Relative Mean Sea Level Research Articles

Geodetic observation of sea-level change and crustal deformation in the Baltic Sea region

Based on tide gauge observations spanning almost 200 years, homogeneous time series of the mean relative sea level were derived for nine sites at the southern coast of the Baltic Sea. Our regionally concentrated data were complemented by long-term relative sea-level records retrieved from the data base of the Permanent Service for Mean Sea Level (PSMSL). From these records relative sea-level change rates were derived at 51 tide gauge stations for the period between 1908 and 2007. A minimum observation time of 60 years is required for the determination of reliable sea-level rates. At present, no anthropogenic acceleration in sea-level rise is detected in the tide gauge observations in the southern Baltic. The spatial variation of the relative sea-level rates reflects the fingerprint of GIA-induced crustal uplift. Time series of extreme sea levels were also inferred from the tide gauge records. They were complemented by water level information from historic storm surge marks preserved along the German Baltic coast. Based on this combined dataset the incidence and spatial variation of extreme sea levels induced by storm surges were analysed yielding important information for hazard assessments. Permanent GPS observations were used to determine recent crustal deformation rates for 44 stations in the Baltic Sea region. The GPS derived height change rates were applied to reduce the relative sea-level changes observed by tide gauges yielding an estimate for the eustatic sea-level change. For 13 tide gauge-GPS colocation sites a mean eustatic sea-level trend of 1.3mm/a was derived for the last 100 years.

Improved estimates of mean sea level changes in the German Bight over the last 166 years

In this paper, mean sea level changes in the German Bight, the south-eastern part of the North Sea, are analysed. Records from 13 tide gauges covering the entire German North Sea coastline and the period from 1843 to 2008 have been used to derive high quality relative mean sea level time series. Changes in mean sea level are assessed using non-linear smoothing techniques and linear trend estimations for different time spans. Time series from individual tide gauges are analysed and then ‘virtual station’ time series are constructed (by combining the individual records) which are representative of the German Bight and the southern and eastern regions of the Bight. An accelerated sea level rise is detected for a period at the end of the nineteenth century and for another one covering the last decades. The results show that there are regional differences in sea level changes along the coastline. Higher rates of relative sea level rise are detected for the eastern part of the German Bight in comparison to the southern part. This is most likely due to different rates of vertical land movement. In addition, different temporal behaviour of sea level change is found in the German Bight compared to wider regional and global changes, highlighting the urgent need to derive reliable regional sea level projections for coastal planning strategies.

Reconstructing middle to late Holocene palaeogeographies of the lower Messenian plain (southwestern Peloponnese, Greece): Coastline migration, vegetation history and sea level change

The glacio-eustatic sea level rise after the Last Glacial Maximum (LGM) led to a worldwide flooding of shelf areas and the evolution of marine embayments and indentations. Its significant deceleration in mid-Holocene times resulted in the overcompensation by sediment yields and shoreline progradation in many areas. At the southeastern part of the lower Messenian plain (southwestern Peloponnese, Greece) detailed investigations of the Holocene stratigraphy revealed a maximum landward shoreline displacement around 3000 BC. Subsequently, aggradational processes started to form a prominent beach ridge in the late 3rd millennium BC. This is the substratum on which the early Iron Age Poseidon Sanctuary of Akovitika was founded approx. 900–850 BC. Palaeogeographic reconstructions based on 18 corings in the sanctuary and its surroundings revealed the later extension of adjacent marshland and gradual surface levelling due to seasonal inundations. These findings represent probable reasons for the abandonment of the ceremonial site around 380–350 BC. Palynological studies of the vegetational changes provide evidence for early land use and reflect regional settlement activities. Initial degradation and burning of woodland during late Neolithic times (c. 3500–3100 BC) as well as significantly reduced human impact during the Protogeometric Dark Ages (c. 1060–900 BC) are proven. Additionally, local relative mean sea level (RSL) change since 5000 BC was reconstructed based on 14C dated paralic peats.

Human impacts overwhelm the effects of sea-level rise on Basque coastal habitats (N Spain) between 1954 and 2004

According to coastal measurements, global mean sea-level has risen at a rate of 1.8 mm yr −1 between 1950 and 2000, with large spatial variability at regional scales. Within the Bay of Biscay, trends computed from coastal tide gauges records have revealed that sea-level rise is accelerating over this period of time; this is in agreement with rates obtained from satellite imagery in the open ocean since 1993. The objectives of the present study are: (1) to assess the evidence of the relative sea-level rise on coastal morphology and habitats in the Gipuzkoan littoral zone (Basque coast, northern Spain) for the period 1954–2004, and (2) to evaluate the relative contribution of local anthropogenic versus sea-level rise impacts for explaining inter-supratidal habitat changes. A high-resolution airborne laser altimetry data (LIDAR) has been used to derive a Digital Terrain Model (DTM) of 15-cm vertical resolution. Coastal habitats were mapped for two periods, using historic airborne photography (1954) and high-resolution imagery (2004). Analysis of tide gauge records from Santander (northern Spain) has revealed that relative mean sea-level has been rising at a rate of 2.08 ± 0.33 mm yr −1 from 1943 to 2004; this is consistent with sea-level trends from other measurements within the area (St. Jean de Luz and Bilbao), obtained over shorter periods of time, and with previous results obtained in the Bay of Biscay. Based upon this sea-level trend and by means of a LIDAR-based DTM, the results have indicated that the predicted change along the Gipuzkoan coast due to sea-level rise was of 11.1 ha within the 50-yr period. In contrast, comparison of historical and recent orthophotography has detected only 2.95 ha of change, originated possibly from sea-level rise, and 98 ha transformed by anthropogenic impacts. Hence, coastal changes due to sea-level rise might be overwhelmed by excessive human impacts, at the spatial and temporal scales of the analysis. This work highlights that local anthropogenic impact is the major threat to Basque coastal and estuarine habitats, compared with natural erosive processes and global climate change driving forces over recent times.

The Spatial Distribution and Evolution Characteristics of North Atlantic Cyclones

Abstract A climatology of extratropical cyclones is produced using an objective method of identifying cyclones based on gradients of 1-km height wet-bulb potential temperature. Cyclone track and genesis density statistics are analyzed and this method is found to compare well with other cyclone identification methods. The North Atlantic storm track is reproduced along with the major regions of genesis. Cyclones are grouped according to their genesis location and the corresponding lysis regions are identified. Most of the cyclones that cross western Europe originate in the east Atlantic where the baroclinicity and the sea surface temperature gradients are weak compared to the west Atlantic. East Atlantic cyclones also have higher 1-km height relative vorticity and lower mean sea level pressure at their genesis point than west Atlantic cyclones. This is consistent with the hypothesis that they are secondary cyclones developing on the trailing fronts of preexisting “parent” cyclones. The evolution characteristics of composite west and east Atlantic cyclones have been compared. The ratio of their upper- to lower-level forcing indicates that type B cyclones are predominant in both the west and east Atlantic, with strong upper- and lower-level features. Among the remaining cyclones, there is a higher proportion of type C cyclones in the east Atlantic, whereas types A and C are equally frequent in the west Atlantic.

Adapting to Pacific Island mangrove responses to sea level rise and climate change

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 32:161-176 (2006) - doi:10.3354/cr032161 Adapting to Pacific Island mangrove responses to sea level rise and climate change Eric L. Gilman1,15,*, Joanna Ellison1, Vainuupo Jungblut2, Hanneke Van Lavieren3, Lisette Wilson4, Francis Areki5, Genevieve Brighouse6, John Bungitak7, Eunice Dus8, Marion Henry9, Mandes Kilman10, Elizabeth Matthews11, Ierupaala Sauni Jr.6, Nenenteiti Teariki-Ruatu12, Sione Tukia13, Kathy Yuknavage14 1University of Tasmania, School of Geography and Environmental Studies, Locked Bag 1-376 Launceston, Tasmania 7250, Australia 2Secretariat of the Pacific Regional Environment Programme, PO Box 240, Apia, Samoa 3United Nations Environment Programme, Regional Seas Programme, PO Box 30552 Room T-232, Nairobi, Kenya 4WWF-South Pacific, PO Box 8280, Boroko, NCD, Papua New Guinea 5WWF-Fiji, 4 Ma’afu Street, Private Mail Bag, Suva, Fiji 6Coastal Management Program, Utulei Executive Office Building, Pago Pago, American Samoa 96799, USA 7Environmental Protection Authority, PO Box 1322, Majuro, MH 96960, Republic of the Marshall Islands 8Wildlife Conservation Society, PO Box 277, Goroka, Eastern Highlands Province, Papua New Guinea 9Department of Economic Affairs, PO Box PS12, Palikir, Pohnpei, FM 96941, Federated States of Micronesia 10Primary Resources Consulting Company, PO Box 1691, Port Vila, Vanuatu 11Palau Conservation Society, Box 1811, Koror, PW 96940, Palau 12Ministry of Environment, Land, and Agricultural Development, PO Box 234, Bikenibeu, Tarawa, Kiribati 13Department of Environment, PO Box 917, Nuku’alofa, Tonga 14Commonwealth of the Northern Mariana Islands Coastal Resources Management Office, Box 10007, Saipan MP 96950, USA 15Present address: 2718 Napuaa Place, Honolulu, Hawaii 96822, USA *Email: egilman@utas.edu.au ABSTRACT: Stresses associated with effects of climate change, including rise in relative mean sea level, present one set of threats to mangroves. Coastal development and ecosystems in the Pacific Islands region are particularly vulnerable to climate change effects. We investigated the capacity of Pacific Island countries and territories to assess mangrove vulnerability to the effects of climate change, and their capacity to adapt to mangrove responses to these forces. Technical and institutional capacity-building priorities include: (1) strengthening management frameworks to conduct site-specific assessment of mangrove vulnerability and incorporate resulting information into land-use plans to prepare for any landward mangrove migration and offsetting anticipated losses; (2) reducing and eliminating stresses on and rehabilitating mangroves, in part, to increase mangrove resilience to climate change effects; and (3) augmenting abilities to establish mangrove baselines, and monitor gradual changes using standardized techniques through a regional network to distinguish local and climate change effects on mangroves. Other priorities are to: (4) assess how mangrove margins have changed over recent decades; (5) determine projections of trends in mean relative sea level and trends in the frequency and elevation of extreme high water events; (6) measure trends in changes in elevations of mangrove surfaces; and (7) incorporate this information into land-use planning processes. Also in (8) some locations require spatial imagery showing topography and locations of mangroves and coastal development. Land-use planners can use information from assessments predicting shoreline responses to projected sea level rise and other climate change effects to reduce risks to coastal development, human safety, and coastal ecosystems. This advanced planning enables coastal managers to minimize social disruption and cost, minimize losses of valued coastal ecosystems, and maximize available options. KEY WORDS: Mangrove · Sea level rise · Climate change · Land-use planning · Pacific Islands Full text in pdf format NextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 32, No. 3. Online publication date: October 26, 2006 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 2006 Inter-Research.

Submarine evidence of Holocene sea-level fluctuations in the Bahía Blanca estuary, Argentina

Sedimentological and micropaleontological studies were carried out on a core representative of regional submarine outcrops located in the external area of the Bahía Blanca estuary. Three different zones were characterized within the core. The lower core section is composed of sediments deposited in a restricted intertidal environment, such as a coastal lagoon or the upper part of extensive and vegetated tidal flats, whereas sedimentation in the middle section was influenced more by the action of tidal currents, as presently occurs in tidal flats closely related to a channel system. The upper section of the core shows the gradual passage toward modern conditions, in which sand is transported as bedload by strong tidal currents. The characteristics of both the lower and middle sections of the core indicate a relative mean sea level located below that of the present. The lower section probably was deposited before the maximum Holocene transgression, and the age of the core middle section indicates an important negative mean sea-level oscillation that could be correlated with a worldwide climatic change around 2700 yr BP. This finding indicates that relatively short perturbations in global climate could have more important consequences than heretofore has been believed.

Water-level changes in the Flevo area, central Netherlands (5300–1500 BC): implications for relative mean sea-level rise in the Western Netherlands

The younger (post 4000 cal BC) part of the water-level curve for the eastern Flevo area, central Netherlands runs below the relative mean sea-level (MSL) curve for the western and northern Netherlands (Mededelingen Rijks Geologische Dienst 36(1) (1982) 93pp). We investigated if this difference can be attributed to (i) root rejuvenation of the bulk-dated basal peat samples on which the curve for the eastern Flevo area is based and/or (ii) underestimation of the water depth in which the dated peat accumulated. It appears that these potential sources of error did not influence significantly the results obtained by Roeleveld and Gotjé (De Holocene laagveenontwikkeling in de randzone van de Nederlandse kustvlakte (Noordoostpolder), unpublished Ph.D. Thesis, Vrije Universiteit Amsterdam, 1993, pp. 76–86). On the basis of new and recently published water-level data from the eastern and southwestern Flevo area we confirm, refine, and tentatively extend the water-level rise reconstruction by Roeleveld and Gotjé and establish a relative MSL-trend curve for the central Netherlands. The systematic age differences of our radiocarbon dates on various fractions of four new basal peat samples from the eastern Flevo area support the interpretation by Roeleveld and Gotjé that the younger part of the 1982-MSL curve may be based on basal peat samples (all from the Rotterdam area), that have been dated 100–200 yr too old. If this interpretation is correct, the fact that the relative MSL curve for the central Netherlands lies below the 1982-MSL curve cannot be interpreted to indicate less crustal subsidence for the Rhine-Meuse delta, as predicted by geophysical modeling (J. Quat. Sci. 17 (2002) 535).

RESPONSES OF COASTAL WETLANDS TO RISING SEA LEVEL

Salt marsh ecosystems are maintained by the dominant macrophytes that regulate the elevation of their habitat within a narrow portion of the intertidal zone by accumulating organic matter and trapping inorganic sediment. The long-term stability of these ecosystems is explained by interactions among sea level, land elevation, primary production, and sediment accretion that regulate the elevation of the sediment surface toward an equilibrium with mean sea level. We show here in a salt marsh that this equilibrium is adjusted upward by increased production of the salt marsh macrophyte Spartina alterniflora and downward by an increasing rate of relative sea-level rise (RSLR). Adjustments in marsh surface elevation are slow in comparison to interannual anomalies and long-period cycles of sea level, and this lag in sediment elevation results in significant variation in annual primary productivity. We describe a theoretical model that predicts that the system will be stable against changes in relative mean sea level when surface elevation is greater than what is optimal for primary production. When surface elevation is less than optimal, the system will be unstable. The model predicts that there is an optimal rate of RSLR at which the equilibrium elevation and depth of tidal flooding will be optimal for plant growth. However, the optimal rate of RSLR also represents an upper limit because at higher rates of RSLR the plant community cannot sustain an elevation that is within its range of tolerance. For estuaries with high sediment loading, such as those on the southeast coast of the United States, the limiting rate of RSLR was predicted to be at most 1.2 cm/yr, which is 3.5 times greater than the current, long-term rate of RSLR.

Evolution of the intra-coastal tidal range in the Rhine-Meuse delta and Flevo Lagoon, 5700-3000 yrs cal B.C.

The evolution of the coastal and intra-coastal tidal range in the western Netherlands during the period 5700-3000 yrs cal B.C. (6875-4400 yrs B.P.) is considered by comparing one coastal mean high water curve and two local mean high water curves (MHW) with respect to three alternative relative mean sea level (MSL) curves: (1) the existing 1982-MSL curve for the western and northern Netherlands, (2) a MSL curve based on the oldest part of the 1982-MSL curve and the youngest part of a recently published MSL curve based on data from the east-central coastal plain, and (3) a hypothetical MSL curve for the east-central coastal area assuming crustal subsidence of 0.10 m/1000 yr relative to the 1982-MSL curve. With regard to coastal tidal range, the first and third MSL curve yield a similar result: a minor increase in coastal tidal range between 5200 yrs cal B.C. (6200 yrs B.P.) and 4200 yrs cal B.C. (5350 yrs B.P.). The second MSL curve gives an increase in coastal tidal range from an assumed value of 2 m by 5200 yrs cal B.C. (6200 yrs B.P.) to ca. 3 m by 4100 yrs cal B.C. (5300 yrs B.P.), conflicting with existing model results. Intra-coastal tidal damping was a widespread phenomenon and played an important role in the evolution of the coastal plain. For the first and second MSL curves, tidal attenuation in the Rhine-Meuse delta and the east-central coastal sector begins around 5250 yrs cal B.C. (6275 yrs B.P.); with the third MSL curve, the reduction of the tidal range starts is 500 years later. The first and third MSL curves result in complete tidal damping in the Rhine-Meuse delta and the east-central coastal area; with the second MSL curve, the tidal range in the Rhine-Meuse delta remains ca. 1.3 m, whereas in the east-central area tidal reduction is complete. In spite of these different results, it is clear that the period 5300-4300 yrs cal B.C. (ca. 6375-5400 yrs B.P.) was very important for the subsequent evolution of the West Netherlands coastal plain given that (a) the relative MSL rise slowed down from about 0.8 m/100 yr to 0.23 m/100 yr, (b) the coastal tidal range increased, possibly by as much as 1 m, resulting in higher sediment input into the intra-coastal area, while (c) further landward transportation of sediment was hampered due to intra-coastal tidal damping, which reduced rates of local MHW rise, tidal current velocities and accommodation space.

Monitoring in the western part of the Dutch Wadden: Sea—sea level and morphology

This paper deals with the methods and results of monitoring sea level (tidal gauges) and with the analysis of depth sounding data. Possible future monitoring by menas of remote sensing techniques will be presented. Some trends, based on water level and morphological monitoring, have been established in the western part of the Dutch Wadden sea: (a) the relative mean sea level is rising persistently by 15 cm/century, observed since the middle of the 19th century. The tidal range is increasing as well; (b) the cross-sectional areas of the most western Dutch Wadden tidal inlets have been increasing over the last two centuries; (c) the intertidal zones of the Texelstroom and Vliestroom tidal basins have shown an increase of surface area over the last decades. The Borndiep tidal basin shows a decrease of 4% of the area shallower than 5 m — Dutch Ordinance Level (DOL) over the last two centuries. Several factors prevent serious predictions about future morphological developments of the tidal Wadden flats: (a) man induced interfering factors, e.g. the construction of the harbour revetments of Den Helder, the construction of the Enclosure Dike and construction of sand drift dikes stabilising the Wadden islands; (b) the limited scope of the present analysis that deals only with the western part of the Dutch Wadden Sea.

Responding to changes in sea level, National academy press, Washington D.C. 1987. ISBN 0–809–03781–6. Committee on engineering implications of changes at relative mean sea level & the marine board, commission on engineering & technical systems, national research council

Responding to changes in sea level, National academy press, Washington D.C. 1987. ISBN 0–809–03781–6. Committee on engineering implications of changes at relative mean sea level & the marine board, commission on engineering & technical systems, national research council

Comment on “Changes in relative sea level”] Changes in sea level: The question of secular motion

I am writing this note in reference to one paragraph of a generally interesting report, “Changes in Relative Mean Sea Level’ [by the IAPSO Advisory Committee on Tides and Mean Sea Level], which appeared in the November 5, 1985 issue of Eos [p. 754]. In this paragraph the authors question the nature and even existence of the secular motion of the earth's rotation pole. The paragraph states that because of supposed extreme irregularities in the observed (ILS) motion, “it may even be that the entire apparent secular motion of the pole is an artifact of systematic efforts [this word should probably read ‘errors’] in the ILS” data.

Reply [to “Comment on ‘Changes in relative mean sea level’”

There is little question that the International Latitude Service (ILS) polar motion time series displays a statistically significant drift in the mean position of the pole. The difficult problem is to determine “Whether this secular motion is apparent (a consequence of the measuring process, local crustal deformation and deflections of the vertical) or real (due to continental drift or a secular motion of the axis of rotation) …,” (K. Lambeck, The Earth's Variable Rotation: Geophysical Causes and Consequences, Cambridge University Press, London, 1980). Neither the n‐sigma nor the theoretical plausibility arguments presented by S.R. Dickman are of much use in answering that question. The best evidence that at least some portion of the observed motion may be real is the loose agreement among the ILS, IPMS, and Doppler series during the limited periods of overlap.

Changes in relative mean sea level

After some decades of comparative neglect, changes in mean sea level relative to land (RSL) are now appreciated by oceanographers and geophysicists as an important integral parameter of ocean climate and vertical land movement that is fairly easy to measure for long periods. Interest has been raised by the relevance of RSL to “El Niño” events, as shown by the new Pacific island network operated by the University of Hawaii, and by several studies of recent secular rise in global RSL in relation to changes in temperature and glaciation. Monthly RSL maps for the entire tropical Pacific are currently issued in near real time by the Integrated Global Ocean Station System Sea Level Pilot Project. A global network of tide gage stations has recently been proposed by the Intergovernmental Oceanographic Commission of the United Nations Educational, Scientific, and Cultural Organization in support of the Tropical Ocean Global Atmosphere (TOGA) and World Ocean Circulation Experiment (WOCE) campaigns.

Archaeological and historical evidence for subsidence in southern Britain

This paper is presented as a warning of the pitfalls which are involved in a too ready and uncritical acceptance of the evidence for apparent changes in relative land and sea level which has been derived from the archaeological and historical remains around the coasts of southern Britain. The general trends of relative sea level changes in the later Holocene are indicated; but I am concerned more to correct some of the misapprehensions and inexact conclusions which have been drawn from the often imprecise data, and to establish a wider recognition of the types of errors and inaccurate assumptions which have been promulgated in some publications, and which erroneously, albeit unwittingly, have been cited by specialists in other disciplines to reinforce or to substantiate conclusions derived from their different data. The optimum conditions for establishing the former positions of relative mean sea level are found in deposits which can be shown to have formed in a known relationship to sea level as part of a continuous halosere from marine sands and clays to freshwater fen deposits (cf. Churchill 1965, p. 240). I would stress that estimates of sea level changes should be based primarily on the analysis of physiographical data; the archaeological and historical data may provide complementary and corroborative evidence of relative land and sea level changes, but they are generally too imprecise to stand alone as definitive indicators of actual mean sea level or tidal heights.

Orford, Suffolk: Further Data on the Quaternary Evolution of the area

SummaryBoreholes at, and seaward of, Lantern Marshes shed additional information on the Quaternary evolution of the Orford, Suffolk, area. The logs indicate:(i) a more complex surface to the London Clay, which is shown to reach depths below those formerly thought;(ii) the reality of the lower planation surface previously recorded. The surface is, however, cut across Scrobicularia and Butley (Red) Crag to a greater extent than anticipated. It proves that at least part, and probably all, of the −8.5 to −11 m surface is post Ludhamian.(iii) a peat sample from −9.4 m indicates that relative mean sea level at 7010 B.P. was at approximately −10.7 m. The peat is overlain by shingle and confirms the residual shingle structures as later than that time.