Concepts and Terminology for Sea Level: Mean, Variability and Change, Both Local and Global

Gregory, Jonathan M.; Griffies, Stephen M.; Hughes, Chris W.; Lowe, Jason; Church, John A.; Fukimori, Ichiro; Gomez, Natalya; Kopp, Robert; Landerer, F. W.; Cozannet, Gonéri Le; Ponte, Rui M.; Stammer, Detlef; Tamisiea, M. E.; Wal, R. S. W. van de

doi:10.1007/s10712-019-09525-z

Cited by 334 publications

(407 citation statements)

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“…There are additionally systematic biases and hence uncertainties not accounted for in each of the observational products' formal error estimates. Using the terminology established by Gregory et al (), ocean mass changes directly observed by GRACE include both manometric changes in sea level, the change in the local mass of the ocean that incorporates the barystatic change and ocean circulation and redistribution, and the gravitational, rotational, and solid‐Earth deformation (gravitational, rotational, and deformation [GRD]) response.…”

Section: Introductionmentioning

confidence: 99%

Can We Resolve the Basin‐Scale Sea Level Trend Budget From GRACE Ocean Mass?

et al. 2020

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Understanding sea level changes at a regional scale is important for improving local sea level projections and coastal management planning. Sea level budget (SLB) estimates derived from the sum of observation of each component close for the global mean. The sum of steric and Gravity Recovery and Climate Experiment (GRACE) ocean mass contributions to sea level calculated from measurements does not match the spatial patterns of sea surface height trends from satellite altimetry at 1 • grid resolution over the period 2005-2015. We investigate potential drivers of this mismatch aggregating to subbasin regions and find that the steric plus GRACE ocean mass observations do not represent the small-scale features seen in the satellite altimetry. In addition, there are discrepancies with large variance apparent at the global and hemispheric scale. Thus, the SLB closure on the global scale to some extent represents a cancelation of errors. The SLB is also sensitive to the glacial isostatic adjustment correction for GRACE and to altimery orbital altitude. Discrepancies in the SLB are largest for the Indian-South Pacific Ocean region. Taking the spread of plausible sea level trends, the SLB closes at the ocean-basin scale (2 ) but with large spread of magnitude, one third or more of the trend signal. Using the most up-to-date observation products, our ocean-region SLB does not close everywhere, and consideration of systematic uncertainties diminishes what information can be gained from the SLB about sea level processes, quantifying contributions, and validating Earth observation systems. Plain Language SummaryAn important check on the accuracy of our global measurement systems and understanding of the processes driving sea level rise is the sea level budget. This describes the comparison of measured sea surface height change from satellite radar altimetry with the sum of its component parts, due to density and mass changes. With over 11 years of very high quality density and mass observations at good spatial scale, the sum of the parts matches the total within some uncertainty at a global scale. If, however, we examine the sea level budget at the ocean basin scale, we find significant discrepancies that are difficult to explain. We investigate different processing and averaging methods and find the density measurements do not include small spatial scales that are recorded by sea surface height measurements. Rather than this mismatch averaging out over basin scales, which we would expect if the errors are random, it instead leads to differences in the ocean basin average. Also, there is a mismatch at the hemispheric and global scale, which we believe comes from the way the satellite measurements are processed.

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Section: Introductionmentioning

confidence: 99%

Can We Resolve the Basin‐Scale Sea Level Trend Budget From GRACE Ocean Mass?

et al. 2020

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“…Regional sea-level changes (∆RSLC) result from the sum of the global and regional sea-level change components. Considering the inverse-barometer correction [53], ∆RSLC is expressed as…”

Section: Regional Sea-level Risementioning

confidence: 99%

“…where ∆Z is the sterodynamic induced sea-level change, ∆R barystatic−GRD is the barystatic-GRD-induced sea-level change (excluding GIA) (GRD: changes in Earth Gravity, Earth Rotation and viscoelastic solid-Earth Deformation) and ∆R GIA is the GIA-induced sea-level change (GIA: Glacial Isostatic Adjustment). Note that the definition of relative sea-level change (following the terminology of Gregory et al [53]) further considers local vertical ground motions, which are, however, neglected in our study. The details of the terms of Equation (1) are described in the following subsections.…”

Section: Regional Sea-level Risementioning

confidence: 99%

“…Note that the latter effect leads to a redistribution of the regional sea-level globally but does not cause a global-mean sea-level rise. Both contributions are combined into a constant geographical pattern called barystatic-GRD fingerprint φ, [53,56] and are proportional to the land water mass change δM. The sum of the barystatic-GRD relative sea-level change due to all the stores i of water on the land is expressed by, [53],…”

Section: Barystatic-grd Induced Sea-level Change (∆R Barystatic−grd )mentioning

confidence: 99%

“…Note that water mass change δM i can be instead expressed as a global sea-level equivalent change ∆SLE i = δM i / ρ f A where ρ f and A are the water density and the area of the global ocean, respectively [53]. In practice, ∆SLE i gives the global sea-level change contribution of each store of water on the land, and its multiplication by the corresponding fingerprint gives its regional distribution.…”

Section: Barystatic-grd Induced Sea-level Change (∆R Barystatic−grd )mentioning

confidence: 99%

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Likely and High-End Impacts of Regional Sea-Level Rise on the Shoreline Change of European Sandy Coasts Under a High Greenhouse Gas Emissions Scenario

Thiéblemont

Cozannet

Toimil

et al. 2019

Water

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Sea-level rise (SLR) is a major concern for coastal hazards such as flooding and erosion in the decades to come. Lately, the value of high-end sea-level scenarios (HESs) to inform stakeholders with low-uncertainty tolerance has been increasingly recognized. Here, we provide high-end projections of SLR-induced sandy shoreline retreats for Europe by the end of the 21st century based on the conservative Bruun rule. Our HESs rely on the upper bound of the RCP8.5 scenario "likely-range" and on high-end estimates of the different components of sea-level projections provided in recent literature. For both HESs, SLR is projected to be higher than 1 m by 2100 for most European coasts. For the strongest HES, the maximum coastal sea-level change of 1.9 m is projected in the North Sea and Mediterranean areas. This translates into a median pan-European coastline retreat of 140 m for the moderate HES and into more than 200 m for the strongest HES. The magnitude and regional distribution of SLR-induced shoreline change projections, however, utterly depend on the local nearshore slope characteristics and the regional distribution of sea-level changes. For some countries, especially in Northern Europe, the impacts of high-end sea-level scenarios are disproportionally high compared to those of likely scenarios.2 of 22 gas emissions. Since the release of the IPCC AR5 (Intergovernmental Panel on Climate Change Fifth Assessment Report) in 2013, the debate on long-term projections of GMSL has strongly focused on the potentially very large contribution of the Antarctica ice-sheet [2,[8][9][10][11], which constitutes a deep source of uncertainty.Sea-level changes at the regional scale can substantially differ from GMSL change. Thermal expansion is modulated regionally by changes in ocean circulation, density, and atmospheric pressure [12,13]. In addition, water mass transfer from land to the ocean-due, e.g., to mountain glaciers and ice-sheets melting or groundwater extraction-induces regional changes by altering the Earth's gravity field, Earth rotation, and solid-Earth deformation [14]. Ongoing changes in the solid Earth are also still caused by the viscous adjustment of the mantle to the important mass redistribution that followed the Last Glacial Maximum (named Glacial Isostatic Adjustment; GIA) [15]. At the European scale, the influence of GIA is particularly prominent in the Scandinavian area. Finally, at a local scale, high-resolution oceanic processes [16] and vertical ground motion [17,18] can affect further the relative sea-level.Projections of future regional sea-level are crucial to support adaptation planning. So far, coastal adaptation practitioners have often relied on IPCC sea-level projections, which are provided in the form of a likely range (probability larger than 66%), and do not reflect the whole range of uncertainties of sea-level projections [19][20][21][22][23]. However, as coastal climate services are being developed [24,25], it is increasingly recognized that different types of sea-level projections are requir...

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A Spatially Variable Time Series of Sea Level Change Due to Artificial Water Impoundment

Hawley

Hay

Mitrovica

et al. 2020

Preprint

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The artificial impoundment of water behind dams causes global mean sea level (GMSL) to fall as reservoirs fill but also generates a local rise in sea level due to the increased mass in the reservoir and the crustal deformation this mass induces. To estimate spatiotemporal fluctuations in sea level due to water impoundment, we use a historical data set that includes 6,329 reservoirs completed between 1900 and 2011, as well as projections of 3,565 reservoirs that are expected to be completed by 2040. The GMSL change associated with the historical data (−0.2 mm yr −1 from 1900-2011) is consistent with previous studies, but the temporal and spatial resolution allows for local studies that were not previously possible, revealing that some locations experience a sea level rise of as much as 40 mm over less than a decade. Future construction of reservoirs through~2040 is projected to cause a GMSL fall whose rate is comparable to that of the last century (−0.3 mm yr −1 ) but with a geographic distribution that will be distinct from the last century, including a rise in sea level in more coastal areas. The analysis of expected construction shows that significant impoundment near coastal communities in the coming decades could enhance the flooding risk already heightened by global sea level rise.Plain Language Summary Filling a reservoir prevents that water from flowing back to the ocean, thus causing sea level to fall. But sea level does not change by the same amount everywhere: The mass of the water in the reservoir causes sea level to rise in locations near the reservoir but fall in locations that are farther away. We use databases that include the locations and capacities of reservoirs to estimate how constructing reservoirs has changed sea level and explore how these changes have varied in space and in time. We find that while constructing reservoirs since 1900 has caused sea level to fall on average, there are some locations that experience sea level rise by as much as 40 mm over a short period of time, usually only a few years. As more reservoirs are built, we expect this trend to continue. In fact, reservoirs that are currently being planned, if completed, will generate a sea level rise of a few millimeters in some low-lying coastal areas. This rise would be in addition to the rise in sea level from many other known factors.

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Concepts and Terminology for Sea Level: Mean, Variability and Change, Both Local and Global

Cited by 334 publications

References 34 publications

Can We Resolve the Basin‐Scale Sea Level Trend Budget From GRACE Ocean Mass?

Can We Resolve the Basin‐Scale Sea Level Trend Budget From GRACE Ocean Mass?

Likely and High-End Impacts of Regional Sea-Level Rise on the Shoreline Change of European Sandy Coasts Under a High Greenhouse Gas Emissions Scenario

A Spatially Variable Time Series of Sea Level Change Due to Artificial Water Impoundment

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