Middle and Late Holocene Sea-Level Changes in Eastern Maine Reconstructed from Foraminiferal Saltmarsh Stratigraphy and AMS 14C Dates on Basal Peat

1999 ◽  
Vol 52 (3) ◽  
pp. 350-359 ◽  
Author(s):  
W.Roland Gehrels
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Tidal Range ◽  
Sea Level Changes ◽  
The Past ◽  
Amplitude Fluctuations ◽  
Vertical Distributions ◽  
Low Amplitude ◽  
Long Term Trend

A relative sea-level history is reconstructed for Machiasport, Maine, spanning the past 6000 calendar year and combining two different methods. The first method establishes the long-term (103 yr) trend of sea-level rise by dating the base of the Holocene saltmarsh peat overlying a Pleistocene substrate. The second method uses detailed analyses of the foraminiferal stratigraphy of two saltmarsh peat cores to quantify fluctuations superimposed on the long-term trend. The indicative meaning of the peat (the height at which the peat was deposited relative to mean tide level) is calculated by a transfer function based on vertical distributions of modern foraminiferal assemblages. The chronology is determined from AMS 14C dates on saltmarsh plant fragments embedded in the peat. The combination of the two different approaches produces a high-resolution, replicable sea-level record, which takes into account the autocompaction of the peat sequence. Long-term mean rates of sea-level rise, corrected for changes in tidal range, are 0.75 mm/yr between 6000 and 1500 cal yr B.P. and 0.43 mm/yr during the past 1500 year. The foraminiferal stratigraphy reveals several low-amplitude fluctuations during a relatively stable period between 1100 and 400 cal yr B.P., and a sea-level rise of 0.5 m during the past 300 year.

scholarly journals Pacific Sea Levels Rising Very Slowly and Not Accelerating

2019 ◽  
Vol 38 (1) ◽  
pp. 179-184 ◽  
Author(s):  
Albert Parker ◽  
Clifford Ollier
Keyword(s):  
Pacific Ocean ◽  
Sea Level ◽  
Relative Rate ◽  
Tide Gauges ◽  
Sea Levels ◽  
The Past ◽  
The Pacific ◽  
The Pacific Ocean ◽  
Long Term Trend

AbstractOver the past decades, detailed surveys of the Pacific Ocean atoll islands show no sign of drowning because of accelerated sea-level rise. Data reveal that no atoll lost land area, 88.6% of islands were either stable or increased in area, and only 11.4% of islands contracted. The Pacific Atolls are not being inundated because the sea level is rising much less than was thought. The average relative rate of rise and acceleration of the 29 long-term-trend (LTT) tide gauges of Japan, Oceania and West Coast of North America, are both negative, −0.02139 mm yr−1and −0.00007 mm yr−2respectively. Since the start of the 1900s, the sea levels of the Pacific Ocean have been remarkably stable.

scholarly journals Stratigraphy and sedimentology of a basement-onlapping shallow marine sandstone succession, the Charcot Bugt Formation, Middle–Upper Jurassic, East Greenland

2003 ◽  
Vol 1 ◽  
pp. 893-930 ◽  
Author(s):  
Michael Larsen ◽  
Stefan Piasecki ◽  
Finn Surlyk
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Upper Jurassic ◽  
Sea Level Changes ◽  
Relative Sea Level ◽  
Western Basin ◽  
Shallow Marine ◽  
East Greenland ◽  
Depositional Systems

A rocky shore developed in early Middle Jurassic times by transgression of the crystalline basement in Milne Land at the western margin of the East Greenland rift basin. The basement is onlapped by shallow marine sandstones of the Charcot Bugt Formation, locally with a thin fluvial unit at the base. The topography of the onlap surface suggests that a relative sea-level rise of at least 300 m took place in Early Bathonian – Middle Oxfordian times. The sea-level rise was punctuated by relative stillstands and falls during which progradation of the shoreline took place. Palynological data tied to the Boreal ammonite stratigraphy have greatly improved time resolution within the Charcot Bugt Formation, and the Jurassic succession in Milne Land can now be understood in terms of genetically-related depositional systems with a proximal to distal decrease in grain size. The sequence stratigraphic interpretation suggests that translation of the depositional systems governed by relative sea-level changes resulted in stacking of sandstone-dominated falling stage deposits in the eastern, basinwards parts of Milne Land, whereas thick, remarkably coarsegrained transgressive systems tract deposits formed along the western basin margin. The bulk of the Charcot Bugt Formation consists of stacked sandstone-dominated shoreface units that prograded during highstands. The overall aggradational to backstepping stacking pattern recognised in the Charcot Bugt Formation is comparable to that in the contemporaneous Pelion Formation of the Jameson Land Basin and in correlative units of the mid-Norway shelf and the Northern North Sea. We suggest that the long-term evolution of the depositional systems may have been controlled by long-term eustatic rise acting in concert with relative sea-level changes reflecting regionally contemporaneous phases of rift initiation, climax and gradual cessation of rifting.

scholarly journals Sea-level rise in Venice: historic and future trends (review article)

2021 ◽  
Vol 21 (8) ◽  
pp. 2643-2678 ◽  
Author(s):  
Davide Zanchettin ◽  
Sara Bruni ◽  
Fabio Raicich ◽  
Piero Lionello ◽  
Fanny Adloff ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Tide Gauge ◽  
Average Rate ◽  
Sea Level Changes ◽  
Relative Sea Level ◽  
The Past ◽  
Gauge Data ◽  
Relative Sea Level Rise ◽  
Sea Level Variations

Abstract. The city of Venice and the surrounding lagoonal ecosystem are highly vulnerable to variations in relative sea level. In the past ∼150 years, this was characterized by an average rate of relative sea-level rise of about 2.5 mm/year resulting from the combined contributions of vertical land movement and sea-level rise. This literature review reassesses and synthesizes the progress achieved in quantification, understanding and prediction of the individual contributions to local relative sea level, with a focus on the most recent studies. Subsidence contributed to about half of the historical relative sea-level rise in Venice. The current best estimate of the average rate of sea-level rise during the observational period from 1872 to 2019 based on tide-gauge data after removal of subsidence effects is 1.23 ± 0.13 mm/year. A higher – but more uncertain – rate of sea-level rise is observed for more recent years. Between 1993 and 2019, an average change of about +2.76 ± 1.75 mm/year is estimated from tide-gauge data after removal of subsidence. Unfortunately, satellite altimetry does not provide reliable sea-level data within the Venice Lagoon. Local sea-level changes in Venice closely depend on sea-level variations in the Adriatic Sea, which in turn are linked to sea-level variations in the Mediterranean Sea. Water mass exchange through the Strait of Gibraltar and its drivers currently constitute a source of substantial uncertainty for estimating future deviations of the Mediterranean mean sea-level trend from the global-mean value. Regional atmospheric and oceanic processes will likely contribute significant interannual and interdecadal future variability in Venetian sea level with a magnitude comparable to that observed in the past. On the basis of regional projections of sea-level rise and an understanding of the local and regional processes affecting relative sea-level trends in Venice, the likely range of atmospherically corrected relative sea-level rise in Venice by 2100 ranges between 32 and 62 cm for the RCP2.6 scenario and between 58 and 110 cm for the RCP8.5 scenario, respectively. A plausible but unlikely high-end scenario linked to strong ice-sheet melting yields about 180 cm of relative sea-level rise in Venice by 2100. Projections of human-induced vertical land motions are currently not available, but historical evidence demonstrates that they have the potential to produce a significant contribution to the relative sea-level rise in Venice, exacerbating the hazard posed by climatically induced sea-level changes.

A long-term trend and temporal fluctuations of the sea level at the Polish Baltic coast

2011 ◽  
Vol 40 (2) ◽  
Author(s):  
Bernard Wiśniewski ◽  
Tomasz Wolski ◽  
Stanisław Musielak
Keyword(s):  
Spectral Analysis ◽  
Sea Level ◽  
Data Series ◽  
Sea Level Changes ◽  
Mean Sea Level ◽  
Term Trend ◽  
Baltic Coast ◽  
Long Term Trend ◽  
Linear Trends

AbstractThe analysis of sea level record series along the Polish coast is presented. The main aim was to identify linear trends in the sea level changes at the coastal (Świnoujście, Kołobrzeg, Ustka, Łeba, Władysławowo, Hel, Gdynia, Gdańsk), lagoonal (Trzebież, Tokmicko) and riverine (Szczecin) gauge stations. The analysis showed individual coastal stations to differ in the rate of sea level changes. During 60 years of continuous observations (1947–2006), the differences varied from 1.0 (the western part of the coast) to 2.5 mm year−1 (the eastern part of the coast). The longest, more than 100-yr-long data series showed the sea level rise in Świnoujście and Kołobrzeg to be about 0.5 mm year−1; 1.57 mm year−1 being revealed in Gdańsk. Spectral analysis applied to the data showed numerous fluctuations and cyclicity in changes of the annual mean sea level at the Polish coast. A distinct, major 3-year cycle was revealed. In addition, three secondary cycles of 4.6, 6.7, and 8.6 years were present in the data, more or less clearly identifiable at individual stations.

scholarly journals Buying Time with Runnels: a Climate Adaptation Tool for Salt Marshes

2022 ◽  
Author(s):  
Alice F. Besterman ◽  
Rachel W. Jakuba ◽  
Wenley Ferguson ◽  
Diana Brennan ◽  
Joseph E. Costa ◽  
...  
Keyword(s):  
Salt Marsh ◽  
Sea Level Rise ◽  
Sea Level ◽  
Salt Marshes ◽  
Climate Adaptation ◽  
Open Water ◽  
Tidal Range ◽  
Management Interventions

AbstractA prominent form of salt marsh loss is interior conversion to open water, driven by sea level rise in interaction with human activity and other stressors. Persistent inundation drowns vegetation and contributes to open water conversion in salt marsh interiors. Runnels are shallow channels originally developed in Australia to control mosquitoes by draining standing water, but recently used to restore marsh vegetation in the USA. Documentation on runnel efficacy is not widely available; yet over the past 10 years dozens of coastal adaptation projects in the northeastern USA have incorporated runnels. To better understand the efficacy of runnels used for restoration, we organized a workshop of 70 experts and stakeholders in coastal resource management. Through the workshop we developed a collective understanding of how runnels might be used to slow or reverse open water conversion, and identified unresolved questions. In this paper we present a synthesis of workshop discussions and results from a promising case study in which vegetation was restored at a degraded marsh within a few years of runnel construction. Despite case study outcomes, key questions remain on long-term runnel efficacy in marshes differing in elevation, tidal range, and management history. Runnel construction is unlikely to improve long-term marsh resilience alone, as it cannot address underlying causes of open water conversion. As a part of holistic climate planning that includes other management interventions, runnels may “buy time” for salt marshes to respond to management action, or adapt to sea level rise.

scholarly journals Technical Note: Mean sea level variation in the Singapore Strait from long-term tide data

2012 ◽  
Vol 9 (3) ◽  
pp. 2255-2271
Author(s):  
P. Tkalich ◽  
M. T. Babu ◽  
P. Vethamony
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
El Niño ◽  
El Nino ◽  
Level Variation ◽  
Sea Level Changes ◽  
Mean Sea Level ◽  
Sea Level Variation ◽  
Singapore Strait

Abstract. Winds over the South China Sea (SCS) are primarily responsible for the observed variability in sea level anomalies (SLAs) in the Singapore Strait (SS). The present study focuses on remote forcing contributing to local mean sea level changes in the SS in seasonal and inter-annual scales, and relating the long term mean sea level variation to El Niño/ENSO. As Tanjong Pagar (TP) tide station in the SS has nearly 23.5 yr (1984–2007) of time series data with less data gaps, this data was subject to harmonic and sea level analyses. The mean sea level changes suggest that the fluctuations are quasi-periodic. Rising and falling of sea level is noticed atleast 7 times in a period of 15 yr, with 3 distinct sharp falls (1984–1987, 1989–1992 and 1995–1996) and 4 sharp rises (1987–1988, 1992–1993, 1994–1995 and 1997–1999). These sea level falls are related to El Niño events. When we segregated the results into 2 time spans, we find that from 1984 to 1999 the sea level was on the rising trend in spite of sharp falls, and from 1999 to 2007 on gradual falling trend. More or less similar trend was observed by other researchers for the SCS with altimetry data. During the El Niño periods of 1987 and 1992, the inter-annual MSL variability is the highest, of the order of 7 cm. In one of the events, sea level recovered from a fall of 60 mm (in 1987) to a rise of 40 mm (in 1988). During 1992 to 1999, sea level was continuously on rising trend (from −50 mm to +60 mm), except in one year (1995–1996). The analysis shows a MSL rise rate of 15.7 mm yr−1, which is very closer to MSL in the SCS. The average rate of sea level rise around Singapore as shown by the Tanjong Pagar tidal station is 1.6 mm yr−1, and this matches with the global sea level rise.

scholarly journals MEDITERRANEAN SEA LEVEL CHANGES FROM TIDAL RECORDS

1986 ◽  
Vol 1 (20) ◽  
pp. 17 ◽  
Author(s):  
Victor Goldsmith ◽  
Michael Gilboa
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Seasonal Changes ◽  
Sea Level Changes ◽  
Local Effects ◽  
Regional Sea Level ◽  
Tide Gage ◽  
Local Tectonics ◽  
Regional Sea Level Rise

Of the more than 90 tide gage records in the Mediterranean, 10 representative gages were analyzed for indications of sea level rise (SLR). No definitive trend of regional sea level rise has been discerned for this area. The lack of SLR may be partially attributed to local effects on sea level such as seasonal water temperature and wind differences, and to local tectonics. The extent of these seasonal changes is in the order of tens of cms/year, and varies greatly from year to year, probably masking the trends of long-term SLR of mm/yr.

scholarly journals The role of sea-level changes in the evolution of coastal barriers – An example from the southwestern Baltic Sea

The Holocene ◽  
2020 ◽  
pp. 095968362098170
Author(s):  
Reinhard Lampe ◽  
Matthias Lampe
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Sediment Supply ◽  
Sea Level Changes ◽  
Climate Fluctuations ◽  
The Past ◽  
Basic Model ◽  
Accommodation Space ◽  
Evolution Scheme

According to a basic model, the formation of the coastal barriers in the southwestern Baltic can be divided into four evolutionary stages which are characterized by different rates of sea-level rise and varying relations between sediment supply and accommodation space. This model is tested using the example of a strandplain of the island Usedom, along with a local sea-level curve that reflects even smaller fluctuations of the water table and a detailed chronostratigraphy based on OSL measurements that allows the correlation of the morphodynamics with specific climatic phases. The resulting evolution scheme generally confirms the basic model but the timing of the stages depends on the inherited relief and has to be adjusted locally. A comparison with barriers from the W and SW Baltic region shows that the development during the past 5000 years was controlled by climate fluctuations which caused minor variations of the rather stable sea level and consequential changes in sediment supply, accommodation space and foredune deposition. Progradation decline can mainly be related to cool and windy climate phases which centered around 4.2, 2.8, 1.1, and 0.3 ka b2k, while increasing progradation correlated with warmer climate around 3.5, 2.0, and 0.9 ka b2k. The climate warming and the increasing sea-level rise in the recent past, however, led to shrinking progradation rates and may indicate a critical point beyond which the main progradation trend of the past turns into erosion.

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