scholarly journals Spatial patterns of linear and nonparametric long-term trends in Baltic sea-level variability

2012 ◽  
Vol 19 (1) ◽  
pp. 95-111 ◽  
Author(s):  
R. V. Donner ◽  
R. Ehrcke ◽  
S. M. Barbosa ◽  
J. Wagner ◽  
J. F. Donges ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Sea Level ◽  
Spatial Patterns ◽  
Tide Gauge ◽  
Sufficient Information ◽  
Sea Level Variability ◽  
Advantages And Disadvantages ◽  
Long Term Trends ◽  
The Impact

Abstract. The study of long-term trends in tide gauge data is important for understanding the present and future risk of changes in sea-level variability for coastal zones, particularly with respect to the ongoing debate on climate change impacts. Traditionally, most corresponding analyses have exclusively focused on trends in mean sea-level. However, such studies are not able to provide sufficient information about changes in the full probability distribution (especially in the more extreme quantiles). As an alternative, in this paper we apply quantile regression (QR) for studying changes in arbitrary quantiles of sea-level variability. For this purpose, we chose two different QR approaches and discuss the advantages and disadvantages of different settings. In particular, traditional linear QR poses very restrictive assumptions that are often not met in reality. For monthly data from 47 tide gauges from along the Baltic Sea coast, the spatial patterns of quantile trends obtained in linear and nonparametric (spline-based) frameworks display marked differences, which need to be understood in order to fully assess the impact of future changes in sea-level variability on coastal areas. In general, QR demonstrates that the general variability of Baltic sea-level has increased over the last decades. Linear quantile trends estimated for sliding windows in time reveal a wide-spread acceleration of trends in the median, but only localised changes in the rates of changes in the lower and upper quantiles.

scholarly journals Geodetic SAR for Height System Unification and Sea Level Research—Observation Concept and Preliminary Results in the Baltic Sea

2020 ◽  
Vol 12 (22) ◽  
pp. 3747
Author(s):  
Thomas Gruber ◽  
Jonas Ågren ◽  
Detlef Angermann ◽  
Artu Ellmann ◽  
Andreas Engfeldt ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Sea Level ◽  
Tide Gauge ◽  
The Baltic Sea ◽  
Early Results ◽  
Height System ◽  
First Results ◽  
The Baltic ◽  
Sea Area ◽  
The Impact

Traditionally, sea level is observed at tide gauge stations, which usually also serve as height reference stations for national leveling networks and therefore define a height system of a country. One of the main deficiencies to use tide gauge data for geodetic sea level research and height systems unification is that only a few stations are connected to the geometric network of a country by operating permanent GNSS receivers next to the tide gauge. As a new observation technique, absolute positioning by SAR using active transponders on ground can fill this gap by systematically observing time series of geometric heights at tide gauge stations. By additionally knowing the tide gauge geoid heights in a global height reference frame, one can finally obtain absolute sea level heights at each tide gauge. With this information the impact of climate change on the sea level can be quantified in an absolute manner and height systems can be connected across the oceans. First results from applying this technique at selected tide gauges at the Baltic coasts are promising but also exhibit some problems related to the new technique. The paper presents the concept of using the new observation type in an integrated sea level observing system and provides some early results for SAR positioning in the Baltic sea area.

scholarly journals Use of Oceanic Reanalysis to Improve Estimates of Extreme Storm Surge

2019 ◽  
Vol 36 (11) ◽  
pp. 2205-2219 ◽  
Author(s):  
Li Zhai ◽  
Blair Greenan ◽  
Richard Thomson ◽  
Scott Tinis
Keyword(s):  
Sea Level ◽  
Storm Surge ◽  
West Coast ◽  
Large Scale ◽  
Tide Gauge ◽  
Steric Effects ◽  
Tide Gauge Records ◽  
The West ◽  
Sea Level Variability

AbstractA storm surge hindcast for the west coast of Canada was generated for the period 1980–2016 using a 2D nonlinear barotropic Princeton Ocean Model forced by hourly Climate Forecast System Reanalysis wind and sea level pressure. Validation of the modeled storm surges using tide gauge records has indicated that there are extensive areas of the British Columbia coast where the model does not capture the processes that determine the sea level variability on intraseasonal and interannual time scales. Some of the discrepancies are linked to large-scale fluctuations, such as those arising from major El Niño and La Niña events. By applying an adjustment to the hindcast using an ocean reanalysis product that incorporates large-scale sea level variability and steric effects, the variance of the error of the adjusted surges is significantly reduced (by up to 50%) compared to that of surges from the barotropic model. The importance of baroclinic dynamics and steric effects to accurate storm surge forecasting in this coastal region is demonstrated, as is the need to incorporate decadal-scale, basin-specific oceanic variability into the estimation of extreme coastal sea levels. The results improve long-term extreme water level estimates and allowances for the west coast of Canada in the absence of long-term tide gauge records data.

scholarly journals Trait-Based Models of Decomposition with Interspecific and Environmental Interactions

2021 ◽  
Vol 267 ◽  
pp. 02029
Author(s):  
SiYu Liu ◽  
RuiXi Wang ◽  
LuYao Dong
Keyword(s):  
Robustness Analysis ◽  
Grey System Theory ◽  
Niche Width ◽  
Extension Rate ◽  
Grey System ◽  
Advantages And Disadvantages ◽  
Environmental Interactions ◽  
Long Term Trends ◽  
The Impact

Most saprotrophic fungi are dominant decomposers, and they play a vital role in the carbon cycle and stability of ecosystem. Previous researchers examined that how traits and environments influence the decomposition rate(DR), but few studies last long enough to scale short-term results up to long-term trends. In this paper, we build several trait-based models of decomposition with interspecific and environmental interactions to describe both short- and long-term trends. First, we build the model of decomposition ratio versus time with covariates – hyphal extension ratio and moisture tolerance for each species. Second, we define Interspecific Interference Ratio (IIR) to reflect interactions between fungi species and rank the relative competitiveness based on Grey System Theory with four evaluation indices: hyphal extension rate, moisture niche width, the hyphal density and thermal niche width. Then, we predict the relative advantages and disadvantages for different species by IIR and analyze the impact of biodiversity. Finally, we perform sensitivity and robustness analysis of our models, which exhibits the wide prospects and a deeper understanding of the role of fungi in the ecosystem.

Annual and inter-annual sea-level variability from coastal altimetry and tide gauge data

2021 ◽  
Author(s):  
Anara Kudabayeva ◽  
Michael Schindelegger ◽  
Rui M. Ponte ◽  
Bernd Uebbing
Keyword(s):  
Sea Level ◽  
Ocean Circulation ◽  
Tide Gauge ◽  
Low Frequency ◽  
Altimeter Data ◽  
Altimetry Data ◽  
Tide Gauges ◽  
Sea Level Variability ◽  
Short Scale ◽  
The Impact

<p> <span>Accurate long-term measurements of coastal sea level are fundamental for understanding changes in ocean circulation and assessing the impact of low-frequency sea-level variability on, e.g., near-shore ecosystems, groundwater dynamics, and coastal flooding. However, tide gauges are sparsely distributed in space and the extent to which satellite altimetry data can be used to infer the complex patterns of sea level near the coast is a subject of debate. Here, we revisit earlier attempts of connecting tide gauge and altimetry observations of low-frequency sea-level changes across the coastal zone. Our interest lies both in short-scale spatial structures indicative of dynamic decoupling between coastal areas and the deep ocean, and in the benefits of using a reprocessed, coastal altimetry product (X-TRACK) for the analysis. The mean annual cycle is chosen as a first benchmark and more than 200 globally distributed tide gauges are examined. We compute statistics between tide gauge and along-track altimeter series within spatial radii of 20 km (“coastal”) and 134 km of the tide gauge location, and additionally split altimetry data inside the 134-km circle into “shallow” and “deep” groups relative to the 200-m isobaths. Globally averaged RMS (root-mean-square) differences in the “coastal” and “shallow” categories are 1.9 and 2.4 cm for the X-TRACK product, somewhat lower than the corresponding values from the non-optimized Integrated Multi-Mission Ocean Altimeter Data for Climate Research Version 4.2 (2.3 and 2.6 cm). Examination of inter-annual sea-level variability from 1993 to 2019 is underway, with initial focus on regions where poor correspondence between satellite and tide gauge sea-level estimates has been noted in the past (e.g., US East Coast and western South America). At most locations analyzed so far, RMS differences decrease and correlations improve as one approaches the coast along the satellite tracks. However, the X-TRACK estimates tend to become erratic within 20–30 km from the tide gauge, suggesting that the usability of classical nadir altimetry measurements for studying short-scale coastal dynamics is still limited despite ongoing reprocessing efforts.</span></p>

scholarly journals Overlapping sea level time series measured using different technologies: an example from the REDMAR Spanish network

2014 ◽  
Vol 14 (3) ◽  
pp. 589-610 ◽  
Author(s):  
B. Pérez ◽  
A. Payo ◽  
D. López ◽  
P. L. Woodworth ◽  
E. Alvarez Fanjul
Keyword(s):  
Time Series ◽  
Sea Level ◽  
Tide Gauge ◽  
Sampling Strategies ◽  
Tide Gauges ◽  
Sea Levels ◽  
Tsunami Detection ◽  
The Impact

Abstract. This paper addresses the problems of overlapping sea level time series measured using different technologies and sometimes from different locations inside a harbour. The renovation of the Spanish REDMAR (RED de MAReógrafos) sea level network is taken here as an example of the difficulties encountered: up to seventeen old tide gauge stations have been replaced by radar tide gauges all around the Spanish coast, in order to fulfil the new international requirements on tsunami detection. Overlapping periods between old and new stations have allowed the comparison of records in different frequency ranges and the determination of the impact of this change of instrumentation on the long-term sea level products such as tides, surges and mean sea levels. The differences encountered are generally within the values expected, taking into account the characteristics of the different sensors, the different sampling strategies and sometimes the different locations inside the harbours. However, our analysis has also revealed in some cases the presence of significant scale errors that, overlapping with datum differences and uncertainties, as well as with hardware problems in many new radar gauges, may hinder the generation of coherent and continuous sea level time series. Comparisons with nearby stations have been combined with comparisons with altimetry time series close to each station in order to better determine the sources of error and to guarantee the precise relationships between the sea level time series from the old and the new tide gauges.

scholarly journals Sea-Level Variability in the Gulf of Naples and the “Acqua Alta” Episodes in Ischia from Tide-Gauge Observations in the Period 2002–2019

Water ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2466
Author(s):  
Berardino Buonocore ◽  
Yuri Cotroneo ◽  
Vincenzo Capozzi ◽  
Giuseppe Aulicino ◽  
Giovanni Zambardino ◽  
...  
Keyword(s):  
Sea Level ◽  
Tide Gauge ◽  
Tyrrhenian Sea ◽  
Sea Level Changes ◽  
Sea Level Variability ◽  
Gulf Of Naples ◽  
Tidal Constituents ◽  
Global Sea Level ◽  
Basic Features ◽  
The Impact

This work presents an 18-year-long (2002–2019) tide-gauge dataset collected on the Island of Ischia (Gulf of Naples, Southern Tyrrhenian Sea) that can contribute to the analysis of the basic features of sea-level variability in this region. Analysis of tidal constituents shows that the Gulf of Naples is characterized by the absence of any amphidromic system. In this area, sea-level changes due to the astronomical component of the tide are generally limited to ±20 cm with respect to the mean sea level, but the impact of this variability is enhanced by global sea-level increase and the effect of regional atmospheric perturbations that might also triple sea-level variations. The effects of these events, whose frequency has increased in recent decades, has been dramatic in coastal areas where intense social and economic activity occurs, e.g., in Ischia. On interannual time scales, the results indicate that the relative sea-level rise in Ischia has a magnitude of 3.9 mm/year. Special attention is dedicated to the “acqua alta” episodes and to their linkage with long-term sea-level trends and atmospheric forcing.

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