In this study, the temporal and spatial changes of sea level in Korean coastal zone were analyzed. First, the error value of 1 hour tide data provided by the Korea Hydrographic and Oceanographic Agency was excluded through preprocessing, the analysis of sea level change was performed by considering long period components through low-pass filtering. Using low-pass filtering data, the monthly mean sea level was calculated and the temporal changes of sea level were verified by data fitting using linear fit and multidimensional smoothing spline. The results of linear fit show that the tide tends to rise at most stations. And the results of multidimensional smoothing spline fit show that the increase and decrease of sea level is repeated every year. Although the amounts of change vary every year, sea levels have been repeated seasonally, with sea levels rising in summer and falling in winter. Also, Hovmöller diagram was prepared for the change of sea level in each east, west, and south coast, and the temporal and spatial changes of sea level were analyzed. Compared to the past, recent sea level changes increased in all points. Especially, in the west coast, the sea level increased more in the south (Mokpo) area than in the north (Yeongjong Bridge), and the south (Mokpo) area of the west coast could be a vulnerable area due to the rise in sea level.

A Study on Analysis Method of Sea Level Change in Korean Coastal Zone

In this study, the analysis of sea level change using Lanczos filtering, a filtering method of Fourier transform, was performed. The high frequency(short period) of tide was excluded by low-pass filter of Lanczos filtering, the analysis of sea level change was carried out considering only low frequency(long period). First, all tide data provided by the Korea Hydrographic and Oceanographic Administration(KHOA) were preprocessed to delete the error value, the astronomical tide and the meteorological tide repeated in short period were excluded by Lanczos filtering. The Mean Sea Level(MSL) for each tidal station was calculated using these results, the MSL tended to rise at most point in the Korean coastal zone. And the rate of sea level change, which means annual sea level change(mm/year), was estimated and compared with previous study results. The rate of sea level change was higher than values in past study, this means that future sea level change may be greater than previous expected. The analysis method applied to this study can be effectively used to improve the accuracy of prediction of sea level change.

Analysis of sea level changes in Balikpapan Bay as basic data for strategic planning the new capital city of Republic of Indonesia

Studies from various sectors are needed regarding the plan to move the capital city of the Republic of Indonesia from Jakarta to Penajam Paser Utara. The aquatic ecosystem that needs attention is Balikpapan Bay which is located in the vicinity of these activities. One of the factors that influence this is global warming. Therefore, it is necessary to analyze the variability and trend of sea level rise in front of Balikpapan Bay. The first mode of Empirical Orthogonal Function (EOF) shows that sea level around Balikpapan Bay has a strong correlation with the Multivariate ENSO Index (MEI). This indicates that the sea level in the area is predominantly influenced by ENSO. A strong correlation between the first principal component and MEI was found to be around -0.85 in Balikpapan Bay (significance level> 95%). Based on sea level anomaly data for the last 20 years, sea level in Balikpapan has increased with a linear trend of 5.4 mm/year, with a decreasing trend due to El Niño and an increasing trend due to La Niña.

THE VERTICAL LAND MOTION OF TIDE GAUGE AND ABSOLUTE SEA LEVEL RISE IN BOHAI SEA

Abstract. The ground vertical movement of the tide gauges around the Bohai sea was firstly analyzed by using the observation data from 2009 to 2017 of the nine co-located GNSS stations. It was found that the change rate of ground vertical motion of four stations was in the same order of magnitude as the sea level change. In particular, the land subsidence rate of BTGU station reaches 11.47 mm/yr, which should be paid special attention to in the analysis of sea level change. Then combined with long-term tide gauges and the satellite altimetry results, the sea level changes in the Bohai sea and adjacent waters from 1993 to 2012 were analyzed. The relative and absolute sea level rise rates of the sea area are 3.81 mm/yr and 3.61 mm/yr, respectively, both are higher than the global average rate of change. At the same time, it is found that the vertical land motion of tide gauge stations is the main factor causing regional differences in relative sea level changes.

Study on the Main Controlling Factors of the Early Ordovician Stromatolites Development in Liujiachang Area of Songzi City

The Early Ordovician stromatolites in the study area are mainly exposed at the bottom and middle and lower parts of the Second Member of Nanjinguan Formation, the top of the Fourth Member of Nanjinguan Formation, the middle of the Second Member of Fenxiang Formation and the bottom of the First Member of Honghuayuan Formation. In order to find out the controlling factors of Lower Ordovician stromatolites development in the study area, the analysis data of carbon, oxygen isotope samples, macro element samples as well as their variation characteristics are studied and then combined them with previous research results, which is eventually beneficial for reaching the conclusion: sea level change is one of the main factors controlling the formation of stromatolites. There are five sea level change cycles in the Early Ordovician period. The analysis of sea level change and accommodation space variation characteristics show that when the growth rate of the accommodation space is approximately equal to that of carbonate, the circulation of seawater is well, and the amount of light and oxygen is sufficient, so that the cyanobacteria organism can be multiplied in large quantities. The growth and development provide favorable conditions, and favorable conditions are provided for the growth and development of stromatolites; The peak changes in CaO content and CaO/MgO ratio indicate that the formation period of stromatolites is arid climate environment with high water temperature and large evaporation. Prokaryote reproduction is suitable for the environments with high seawater cleanliness. When the amount of land-based debris injected into the sea increases, the turbidity of water will lead to a large number of deaths of algae microorganisms that form stromatolites, and the stromatolitic microbial mats cannot be preserved. In addition, the growth and predation of macro-organisms play a restrictive role in the development of stromatolite-forming micro-organisms blue-green algae. According to the actual situation of the development of the laminated rocks in the study area, what is the dominant function in the formation and decline of stromatolites between the evolution of metazoans and changing environments is discussed in the study.

Analysis of sea level changes in the Caspian Sea related to Cosmo-geophysical processes based on satellite and terrestrial data

Analysis results of the average annual sea levels in the Caspian Sea obtained from ground and satellite observations, corresponding to solar activity characteristics, magnetic field data, and length of day are presented. Spectra of the indicated processes were investigated and their approximation models were also built. Previously assumed statistical relationships between space-geophysical processes and Caspian Sea level (CSL) changes were confirmed. A close connection was revealed between the low-frequency models of the solar and geomagnetic activity parameters and the CSL changes. Predictions extending into the next decades showed a high probability of an increase in the CSL and a decrease of the compared space-geophysical parameters.

Spatial-temporal analysis of sea level changes in China seas and neighboring oceans by merged altimeter data

The knowledge of sea level changes is critical important for social, economic and scientific development in coastal areas. Satellite altimeter makes it possible to observe long term and large scale dynamic changes in the ocean, contiguous shelf seas and coastal zone. In this paper, 1993-2015 altimeter data of Topex/Poseidon and its follow-on missions is used to get a time serious of continuous and homogeneous sea level anomaly gridding product. The sea level rising rate is 0.39 cm/yr in China Seas and the neighboring oceans, 0.37 cm/yr in the Bo and Yellow Sea, 0.29 cm/yr in the East China Sea and 0.40 cm/yr in the South China Sea. The mean sea level and its rising rate are spatial-temporal non-homogeneous. The mean sea level shows opposite characteristics in coastal seas versus open oceans. The Bo and Yellow Sea has the most significant seasonal variability. The results are consistent with in situ data observation by the Nation Ocean Agency of China. The coefficient of variability model is introduced to describe the spatial-temporal variability. Results show that the variability in coastal seas is stronger than that in open oceans, especially the seas off the entrance area of the river, indicating that the validation of altimeter data is less reasonable in these seas.

Paleoecology of Early Ordovician Reefs in the Yichang Area, Hubei: a Correlation of Organic Reefs Between Early Ordovician and Jurassic

Abstract:The Early Ordovician System is composed mainly of a series of carbonate platform deposits interbedded with shale and is especially characterized by a large number of organic reefs or buildups that occur widely in the research area. The reefs have different thicknesses ranging from 0.5 m to 11.5 m and lengths varying from 1 m to 130 m. The reef‐building organisms include Archaeoscyphia, Recepthaculitids, Batostoma, Cyanobacteria and Pulchrilamina. Through the research of characteristics of the reef‐bearing strata of the Early Ordovician in the Yichang area, four sorts of biofacies are recognized, which are (1) shelly biofacies: containing Tritoechia‐Pelmatozans community and Tritoechia‐Pomatotrema community; (2) reef biofacies: including the Batostoma, Calathium‐Archaeoscyphia, Pelmatozoa‐Batostoma, Archeoscyphia and Calathium‐Cyanobacteria communities; (3) standing‐water biofacies: including the Acanthograptus‐Dendrogptus and Yichangopora communities; and (4) allochthonous biofacies: containing Nanorthis‐Psilocephlina taphocoense community. The analysis of sea‐level changes indicates that there are four cycles of sea‐level changes during the period when reef‐bearing strata were formed in this area, and the development of reefs is obviously controlled by the velocity of sea‐level changes and the growth of accommodation space. The authors hold that reefs were mostly formed in the high sea level periods. Because of the development of several subordinate cycles during the sea‐level rising, the reefs are characterized by great quantity, wide distribution, thin thickness and small scale, which are similar to that of Juassic reefs in northern Tibet. The research on the evolution of communities shows that succession and replacement are the main forms. The former is favorable to the development of reefs and the latter indicates the disappearance of reefs.

Phase-lagged amplitude modulation of hemipelagic cycles: A potential tool for recognition and analysis of sea-level change

Many ancient rhythmic hemipelagic sequences have been interpreted to record orbital variations, but the exact nature of the climatic and depositional transfer functions responsible for this link remains poorly understood. Two-dimensional numerical simulations were used to explore selected aspects of orbital signal distortion in linked siliciclastic and hemipelagic systems. The models suggest that transfer of multiorder (e.g., 20, 100, and 400 k.y.) oscillations in relative sea level into the hemipelagic record produces an inherent amplitude distortion of the shorter-period (e.g., 20 k.y.) cycle. This distortion gives rise to amplitude modulation (AM), which is qualitatively similar to AM of orbitally driven changes in insolation (e.g., eccentricity modulation of precession-driven cycles). However, unlike the orbitally driven AM, synthesized AM is distinctly phase shifted relative to the stratigraphic record of the long-period (e.g., 100 k.y., 400 k.y.) cycle as a result of sealevel‐driven changes in the storage capacity of nearshore through alluvial parts of the source siliciclastic system. Hence, multiorder changes in sea level can leave a distinct AM signature in dilution-affected hemipelagic records, thus making hemipelagic rhythms due to eccentricity-forced sea-level changes distinguishable from other types of orbitally driven hemipelagic cyclicity.

Stratigraphic correlation of Miocene to Plio-/Pleistocene sequences on the New Jersey shelf based on petrophysical measurements from ODP leg 174A

Ocean Drilling Program (ODP) Leg 174A is the latest of a series of drilling operations forming a transect from the New Jersey shelf to the slope, and designed for analysis of sea-level changes and calibration of seismic profiles. Two sites on the outer shelf and one on the upper slope were drilled. Sand-prone units reduced core recovery and caused technical problems during drilling. Downhole measurements were undertaken at all three drill sites and the interpretation of logging data in terms of sequence stratigraphy is the focus of this study. Our logging data provide a continuous record; filling the gaps in core recovery and resulting in an enhanced image of the drilled sequences. The development of sequences and their lateral changes are characterized by changes in the physical properties of the sediments, such as total natural gamma radiation and resistivity. However, the interpretation of the total gamma ray log can be misleading, since glauconite, a potassium-rich clay, is locally enriched in all types of sediments. Therefore, it is essential to use the individual potassium, thorium and uranium logs, which contribute to the total gamma radiation. Within sequences, cyclic changes in grain size reflected in the spectral gamma ray and resistivity logs are interpreted to indicate small-scale sea-level changes. Lateral changes in sediment successions are well observed on the shelf and the slope. In addition to the logs, the magnetic susceptibility, measured continuously on the cores, is a helpful indicator of facies changes. The variation in magnetic susceptibility with depth is important for hole-to-hole correlation and complements the core and log analyses.

Relative land-sea-level changes in southeastern England during the Pleistocene

During the Pleistocene, a period covering the last two million years, sea level is known to have risen above and fallen below the present sea level. The evidence for such fluctuations comes from marine and estuarine sediments, including beaches, far above present sea level and from freshwater sediments, beaches and valley systems now submerged. In southeast England there are Lower Pleistocene marine deposits at 183 m O.D . at Netley Heath in Surrey and upper Pleistocene freshwater sediments at - 35 m O.D . in the Channel. Thus we have in this area evidence of an amplitude of sea-level fluctuation relative to the present sea level of some 218 m. While such limits of relative sea-level fluctuation are not so difficult to identify, very considerable difficulties arise in determining the relation of sea-level change to the passage of time, and in the analysis of sea-level change - whether it be a real lowering of sea level relative to land, or an uplift of land relative to sea level. Let us briefly consider each of these two fields of difficulty. To date a particular stand of sea level, we have to know the relation of a particular deposit, say beach or shallow marine sediment to sea level at the time, and we have to know the correlation of this deposit to a part of the sequence of geological events which make up the Pleistocene. Both of these aspects may be problematical. It may not be certain what depth of water a deposit was formed in, and the age and correlation of the deposit may be doubtful.