SEPARATION OF CLIMATIC FLUCTUATIONS AND IMPACTS OF ENGINEERING ACTIVITIES IN ESTUARIES

Using salinity as an example of dissolved substances in estuarine waters it is shown how the long term trend of concentrations can be split up into a man-made and a climatic contribution. The understanding of long term mixing processes and adequate sampling techniques are essential for this purpose. The physical state of the estuary can be described in terms of 3 basic variables, the river discharge, the filtered water level and the filtered salinity. The river discharge represents the climatic fluctuations in the catchment area, and the filtered water level is a record of the large scale weather pattern over the adjacent ocean basin. Salinity trends which cannot be attributed to these two variables must originate from man-made actions, such as dredging or other engineering activities which change the geometry of an estuary. Two models are used for the trend analysis, the simplest possible mixing equation (which always holds for a sufficiently long time scale), and a salt flux consideration.

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Natural Analogues: Their Application to the Prediction of the Long-Term Behavior of Nuclear Waste Forms

MRS Proceedings ◽

10.1557/proc-84-67 ◽

1986 ◽

Vol 84 ◽

Cited By ~ 22

Author(s):

Rodney C. Ewing ◽

Michael J. Jercinovic

Keyword(s):

Nuclear Waste ◽

Borosilicate Glass ◽

Large Scale ◽

Laboratory Data ◽

Waste Form ◽

Long Time ◽

Natural Analogues ◽

Long Term Behavior ◽

Nuclear Waste Forms

AbstractOne of the unique and scientifically most difficult aspects of nuclear waste isolation is the extrapolation ofshot-term laboratory data (hours to years) to the long time periods (103-105 years) required by regulatory agencies for performance assessment. The direct verification of these extrapolations is not possible, but methods must be developed to demonstrate compliance with government regulations and to satisfy the lay public that there is a demonstrable and reasonable basis for accepting the long-term extrapolations. Natural analogues of both the repository environment (e.g. radionuclide migration at Oklo) and nuclear waste form behavior (e.g. alteration of basaltic glasses and radiation damage in minerals) have been used to demonstrate the long-term behavior of large scale geologic systems and, on a smaller scale, waste form durability. This paper reviews the use of natural analogues to predict the long-term behavior of nuclear waste form glasses. Particular emphasis is placed on the inherent limitations of any conclusions that are based on “proof” by analogy. An example -- corrosion of borosilicate glass -- is discussed in detail with specific attention to the proper and successful use of natural analogues (basaltic glass) in understanding the long-term corrosion behavior of borosilicate glass.

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Preliminary Study on Long-Term Flooding After the Tsunami

Journal of Disaster Research ◽

10.20965/jdr.2017.p0741 ◽

2017 ◽

Vol 12 (4) ◽

pp. 741-747

Author(s):

Toshitaka Baba ◽

Junichi Taniguchi ◽

Noriko Kusunoki ◽

Manabu Miyoshi ◽

Hiroshi Aki ◽

...

Keyword(s):

Numerical Analysis ◽

Large Scale ◽

Water Exchange ◽

Ground Surface ◽

Flow Modeling ◽

Tsunami Waveforms ◽

Long Time ◽

Preliminary Study ◽

Nankai Earthquake

After the Nankai earthquake in 1946, the resultant flooding lasted for a long time, because seawater remained on land after the tsunami in Kochi city. Large-scale flooding occurred in Ishinomaki city immediately after the Great East Japan Earthquake in 2011. Long-term flooding may hamper disaster responses such as rescue and recovery activities. This paper studied the risks of long-term flooding after the Nankai earthquake in Tokushima city based on a paleographical survey and numerical analysis. The paleographical survey identified statements such as “seawater sometimes flowed onto the land at the full tide,” suggesting occurrences of long-term flooding after previous Nankai earthquakes. The numerical analysis separately calculated values inside and outside the levee. The tsunami waveforms outside the analysis area obtained by tsunami numerical simulation was used as the boundary condition of the inland flow modeling, that is water was introduced inside the levee when the tsunami water level exceeded the upper end of the levee. The two layers of ground surface and the drain were defined to calculate the flow, including water exchange between the two layers, and the water was drained forcefully outside the levee using a drainage pump. The possibility of long-term flooding in the analysis area is suggested when a large-scale earthquake occurs in the Nankai trough.

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Trends in the Seaward Extent of Saltmarshes across Europe from Long-Term Satellite Data

Remote Sensing ◽

10.3390/rs11141653 ◽

2019 ◽

Vol 11 (14) ◽

pp. 1653 ◽

Cited By ~ 4

Author(s):

Marieke Liesa Laengner ◽

Koen Siteur ◽

Daphne van der Wal

Keyword(s):

Satellite Data ◽

Large Scale ◽

Open Water ◽

Classification Performance ◽

Environmental Drivers ◽

Decision Tree Classification ◽

Time Period ◽

Long Time ◽

Water Level Variations

Saltmarshes provide crucial functions for flora, fauna, and humankind. Thus far, studies of their dynamics and response to environmental drivers are limited in space and time. Satellite data allow for looking at saltmarshes on a large scale and over a long time period. We developed an unsupervised decision tree classification method to classify satellite images into saltmarsh vegetation, mudflat and open water, integrating additional land cover information. By using consecutive stacks of three years, we considered trends while taking into account water level variations. We used Landsat 5 TM data but found that other satellite data can be used as well. Classification performance for different periods of the Western Scheldt was almost perfect for this site, with overall accuracies above 90% and Kappa coefficients of over 0.85. Sensitivity analysis characterizes the method as being robust. Generated time series for 125 sites across Europe show saltmarsh area changes between 1986 and 2010. The method also worked using a global approach for these sites. We reveal transitions between saltmarsh, mudflat and open water, both at the saltmarsh lower edge and interior, but our method cannot detect changes at the saltmarsh-upland boundary. Resulting trends in saltmarsh dynamics can be coupled to environmental drivers, such as sea level, tidal currents, waves, and sediment availability.

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Understanding Long-Term Changes of Coastal Saltmarshes from Satellite Remote Sensing

10.5194/egusphere-egu2020-2570 ◽

2020 ◽

Author(s):

Marieke Laengner ◽

Daphne van der Wal

Keyword(s):

Satellite Remote Sensing ◽

Large Scale ◽

Open Water ◽

Google Earth ◽

Environmental Drivers ◽

Decision Tree Classification ◽

Tidal Forces ◽

Time Period ◽

Long Time

Saltmarshes are known to be very important coastal ecosystems. They provide crucial functions for flora and fauna, as well as valuable ecosystem services for humankind. Many methods that are used to investigate these ecosystems are limited in space and time. Long time series of global satellite data enable to observe changes in the extent of saltmarshes on a large scale and over a long time period. We developed an unsupervised decision tree classification method in Google Earth Engine that automatically classifies satellite images into saltmarsh vegetation, mudflats, and open water. We applied the method using Landsat 5 TM data between 1985 and 2011. With this, we are able to detect trends in the seaward extent of saltmarshes globally. We reveal transitions between saltmarsh, mudflat and open water. Furthermore, we put saltmarsh habitat changes in a spatial context and couple trends in saltmarsh dynamics to environmental drivers, such as sea level rise, tidal forces, waves, and sediment availability.

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Influence of river pattern and sediment input on estuary morphology

10.5194/egusphere-egu2020-7238 ◽

2020 ◽

Author(s):

Anne Baar ◽

Elena Bastianon ◽

Lisanne Braat ◽

Daniel Parsons

Keyword(s):

River Discharge ◽

Large Scale ◽

Numerical Models ◽

Sediment Supply ◽

Tidal Amplitude ◽

Model Studies ◽

Braiding Index ◽

Sediment Input ◽

River Pattern

Alluvial estuaries are dynamic landscapes that are very sensitive to changes in boundary conditions such as river discharge and sediment supply. A better understanding of the influence of upstream river discharge and sediment input on the development of estuaries under various scenarios requires long-term morphodynamic models, to both predict future changes and improve geological interpretations by storing the stratigraphy. Past 1D model studies have shown that upstream river discharge has a significant effect on the equilibrium bed profile of estuaries, but these studies ignore the effect of 2D bar and channel formation. Using 2D numerical models to predict the development of these systems on the scale of millennia proved to be difficult, since the modelled morphology is very sensitive to the choice in e.g. sediment transport predictor and bed slope effect. In this study, we use the knowledge of previous research that determined best parameter settings for realistic river and bar patterns to model long-term and large-scale estuary morphodynamics in Delft3D. Our objective is to quantify the effects&#160;of river discharge and sediment supply on the shape of estuaries and its deposits. Firstly, we systematically varied upstream river width and tidal amplitude to examine the relation between upstream river pattern and estuary dimensions. We quantified e.g. braiding index, bar dimensions, and tidal excursion length. Results show that flood flow velocities and tidal prism are less influenced by river discharge than suggested by 1D models, and are significantly influenced by the braiding index of the river. With relatively high tides, estuary bar patterns depend on tidal amplitude, while with lower tides estuary depth and braiding index are related to upstream river width and discharge. Next steps will include varying discharge to study the effect on the rate of adaptation of the river and estuary, and varying the grain size of the sediment input at the upstream boundary. We will input coarse sediment to explore differences between fluvial deposits and tidal currents, and fine sediment to use the model for research related to biofilm.

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A Numerical Investigation on Tidally Induced Sediment Transport and Morphological Changes with Changing Sea Level in South-East England

Geosciences ◽

10.3390/geosciences9030140 ◽

2019 ◽

Vol 9 (3) ◽

pp. 140

Author(s):

Nicoletta Leonardi ◽

Xiaorong Li ◽

Iacopo Carnacina

Keyword(s):

Sediment Transport ◽

Sea Level Rise ◽

Water Level ◽

Sea Level ◽

Large Scale ◽

Morphological Changes ◽

Morphological Evolution ◽

Morphodynamic Equilibrium ◽

South East England

The impact of tide-induced morphological changes and water level variations on the sediment transport in a tidally dominated system has been investigated using the numerical model Delft3D and South-East England as a test case. The goal of this manuscript is to explore the long-term changes in morphology due to sea level rise and the large-scale morphodynamic equilibrium of the South-East England. Our results suggest that the long term (century scale) tidally-induced morphological evolution of the seabed slows down in time and promotes a vanishing net transport across the large scale system. Century-scale morphologically updated simulations show that both morphological changes and net transport values tend to decrease in time as the system attains a dynamic equilibrium configuration. Results further suggest that the presence of a gradual increase in mean sea level accelerates the initial morphological evolution of the system whose morphological rate of change gradually attains, however, same plateau values as in the absence of sea level rise. Given the same base morphology, increasing water levels enhance residual currents and the net transport near the coastline; and vice-versa, decreasing sea levels minimize both residuals and net transport near the coastline. The areas that are more affected by, water level and morphological changes, are the ones where the net transport is the highest. This manuscript explores and allows extending the idea of morphodynamic equilibrium at a regional scale, larger than the one for which this concept has been generally explored i.e., estuarine scale.

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Holocene Climate Variability in Antarctica Based on 11 Ice-Core Isotopic Records

Quaternary Research ◽

10.1006/qres.2000.2172 ◽

2000 ◽

Vol 54 (3) ◽

pp. 348-358 ◽

Cited By ~ 239

Author(s):

Valérie Masson ◽

Françoise Vimeux ◽

Jean Jouzel ◽

Vin Morgan ◽

Marc Delmotte ◽

...

Keyword(s):

Time Trend ◽

Ross Sea ◽

Ice Core ◽

Ice Cores ◽

West Antarctica ◽

Climatic Fluctuations ◽

Long Time ◽

Long Term Trends ◽

Isotopic Records

A comparison is made of the Holocene records obtained from water isotope measurements along 11 ice cores from coastal and central sites in east Antarctica (Vostok, Dome B, Plateau Remote, Komsomolskaia, Dome C, Taylor Dome, Dominion Range, D47, KM105, and Law Dome) and west Antarctica (Byrd), with temporal resolution from 20 to 50 yr. The long-term trends possibly reflect local ice sheet elevation fluctuations superimposed on common climatic fluctuations. All the records confirm the widespread Antarctic early Holocene optimum between 11,500 and 9000 yr; in the Ross Sea sector, a secondary optimum is identified between 7000 and 5000 yr, whereas all eastern Antarctic sites show a late optimum between 6000 and 3000 yr. Superimposed on the long time trend, all the records exhibit 9 aperiodic millennial-scale oscillations. Climatic optima show a reduced pacing between warm events (typically 800 yr), whereas cooler periods are associated with less-frequent warm events (pacing >1200 yr).

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Ecological research and large scale land-atmosphere feedbacks: lesson from the Bouchet's complementary relationship

Biogeosciences Discussions ◽

10.5194/bgd-8-6077-2011 ◽

2011 ◽

Vol 8 (3) ◽

pp. 6077-6094

Author(s):

E. Lugato ◽

G. Alberti ◽

B. Gioli ◽

J. O. Kaplan ◽

A. Peressotti ◽

...

Keyword(s):

Large Scale ◽

Water Cycle ◽

Potential Evapotranspiration ◽

Short Term ◽

Global Water Cycle ◽

Long Time ◽

Large Scale Land ◽

Global Vegetation ◽

Term Analysis

Abstract. Acceleration of the global water cycle over recent decades, which is hypothesized by several studies, remains uncertain because of the high inter-annual variability of its components. Observations of pan evaporation (Epan), a proxy of potential evapotranspiration (ETp), may help to identify trends in the water cycle over long time periods. The complementary relation (CR; Bouchet, 1963) states ETp and actual evapotranspiration (ETa) depend on each other in a complementary manner, through land-atmosphere feedbacks in water limited environments. Using a long time series of Epan observations in Australia, we estimated monthly ETa values using the CR and compared our estimates with ETa measured at eddy covariance stations in Fluxnet. Our results confirm that CR can be reliably applied to estimate ETa and produces better results than a global vegetation model run without specific calibration. In addition, our analysis indicated that, on average, ETa did not show any significant trend between 1975 and 2009 in Australia, but short-term analysis including anomaly periods may give the idea of a rapid climate change that is not perceived in a long-term perspective.

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Estimation of River Discharge using Multi-Mission Satellite Altimetry and Optical Remote Sensing Imagery

10.5194/egusphere-egu2020-2650 ◽

2020 ◽

Author(s):

Daniel Scherer ◽

Christian Schwatke ◽

Denise Dettmering

Keyword(s):

Remote Sensing ◽

Time Series ◽

Water Level ◽

River Discharge ◽

Water Surface ◽

Satellite Altimetry ◽

Remote Sensing Data ◽

Sensing Data

Despite increasing interest in monitoring the global water cycle, the availability of in-situ discharge time series is decreasing. However, this lack of ground data can be compensated by using remote sensing techniques to observe river discharge.In this contribution, a new approach for estimating the discharge of large rivers by combining various long-term remote sensing data with physical flow equations is presented. For this purpose, water levels derived from multi-mission satellite altimetry and water surface extents extracted from optical satellite images are used, both provided by DGFI-TUM&#8217;s &#8220;Database of Hydrological Time series of Inland Waters&#8221; (DAHITI, https://dahiti.dgfi.tum.de). The datasets are combined by fitting a hypsometric curve in order to describe the stage-width relation, which is then used to derive the water level for each acquisition epoch of the long-term multi-spectral remote sensing missions. In this way, the chance of detecting water level extremes is increased and a bathymetry can be estimated from water surface extent observations. Below the minimum hypsometric water level, the river bed elevation is estimated using an empirical width-to-depth relationship in order to determine the final cross-sectional geometry. The required flow gradient is computed based on a linear adjustment of river surface slope using all altimetry-observed water level differences between synchronous measurements at various virtual stations along the river. The roughness coefficient is set based on geomorphological features quantified by adjustment factors. These are chosen using remote sensing data and a literature decision guide.Within this study, all parameters are estimated purely based on remote sensing data, without using any ground data. In-situ data is only used for the validation of the method at the Lower Mississippi River. It shows that the presented approach yields best results for uniform and straight river sections. The resulting normalized root mean square error for those targets varies between 10% to 35% and is comparable with other studies.

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Water Volume Variations Estimation and Analysis Using Multisource Satellite Data: A Case Study of Lake Victoria

Remote Sensing ◽

10.3390/rs12183052 ◽

2020 ◽

Vol 12 (18) ◽

pp. 3052

Author(s):

Yi Lin ◽

Xin Li ◽

Tinghui Zhang ◽

Nengfang Chao ◽

Jie Yu ◽

...

Keyword(s):

Water Resources ◽

Water Level ◽

Satellite Data ◽

Large Scale ◽

Water Cycle ◽

Lake Victoria ◽

Ecological Environment ◽

Water Volume ◽

Lake Area

The spatiotemporal changes of lake water resources objectively reflect not only the process of the water resources balance, but also the ecological environment changes in the lake area. In recent decades, climate changes and human activities have caused great impacts on the spatial distribution of the earth’s water resources and the spatiotemporal process of the surface water cycle, which has caused a series of ecological crises and environmental problems, such as the drying-up of inland lakes, the disappearance of the oasis, water shortage or flooding and water pollution. Therefore, monitoring and fully understanding the dynamic changes of lakes is of great scientific significance for grasping regional water balance, water resources management, and sustainable development of the ecological environment. In this study, we focus on using multi-source satellite data on the estimation of water volume and multi-timescale variations analysis for large scale lakes. This study combines the problems in the practical application of “African Water Action”, taking the largest lake in Africa, Lake Victoria, as the study area, and utilizes long-term serial multi-source satellite data of the past 15 years (2003–2017), including Moderate-resolution Imaging Spectroradiometer (MODIS), Jason-1/-2/-3 and Gravity Recovery and Climate Experiment (GRACE) to perform the comprehensive analysis on the water volume change estimation. Firstly, the satellite altimetry data of Jason-1/-2/-3 and MODIS imagery was used to calculate series of water level, and to extract series of water surface area, respectively. On this basis, a more accurate regression model between the area and water level variation (ΔH) was constructed. Then, the model between water volume variation (ΔV) and ΔH, derived from area-ΔH model, was applied to calculate the relative water volume of Lake Victoria. Meanwhile, terrestrial water storage (TWS) changes between 2003 and 2016, derived from GRACE data, were also used for a comparative verification of the ΔV results. The results show the long-term series change trends of ΔV and the TWS are the same. Finally, the multi-timescale analysis of water volume changes was carried out on different time scales, such as the inter-annual, inter-monthly, and variation period.

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