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Sea-level Trend Analysis for Coastal Management
Abstract
A proper coastal management requires an accurate estimation of sea level trends locally and globally. It is claimed that the sea levels are rising following an exponential growth since the 1990s, and because of that coastal communities are facing huge challenges. Many local governments throughout Australia, including those on the coast, have responded to the various warnings about changes in climate and increases in sea levels by undertaking detailed climate change risk management exercises. These exercises, which use projections passed on by the relevant state bodies, are expensive, but still a fraction of the cost of the capital works that they recommend. Several councils have complained to an Australian Productivity Commission report on climate change adaptation they do not have the money for the capital works required. It is shown here that the exponential growth claim is not supported by any measurement of enough length and quality when properly analysed. The tide gauge results do not support the exponential growth theory. The projections by the relevant state bodies should therefore be revised by considering the measurements and not the models to compute the future sea level rises for the next 30 years following the same trend experienced over the last 30 years.
... The world tide gauges have different inter-annual and multi-decadal periodicities of up to quasi-60 years (Chambers et al. 2012;Parker et al. 2013;Parker 2013aParker , b, 2014. Chambers et al. (2012) examined the long tide gauge records in every ocean basin to find that there is a significant oscillation with a period around 60-years in most the tide gauges examined and that it appears in every ocean basin. ...
... The only sampled region with no apparent quasi-60-year fluctuation in the analysis by Chambers et al. (2012) was the Central/Eastern North Pacific. Parker et al. (2013) indicated the need to use at least 60 years of data to infer reasonable trends of sea-level rise by using global and Australian data. Parker (2013a) analysed the sea-level trends at those locations in the USA with more than 100 years of recording to conclude that the sea levels have been only oscillating since the start of the twentieth century, with significant multi-decadal periodicities on both the Pacific and Atlantic Coasts. ...
... Other approaches have been proposed to compute the sea-level acceleration (see, e.g. Parker et al. 2013 or http:// tidesandcurrents.noaa.gov/sltrends). ...
Long records of sea level show decadal and multi-decadal oscillations of synchronous and asynchronous phases, which cannot be detected in short-term records. Without incorporating these oscillations, it is impossible to make useful assessments of present global accelerations and reliable predictions of future changes of sea level. Furthermore, it is well known that local sea-level changes occur also because of local factors such as subsidence due to groundwater or oil extraction, or tectonic movements that may be either up or down.
... One solution to this problem could lie in the use of compact autonomous depth sensing data loggers (fish tags) which, when combined with high resolution GPS, can give precision data for scattered sites (Mossman et al. 2012c). It should also be noted that there are gaps to be filled at the large scale in relation to the analysis of long term sea level changes and that assumptions of exponential growth may not be well founded (Parker et al. 2013). ...
... Reference has already been made to the need to consider the accessibility of managed realignment sites in terms of the import of seeds or other propagules of key salt marsh species (Boorman et al. 2002). It was also noted that this process may also be affected by changes in climate (Green et al. 2009) as well as changes in the rates of sea level rise (Parker et al. 2013). It is suggested that a combination of techniques incorporating the planting of species likely to have slow establishment rates and the encouragement of natural colonisers and taken with surveys of seed sources will provide guidance as to the necessity of further steps. ...
... There is a need for more accurate models and predictions of sea level rise (Parker et al. 2013). They report that the results from models used to predict sea level rise by some local governments in Australia are not in agreement with many measurements made by tide gauges. ...
Managed re-alignment of sea defences is seen as the way to strengthen these by rationalising the line between land and sea and creating a buffer of inter-tidal habitat in front of them. This buffer is most commonly salt marsh which absorbs wave energy thus protecting the defences. The global area of salt marsh is in decline due to a range of issues and managed re-alignment is a way of creating or recreating this important habitat. This review examines managed re-alignment schemes in the light of salt marsh loss, rising sea levels and a changing climate. The ecosystem services and benefits provided by salt marsh can be assessed and given a monetary value. Managed re-alignment can be an important tool for salt marsh creation and coastal zone management. The number and size of schemes in the UK has increased in recent years but the area of recreated salt marsh is still insufficient to replace that lost by erosion and other processes. Background data from a proposed site, and adjacent areas likely to be affected, need to be collected prior to embarking on a scheme that may prove successful. Stakeholder interests cannot be neglected and there will also be a need for long-term monitoring. Re-created salt marshes may form an effective sea defence buffer but they remain significantly different from adjacent natural marshes for many years both in their vegetation and functional equivalence.
... Sea level rise scenarios of 1 to 7 m by 2100 due to melting glaciers and thermally expanding ocean masses are possible only with warming that is implausible because while the as carbon dioxide emissions grow exponentially, global temperatures are naturally oscillating [1][2][3][4][5][6][7] , measurements of mean sea levels from long term tide gauges are free of any acceleration [1,2,[8][9][10] , the temperature and salinity of the world oceans 0-2000 m has not changed over the first decade it has been measured [11] and while the Arctic ice sheets are reducing, the Antarctic ice sheets are actually expanding over the 35 years they have been monitored by satellite [12] . ...
... Even if the IPCC continues to support the theory that the carbon dioxide emission is warming the planet exponentially and global sea levels are exponentially accelerating because of thermal expansion and melting of glaciers, during this century of lack of any warming in properly measured temperatures [1][2][3][4][5][6][7]15] , lack of any acceleration in properly measured sea levels [1,2,[8][9][10]15,[18][19][20][21][22][23][24][25][26][27][28][29][30] , and lack of any loss of ice sheets [11] , it does not appear likely that the sea levels will rise more than the few centimetres of the past century during this century no matter what the carbon dioxide emissions could be. ...
... The situation only marginally improves in the second half of the 1800s, where the supporting tide gauges are still restricted to very few locations. While the number of stations used is less than 10 in the first part of the 1800s, it is larger than 200 in the second half of the 1900s. This is the reason why the ST curve of the study of Olivieri and Spada [34] has a decreasing sea level 1810 to 1830, and then a rising sea level 1830 to present, with a positive averaged acceleration, further boosted by using many recent short records for high rates of rise areas as the Pacific. ...
The near future of coastal life is threated by the claim of global warming alarmist that sea levels
will rise by one to seven metres by 2100, destroying many coastal cities and habitats. This paper
shows that sea levels will more likely rise no more than just a few centimetres during this century
as the Earth defrosts from the Little Ice Age 500 years ago with a mild warming.
... The periodic oscillations of the sea levels may suggest much larger or much smaller than legitimate sea level rises if improperly accounted. It is therefore important to develop a proper mathematical framework to compute a rate of rise for the relative sea level depurated of the oscillations, and then to separate the land subsidence component from the long term component due to the thermal expansion of the oceans and the mass addition from melting of ices [1][2][3][4][5], i.e. the global warming component. ...
... The implication for policy makers and environmental managers of the global warming component is what makes small differences extremely relevant. If on a worldwide basis, the tide gauge signals do not show significant acceleration components, as it has been shown in [1][2][3][4][5], then, locally, coastal planning may proceed on the basis of proven local results without any accountancy of sea level rise scenarios computed by models [21]. Conversely, if some acceleration will appear, then the use in local coastal planning of modelled global sea level rises linked to emission scenarios as [22] could become realistic and worth considering. ...
... The world tide gauges measure the local relative sea level that is oscillating with many periodicities. Because of the oscillatory behaviour, with important periodicities up to a quasi-60 years, more than 60 years of data recorded without major gaps and in absence of perturbing events are needed to infer the local relative rate of rise of the sea level and the time rate of change of this parameter representing the sea level acceleration [1,2]. ...
The tide gauges measure the local oscillations of the sea level vs. the tide gauge instrument. The tide gauge instrument is generally subjected to the general subsidence or uplift of the nearby inland, plus some additional subsidence for land compaction and other localised phenomena. The paper proposes a non-linear model of the relative sea level oscillations including a long term trend for the absolute sea level rise, another term for the subsidence of the instrument, and finally a sinusoidal approximation for the cyclic oscillations of periodicities up to decades. This non-linear model is applied to the tide gauges of China. The paper shows that the limited information available for China does not permit to infer any proper trend for the relative rates of rise, as the tide gauge records are all short or incomplete and the vertical movement of the tide gauge instruments is unassessed. The only tide gauge record of sufficient length that may be assembled for China is obtained by combining the North Point and Quarry Bay tide gauges in Hong Kong (NPQB). This NQPB composite tide gauge record is shown to have similarities with the tide gauge records of Sydney, equally in the West pacific, and San Diego, in the east Pacific, oscillating about the longer term trend mostly determined by the local subsidence. As it is very well known that China generally suffers of land subsidence, and the tide gauge installations may suffer of additional subsidence vs. the inland, it may be concluded from the analysis of the other worldwide tide gauges that the sea levels of China are very likely rising about the same amount of the subsidence of the tide gauges, with the sea level acceleration component still negligible.
... The non-accelerating sea levels worldwide and in Australia have been the subject of many papers, as [3][4][5][6]. The worldwide average of tide gauges of sufficient quality and length in the Permanent Service on Mean Sea Level (PSMSL) data base [38] show slow rise of relative sea level of 0.24 mm/year without any acceleration over the last few decades [6]. ...
... As none of the tide gauges of Victoria satisfy the minimum 60 years of data [3][4][5], the Sydney composite tide gauge with data obtained from [48] is also considered. Sydney has 2 tide gauges in same location, Fort Denison. ...
... Fig. 10 presents the monthly average mean sea levels (MSL) measured in Sydney, the history of the relative rate of rise computed in Sydney since measurement started, and finally the present relative rate of rise in Sydney with a variable start of record. In addition to the measured data, the values computed by using a linear function and multiple sinusoidal functions of parameters determined by best fitting to the measured data are also shown [3]. Clearly, the measured and fitted results are very close each other and the changes of relative rate of rise are therefore fully explained by sinusoidal oscillations and not by global warming. ...
... It has been shown in recent papers, that all the long term tide gauges of the world recording the monthly sea levels since the latest 1800s -beginning of the 1900s consistently show periodic oscillations about an almost per-fectly linear trend over the last century [4][5][6][7][8][9][10][11]. The longer of these oscillations have a quasi-60 year periodicity, and it has been suggested that what has been claimed as present sea level acceleration and presently higher than before rates of rise of sea levels is only the result of the selective focusing on the latest valley to peak movement of a multi decadal oscillation [4][5][6][7][8][9][10][11]. ...
... It has been shown in recent papers, that all the long term tide gauges of the world recording the monthly sea levels since the latest 1800s -beginning of the 1900s consistently show periodic oscillations about an almost per-fectly linear trend over the last century [4][5][6][7][8][9][10][11]. The longer of these oscillations have a quasi-60 year periodicity, and it has been suggested that what has been claimed as present sea level acceleration and presently higher than before rates of rise of sea levels is only the result of the selective focusing on the latest valley to peak movement of a multi decadal oscillation [4][5][6][7][8][9][10][11]. ...
... The method is described in details in the references, in particular [7] and [11]. From a distribution of measured points x i , y i i=1,n where x is the time and y is the climate parameter of interest, the monthly average sea level or a climate index, the linear trend is first computed by linearly fitting the distribution. ...
Sea levels generally oscillate with multi-decadal
periodicities worldwide with up to the quasi-60 years detected
in many tide gauges. Nevertheless, the most part of
the literature on sea levels computes apparent rates of rise
of sea levels much larger than the legitimate by using short
time windows in selected locations only covering part of a
valley-to-peak of this multi-decadal oscillation. It is shown
in this paper that along the Pacific coast of Australia the
sea levels oscillate with a frequency close to the Southern
Ocean Index (SOI) oscillation of 19 years and a lower frequency
of about 60 years. The rates of rise of sea levels
computed by linear fitting of the data recorded since the
early 1990s in selected locations of the Australian Pacific
coastline and in the tropical Pacific islands are from a valley
of the peak and valley oscillations and are much higher
than the legitimate long term values.
... The sea levels around the world are rising, and it is claimed on the basis of tide gauge and satellite altimeter measurements that the global rate of rise of sea levels has been considerably increased especially over the last 25 years [1][2][3]. It has been shown in recent papers, that however all the long term tide gauges of the world recording the monthly sea levels since the second half of the 1800s or the beginning of the 1900s consistently show periodic oscillations about an almost perfectly linear trend since the beginning of the 1900s [4][5][6][7][8][9][10][11]. The longer of these oscillations has a quasi-60 year periodicity, and it has been suggested that what has been claimed as present sea level acceleration and presently higher than before rates of rise of sea levels is only the result of the selective focusing on the latest valley to peak movement of a multi decadal oscillation [4][5][6][7][8][9][10][11]. ...
... It has been shown in recent papers, that however all the long term tide gauges of the world recording the monthly sea levels since the second half of the 1800s or the beginning of the 1900s consistently show periodic oscillations about an almost perfectly linear trend since the beginning of the 1900s [4][5][6][7][8][9][10][11]. The longer of these oscillations has a quasi-60 year periodicity, and it has been suggested that what has been claimed as present sea level acceleration and presently higher than before rates of rise of sea levels is only the result of the selective focusing on the latest valley to peak movement of a multi decadal oscillation [4][5][6][7][8][9][10][11]. ...
... Further analyses of the San Franscisco tide gauge and other tide gauges of the West coast of the US and Canada may be found in [7,10,11] where it is shown that these tide gauges are all acceleration free. ...
While sea levels are known to oscillate with
multi-decadal periodicities worldwide up to quasi-60 years,
the most part of the literature on sea levels computes apparent
rates of rise of sea levels much larger than the legitimate
by using short time windows covering only part of a valleyto-
peak quasi-60 year multi-decadal oscillation. It is shown
that along the North Atlantic coast of the United States the
sea levels oscillate closely to the AMO index, and the rate
of rise of sea levels computed by linear fitting of the last
30-36 years of data is much higher than the true value. It is
also shown that similar minimum requirement of 60 years
of recording is needed along the North Pacific coast of the
US, where the longer periodicity of the oscillations is not
clearly defined; possibly for the strong ENSO signal covering
a quasi-60 years oscillation.
... Changes in the rate of global sea-level are, for example, known to be influenced by a 50-60 year rhythm related to oceanic internal variability e.g., Pacific Decadal Oscillation, PDO; Atlantic Meridional Oscillation, AMO (e.g. [5,6,7,8,9]). Long period tidal constituents (the 18.6 lunar nodal cycle, for example) also exert an influence on sea-level height (e.g. ...
... Many tide gauges are recording the relative sea levels since the 1800s and the early 1900s in coastal locations worldwide and the linear analysis of the monthly average values has been historically the method of determining the relative rate of rise [8]. Because of the quasi-60 years oscillations, [1] concluded that sea-level records longer than 60 years, and even better longer than 120 years, are required to identify any longterm trends that might, or might not, occur in the data. ...
... Because of the quasi-60 years oscillations, [1] concluded that sea-level records longer than 60 years, and even better longer than 120 years, are required to identify any longterm trends that might, or might not, occur in the data. Considering not too many tide gauges are measuring sea levels since more than 120 years ago without any quality issues, [8,2] suggested using tide gauge signals continuously covering more than 60 years without many gaps and without any perturbing event as the relocation or substitution of the tide gauge. ...
... As already written in [4][5][6], the sea levels oscillate with periodicities up to a quasi-60 years periodicity detected, possibly because the temperatures oscillate with this same periodicity [7][8][9], about a longer term trend. While this longer term trend for temperatures is possibly also a longer term oscillation [4][5][6], for the sea levels is a linear function of time. ...
... As already written in [4][5][6], the sea levels oscillate with periodicities up to a quasi-60 years periodicity detected, possibly because the temperatures oscillate with this same periodicity [7][8][9], about a longer term trend. While this longer term trend for temperatures is possibly also a longer term oscillation [4][5][6], for the sea levels is a linear function of time. While other shorter periodicities are also relevant for the temperatures and sea levels, it does not make too much sense to focus on records of sea levels shorter than 60 years to infer the sea level rate of rise, and it does make even less sense to focus only on the records started in a recent valley of a multi decadal oscillations only 20 years away as done in the Australian and South Paci c sea level monitoring projects and partially done in the paper [1] that support the use of the 1993 -2011 time window. ...
... At a certain time x k, x j is taken as (x k -20), (x k -30) or (x k -60) years respectively when computing the SLR , SLR and SLR , or as x when computing the SLR A over all the years. As shown in Figure 2 of [6], the sea level rates of rise computed at any time by using 20, 30, 60 years or all the available data are largely oscillating in long term tide gauges as Sydney and Fremantle, the only two centenary tide gauges of Australia, as a result of the decadal and multi-decadal oscillations. The SLR and SLR oscillate signi cantly, and the SLR also oscillate even if much less. ...
Even if sea levels fluctuate with decadal and
multi decadal periodicities about a linear trend without
any positive acceleration component, many papers continue
to compare different compilations of tide gauges of
different length and different locations or assemble selected
tide gauges of selected length and location to prove
that sea levels are accelerating in Australia and elsewhere
in the world when they are not.
It is proposed here a novel procedure fitting the tide gauge
data with linear and multiple sinus functions that also iteratively
completes the gaps in the recorded data with subsequent
guess of the fitted function. It is shown that the tide
gauges of Sydney and Fremantle, the only two exceeding
a century in Australia, are acceleration free and naturally
oscillating with different periodicities, phases and amplitudes
for the Indian and Pacific Ocean locations. It is also
shown that tide gauge records of length smaller than 60
years have rates of rise differing considerably from the legitimate
long term trends, and these values may change
significantly from an update to the other because of the
natural oscillations. It is definitively assessed that tide
gauge records of length about 20 years, with a starting
point at the time of a valley of one peak and valley multi
decadal oscillation for the specific of the most part of the
coastline of Australia, return completely unrealistic values
for the rate of rise of sea levels. The only reliable assessment
of sea level trends along the coastline of Australia
continues to be the determination of the rate of rise by linear
fitting of all the available data in all the available station,
providing the total numbers of years recorded exceed
at least 25 years to make the population significant, as historically
done by theNational Tide Centre of theAustralian
Bureau of Meteorology prior of the censored 2009 survey.
While some changes are expected in the individual values
of the rate of rise fromone of these surveys to the other, and
the introduction of new stations satisfying the 25 years requirement
could also affect the average tide gauge result,
these sea level surveys conducted without cherry picking
the station and the time window generally provide about
same average sea level rates of rise survey after survey.
... Here the rate of sea-level returns as the slope b. This classic approach needs enough length of recorded data to avoid the computation of longterm sea-level rise variation from a valley to a peak of a multidecadal oscillation (Parker et al. 2013). Now if we fit the above the y t and t in a quadratic equation such as: ...
... However, detection of acceleration presence or absence is possible by monthly or yearly average sealevel graph, or it can be detected by monthly or yearly linear trend versus deviations. Assessment of negative or positive acceleration is impossible without considering the monthly departure from the parabolic trend (Parker et al. 2013). ...
The study investigates sea-level measurements observed from 12 tide gauge sites over the Indian coastal area during the last two decades. Initially, the rise of sea-level (slope) and acceleration is estimated by fitting the linear and parabolic equations in the recorded data from tide gauge measurements. The estimated results show the abrupt change of relative sea-level measurements at the distinct site depends upon the tide gauge site locations. To accurately analyse the regional coastal sea level pattern, the tide gauge time series data are decomposed in sine and cosine functions at different frequencies followed by the spectral analysis. Analysis of the results confirm that the tide gauges peaks do not occur at the fixed period at each tide gauge site, instead they repeat with varying time periods. The spectrum peaks width fluctuate at distinct sites and the general pattern of frequency spectrum does not follow a unique model. Such type of characteristic variation with the time is possibly because of the effective variables, which affects the steadiness of sea-level changes. The study concludes that the experimental results from the Indian coastal region must be included during the comparison of global data sets and other contemporary oceanic models.
... before 1970) and ±4 mm with a 20 cm float (after 1970). The uncertainty for the stilling well was ±25 mm for temperature and salinity layering; the bias may increase in the case of waves, marine currents around the well or growth of biofouling on the orifice (Camuffo et al. 1972;Parker 1991). The total uncertainty is mostly due to the well; it might have been around ±50 mm in the early period, ±35 mm from 1923 to 1970 and ±29 mm after 1970. ...
... The exponential is another, but controversial, candidate to describe the RSL in times of global warming (Parker et al. 2013;Hunter 2014), possibly related to the ice mass loss from the most vulnerable ice (Hansen et al. 2016). The equation y = h o + C exp. (λt) is determined by a starting level that for Venice is h o = −1866 ± 146 mm, an amplification coefficient C = 67 ± 32 mm, and the growth rate λ = 0.00163 ± 0.0002 year −1 . ...
The evolution of relative sea level (RSL) in Venice, Italy, is crucial for the safeguarding of the city and it is now possible to extend our knowledge back to 1350, including the whole Little Ice Age and modern global warming. The existing tide gauge record is extensive, going back to 1871, but it is affected by the superposition of multidecadal swings and short-term fluctuations, including both natural and manmade forcing factors. A biological proxy, i.e. the green algae belt reported on paintings made with the help of a camera obscura by the Venetian painters Canaletto and Bellotto (eighteenth century) and Veronese (sixteenth century), helps us to go back to 1571. This paper presents an exceptionally long series (i.e. 664 years) and adds a novel proxy: the submersion of water stairs of the historic palaces facing the Grand Canal. Originally, the bottom step of the water stairs was built in relation to the sea level and the slippery algae belt, while today, the water stairs are mostly submerged. An underwater survey of 78 water stairs has provided new data about the RSL since 1350. The results show that RSL in Venice was always rising at an increasingly fast rate. By subtracting local land subsidence (LLS) from RSL, absolute (eustatic) sea level (ASL) has been calculated. For both RSL and ASL, the apparent acceleration is +0.0030 ± 0.0004 mm year⁻². This figure becomes unstable when the record length is reduced. A discussion is made about the interpolation functions, i.e. the second-order polynomial and the exponential that provide almost the same best-fit over the common period. The RSL and ASL trend lines and the possibility of turning points are also discussed and compared with other scholarly studies. A eustatic turning point is suggested for the mid fifteenth century, consistent with the literature. However, the comparison between scholarly papers is difficult due to geographic and geological differences between sites and record durations.
... If the time series of the monthly average mean sea levels de-trended vs. the linear trend are decomposed with a series of sinusoidal components, the amplitude, periodicity and phase of the sinusoids changes from area to area, with however often quasi-20 and quasi-60 years' periodicities evidenced [20]. ...
... While ocean and atmospheric patterns are certainly related, we do not certainly expect that the sea levels oscillate same of atmospheric pressure, temperature or rainfall. We already wrote [19,20,24], as many other did, that the time series from the Pacific tide gauges exhibit strong multidecadal variabilities of quasi-20 and quasi-60 years, with however variables phases and amplitudes across the Pacific ocean. Relevant teleconnections for the Pacific are El Nińo/Southern Oscillation (ENSO), a periodic fluctuation in sea surface temperature and atmospheric pressure in the equatorial Pacific Ocean, and the Pacific Decadal Oscillation (PDO) a long-lived El Nino-like pattern of Pacific climate variability. ...
The major cause of the Hawaiian Islands coastal erosion is shown to be not global warming, but the sinking of the volcanic islands. The geologic “circle-of-life” beyond the Hawaiian hot spot is the true explanation of the beach erosion. The sea levels are slow rising and not accelerating worldwide as well as in the United States. In the specific of the Hawaii Islands, they have been decelerating over the last 3 decades because of the phasing of the multi-decadal oscillations for this area of the Pacific. There is therefore no evidence coastal erosion will double in the Hawaii by 2050 because of global warming.
... Sea levels have long been measured by tide gauges and tide gauge records of sufficient length permit the computation of reliable relative rates of rise or fall of sea levels (Parker et al. 2013, Parker 2014. The relative sea level at the tide gauge is largely variable from one location to another because of the different subsidence at the tide gauge, the different record length and the different phasing of the inter-annual and multi-decadal oscillations. ...
... As is well known ,the climate indices oscillate with a quasi-60 years periodicity (Schlesinger, Ramankutty 1994) and the sea levels also oscillate worldwide with a quasi-60 years periodicity, of different amplitudes and phases from one tide gauge to the other (Chambers et al. 2012). Tide gauge records of length less than 60 years may overestimate or underestimate the relative rate of rise (Parker et al. 2013, Parker 2014. Considering only the tide gauges with 60 years of data, these 170 tide gauges have a naïve averaged relative sea level rise of +0.248 mm/year with maximum of +9.060 mm/year and minimum of -13.250 mm/ year. ...
We show here the presence of significant “coldspot” of sea level rise along the West Coast of the United States and Canada (including Alaska). The 30-years sea level for the area are mostly falling also at subsiding locations as San Francisco and Seattle where subsidence is responsible for a long term positive rate of rise. The 20 long term tide gauges of the area of length exceeding the 60-years length have a naïve average rate of rise −0.729 mm/year in the update 30-Apr-2015, down from −0.624 mm/year in the update 14-Feb-2014. Therefore, along the West Coast of the United States and Canada the sea levels are on average falling, and becoming more and more negative.
... In this context, we note that the contested study of Boretti [2012] uses second-order polynomials only. The same holds for Parker et al. [2013] who propose to fit an exponential growth curve over the period 1990-2100. ...
... Furthermore, a central topic in the debate is a lack of acceleration in relation to future projections. Some authors claim that the lack of accelerations (or the presence of small decelerations) in tide gauge data questions future projections such as given by the IPCC [e.g., Houston and Dean, 2011a, 2011b, 2011c, 2011dBoretti, 2012;Parker et al., 2013]. However, such conclusions do not take uncertainties into account and neglect the fact that the anthropogenic signal in projections requires decades to become distinguishable from climate noise [Dangendorf et al., 2014b;Haigh et al., 2014;Lyu et al., 2014;Richter and Marzeion, 2014]. ...
Global sea levels have been rising through the past century and are projected to rise at an accelerated rate throughout the 21st century. This has motivated a number of authors to search for already existing accelerations in observations, which would be, if present, vital for coastal protection planning purposes. No scientific consensus has been reached yet as to how a possible acceleration could be separated from intrinsic climate variability in sea level records. This has led to an intensive debate on its existence and, if absent, also on the general validity of current future projections. Here we shed light on the controversial discussion from a methodological point of view. To do so, we provide a comprehensive review of trend methods used in the community so far. This resulted in an overview of 30 methods, each having its individual mathematical formulation, flexibilities, and characteristics. We illustrate that varying trend approaches may lead to contradictory acceleration-deceleration inferences. As for statistics-oriented trend methods, we argue that checks on model assumptions and model selection techniques yield a way out. However, since these selection methods all have implicit assumptions, we show that good modeling practices are of importance too. We conclude at this point that (i) several differently characterized methods should be applied and discussed simultaneously, (ii) uncertainties should be taken into account to prevent biased or wrong conclusions, and (iii) removing internally generated climate variability by incorporating atmospheric or oceanographic information helps to uncover externally forced climate change signals.
... Therefore it is important to use the regional projections of SLR for simulating the hydrodynamic model to obtain appropriate predictions of future extreme events. Parker et al. (2013) estimated relative sea level trends for 47 tide gauges around Australia which have more than 25 years of recorded data. To the best of our knowledge, this is the most up-to-date and accurate study of sea level trends for this study area. ...
... To the best of our knowledge, this is the most up-to-date and accurate study of sea level trends for this study area. According to the recommendation of Parker et al. (2013), a 1.95 mm/year projected SLR has been considered in this study for the development of scenarios. ...
Flood modelling of a large basin like the Fitzroy is a difficult task due to its large catchment size, the long duration of flood events, the non-uniform spatial distribution of rainfall and a lack of required data for modelling purposes. This paper presents a systematic methodology for the flood modelling of the Fitzroy Basin using hydrologic and hydrodynamic modelling approach with Geographic Information System (GIS) capabilities. This study developed five flood scenarios analysing historical flood events and considering three impacts of climate change: upstream subcatchments flooding, local rainfall fluctuations and sea level rise. A hydrologic model was developed within the wider Fitzroy Basin with the five upstream subcatchments and the upper Fitzroy subcatchment in order to simulate discharge data for these scenarios at the Gap measurement location. An integrated hydrologic-hydrodynamic model was developed for the lower Fitzroy subcatchment where output discharges of the hydrologic model were considered as the upstream boundaries. The peak flood levels, peak flow rates and flood inundation durations at Rockhampton city were identified using this integrated model. GIS capabilities were specially used for automatic watershed delineation and river cross-section extraction from Digital Elevation Model (DEM) data. The methodology proposed here is a case study and can be applied to other similar basins or catchments. © 2015 The Chartered Institution of Water and Environmental Management (CIWEM) and John Wiley & Sons Ltd.
... All the measurements of sea levels indicate a smooth behaviour made up of shorter term oscillations about a longer term rise almost linear without any sign of the sharp departure postulated by the models. (Watson 2011;Houston and Dean 2011;Donner 2012;Boretti 2012a,b;Watson 2012, 2013;Jevrejeva, Moore, Grinsted and Woodworth 2008;Mörner 2004Mörner , 2007Mörner , 2010aMörner ,b, 2011aGray 2010;Daly 2000;Testut et al. 2010;Unnikrishnan & Shankar 2007;Parker 2013a,b,c;Parker et al. 2013 are some of the recent papers challenging the abrupt sea level acceleration theory understandably disregarded in the forthcoming IPCCWGI Fifth Assessment Report). ...
... Without considering the monthly departures from the parabolic trend, the assessment of positive or negative present accelerations is impossible, but again the visual scanning of the departures is not a quantitative truly scientific approach. A better methodology has been proposed by Parker (2013a,b,c) and Parker et al. (2013). . At any time, a rate of rise of sea levels may be computed by linear fitting of all the data collected up to that time, or the last 20, 30, 40, 50 or 60 years recorded. ...
Many recent papers claim that the climate model-based projections made until the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC) yielding a 21st century rise spanning nearly 20–60 cm are likely to underestimate sea-level change in response to rapid climatic variations. These authors project the sea-level rise of 2100 and beyond with semi-empirical methods coupled to a simple climate model finding that sea level is predicted to rise by at least ∼ 80 cm at the end of this century and is expected to continue rising for at least the next two hundred years. It is pointed out in this comment that there has been so far no sign in any measured quantity of the positive acceleration predicted by the climate models since the 1990 and the lower bounds to sea level rises in the next few decades in every worldwide location are therefore simply the continuation of the linear trend locally measured up to present.
... In Figure 2 are the reconstructed monthly average global air temperatures for the land and sea surface (from [9]), plus the values corrected as explained in [10,11] for the GISS warming exceeding the measured warming in rural and remote areas with long, unbiased, temperature records. Figure 2 also shows the monthly averaged mean sea levels measured in San Francisco and Bergen, two of the long term tide gauge records in the world all free of any acceleration [12,13]. ...
... The relative sea levels measured by the long term tide gauges over the last 100 years are characterized by oscillations with many periodicities up to a quasi-60 years about an almost perfectly linear trend. Clearly, without at least 60 years of data, the rate of rise of sea level by linear tting is impossible to compute, and this rate of rise may be subject to uctuations without representing any global thermal expansion trend but only as the result of the oscillations [12,13]. For San Francisco, the relative rate of rise is positive, Figure 2c. ...
Popular semi empirical formulae link the rate of
rise of sea level to the global land and sea surface temperature.
The physical and mathematical incongruences of
these formulations are discusses in the paper. It is shown
that the rate of rise of sea levels due to thermal expansion
is actually proportional to the time rate of change of the
average temperature of the oceans. It is also shown that
since the start of the ARGO project in the early 2000s, the
temperature and salinity 0 to 2000 metres depth have not
changed at all. This result, plus the stable global surface
air temperatures and stable sea ice extent for the North
and South Poles from the satellite, all suggest that since
the early 2000s there has been no sea level rise due to the
warming of the oceans or the melting of ices.
... There are regional variations and these variations have been dominated by thermal expansion since the 1990s, as well as other factors, such as, ocean salinity and responses from the Earth's crust from the last deglaciation. Sea-level rise in Australia for the period 1920e2000 was approximately 1.2 mm per year, which is less than the global average for this period (Church et al., 2006;Parker et al., 2013). However, the rise in Australian sea levels is believed to have been less than the global average from the mid-1970s to the mid-1990s because of more frequent ENSO events, but has recently exceeded this average from the end of the 20th century (Church et al., 2006). ...
... Fluctuations caused by climate variability can mask long-term sea-level rise on records that are less than three decades in length. Therefore, it is desirable to have records of least at 60 yrs in length (Douglas et al., 2001;Parker et al., 2013;Scafetta, 2013). Sophisticated methods are necessary to analyse them rather than simply linearly regressing the fluctuations (M€ orner, 2004) and a large number of tidal stations are required to counter geographic bias in the results. ...
... Therefore, alternative methods have been devised, e.g. using variable windows and sliding the window year-by-year along the observation period (Jevrejeva et al. 2014). An exponential equation was proposed to represent the sea level trend for coastal management in Australia, but this caused a dispute between Parker et al. (2013) and Hunter (2014). ...
The paper discusses the equations used to represent the sea level rise, and in particular the second-order polynomial, generally preferred because its second-order coefficient is related to acceleration. The long series of the sea level rise in Venice offers a particularly useful case study from 1350 to 2016, because it may be equally represented, at the same level of explained variance, by an exponential or a quadratic best-fit equation. The first-order and the second-order derivatives, respectively, represent the rate and the acceleration of sea level rise. The derivatives obtained from the second-order polynomial representation generate a linear rate and a constant acceleration, while those derived from an exponential preserve the exponential character. The two rates (i.e. from the quadratic and the exponential equations), and the two accelerations are characterized by different equations and different plots, but their average values are the same. The second-order polynomial with constant acceleration is in line with a climate with constant forcing factors; the exponential with a dynamic condition with increasing forcing factors and acceleration. Mathematical formulae and physical consequences are discussed in the framework of different scenarios. Finally, the trend-forecast extrapolation is discussed and applied to the case study of Venice. It is shown that, in the most optimistic assumption of forcing increasing at unchanged rate, the sea level in Venice will rise by 33.8 ± 4 cm over this century. This extrapolation is compared to the most recent projections of the Intergovernmental Panel on Climate Change (IPCC).
... As a long-term variation, studies on sea level rise emphasized more on the rise process, rather than the final sea level. For instance, both linear and parabolic growth of sea level rise were considered by Parker et al. [50] for coastal management purposes. ...
A tidal lagoon system has multiple environmental, societal, and economic implications.To investigate the mechanism of influence of the geomorphological evolution of a tidal lagoon, theeffect of critical erosion shear stress, critical deposition shear stress, sediment settling velocity, andinitial bed elevation were assessed by applying the MIKE hydro- and morpho-dynamic model to atypical tidal lagoon, Qilihai Lagoon. According to the simulation results, without sediment supply,an increase of critical erosion, deposition shear stress, or sediment settling velocity gives rise to tidalnetworks with a stable terrain. Such an equilibrium state can be defined as when the change of neterosion has little variation, which can be achieved due to counter actions between the erosion anddeposition effect. Moreover, the influence of the initial bed elevation depends on the lowest tidallevel. When the initial bed elevation is below the lowest tidal level, the tidal networks tend to befully developed. A Spearman correlation analysis indicated that the geomorphological evolution ismore sensitive to critical erosion or deposition shear stress than sediment settling velocity and initialbed elevation. Exponential sea level rise contributes to more intensive erosion than the linear or theparabolic sea level rise in the long-term evolution of a tidal lagoon.
... The significant consequences of coastal erosion have been addressed in several studies on extreme events, coastal vulnerability, climate change adaptation and coastal resilience (e.g. Ranasinghe and Stive, 2009;Chust et al., 2010;Mulder et al., 2011;Parker et al., 2013;Masselink et al., 2016). The evidence of coastal erosion worldwide is irrefutable but the rates at which it occurs are still debatable. ...
Coastal erosion in 45 sandy beaches covering nearly 2000 km along the tectonically active Chilean coast is assessed during the last four decades. The historical analysis is based on the assessment of decadal changes of the shoreline position extracted from topographic surveys, aerial photographs, satellite images and survey maps using the DSAS software. Results show that 80% of the sites presented erosion rates (>−0.2 m/y), 7% beaches accreted (>0.2 m/y) while 13% remained stable. Eroded beaches include headland bay beaches, embayed and pocket beaches. A discussion on the possible causes explaining these results is conducted. While changes in offshore wave climate are spatially smooth within the region, relative mean sea level changes are highly variable and modulated by tectonic activity; the reduction of the sediment supply explains erosion rates in few cases.
... variable windows and sliding the window year-by-year along the observation period (Jevrejeva et 23 al. 2014). An exponential equation was proposed to represent the sea level trend for coastal 24 management in Australia, but this caused a dispute between Parker et al. (2013) and Hunter (2014). 25 Basically, two different views are involved: who prefers to rely on some basic equations to follow 26 the physical process; who prefers to rely on the statistical analysis, take a long-term record and 27 determine from it the equations derived from a best-fit interpolation. ...
The paper discusses the equations used to represent the sea level rise, and in particular the second-order polynomial, generally preferred because its second-order coefficient is related to acceleration. The long series of the sea level rise in Venice offers a particularly useful case study from 1350 to 2016, because it may be equally represented, at the same level of explained variance, by an exponential or a quadratic best-fit equation. The first-order and the second-order derivatives respectively represent the rate and the acceleration of sea level rise. The derivatives obtained from the second-order polynomial representation generate a linear rate and a constant acceleration, while those derived from an exponential preserve the exponential character. The two rates (i.e. from the quadratic and the exponential equations), and the two accelerations are characterized by different equations and different plots, but their average values are the same. The second-order polynomial with constant acceleration is in line with a climate with constant forcing factors; the exponential with a dynamic condition with increasing forcing factors and acceleration. Mathematical formulae and physical consequences are discussed in the framework of different scenarios. Finally, the trend-forecast extrapolation is discussed and applied to the case study of Venice. It is shown that, in the most optimistic assumption of forcing increasing at unchanged rate, the sea level in Venice will rise by 33.8 ± 4 cm over this century, that may be compared to the 31 cm of the similar, most optimistic prediction made by IPCC for business-as-usual.
... Rahmstorf and Vermeer (2011) demonstrated using a reassessment study that there is no deceleration, and that acceleration can indeed be found if the data is analysed using different techniques with a longer time span. A similar acceleration-deceleration dichotomy is observed in Australia where the claim of deceleration in sea level rise by (Parker et al., 2013) was refuted by (Hunter, 2014). To resolve these differences, a large number of researchers have attempted to identify the best model for estimating sea level trend but in reality, there is no right answer to the 'best/right model' question since the real trend is unknown. ...
Significant developments have been made in the observation systems and techniques of estimating sea level towards meeting the standard accuracy requirement of Global Climate Observation Systems (GCOS). This study undertakes a systematic review of the current advances in estimating sea level change in the context of the 4th industrial revolution. Trends in the use of main observation systems such as tide gauges, satellite altimetry, and ancillary systems such as GNSS and Autonomous Surface Vehicles were explored. Crucially, we examined the contribution of dedicated waveform retracking strategies, advanced corrections and radar technology such as Ka-band altimetry of SARAL/Altika and SAR mode innovations to the progress in coastal altimetry. Further, we show the role of emerging spatial data science concepts and processing workflows in sea level study. Findings suggest that in-situ sea level observation through tide gauges remains the best approach for long-term coastal sea level study despite its limitations while satellite altimetry is suitable for contemporary global and regional scales. Detailed understating of global, regional and local mean sea level change will require an augmentation of tide gauge, satellite altimetry and other ancillary remote sensing and in situ systems. Densification of tide gauges and co-located GNSS networks at sparsely covered regions and improvement in precision of satellite altimetry data for coastal use are also essential for a fully integrated sea level observation system. From the analysis of over 30 trend models that span exploratory, parametric, non-parametric, stochastic and advanced classes in the literature , we conclude that the best model is the one with good statistical foundation and similar assumption with the sea level pattern.
... The coastline is the boundary line between sea and land for dividing marine area and terrestrial administrative area [1]. Measuring and monitoring coastline change is a very important and fundamental task for coastal zone management [2], and it is a major environmental safety issue for humans, such as sea level changes [3] and coastal zone evolution [4]. At the same time, the shoreline change, as one of the important parameters of various Coastal Vulnerability Indices, plays an important role in assessing the physical vulnerability of the coasts to the anticipated sea-level rise and to the climate-change related coastal hazards, such as storm surges [5][6][7][8]. ...
To meet the needs of coastline efficient extraction and dynamic monitoring, this paper proposes a new method for coastline extraction by combining the tidal level and the digital elevation model (DEM) of the coastal zone from tilt photography. Firstly, the DEM of coastal zone was obtained by using unmanned aerial vehicle (UAV) tilt photography; at the same time, the accuracy of aerial triangulation(AT) is improved referencing to the constraint of water boundary points, and then the mean high water spring tide was obtained by combining tidal harmonic analysis and Global Navigation Satellite System (GNSS) tidal level. Finally, the coastline and the dynamic water-surface line are extracted from the DEM of the coastal zone by tracking the contour lines with the elevation of the mean high water springs (MHWS) and the instantaneous sea-surface elevation, respectively. The experiments carried out in the coastal zones of Liaoning Province, China, proved the proposed method and achieved better than 0.2 m of horizontal position accuracy and 0.1m of the vertical accuracy.
... However, such efforts are usually hampered by the (a) scarcity of relevant information in many coastal areas, and (b) dearth in the necessary human and financial resources (e.g. Parker et al., 2013); this is particularly true when assessments of beach erosion are carried out over larger spatial scales. All the same, it is necessary to assess future beach retreat/erosion and flood risk at large spatial scales, in order to identify 'hot spots' and plan for effective adaptation policies and efficient allocation of resources. ...
Case study Saint Lucia, https://SIDS-port-ClimateAdapt.unctad.org
... However, such efforts are usually hampered by the (a) scarcity of relevant information in many coastal areas, and (b) dearth in the necessary human and financial resources (e.g. Parker et al., 2013); this is particularly true when assessments of beach erosion are carried out over larger spatial scales. ...
Climate Risk and Vulnerability Assessment Framework for Caribbean Coastal Transport Infrastructure - Methodology
... Long water-level records (on the order of decades) at various points on the globe reveal no strong evidence for substantial deviation from a linear rate of sea-level increase (Parker, Saleem, and Lawson, 2013). A small decrease in the rate of sealevel increase is even detected in long-term tide gauge data sets. ...
Antunes do Carmo, J.S., 2018. Climate change, adaptation measures, and integrated coastal zone management: The new protection paradigm for the Portuguese coastal zone. Journal of Coastal Research, 34(3), 687-703. Coconut Creek (Florida), ISSN 0749-0208. The efforts made to reduce the causes and mitigate the effects of global climate change continue to be critical in coastal areas. Many adaptation strategies implemented in coastal areas remain inadequate or ineffective. Using primarily events and interventions carried out along the Portuguese Atlantic coast, this work aims to show the paradigm shift that has occurred in Portugal since the last century (the 1990s) within the scope of the National Coastal Zone Management Strategy, taking into account the new guidelines for the implementation of coastal defence works. In this context, this paper also aims to assist coastal communities in carrying out operational coastal management by presenting and discussing management tools and primary options that should be considered in any adaptation programme that is to be implemented. Both nonstructural and structural measures are considered. Action plans, warning systems, emergency plans, and evacuation plans belong to the first category. Education and training are also considered, because they play a key role in the sustainability of coastal areas, especially in the coming generations. Structural measures are adaptation options that are designed to increase the safety of people and reduce risks. They are discussed and grouped into categories that include accommodation, protection, and retreat. Recent cases of successful accommodation and protection measures implemented along the Portuguese coast are also presented and discussed. ADDITIONAL INDEX WORDS: Storms, multifunctional options, management tools, public participation.
... Long water-level records (on the order of decades) at various points on the globe reveal no strong evidence for substantial deviation from a linear rate of sea-level increase (Parker, Saleem, and Lawson, 2013). A small decrease in the rate of sealevel increase is even detected in long-term tide gauge data sets. ...
The efforts made to reduce the causes and mitigate the effects of global climate change continue to be critical in coastal areas. Many of the adaptation strategies implemented in coastal areas remain inadequate or ineffective. Using primarily events and interventions carried out along the Portuguese Atlantic coast, this work aims to show the paradigm shift that has occurred in Portugal since the last century (the 1990s) within the scope of the National Coastal Zone Management Strategy and taking into account the new guidelines for the implementation of coastal defence works. In this context, this paper also aims to assist coastal communities in carrying out operational coastal management by presenting and discussing management tools and primary options that should be considered in any adaptation programme that is to be implemented. Both nonstructural and structural measures are considered. Action plans, warning systems, emergency plans and evacuation plans belong to the first category. Education and training are also considered, as they play a key role in the sustainability of coastal areas, especially in the coming generations. Structural measures are adaptation options that are designed to increase the safety of people and reduce risks. They are discussed and grouped into categories that include accommodation, protection and retreat. Recent cases of successful accommodation and protection measures implemented along the Portuguese coast are also presented and discussed.
... Therefore, assessments of the beach morphological evolution at different spatiotemporal scales are required based on advanced numerical, analytical and/or empirical models constructed and applied by experienced operators and set up/validated using appropriate field data and backed by expert analysis (e.g., Roelvink et al., 2009;Bosom and Jiménez, 2010;Ding et al., 2013). However, such efforts are usually hampered by the (a) scarcity of relevant information in many coastal areas and (b) dearth in the necessary human and financial resources (e.g., Parker et al., 2013); this is particularly true when assessments of beach erosion are carried out over larger spatial scales. Nevertheless, it is necessary to assess future beach retreat/erosion and flood risk at large spatial scales in order to identify "hot spots" and plan for effective adaptation policies and efficient allocation of resources. ...
The present contribution constitutes the first
comprehensive attempt to (a) record the spatial characteristics of the
beaches of the Aegean archipelago (Greece), a critical resource for both the
local and national economy, and (b) provide a rapid assessment of the
impacts of the long-term and episodic sea level rise (SLR) under different
scenarios. Spatial information and other attributes (e.g., presence of
coastal protection works and backshore development) of the beaches of the 58
largest islands of the archipelago were obtained on the basis of
remote-sensed images available on the web. Ranges of SLR-induced beach
retreats under different morphological, sedimentological and hydrodynamic
forcing, and SLR scenarios were estimated using suitable ensembles of
cross-shore (1-D) morphodynamic models. These ranges, combined with
empirically derived estimations of wave run-up induced flooding, were then
compared with the recorded maximum beach widths to provide ranges of
retreat/erosion and flooding at the archipelago scale. The spatial
information shows that the Aegean pocket beaches may be particularly
vulnerable to mean sea level rise (MSLR) and episodic SLRs due to (i) their narrow widths
(about 59 % of the beaches have maximum widths < 20 m), (ii) their limited terrestrial sediment supply, (iii) the substantial coastal
development and (iv) the limited existing coastal protection. Modeling
results indeed project severe impacts under mean and episodic SLRs, which by
2100 could be devastating. For example, under MSLR of 0.5 m – representative concentration pathway (RCP)
4.5 of the Fifth Assessment Report (AR5) of the Intergovernmental Panel on
Climate change (IPCC)
– a storm-induced sea level rise of 0.6 m is projected to result in a complete
erosion of between 31 and 88 % of all beaches (29–87 % of beaches
are currently fronting coastal infrastructure and assets), at least temporarily.
Our results suggest a very considerable risk which will require significant
effort, financial resources and policies/regulation in order to
protect/maintain the critical economic resource of the Aegean archipelago.
... However, such efforts are usually hampered by the (a) scarcity of relevant information in many coastal areas, and (b) dearth in the necessary human and financial resources (e.g. Parker et al., 2013); this is particularly true when assessments of beach erosion are carried out over large spatial scales. All the same, it is Nat. ...
The present contribution constitutes the first comprehensive attempt to (a) record the spatial characteristics of the beaches of the Aegean Archipelago (Greece), a critical resource for both the local and national economy; and (b) provide a rapid assessment of the impacts of the long-term and episodic sea level rise (SLR), under different scenarios. Spatial information and other attributes (e.g. presence of coastal protection works and backshore development) of the beaches of the 58 largest islands of the Archipelago were obtained on the basis of remote-sensed images available in the web. Ranges of SLR-induced beach retreats under different morphological, sedimentological and hydrodynamic forcing and SLR scenarios were estimated, using suitable ensembles of cross-shore (1-D) morphodynamic models. These ranges, combined with empirically-derived estimations of wave run up-induced flooding, were then compared with the recorded maximum beach widths, to provide ranges of retreat/erosion and flooding at the Archipelago scale. The spatial information shows that the Aegean beaches may be particularly vulnerable to mean (MSLR) and episodic SLRs due to: (i) their narrow widths (about 59 % of the beaches have maximum widths
... The inconsistency between the reconstructed GMSL that are continuously accelerating over the twentiethcentury and the actual measurements at the tide gauges has been noticed in many papers by the author and others (see to name but a few). We recall here only as an example the works [2][3][4][5][6][7][8][9][10][11][12][13][14][15]. ...
Contrary towhat is claimed by reconstructions of the Global Mean Sea Level (GMSL) indicating accelerating sea level rates of rise over the twentieth-century, the actual measurements at the tide gauges show the sea levels have not risen nor accelerated that much. The most recent estimation by Hay et al. [1] of the twentieth-century global mean sea level (GMSL) rise is the last attempt to give exact reconstructions without having enough information of the state of the world oceans over a century where unfortunately the good measurements were not that many. The information on relative rates of rise at the tide gauges and land subsidence of global positioning system (GPS) domes suggest the relative rate of rise is about 0.25 mm/year, without any detectable acceleration. [The naive average of all the world tide gauges of sufficient quality and length of the Permanent Service to Mean Sea Level (PSMSL) data base], Both the relative rates of rise at the tide gauges and the land vertical velocity of GPS domes of the Systeme d’Observation du Niveau des Eaux Littorales (SONEL) data base are strongly variable in space and time to make a nonsense the GMSL estimation.
... For example, the vertical stability of the Australian continent and its suitability as a datum for MSL observations has been debated for decades [e.g., Emery, 1986, 1988;Bryant et al., 1988;Amin, 1993;Belperio, 1993;Feng et al., 2004;Sandiford, 2007;Moucha et al., 2008;Watson, 2011;Lewis et al., 2012]. Hay et al. [2015], Haigh et al. [2014], Hogarth [2014], Holgate and Woodworth [2004], Jevrejeva et al. [2014], Jord a [2014], Merrifield et al. [2009], Olivieri and Spada [2013], Watson et al. [2015], and Woodworth et al. [2009and Woodworth et al. [ , 2011; those that claim deceleration include Boretti [2012], Boretti and Watson [2012], Parker et al. [2013], and Watson [2011]; those that claim neither include Schr€ oter [2010, 2014]. ...
A combination of independent evidence (continuous GPS, repeat geodetic leveling, groundwater abstraction, satellite altimetry and tide gauge (TG) records) shows that the long-recording Fremantle TG has been subsiding in a non-linear way since the mid-1970s due to time-variable groundwater abstraction. The vertical land motion (VLM) rates vary from approximately −2 mm/yr to −4 mm/yr (i.e., subsidence), thus producing a small apparent acceleration in mean sea level computed from the Fremantle TG records. We exemplify that GPS-derived VLM must be geodetically connected to the TG to eliminate the commonly used assumption that there is no differential VLM when the GPS is not co-located with the TG. In the Perth Basin, we show that groundwater abstraction can be used as a diagnostic tool for identifying non-linear VLM that is not evident in GPS time series alone. This article is protected by copyright. All rights reserved.
... These extreme scenarios are also valuable when the sea level rise combines with extreme climatic events, such as hurricane surge and waves (Smith et al. 2010). Many recent studies propose adaptation strategies in the planning for the future coastal communities based on the revised values of the sea level rise of 1 m, 2 m or even 5 m by the end of the century (Parker et al. 2013). Other site specific conditions such as enhanced sediment accretion (Wolanski et al. 2004) or accelerated erosion caused by human activities (Castillo et al. 2000) or related to climate change, i.e. sea-level rise and increased wind and wave activity (Kim et al. 2011), may be also implied in the response of estuarine systems to sea level rise (Pont et al. 2002) and thus, local topographic variables are needed to ameliorate predictions in a given site. ...
Background and aims – Salt marsh plant communities will be among the first to be exposed to the predicted increase in sea level and to the associated environmental changes. The objectives of this study were to evaluate the influence of three major environmental variables
(elevation above sea level, distance from the sea, vegetation age) on vegetation diversity in salt marshes and to predict vegetation changes in the year 2100 according to different scenarios of sea level rise.
Methods – Plant communities were sampled in 1257 plots of 1 m2
distributed along transects randomly positioned perpendicular to the shoreline in the Bay of Somme (Picardy, France). Digital elevation model data were used to determine the plot elevation and the distance between the plots and the shoreline. Three centuries of changes in the vegetation cover
were reconstructed using historical maps and aerial photographs to estimate the vegetation age. We investigated the relationships between elevation above sea level, distance from the sea, vegetation age and vegetation richness and composition using mixed models. Predictive models of species
richness and cover of dominant halophytes were built using the parameter estimates of the previous mixed models and the projections of the explanatory variables in 2100 according to the different sea level scenarios from +0.5 m to +2.5 m.
Key results – Mixed models showed
that species richness mainly increased with vegetation age. The halophytes exhibited contrasting patterns along elevation and age gradients. Sedimentation rates may counteract the sea level rise until the latter reaches a critical rate that drowns the marsh vegetation.
Conclusions
– Because the proportions of ancient vegetation will be higher in the bay, mean plant species richness may be higher in predicted communities in 2100 than in recently sampled communities.
... These extreme scenarios are also valuable when the sea level rise combines with extreme climatic events, such as hurricane surge and waves (Smith et al. 2010). Many recent studies propose adaptation strategies in the planning for the future coastal communities based on the revised values of the sea level rise of 1 m, 2 m or even 5 m by the end of the century (Parker et al. 2013). Other site specific conditions such as enhanced sediment accretion (Wolanski et al. 2004) or accelerated erosion caused by human activities (Castillo et al. 2000) or related to climate change, i.e. sea-level rise and increased wind and wave activity (Kim et al. 2011), may be also implied in the response of estuarine systems to sea level rise (Pont et al. 2002) and thus, local topographic variables are needed to ameliorate predictions in a given site. ...
... A mild warming of the air temperature land and sea surface is fully compatible with the slowly rising seas without any acceleration component of the long term tide gauge records (Parker, Saad Saleem & Lawson [10]; Parker [11,12]). However, air temperatures and bulk deep oceans' temperatures are di erent, and the two temperatures would change di erently if the planet would be subject to an increased heat uptake. ...
There is an overwhelming evidence for the South
Pole of stable temperatures, with all the latest news reporting
on presently cooling temperatures and increasing
ice coverage. The thermometer records for the stations of
Byrd, Bellingshausen, Novolazarevskaya, Mirny, Vostok,
Progress, Russkaya,Molodeznaya and Leningradskaya are
analysed together with the satellite measurements of surface
air temperatures and sea ice extent. The thermometer
records are often scattered data biased by heat release
and heat storage processes nearby the thermometer location,
but globally they do not support any particularwarming
trend over the full length of the records that in the best
cases is 55 years long. The satellite measurements of temperatures
and sea ice extent conversely clearly support a
cooling trend over the 35 years of the record. The Antarctic
region is undoubtely presently cooling, as the ice surrounding
Antarctica is expanding, and the coolest place
on Earth was recently discovered in Antarctica.
... Parker (2013) states that the most popular models used to estimate the impacts of climate-change are very simplistic assumption as in Rahmstorf (2007). This appears to be an incorrect transcription of the version give by Parker et al. (2013), which was the most popular models used to estimate the impacts of climate-change are based on very simplistic assumption, as for example Rahmstorf (2007). However, as indicated above and by Hunter (2013), this completely ignores the AOGCMs, and models of land ice, which together are used to generate the sea-level projections of the Intergovernmental Panel on Climate Change (IPCC). ...
The paper Lower Bounds to Future Sea-Level Rise (Parker, 2013) bears many similarities to an earlier one (Parker et al., 2013). In particular, the first pair of equations in both papers are almost identical and wrong, as pointed out by Hunter (2013). In addition, a crucial statement in the Abstract suggests that present observations of sea-level rise show no acceleration and therefore cast doubt on present projections of sea-level rise; this conclusion has previously been shown to be false (Hunter and Brown, 2013). It should be noted that this is by no means a comprehensive exploration of all the possible errors in Parker's paper.
Low frequency internal signals bring challenges to signify the role of anthropogenic factors in sea level rise and to attain a certain accuracy in trend and acceleration estimations. Due to both spatially and temporally poor coverage of the relevant data sets, identification of internal variability patterns is not straightforward. In this study, the identification and the role of low frequency internal variability (decadal and multidecadal) in sea level change of Fremantle tide gauge station is analyzed using two climate indices, Pacific Decadal Oscillation (PDO) and Tripole Interdecadal Pacific Oscillation (TPI). It is shown that the multidecadal sea level variability is anticorrelated with corresponding components of climate indices in the Pacific Ocean, with correlation coefficients of −0.9 and −0.76 for TPI and PDO, respectively. The correlations are comparatively low on decadal time scale, −0.5 for both indices. This shows that internal variability on decadal and multidecadal scales affects the sea level variation in Fremantle unequally and thus, separate terms are required in trajectory models. To estimate trend and acceleration in Fremantle, three trajectory models are tested. The first model is a simple second-degree polynomial comprising trend and acceleration terms. Low passed PDO, representing decadal and interdecadal variabilities in Pacific Ocean, added to the first model to form the second model. For the third model, decomposed signals of decadal and multidecadal variability of TPI are added to the first model. In overall, TPI represents the low frequency internal variability slightly better than PDO for sea level variation in Fremantle. Although the estimated trends do not change significantly, the estimated accelerations varies for the three models. The accelerations estimated from the first and second models are statistically insignificant, 0.006 ± 0.012 mm yr ⁻² and 0.01 ± 0.01 mm yr ⁻² , respectively, while this figure for the third model is 0.018 ± 0.011 mm yr ⁻² . The outcome exemplifies the importance of modelling low frequency internal variability in acceleration estimations for sea level rise in regional scale.
Abstract Adaptive and accurate trend estimation of the sea level record is critically important for characterizing its nonlinear variations and its study as a consequence of anthropogenic climate change. Sea level change is a nonstationary or nonlinear process. The present modeling methods, such as least squares fitting, are unable to accommodate nonlinear changes, including the choice of a priori information to help constrain the modeling. All these problems affect the accuracy and adaptability of nonlinear trend estimation. Here, we propose a method called EMD‐SSA, that effectively combines adaptive empirical mode decomposition (EMD) and singular spectrum analysis (SSA). First, the sea level change time series is decomposed by EMD to estimate the intrinsic mode functions. Second, the periodic or quasiperiodic signals in the intrinsic mode functions can be determined using Lomb‐Scargle spectral analysis. Third, the numbers of the identified periodicities/quasiperiodicities are used as embedding dimensions of SSA to identify possible nonlinear trends. Then, the optimal nonlinear trend with the largest absolute Mann‐Kendall rank is selected as the final trend for the sea level change. Based on a comprehensive experiment using simulated sea level change time series, we concluded that the EMD‐SSA method can adaptively provide better estimate of the nonlinear trend in a realistic sea level change time series with consistency or high accuracy. We suggest that EMD‐SSA can be used not only to robustly extract nonlinear trends in sea level data, but also for trends in other geodetic or climatic records, including gravity, GNSS observed displacements, and altimetry observations.
The research issue of which are the present relative and absolute rates of rise and accelerations for North America is here addressed. The data of the 20 long-term-trend (LTT) tide stations of the West Coast of North America with more than 80 years of recorded data are shown. The absolute rates of rise are computed by considering the absolute vertical velocity of Global Navigation Satellite System (GNSS) antennas near the tide gauges, and the relative rate of sea-level rise from the tide gauge signals. The 20 LTT stations along the West Coast of North America show an average relative rate of rise of -0.38 mm/yr., an average acceleration of +0.0012 mm/yr2, and an average absolute rate of rise of +0.73 mm/yr. This is the first paper publishing a comprehensive survey of the absolute sea-level rates of rise along the West Coast of North America using the reliable information of relative sea-level rates of rise from LTT tide gauges plus the absolute subsidence rates from different GNSS antennas close to the tide gauge installations.
The effects of sea level rise (SLR) are relevant to the future evolution of coasts and estuaries. This study analyses the importance of different SLR trends on the morphological evolution of a mixed-energy fine-sediment coast (the Caofeidian Sea in Bohai Bay, China) using a validated numerical model. Results show that SLR produces spatially non-uniform relative morphodynamic responses, depending on the local coastline (uninterrupted or inlet-interrupted) and wave exposure. In the Caofeidian Sea, the uninterrupted coast is exposed to wind waves and tidal currents, and SLR reduces the accretion of tidal flats via heightening waves. On the inlet-interrupted coast, the morphological response to SLR is dominated by changes in tidal asymmetry and current velocity. In low SLR scenarios, the enhanced flood tidal asymmetry makes the system initially resilient to SLR. For high SLR scenarios, tidal sediment transport capacity is dampened by the reduction in current velocities, which accelerates the degradation of tidal flats along the inlet-interrupted coast. Differences among results with eight theoretical SLR trends show that the magnitude of SLR-induced morphological change is influenced by the target value (0.5 and 1.0 m) and rising mode (abrupt growth, linear growth, parabolic growth, and exponential growth) of the SLR. A newly-introduced parameter (equivalent SLR, ESLR), which reflects the time-weighted average value of an SLR trend for a period of time, shows a strong linear relationship with SLR-induced morphological change. Results suggest that the morphological response to other SLR scenarios for the Caofeidian Sea is expected to be interpolated from the ESLR ratios without performing extra time-consuming simulations.
The relative rate of rise of the sea levels measured by a tide gauge is made of a sea and a land component. The first is usually restricted to the global short-term effect of melting icecaps and expansion of water mass due to global temperature change. The second is often limited to the regional long-term effects of glacial isostatic adjustment (GIA). Sometimes, the regional subsidence, due to compaction and ground water withdrawal, is considered. Here we show as this assumption of regional subsidence fails to represent the relative sea level patterns of Sandy Hook, NJ, and The Battery, NY, as well as of Venezia Punta Della Salute, Venezia II, Trieste and Trieste II. The subsidence of the tide gauge instrument may only be addressed by the precise monitoring of the tide gauge vs. a Global Navigation Satellite System (GNSS) antenna, even if the GNSS tracking is only recent and not yet very accurate. The relative sea level records are much more complicated than what is thought.
There are two related measures of sea level, the absolute sea level, which is the increase in the sea level in an absolute reference frame, and relative sea level, which is the increase in sea level recorded by tide gauges. The first measure is a rather abstract computation, far from being reliable, and is preferred by activists and politicians for no scientific reason. For local and global problems it is better to use local tide gauge data. Proper coastal management should be based on proved measurements of sea level. Tide gauges provide the most reliable measurements, and best data to assess the rate of change. We show as the naïve averaging of all the tide gauges included in the PSMSL surveys show “relative” rates of rise about +1.04 mm/year (570 tide gauges of any length). If we consider only 100 tide gauges with more than 80 years of recording the rise is only +0.25 mm/year. This naïve averaging has been stable and shows that the sea levels are slowly rising but not accelerating. We also show as the additional information provided by GPS and satellite altimetry is of very little help. Computations of “absolute” sea levels suffer from inaccuracies with errors larger than the estimated trends. The GPS is more reliable than satellite altimetry, but the accuracy of the estimation of the vertical velocity at GPS domes is still well above ±1 mm/year and the relative motion of tide gauges vs. GPS domes is mostly unassessed. The satellite altimetry returns a noisy signal so that a +3.2 mm/year trend is only achieved by arbitrary “corrections”. We conclude that if the sea levels are only oscillating about constant trends everywhere as suggested by the tide gauges, then the effects of climate change are negligible, and the local patterns may be used for local coastal planning without any need of purely speculative global trends based on emission scenarios. Ocean and coastal management should acknowledge all these facts. As the relative rates of rises are stable worldwide, coastal protection should be introduced only where the rate of rise of sea levels as determined from historical data show a tangible short term threat. As the first signs the sea levels will rise catastrophically within few years are nowhere to be seen, people should start really thinking about the warnings not to demolish everything for a case nobody knows will indeed happen.
Tide gauges are measuring the sea level relative to a datum in the best cases since the mid to late 1800s. Because the land is subject to isostasy or subsidy, this measure does not give the absolute but only the relative sea level fluctuations. It is shown that these relative fluctuations have many periodicities up to detected quasi-60 years, but longer periodicities may also exist, even if the records length does not permit to fully clarify. A simple but reliable procedure is presented to compute the relative sea level velocity and the relative sea level acceleration as it is needed for coastal planning.
The paper by Peterson and Li (Environ Earth Sci, doi:10.1007/s12665-014-3498-9, 2014) assumes sea level rise induced by global warming is real, and sea levels may rise by 2100 m, and they go on to derive ecological conclusions from this. We show here that sea levels are rising slowly, both worldwide and in North Carolina, based on real tide gauge data. This is unlikely to lead to any ecological catastrophes in North Carolina.
The paper revisits the Isle of the Dead benchmark and the Sydney, Fort Denison tide gauge to confirm that long term, high quality tide gauges are acceleration free, consistently to the analysis of key sites suggesting the sea levels are not sharply raising following the carbon dioxide emissions. The paper also discusses the flaws of the IPCC AR5 Chapter13 Sea levels. The time history of the relative rate of rise computed by linear fitting of the data locally collected by tide gauges is the best parameter to assess the effect of global warming providing length and quality requirements are satisfied. There is no reason to search for less reliable alternative methods because the climate models predicted different trends. The Global Positioning System (GPS) inferred vertical tide gauge velocity suffers of significant inaccuracies. Larger inaccuracies are provided by the satellite altimetry Global Mean Sea Level (GMSL) that is a computation and not a measurement.
The global mean sea level (GMSL) changes derived from modelling do not match actual measurements of sea level and should not be trusted. Compilations of individual tide gauges of sufficient quality and length provide much more reliable information. The present work is a contribution towards a better understanding of the observed of sea levels in India and its relation to worldwide observations. The latest average relative rate of rise of worldwide sea levels from a compilation of 170 stations with more than 60 years of data returns an average relative rate of rise +0.25 mm/year. The individual rates of rise are about constant in between subsequent updates suggesting the absence of any acceleration. Observation in key sites suggests a similarly stable pattern. Along the coastline of India, the average rate of rise of sea level is +1.06 mm/year computed by considering the 11 longest tide gauges of average length 51 years. Shorter records may overrate the sea level rate of rise because of the local phasing of the quasi-60-year oscillation. In the longest records, the rates of rise are decreasing since 1955. The lack of any GPS monitoring of the vertical position of the tide gauge does not permit the determination of the absolute rates of rise.
Increasing ocean heat content has been suggested on the basis of theories. Reconstructions (modelling results based on selected scattered measurements) and simulations (modelling results not based on observations) have both shown a significant warming since the year 1970 that increased at an ever faster rate over the 14 years this century. It is shown here that, contrary to this claim, the detailed measurements of the ocean temperature and salinity by the sampling buoys of the ARGO project show only minor changes of temperature and salinity since the early 2000s. The ARGO results cover the ocean layers 0–2000 m except for the North and South Poles. The satellite NSSTC surface air temperature measurements over the world oceans show a global cooling over the last 11 years, and the satellite NSDIC sea ice extent measurements show globally increasing ice coverage over the North and South Poles. The North Pole sea ice is certainly reducing, but over the last 11 years the growth of the South Pole sea ice has more than compensated that loss. The true measurements are in marked contrast to theoretical reconstructions and simulations. This result has a huge implication on coastal management that should be based on observationally derived forecasts rather than “projections” of models lacking validation.
At dawn on 20 November 1943, U.S. marines launched an assault on Tarawa,
a Japanese-held atoll in the British Protectorate of the Gilbert and
Ellice Islands. The water in the lagoon was only 3 feet deep that
morning, less than the 4-5 feet required by a fully loaded
personnel carrier to navigate the waters. As a result, marines saddled
with equipment were forced to wade almost a mile across the lagoon under
heavy Japanese fire. The United States won the Battle of Tarawa, but it
proved to be one of the bloodiest battles of the war; almost 6000
Japanese, Americans, and Gilbertese were killed in just 3 days of
fighting. Of the American fatalities, almost half occurred because U.S.
military planners ignored warnings about the local tides on the morning
of the assault [e.g., Wright, 2000].
Climate-change–based global sea-level rise is of concern because it contributes to significant loss of coastal wetlands and mangroves and to increasing damage from coastal flooding in many regions of the world. Physical mechanisms that describe the dynamic global climate systems and the effect of this system behavior on sea-level rise are inherently complex. In this study, conducted using systematic analysis of historic data on temperature change and sea-level rise, a linear dynamic system model is proposed to predict global sea-level rise and mean surface temperatures. Unlike the semiempirical approaches proposed in the recent literature, this model incorporates the inherent interaction between temperature and sea-level rise into the model. The resulting model, recognized from the historic data, shows that the rate of sea-level rise is proportional to temperature, and this rise is also a function of the temporal state of the sea level. Similarly, the rate of temperature change is a function of the temporal state of the temperature and is also affected by the sea-level rise. The proposed model is also used to predict the sea-level rise during the 21st century. DOI: 10.1061/(ASCE)HE.1943-5584.0000447. © 2012 American Society of Civil Engineers.
Morphological and stratigraphical observational facts in the Sundarban delta provide data for a novel sea level reconstruction of the area. This sea level documentation lacks traces of a global sea level rise. This implies totally new perspectives for the future of Bangladesh. No longer are there any reasons to fear an extensive sea level inundation in the near future. Sea level estimates based on linear trend analyses of tide gauge data should be avoided and seem often to be directly misleading, as was the case with previous, divergent, claims of a strong global sea level rise component.
A data archeology exercise was carried out on sea level observations recorded during the transit of Venus across the Sun observed in 1874 from Saint Paul Island (38°41′S, 77°31 E) in the southern Indian Ocean. Historical (1874) and recent (1994–2009) sea level observations were assembled into a consistent time series. A thorough check of the data and its precise geodetic connection to the same datum was only possible thanks to the recent installation of new technologies (GPS buoy and radar water level sensor) and leveling campaigns. The estimated rate of relative sea level change, spanning the last 135 years at Saint Paul Island, was not significantly different from zero (−0.1 ± 0.3 mm yr−1), a value which could be reconciled with estimates of global average sea level rise for the 20th century assuming the DORIS vertical velocity estimate at Amsterdam Island (100 km distant) could be applied to correct for the land motion at the tide gauge. Considering the scarcity of long-term sea level data in the Southern Hemisphere, the exercise provides an invaluable additional observational constraint for further investigations of the spatial variability of sea level change, once vertical land rates can be determined.
Sea-level rise rates have become important drivers for policy makers dealing with the long-term protection of coastal populations. Scenario studies suggest that an acceleration in sea-level rise is imminent. The anticipated acceleration is hard to detect because of spatial and temporal variability, which consequently, have become important research topics. A known decadal-scale variation is the 18.6-year nodal cycle. Here, we show how failing to account for the nodal cycle resulted in an overestimation of Dutch sea-level rise. The nodal cycle is present across the globe with a varying phase and a median amplitude of 2.2 cm. Accounting for the nodal cycle increases the probability of detecting acceleration in the rate of sea-level rise. In an analysis of the Dutch coast, however, still no significant acceleration was found. The nodal cycle causes sea level to drop or to rise at an increased rate; therefore, accounting for it is crucial to accurately estimate regional sea-level rise.
As an island nation with some 85% of the population residing within 50 km of the coast, Australia faces significant threats into the future from sea level rise. Further, with over 710,000 addresses within 3 km of the coast and below 6-m elevation, the implication of a projected global rise in mean sea level of up to 100 cm over the 21st century will have profound economic, social, environmental, and planning consequences. In this context, it is becoming increasingly important to monitor trends emerging from local (regional) records to augment global average measurements and future projections. The Australasian region has four very long, continuous tide gauge records, at Fremantle (1897), Auckland (1903), Fort Denison (1914), and Newcastle (1925), which are invaluable for considering whether there is evidence that the rise in mean sea level is accelerating over the longer term at these locations in line with various global average sea level time-series reconstructions. These long records have been converted to relative 20-year moving average water level time series and fitted to second-order polynomial functions to consider trends of acceleration in mean sea level over time. The analysis reveals a consistent trend of weak deceleration at each of these gauge sites throughout Australasia over the period from 1940 to 2000. Short period trends of acceleration in mean sea level after 1990 are evident at each site, although these are not abnormal or higher than other short-term rates measured throughout the historical record.
Although rising global sea levels will affect the shape of coastlines over the coming decades(1,2), the most severe and catastrophic shoreline changes occur as a consequence of local and regional-scale processes. Changes in sediment supply(3) and deltaic subsidence(4,5), both natural or anthropogenic, and the occurrences of tropical cyclones(4,5) and tsunamis(6) have been shown to be the leading controls on coastal erosion. Here, we use satellite images of South American mangrove-colonized mud banks collected over the past twenty years to reconstruct changes in the extent of the shoreline between the Amazon and Orinoco rivers. The observed timing of the redistribution of sediment and migration of the mud banks along the 1,500km muddy coast suggests the dominant control of ocean forcing by the 18.6 year nodal tidal cycle(7). Other factors affecting sea level such as global warming or El Nino and La Nina events show only secondary influences on the recorded changes. In the coming decade, the 18.6 year cycle will result in an increase of mean high water levels of 6 cm along the coast of French Guiana, which will lead to a 90 m shoreline retreat.
The western tropical Pacific is usually considered as one of the most vulnerable regions of the world under present-day and future global warming. It is often reported that some islands of the region already suffer significant sea level rise. To clarify the latter concern, in the present study we estimate sea level rise and variability since 1950 in the western tropical Pacific region (20 degrees S-15 degrees N; 120 degrees E-135 degrees W). We estimate the total rate of sea level change at selected individual islands, as a result of climate variability and change, plus vertical ground motion where available. For that purpose, we reconstruct a global sea level field from 1950 to 2009, combining long (over 1950-2009) good quality tide gauge records with 50-year-long (1958-2007) gridded sea surface heights from the Ocean General Circulation Model DRAKKAR. The results confirm that El Nino-Southern Oscillation (ENSO) events have a strong modulating effect on the interannual sea level variability of the western tropical Pacific, with lower/higher-than-average sea level during El Nino/La Nina events, of the order of +/- 20-30 cm. Besides this sub-decadal ENSO signature, sea level of the studied region also shows low-frequency (multi decadal) variability which superimposes to, thus in some areas amplifies current global mean sea level rise due to ocean warming and land ice loss. We use GPS precise positioning records whenever possible to estimate the vertical ground motion component that is locally superimposed to the climate-related sea level components. Superposition of global mean sea level rise, low-frequency regional variability and vertical ground motion shows that some islands of the region suffered significant 'total' sea level rise (i.e., that felt by the population) during the past 60 years. This is especially the case for the Funafuti Island (Tuvalu) where the "total" rate of rise is found to be about 3 times larger than the global mean sea level rise over 1950-2009.
Like any coastal nation, Maldives has always been threatened by great waves at extreme storms or, even worse, at tsunami events. In the past 4,000 years, it has experienced several short-term sea level highs in the order of +0.6-1.2 m. One cannot blame glacial eustasy for those oscillations, rather ocean dynamic factors like drastic changes in evaporation/precipitation or redistributions of the water masses. Sea level changes and coastal evolution launched an international sea level project in Maldives, partly because this is an area, where multiple sea level parameters interact and partly because this was a key area for the proposed sea level rise as a function of global warming. On the expedition by the sea level scientist, significant evidence was found that there is a rapid drop in the sea level in Maldives. On island after island, a recent redeposition of sand graded to a lower level than previously is observed. The fact that sea level fell by 20 cm in the 1970s implies that one got a fresh zero-level to explore for possible traces of movements. Observational facts do not verify the story of a rapidly rising sea level in the Maldives. On the contrary, stability in sea level is well documented for the last 30-40 years.
There is a claim that, by the end of this century, Australian coastal communities will experience rising sea levels of up to more than 1 metre because of the anthropogenic carbon dioxide emissions causing global warming. This is the major argument supporting the Australia's Carbon Tax set to become law early next year. Under this legislation, 500 large Industrial manufacturers who emit carbon dioxide will be compelled to pay, from profitable income, for every tonne of carbon dioxide. Most of these emitters are electrical power generation and mining companies and heavy industry manufacturers. To compensate households for projected rising costs, due to the increased taxing pricing caused by this Carbon Tax, the government will cut income tax for smaller industries, boost payments to pensioners and offer various lump sum payments to small companies. This Australian scheme covers approximately 60% of Australia's emissions, making it the most broad-based scheme presented to the world. This carbon pricing will affectively apply to the 22.6 million Australians (2011) living in a 7,682,300 square kilometres country which is a relatively small number, proportional to the 7 billion people worldwide. The paper shows that locally and globally measured data, collected over short and long time scales, prove that the claim of sea level sharply accelerating is false.
Hunter and Brown try to demonstrate in their discussion of the long term
tide gauge data published in my previous paper that the sea levels are
accelerating when they are not. The sea levels are mostly oscillating
and certainly not positively accelerating at the present time. As shown
in the graphs proposed here after, having an understanding of the
oscillatory behaviour of sea levels and by using linear and parabolic
fittings but not being selective in the time window to consider, the
tide gauge of Sydney exhibits clear multi decadal and inter-annual
periodicities but no detectable component of acceleration, similarly to
the many others tide gauges of the Pacific or the rest of the world
having enough quality and length. If all the long term tide gauges do
not exhibit any present accelerating pattern, possibly some simulations
and reconstructions may be wrong similarly to the selective assessment
of the sea level rise by fitting only the few years of data useful to
support the positive acceleration claim.
The paper presents the sea level rises (SLR) computed for the United States tide gauges with more than 100 years of recording. It is shown that the monthly sea levels oscillate about an almost linear longer-term trend with important multidecadal periodicities. The SLR time history is computed by linear fitting of 20, 30 and 60 years of data up to a given time (SLR20, SLR30 and SLR60) and is compared to the value obtained by considering all the data. It is shown that SLR60 has smaller oscillations, while SLR20 and SLR30 have much larger and frequent fluctuations. While SLR60 may oscillate ±10–30 % about the latest longer-term value, SLR30 may fluctuate ±50–100 % and SLR20 ± 100–200 %. The values obtained by considering all the data with a minimum of 60 years (SLRA) also fluctuate ±5–15 % about the latest longer-term value. This indicates the need to use the time history of SLR60 or SLRA when the record is longer than 60 years to assess the accelerating trend. For all the stations, the sea levels regularly oscillate about the linear longer-term trend, and if acceleration has to be computed, this is eventually negative, that is, the SLR is reducing.
It is shown in the short comment that the sea levels are oscillating about a longer-term trend and that the sea level rise (SLR) computed with time windows of 20, 30 or 60 years also oscillates, with the amplitude of these latter oscillations reducing as the time window increases. The use of only two values of the SLR distribution is misleading to infer conclusions about the accelerating behaviour. In particular, the comparison of the 30-year SLR 1950–1979 with the 30-year SLR 1980–2009 for the tide gauges along the Atlantic coast of North America north of Cape Hatteras to infer an accelerating behaviour is particularly wrong because the 30-year time window is a too short interval to appreciate the longer-term sea level trend cleared of the multi-decadal oscillations, and the two values from the SLR distribution are computed, respectively, at the times of a valley and a peak for the 60-year Atlantic Ocean multi-decadal oscillation. By using a 60-year time window or all the data since opening when more than 60 years of recording are available and by analysing the SLR time history, the only conclusion that can be inferred from the analysis of the tide gauges along the North American Atlantic coast is that the sea levels are oscillating without too much of a positive acceleration along their longer-term trend.
Sea level rise threatens to increase the impacts of future storms and hurricanes on coastal communities. However, many coastal hazard mitigation plans do not consider sea level rise when assessing storm surge risk. Here we apply a GIS-based approach to quantify potential changes in storm surge risk due to sea level rise on Long Island, New York. We demonstrate a method for combining hazard exposure and community vulnerability to spatially characterize risk for both present and future sea level conditions using commonly available national data sets. Our results show that sea level rise will likely increase risk in many coastal areas and will potentially create risk where it was not before. We find that even modest and probable sea level rise (.5 m by 2080) vastly increases the numbers of people (47% increase) and property loss (73% increase) impacted by storm surge. In addition, the resulting maps of hazard exposure and community vulnerability provide a clear and useful example of the visual representation of the spatial distribution of the components of risk that can be helpful for developing targeted hazard mitigation and climate change adaptation strategies. Our results suggest that coastal agencies tasked with managing storm surge risk must consider the effects of sea level rise if they are to ensure safe and sustainable coastal communities in the future.
The Gold Coast, Australia is a coastal resort city whose urban environment has evolved through a series of human interventions on the natural shoreline. Such cities rely on a perceived high quality environment which in turn is reliant on continuing maintenance (e.g. beach nourishment, inlet dredging, drainage). Climate change consequently holds particular challenges for coastal resort cities. Sea-level rise impacts are likely to be manifest in increased frequency of flooding and beach erosion episodes. Here we consider adaptation options for the city under various future sea-level rise (SLR) scenarios at the high end of current predictions for the next century (+1 m, +2 m and +5 m) with the proviso that the beach and waterways must be preserved to enable the city to continue to exist as a resort.We conclude that pre-planned adaptation would probably enable the city to survive SLR of 1 m. An unplanned response to the same SLR would likely be characterised by periodic crises, growing uncertainty and public unease and would have marginal chances of success. For a 2 m SLR we contend that even with an adaptation plan in place, the scale of measures required would severely stretch the city's resources. Under a 5 m SLR over the next century we do not believe that any amount of planning would enable the city to survive as a coastal resort.Any adaptation to SLR would involve increased cost to maintain the artificial coastal environment. Adaptation options are particularly constrained by the widespread development around the waterways of the back-barrier area. Unlike other coastal cities, resorts depend on a public perception of a high quality environment. Maintaining this perception under SLR imposes particular adaptation constraints on resort cities.
The government of Australia is supporting the statement that sea levels are rising faster than ever before as a result of increased carbon dioxide emissions. Consequent to this, low-lying coastal areas, where the majority of Australians are concentrated, have been declared at risk of sea level inundations. Maps with 0.5, 0.8 and 1.1 m sea level rise have been proposed for Sydney, the major Australian city. However, long term tide gauges, recording sea levels worldwide, as well as along the coastline of Australia, and within the bay of Sydney, do not show any sign of accelerating sea level rises at present time.
The combination of sea level rise and population growth in coastal regions makes it essential to continue improving flood management strategies. Flooding estimates must take into account both local vertical land motion and estimated rates of sea level rise linked to global climate change. Several extreme value distributions are compared using multiple statistical measures for the modeling of maximum annual storm surges based on the 105-year record of Galveston Pier 21, Texas. Increases in inundation frequencies are computed based on two possible sea level rise scenarios, a conservative linear continuation of the past century trend, and a scenario based on the upper limit of the sea level range in the IPCC AR4 report, i.e. the A1FI scenario. The research shows that by the year 2100 exceedance probabilities may double for the impact of the largest storms such as Hurricane Ike, but may increase by 6–7 times for the smaller surges associated locally with the impact of storms such as Hurricanes Cindy, Alicia, and Rita. While individually not as devastating or costly as large hurricanes, the cumulative and regular cost of smaller surge events could well be a bigger threat to coastal communities as sea level rises.
Climate models (http://climatecommission.govspace.gov.au/files/2011/05/4108-CC-Science-Update-PRINT-CHANGES.pdf, 2011; http://www.ipcc.ch/publications_and_data/publications_ipcc_fourth_assessment_report_synthesis_report.htm, 2011; Rahmstorf, 2007, 2010) calculate that temperatures are increasing globally and sea level rises are increasing due to anthropogenic carbon dioxide emissions. More recent predictions (http://climatecommission.govspace.gov.au/files/2011/05/4108-CC-Science-Update-PRINT-CHANGES.pdf, 2011; Rahmstorf, 2007, 2010) have forecasted that sea level rises by 2100 will be higher than the 2007 projections by the Intergovernmental Panel on Climate Change (http://www.ipcc.ch/publications_and_data/publications_ipcc_fourth_assessment_report_synthesis_report.htm, 2011), with projected sea level rises increasing from 18–59cm to 100cm. In this brief communication, the predictions of Rahmstorf (2007) are validated against the experimental evidence over a 20year period. The University of Colorado Sea Level satellite monitoring shows that the rate of rise of the sea level is not only well below the values computed in http://climatecommission.govspace.gov.au/files/2011/05/4108-CC-Science-Update-PRINT-CHANGES.pdf (2011) and Rahmstorf (2007, 2010), but actually reducing rather than increasing (http://sealevel.colorado.edu/, 2011b; 10,11). These results suggest that sea level predictions based solely on the presumed temperature evolution may fail to accurately predict the long term sea levels at the end of the century.
Positive deviations from linear sea-level trends represent important climate signals if they are persistent and geographically widespread. This paper documents rapid sea-level rise reconstructed from sedimentary records obtained from salt marshes in the Southwest Pacific region (Tasmania and New Zealand). A new late Holocene relative sea-level record from eastern Tasmania was dated by AMS14C (conventional, high precision and bomb-spike), 137Cs, 210Pb, stable Pb isotopic ratios, trace metals, pollen and charcoal analyses. Palaeosea-level positions were determined by foraminiferal analyses. Relative sea level in Tasmania was within half a metre of present sea level for much of the last 6000yr. Between 1900 and 1950 relative sea level rose at an average rate of 4.2±0.1mm/yr. During the latter half of the 20th century the reconstructed rate of relative sea-level rise was 0.7±0.6mm/yr. Our study is consistent with a similar pattern of relative sea-level change recently reconstructed for southern New Zealand. The change in the rate of sea-level rise in the SW Pacific during the early 20th century was larger than in the North Atlantic and could suggest that northern hemisphere land-based ice was the most significant melt source for global sea-level rise.
The ocean level is constantly changing and there are many different forcing functions. Today, we realize that a rise in one area may, in fact, correspond to a fall in another area. A number of problems or pit-falls in sea level analyses are highlighted; viz. the significance of shore morphology, the multiple possible causes of coastal erosion, the necessity to consider cyclic changes, not least the 18.6 tidal cycle and its relation to our tide-gauge records, the effects of redistribution of ocean water masses, the problems with many sea level curves based solely on isolation levels, and the problems of transferring time/depth graphs into rates of sedimentation and sea level rise without having investigated and calibrated for on-going consolidation in the top-part of the sediment sequence; i.e. the zone of active compaction. Therefore, the necessity of multi-parameter analyses is strongly proposed.
Without sea-level acceleration, the 20th-century sea-level trend of 1.7 mm/y would produce a rise of only approximately 0.15 m from 2010 to 2100; therefore, sea-level acceleration is a critical component of projected sea-level rise. To determine this acceleration, we analyze monthly-averaged records for 57 U.S. tide gauges in the Permanent Service for Mean Sea Level (PSMSL) data base that have lengths of 60–156 years. Least-squares quadratic analysis of each of the 57 records are performed to quantify accelerations, and 25 gauge records having data spanning from 1930 to 2010 are analyzed. In both cases we obtain small average sea-level decelerations. To compare these results with worldwide data, we extend the analysis of Douglas (1992) by an additional 25 years and analyze revised data of Church and White (2006) from 1930 to 2007 and also obtain small sea-level decelerations similar to those we obtain from U.S. gauge records.
We present a reconstruction of global sea level (GSL) since 1700 calculated from tide gauge records and analyse the evolution of global sea level acceleration during the past 300 years. We provide observational evidence that sea level acceleration up to the present has been about 0.01 mm/yr2 and appears to have started at the end of the 18th century. Sea level rose by 6 cm during the 19th century and 19 cm in the 20th century. Superimposed on the long-term acceleration are quasi-periodic fluctuations with a period of about 60 years. If the conditions that established the acceleration continue, then sea level will rise 34 cm over the 21st century. Long time constants in oceanic heat content and increased ice sheet melting imply that the latest Intergovernmental Panel on Climate Change (IPCC) estimates of sea level are probably too low.
ISSN 0749-0208. Without sea-level acceleration, the 20th-century sea-level trend of 1.7 mm/y would produce a rise of only approximately 0.15 m from 2010 to 2100; therefore, sea-level acceleration is a critical component of projected sea-level rise. To determine this acceleration, we analyze monthly-averaged records for 57 U.S. tide gauges in the Permanent Service for Mean Sea Level (PSMSL) data base that have lengths of 60–156 years. Least-squares quadratic analysis of each of the 57 records are performed to quantify accelerations, and 25 gauge records having data spanning from 1930 to 2010 are analyzed. In both cases we obtain small average sea-level decelerations. To compare these results with worldwide data, we extend the analysis of Douglas (1992) by an additional 25 years and analyze revised data of Church and White (2006) from 1930 to 2007 and also obtain small sea-level decelerations similar to those we obtain from U.S. gauge records.
In the last 5000 years, global mean sea level has been dominated by the redistribution of water masses over the globe. In the last 300 years, sea level has been oscillation close to the present with peak rates in the period 1890–1930. Between 1930 and 1950, sea fell. The late 20th century lack any sign of acceleration. Satellite altimetry indicates virtually no changes in the last decade. Therefore, observationally based predictions of future sea level in the year 2100 will give a value of +10±10 cm (or +5±15 cm), by this discarding model outputs by IPCC as well as global loading models. This implies that there is no fear of any massive future flooding as claimed in most global warming scenarios.
Mean-sea-level data from coastal tide gauges in the north Indian Ocean were used to show that low-frequency variability is consistent among the stations in the basin. Statistically significant trends obtained from records longer than 40 years yielded sea-level-rise estimates between 1.06–1.75 mm yr− 1, with a regional average of 1.29 mm yr− 1, when corrected for global isostatic adjustment (GIA) using model data. These estimates are consistent with the 1–2 mm yr− 1 global sea-level-rise estimates reported by the Intergovernmental Panel on Climate Change.
We investigate whether or not the decadal and multi-decadal climate oscillations have an astronomical origin. Several global surface temperature records since 1850 and records deduced from the orbits of the planets present very similar power spectra. Eleven frequencies with period between 5 and 100 years closely correspond in the two records. Among them, large climate oscillations with peak-to-trough amplitude of about 0.1 and 0.25°C, and periods of about 20 and 60 years, respectively, are synchronized to the orbital periods of Jupiter and Saturn. Schwabe and Hale solar cycles are also visible in the temperature records. A 9.1-year cycle is synchronized to the Moon's orbital cycles. A phenomenological model based on these astronomical cycles can be used to well reconstruct the temperature oscillations since 1850 and to make partial forecasts for the 21st century. It is found that at least 60% of the global warming observed since 1970 has been induced by the combined effect of the above natural climate oscillations. The partial forecast indicates that climate may stabilize or cool until 2030–2040. Possible physical mechanisms are qualitatively discussed with an emphasis on the phenomenon of collective synchronization of coupled oscillators.
A semi-empirical relation is presented that connects global sea-level rise to global mean surface temperature. It is proposed
that, for time scales relevant to anthropogenic warming, the rate of sea-level rise is roughly proportional to the magnitude
of warming above the temperatures of the pre–Industrial Age. This holds to good approximation for temperature and sea-level
changes during the 20th century, with a proportionality constant of 3.4 millimeters/year per °C. When applied to future warming
scenarios of the Intergovernmental Panel on Climate Change, this relationship results in a projected sea-level rise in 2100
of 0.5 to 1.4 meters above the 1990 level.
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