High Stands of Holocene Sea Levels in the Northwest Pacific

1978 ◽  
Vol 10 (1) ◽  
pp. 1-29 ◽  
Author(s):  
Paolo A. Pirazzoli
Keyword(s):  
Sea Level ◽  
Outer Zone ◽  
Local Scale ◽  
Northwest Pacific ◽  
The Sea Of Japan ◽  
Sea Levels ◽  
Level Change ◽  
Recent Emergence ◽  
The Japanese Archipelago

Evidence of Holocene sea levels higher than the present level have often been reported from the Northwest Pacific. Eustatic interpretations have been propounded, but age and level of the maximum transgression vary with each new analysis. In this investigation, after an inventory of approximately 250 items of data, some of which are new, a tentative synthesis transcending local scale is advanced. The highest levels are reported from Taiwan, where they often reach several tens of meters in altitude. In the Ryûkyûs and in the main islands of the Japanese Archipelago, evidence of recent emergence is found along most of the coasts. Elevation increases towards the oceanic trenches, but former sea levels at above 6 m and even higher may also be recognized along the coasts of the Sea of Japan. In a few areas, such as in the Niigata Plain, marks of Holocene sea levels higher than at present are lacking. On the other hand, in other basins regarded as subsiding, such as those in the Nôbi and the Kantô plains, evidence of recent emergence is quite frequent. In many places, marks of several sea levels indicate that a step-by-step uplift has occurred. All the investigated insular arcs, therefore, seem to be situated in epeirogenic areas formed by several more or less large blocks affected by relative movements. The blocks are larger in the Outer Zone of Southwestern Japan; in the Inner Zone, an intricate network of fault lines marks the boundaries of many smaller independent blocks. During great earthquakes, relative movements of uplift, subsidence, tilting, or undulation occur in one or several blocks, depending on the position of the epicentres. Subsidence, however, must often be simply of a temporary nature, because a long-term uplift trend seems to prevail in most regions, even if it occurs at different rates. This interpretation may explain the cause of the great variety of ages and elevations of the former sea levels (with the oldest ages corresponding to the highest elevations) and the great number of indicators of step-by-step sea-level change. The inference, drawn by several authors, that the Holocene sea level in the Northwest Pacific was higher than at present, is, therefore, reasonable on a local scale, but does not define an eustatic sea level.

Mean Sea Level as a Reference for Geodetic Leveling

1974 ◽  
Vol 28 (5) ◽  
pp. 524-530 ◽  
Author(s):  
G. W. Lennon
Keyword(s):  
Sea Level ◽  
World Ocean ◽  
Equipotential Surface ◽  
Scientific Discipline ◽  
Mean Sea Level ◽  
Sea Levels ◽  
Coastal Sea ◽  
Long Time ◽  
Marine System

The use of mean sea level as a surface of reference that might provide an independent control for geodetic leveling has been a long term goal arising from the classical analogy between the geoid as an equipotential surface and the surface assumed by a hypothetical undisturbed world ocean. The problems associated with this aim are now known to be vast, and are associated with the dynamics of the marine system, notably its response to meteorological forces, to variations in density and to the effects of basic circulation patterns. In consequence the mean sea level surface varies rapidly in both time and space. This identifies in fact a distinctive scientific discipline, coastal geodesy, in which contributions are required by both geodesists and oceanographers. It has come to be recognized that the coastal zone is a hazardous environment for all observational techniques concerned. On the one hand, the difficulties of measurement of coastal sea levels have only recently been understood; on the other hand, precise leveling procedures are now known to be influenced by the attraction of marine tides and by crustal deformation of tidal loading. Much of the data available for study are therefore inadequate and, moreover, it should be noted that long-time series are required. It is now possible to lay plans for both geodetic and oceanographic procedures to remedy these deficiencies in the long-term interests of the study.

Revising key parameters for long-term carbon cycle models

2021 ◽  
Author(s):  
Chloé M. Marcilly ◽  
Trond H. Torsvik ◽  
Mathew Domeier ◽  
Dana L. Royer
Keyword(s):  
Sea Level ◽  
Age Distribution ◽  
Silicate Weathering ◽  
Geological Time ◽  
Sea Levels ◽  
Climate Fluctuations ◽  
Climate Gradients ◽  
Sea Level Fluctuations ◽  
Temperature And Precipitation

<p>CO<sub>2</sub> is the most important greenhouse gas in the Earth’s atmosphere and has fluctuated considerably over geological time. However, proxies for past CO<sub>2 </sub>concentrations have large uncertainties and are mostly limited to Devonian and younger times. Consequently, CO<sub>2</sub> modelling plays a key role in reconstructing past climate fluctuations. Facing the limitations with the current CO<sub>2</sub> models, we aim to refine two important forcings for CO<sub>2</sub> levels over the Phanerozoic, namely carbon degassing and silicate weathering.</p><p>Silicate weathering and carbonate deposition is widely recognized as a primary sink of carbon on geological timescales and is largely influenced by changes in climate, which in turn is linked to changes in paleogeography. The role of paleogeography on silicate weathering fluxes has been the focus of several studies in recent years. Their aims were mostly to constrain climatic parameters such as temperature and precipitation affecting weathering rates through time. However, constraining the availability of exposed land is crucial in assessing the theoretical amount of weathering on geological time scales. Associated with changes in climatic zones, the fluctuation of sea-level is critical for defining the amount of land exposed to weathering. The current reconstructions used in<sub></sub>models tend to overestimate the amount of exposed land to weathering at periods with high sea levels. Through the construction of continental flooding maps, we constrain the effective land area undergoing silicate weathering for the past 520 million years. Our maps not only reflect sea-level fluctuations but also contain climate-sensitive indicators such as coal (since the Early Devonian) and evaporites to evaluate climate gradients and potential weatherablity through time. This is particularly important after the Pangea supercontinent formed but also for some time after its break-up.</p><p>Whilst silicate weathering is an important CO<sub>2</sub> sink, volcanic carbon degassing is a major source but one of the least constrained climate forcing parameters. There is no clear consensus on the history of degassing through geological time as there are no direct proxies for reconstructing carbon degassing, but various proxy methods have been postulated. We propose new estimates of plate tectonic degassing for the Phanerozoic using both subduction flux from full-plate models and zircon age distribution from arcs (arc-activity) as proxies.</p><p>The effect of revised modelling parameters for weathering and degassing was tested in the well-known long-term models GEOCARBSULF and COPSE. They revealed the high influence of degassing on CO<sub>2</sub> levels using those models, highlighting the need for enhanced research in this direction. The use of arc-activity as a proxy for carbon degassing leads to interesting responses in the Mesozoic and brings model estimates closer to CO<sub>2 </sub> proxy values. However, from simulations using simultaneously the revised input parameters (i.e weathering and degassing) large model-proxy discrepancies remain and notably for the Triassic and Jurassic.</p><p> </p>

scholarly journals The Effect of Wind Stress on Seasonal Sea-Level Change on the Northwestern European Shelf

2022 ◽  
pp. 1-31
Keyword(s):  
Sea Level ◽  
Wind Stress ◽  
Sea Level Change ◽  
Ocean Model ◽  
Seasonal Differences ◽  
Sea Levels ◽  
Level Change ◽  
Stress Changes ◽  
European Shelf ◽  
Emissions Scenario

Abstract Projections of relative sea-level change (RSLC) are commonly reported at an annual mean basis. The seasonality of RSLC is often not considered, even though it may modulate the impacts of annual mean RSLC. Here, we study seasonal differences in 21st-century ocean dynamic sea-level change (DSLC, 2081-2100 minus 1995-2014) on the Northwestern European Shelf (NWES) and their drivers, using an ensemble of 33 CMIP6 models complemented with experiments performed with a regional ocean model. For the high-end emissions scenario SSP5-8.5, we find substantial seasonal differences in ensemble mean DSLC, especially in the southeastern North Sea. For example, at Esbjerg (Denmark), winter mean DSLC is on average 8.4 cm higher than summer mean DSLC. Along all coasts on the NWES, DSLC is higher in winter and spring than in summer and autumn. For the low-end emissions scenario SSP1-2.6, these seasonal differences are smaller. Our experiments indicate that the changes in winter and summer sea-level anomalies are mainly driven by regional changes in wind-stress anomalies, which are generally southwesterly and east-northeasterly over the NWES, respectively. In spring and autumn, regional wind-stress changes play a smaller role. We also show that CMIP6 models not resolving currents through the English Channel cannot accurately simulate the effect of seasonal wind-stress changes on he NWES. Our results imply that using projections of annual mean RSLC may underestimate the projected changes in extreme coastal sea levels in spring and winter. Additionally, changes in the seasonal sea-level cycle may affect groundwater dynamics and the inundation characteristics of intertidal ecosystems.

scholarly journals Impacts of Atmospheric Pressure on the Annual Maximum of Monthly Sea-Levels in the Northeast Asian Marginal Seas

2020 ◽  
Vol 8 (6) ◽  
pp. 425 ◽  
Author(s):  
MyeongHee Han ◽  
Yang-Ki Cho ◽  
Hyoun-Woo Kang ◽  
SungHyun Nam ◽  
Do-Seong Byun ◽  
...  
Keyword(s):  
Sea Level ◽  
Correlation Coefficient ◽  
Atmospheric Pressure ◽  
Northwest Pacific ◽  
Pressure Gradients ◽  
Northwest Pacific Ocean ◽  
Sea Levels ◽  
Marginal Seas ◽  
Pressure Zone ◽  
Northeast Asian

Monthly mean sea-levels have annual maxima in August in the northeast Asian marginal seas (NEAMS). Based on satellite altimetry data, the rising rate of the August NEAMS sea-level (ANS, 4.2 mm∙yr−1) is greater than those of the NEAMS (3.6 mm∙yr−1) and global (3.4 mm∙yr−1) annual mean sea-levels. Thus, the interannual variations of ANS are classified as relatively high (period H) and low (period L) years and have been analysed because of the high risk of sea-level fluctuation to the coastal regions in August. In period H, there are large atmospheric pressure gradients between the high pressure zone in the Kuroshio Extension (KE) and the low pressure zone in the west of Taiwan (WT). In period L, the atmospheric pressure gradients are small between the above-mentioned zones. Large atmospheric pressure gradients induce strong west-northwestward wind stresses and more Ekman transport from the northwest Pacific Ocean into the NEAMS. The correlation coefficient between August NEAMS sea-level index (ANSI), which is the difference of atmospheric pressure anomalies between the KE and the WT, and the August NEAMS sea-level anomaly (ANSA) is 0.73. Although there is a significant correlation (coefficient: 0.64) between ANSA and the East Asian summer monsoon index (EASMI), ANSI might be more useful in estimating the variability of ANSA.

Mapping the soft and ethical dimensions of sea level rise in southern Sweden

2020 ◽  
Author(s):  
Lisa Van Well ◽  
Anette Björlin ◽  
Per Danielsson ◽  
Godefroid Godefroid Ndayikengurukiye ◽  
Gunnel Göransson
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Coastal Areas ◽  
Ecological Impacts ◽  
Gis Mapping ◽  
Ethical Values ◽  
Southern Sweden ◽  
Sea Levels ◽  
Rising Sea Levels

<p>Sea level rise poses profound challenges within current municipal and regional governance since it requires unusually long planning horizons, is surrounded by great uncertainties, and gives rise to novel ethical challenges. Adaptation to climate change is fundamentally an ethical issue because the aim of any proposed adaptation measure is to protect that which is valued in society. One of the most salient ethical issues discussed in the adaptation literature relates to the distribution of climate related risks, vulnerabilities and benefits across populations and over time. Raising sea-walls is typically associated with high costs and potentially negative ecological impacts as well as substantial equity concerns; managed retreat or realignment often causes problems related to property rights; and migration out of low-lying areas can involve the loss of sense and cultural identity and impact on receiving communities.</p><p>How can the soft and ethical dimensions of rising mean sea levels be characterized and how can their consequences be mapped? To help municipalities to understand the values and ethics attached to measures to deal with long-term rising sea levels in southern Sweden, we are developing a methodology of soft or ethical values to complement to GIS-mapping of coastal vulnerability based on coastal characteristics and socio-economic factors.</p><p>Rather than determining these values a priori, they are being discerned through workshops with relevant stakeholders and in interviews with citizens residing in and utilizing the coastal areas. The methodology attempts to determine the place-based of values within coastal communities with a focus on “whose” values, “what” values, and the long-term or short-term nature of values. It builds on an analytical framework developed to acquire information on the behavior, knowledge, perception and feelings of people living, working and enjoying the coastal areas.  In turn this stakeholder-based information is used to co-create “story maps” as tools to communicate complicated vulnerability analyses, highlight the ethical dimensions of various adaptation measures, raise awareness and aid decisionmakers in taking uncomfortable decisions to “wicked” planning problems around the negative effects of sea level rise, coastal erosion and urban flooding.</p><p>This paper presents the methodological development of the task as well as the results the study in four Swedish municipalities. The representation of the “soft” and ethical values provides an opportunity to help clarify these values to policymakers and increase resilience to rising sea levels.</p>

Sea level in the Global Geodetic Observing System

2020 ◽  
Author(s):  
Elizabeth Bradshaw ◽  
Andy Matthews ◽  
Kathy Gordon ◽  
Angela Hibbert ◽  
Sveta Jevrejeva ◽  
...  
Keyword(s):  
Sea Level ◽  
Working Group ◽  
Sea Level Change ◽  
Tide Gauges ◽  
Controlled Vocabularies ◽  
Mean Sea Level ◽  
Level Change ◽  
Level Data ◽  
Metadata Standards

<p>The Permanent Service for Mean Sea Level (PSMSL) is the global databank for long-term mean sea level data and is a member of the Global Geodetic Observing System (GGOS) Bureau of Networks and Observations. As well as curating long-term sea level change information from tide gauges, PSMSL is also involved in developing other products and services including the automatic quality control of near real-time sea level data, distributing Global Navigation Satellite System (GNSS) sea level data and advising on sea level metadata development.<br>At the GGOS Days meeting in November 2019, the GGOS Focus Area 3 on Sea Level Change, Variability and Forecasting was wrapped up, but there is still a requirement in 2020 for GGOS to integrate and support tide gauges and we will discuss how we will interact in the future. A recent paper (Ponte et al., 2019) identified that only “29% of the GLOSS [Global Sea Level Observing System] GNSS-co-located tide gauges have a geodetic tie available at SONEL [Système d'Observation du Niveau des Eaux Littorales]” and we as a community still need to improve the ties between the GNSS sensor and tide gauges. This may progress as new GNSS Interferometric Reflectometry (GNSS-IR) sensors are installed to provide an alternative method to observe sea level. As well as recording the sea level, these sensors will also provide vertical land movement information from one location. PSMSL are currently developing an online portal of uplift/subsidence land data and GNSS-IR sea level observation data. To distribute the data, we are creating/populating controlled vocabularies and generating discovery metadata.<br>We are working towards FAIR data management principles (data are findable, accessible, interoperable and reusable) which will improve the flow of quality controlled sea level data and in 2020 we will issue the PSMSL dataset with a Digital Object Identifier. We have been working on improving our discovery and descriptive metadata including creating a use case for the Research Data Alliance Persistent (RDA) Identification of Instruments Working Group to help improve the description of a time series where the sensor and platform may change and move many times. Representatives from PSMSL will sit on the GGOS DOIs for Data Working Group and would like to contribute help with controlled vocabularies, identifying metadata standards etc. We will also contribute to the next GGOS implementation plan.<br>Ponte, Rui M., et al. (2019) "Towards comprehensive observing and modeling systems for monitoring and predicting regional to coastal sea level." <em>Frontiers in Marine Science</em> 6(437).</p>

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