scholarly journals Assessing the impact of vertical land motion on twentieth century global mean sea level estimates

2016 ◽  
Vol 121 (7) ◽  
pp. 4980-4993 ◽  
Author(s):  
B. D. Hamlington ◽  
P. Thompson ◽  
W. C. Hammond ◽  
G. Blewitt ◽  
R. D. Ray
Keyword(s):  
Twentieth Century ◽  
Sea Level ◽  
Mean Sea Level ◽  
Vertical Land Motion ◽  
Global Mean Sea Level ◽  
The Impact ◽  
Global Mean

scholarly journals The imprints of contemporary mass redistribution on local sea level and vertical land motion observations

Solid Earth ◽  
2019 ◽  
Vol 10 (6) ◽  
pp. 1971-1987 ◽  
Author(s):  
Thomas Frederikse ◽  
Felix W. Landerer ◽  
Lambert Caron
Keyword(s):  
Sea Level ◽  
Tide Gauge ◽  
Tide Gauge Records ◽  
Mean Sea Level ◽  
Sea Floor ◽  
Vertical Land Motion ◽  
Mass Redistribution ◽  
Global Mean Sea Level ◽  
The Impact ◽  
Global Mean

Abstract. Observations from permanent Global Navigation Satellite System (GNSS) stations are commonly used to correct tide-gauge observations for vertical land motion (VLM). We combine GRACE (Gravity Recovery and Climate Experiment) observations and an ensemble of glacial isostatic adjustment (GIA) predictions to assess and evaluate the impact of solid-Earth deformation (SED) due to contemporary mass redistribution and GIA on VLM trends derived from GNSS stations. This mass redistribution causes relative sea-level (RSL) and SED patterns that not only vary in space but also exhibit large interannual variability signals. We find that for many stations, including stations in coastal locations, this deformation causes VLM trends on the order of 1 mm yr−1 or higher. In multiple regions, including the Amazon Basin and large parts of Australia, the SED trend flips sign between the first half and second half of the 15-year GRACE record. GNSS records often only span a few years, and due to these interannual variations SED causes substantial biases when the linear trends in these short records are extrapolated back in time. We propose a new method to avoid this potential bias in the VLM-corrected tide-gauge record: instead of correcting tide-gauge records for the observed VLM trend, we first remove the effects from GIA and contemporary mass redistributions from the VLM observations before computing the VLM trend. This procedure reduces the extrapolation bias induced by SED, and it also avoids the bias due to sea-floor deformation: SED includes net sea-floor deformation, which is ignored in global-mean sea-level reconstructions based on VLM-corrected tide-gauge data. We apply this method to 8166 GNSS stations. With this separation, we are able to explain a large fraction of the discrepancy between observed sea-level trends at multiple long tide-gauge records and the global-mean sea-level trend from recent reconstructions.

Estimating global mean sea-level rise and its uncertainties by 2100 and 2300 from expert assessment

2020 ◽  
Author(s):  
Benjamin Horton ◽  
Nicole Khan ◽  
Niamh Cahill ◽  
Janice Lee ◽  
Tim Shaw ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Exceedance Probability ◽  
Mean Sea Level ◽  
Mitigation And Adaptation ◽  
Climate Change Responses ◽  
Global Mean Sea Level ◽  
Original Survey ◽  
The Impact ◽  
Global Mean

<p>Sea-level rise projections and knowledge of their uncertainties are vital to make informed mitigation and adaptation decisions. To elicit expert judgments from members of the scientific community regarding future global mean sea-level (GMSL) rise and its uncertainties, we repeated a survey originally conducted five years ago. Under Representative Concentration Pathway (RCP) 2.6, 106 experts projected a likely (at least 66% probability) GMSL rise of 0.30–0.65 m by 2100, and 0.54–2.15 m by 2300, relative to 1986–2005. Under RCP 8.5, the same experts projected a likely GMSL rise of 0.63–1.32 m by 2100, and 1.67–5.61 m by 2300. Expert projections for 2100 are similar to those from the original survey, although the projection for 2300 has extended tails and is higher than the original survey. Experts give a likelihood of 42% (original survey) and 45% (current survey) that under the high emissions scenario GMSL rise will exceed the upper bound (0.98 m) of the likely (i.e. an exceedance probability of 17%) range estimated by the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Responses to open-ended questions suggest that the increases in upper-end estimates and uncertainties arose from recent influential studies about the impact of marine ice cliff instability on the meltwater contribution to GMSL rise from the Antarctic Ice Sheet.</p>

scholarly journals Evaluating Model Simulations of Twentieth-Century Sea Level Rise. Part I: Global Mean Sea Level Change

2017 ◽  
Vol 30 (21) ◽  
pp. 8539-8563 ◽  
Author(s):  
Aimée B. A. Slangen ◽  
Benoit Meyssignac ◽  
Cecile Agosta ◽  
Nicolas Champollion ◽  
John A. Church ◽  
...  
Keyword(s):  
Twentieth Century ◽  
Thermal Expansion ◽  
Sea Level Rise ◽  
Sea Level ◽  
Sea Level Change ◽  
Mean Sea Level ◽  
Level Change ◽  
The World ◽  
Global Mean Sea Level ◽  
Global Mean

Sea level change is one of the major consequences of climate change and is projected to affect coastal communities around the world. Here, global mean sea level (GMSL) change estimated by 12 climate models from phase 5 of the World Climate Research Programme’s Climate Model Intercomparison Project (CMIP5) is compared to observational estimates for the period 1900–2015. Observed and simulated individual contributions to GMSL change (thermal expansion, glacier mass change, ice sheet mass change, landwater storage change) are analyzed and compared to observed GMSL change over the period 1900–2007 using tide gauge reconstructions, and over the period 1993–2015 using satellite altimetry estimates. The model-simulated contributions explain 50% ± 30% (uncertainties 1.65 σ unless indicated otherwise) of the mean observed change from 1901–20 to 1988–2007. Based on attributable biases between observations and models, a number of corrections are proposed, which result in an improved explanation of 75% ± 38% of the observed change. For the satellite era (from 1993–97 to 2011–15) an improved budget closure of 102% ± 33% is found (105% ± 35% when including the proposed bias corrections). Simulated decadal trends increase over the twentieth century, both in the thermal expansion and the combined mass contributions (glaciers, ice sheets, and landwater storage). The mass components explain the majority of sea level rise over the twentieth century, but the thermal expansion has increasingly contributed to sea level rise, starting from 1910 onward and in 2015 accounting for 46% of the total simulated sea level change.

scholarly journals Reassessment of 20th century global mean sea level rise

2017 ◽  
Vol 114 (23) ◽  
pp. 5946-5951 ◽  
Author(s):  
Sönke Dangendorf ◽  
Marta Marcos ◽  
Guy Wöppelmann ◽  
Clinton P. Conrad ◽  
Thomas Frederikse ◽  
...  
Keyword(s):  
Sea Level ◽  
20Th Century ◽  
Tide Gauge ◽  
Equal Proportion ◽  
Tide Gauge Records ◽  
Intergovernmental Panel ◽  
Mean Sea Level ◽  
Vertical Land Motion ◽  
Global Mean Sea Level ◽  
Global Mean

The rate at which global mean sea level (GMSL) rose during the 20th century is uncertain, with little consensus between various reconstructions that indicate rates of rise ranging from 1.3 to 2 mm⋅y−1. Here we present a 20th-century GMSL reconstruction computed using an area-weighting technique for averaging tide gauge records that both incorporates up-to-date observations of vertical land motion (VLM) and corrections for local geoid changes resulting from ice melting and terrestrial freshwater storage and allows for the identification of possible differences compared with earlier attempts. Our reconstructed GMSL trend of 1.1 ± 0.3 mm⋅y−1 (1σ) before 1990 falls below previous estimates, whereas our estimate of 3.1 ± 1.4 mm⋅y−1 from 1993 to 2012 is consistent with independent estimates from satellite altimetry, leading to overall acceleration larger than previously suggested. This feature is geographically dominated by the Indian Ocean–Southern Pacific region, marking a transition from lower-than-average rates before 1990 toward unprecedented high rates in recent decades. We demonstrate that VLM corrections, area weighting, and our use of a common reference datum for tide gauges may explain the lower rates compared with earlier GMSL estimates in approximately equal proportion. The trends and multidecadal variability of our GMSL curve also compare well to the sum of individual contributions obtained from historical outputs of the Coupled Model Intercomparison Project Phase 5. This, in turn, increases our confidence in process-based projections presented in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change.

The actual measurements at the tide gauges do not support strongly accelerating twentieth-century sea-level rise reconstructions

2016 ◽  
Vol 5 (1) ◽  
Author(s):  
A. Parker
Keyword(s):  
Twentieth Century ◽  
Sea Level Rise ◽  
Sea Level ◽  
Tide Gauges ◽  
Mean Sea Level ◽  
Sea Levels ◽  
Global Mean Sea Level ◽  
Global Mean

AbstractContrary to what 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 [

scholarly journals Simulated Global-Mean Sea Level Changes over the Last Half-Millennium

2006 ◽  
Vol 19 (18) ◽  
pp. 4576-4591 ◽  
Author(s):  
J. M. Gregory ◽  
J. A. Lowe ◽  
S. F. B. Tett
Keyword(s):  
Twentieth Century ◽  
Thermal Expansion ◽  
Sea Level Rise ◽  
Sea Level ◽  
Decadal Variability ◽  
Volcanic Eruptions ◽  
Surface Temperature Change ◽  
Mean Sea Level ◽  
Global Mean Sea Level ◽  
Global Mean

Abstract Simulations of the last 500 yr carried out using the Third Hadley Centre Coupled Ocean–Atmosphere GCM (HadCM3) with anthropogenic and natural (solar and volcanic) forcings have been analyzed. Global-mean surface temperature change during the twentieth century is well reproduced. Simulated contributions to global-mean sea level rise during recent decades due to thermal expansion (the largest term) and to mass loss from glaciers and ice caps agree within uncertainties with observational estimates of these terms, but their sum falls short of the observed rate of sea level rise. This discrepancy has been discussed by previous authors; a completely satisfactory explanation of twentieth-century sea level rise is lacking. The model suggests that the apparent onset of sea level rise and glacier retreat during the first part of the nineteenth century was due to natural forcing. The rate of sea level rise was larger during the twentieth century than during the previous centuries because of anthropogenic forcing, but decreasing natural forcing during the second half of the twentieth century tended to offset the anthropogenic acceleration in the rate. Volcanic eruptions cause rapid falls in sea level, followed by recovery over several decades. The model shows substantially less decadal variability in sea level and its thermal expansion component than twentieth-century observations indicate, either because it does not generate sufficient ocean internal variability, or because the observational analyses overestimate the variability.

scholarly journals Projecting Global Mean Sea-Level Change Using CMIP6 Models

2021 ◽  
Author(s):  
Tim Hermans ◽  
Jonathan Gregory ◽  
Matthew Palmer ◽  
Mark Ringer ◽  
Caroline Katsman ◽  
...  
Keyword(s):  
Sea Level ◽  
Climate Models ◽  
Sea Level Change ◽  
Global Climate Models ◽  
Mean Sea Level ◽  
Level Change ◽  
Global Mean Sea Level ◽  
The Impact ◽  
Global Mean ◽  
Emissions Scenario

<p>The effective climate sensitivity (EffCS) of models in the Coupled Model Intercomparison Project 6 (CMIP6) has increased relative to CMIP5. Consequently, using CMIP6 models tends to lead to larger projections of global mean surface air temperature (GSAT) increase for a given emissions scenario. The effect of increased EffCS on projections of global mean sea-level (GMSL) change however, has so far only been studied using a reduced complexity model. Here, we explore the implications of increased EffCS in CMIP6 models for GMSL change projections in 2100 for three emissions scenarios: SSP5-8.5, SSP2-4.5 and SSP1-2.6.</p><p>Whereas CMIP6 projections of GSAT change are substantially higher than in CMIP5, projections of global mean thermal expansion (GTE) are only slightly higher. We use these projections as input to construct projections of GMSL change, using the Monte Carlo approach of IPCC AR5. Isolating the impact of the CMIP6 simulations using consistent methods is an important step to ensure traceability to past IPCC projections of global and regional sea-level change. The resulting 95<sup>th</sup> percentile of projected GMSL change at 2100 is only 3-7 cm higher for CMIP6 than for CMIP5, depending on the emissions scenario. Projected rates of GMSL rise around 2100 increase more strongly from CMIP5 to CMIP6, though, implying more pronounced differences beyond 2100 and greater committed sea-level rise. GMSL change in 2100 is accurately predicted by time-integrated temperature change and therefore mitigation requires early reduction of emissions.</p><p>We also find that the 95<sup>th</sup> percentile projections based on individual CMIP6 models can differ as much as 51 cm and that the 5-95% range of projected GMSL change for individual CMIP6 models can be substantially outside of the 5-95% range of the CMIP6 multi-model ensemble. Thus, through subsetting the CMIP6 ensemble using EffCS, a choice can be made between characterizing the central part of the probability distribution and more comprehensively sampling the high end of the GMSL projection space, which is relevant to risk-averse stakeholders. Our results show this may substantially alter ensemble projections, underlining the need to constrain EffCS in global climate models in order to reduce uncertainty in sea-level projections.</p>

scholarly journals Twentieth-Century Global-Mean Sea Level Rise: Is the Whole Greater than the Sum of the Parts?

2013 ◽  
Vol 26 (13) ◽  
pp. 4476-4499 ◽  
Author(s):  
J. M. Gregory ◽  
N. J. White ◽  
J. A. Church ◽  
M. F. P. Bierkens ◽  
J. E. Box ◽  
...  
Keyword(s):  
Twentieth Century ◽  
Thermal Expansion ◽  
Mass Loss ◽  
Sea Level Rise ◽  
Sea Level ◽  
Ice Sheet ◽  
Mean Sea Level ◽  
Reservoir Impoundment ◽  
Global Mean Sea Level ◽  
Global Mean

Abstract Confidence in projections of global-mean sea level rise (GMSLR) depends on an ability to account for GMSLR during the twentieth century. There are contributions from ocean thermal expansion, mass loss from glaciers and ice sheets, groundwater extraction, and reservoir impoundment. Progress has been made toward solving the “enigma” of twentieth-century GMSLR, which is that the observed GMSLR has previously been found to exceed the sum of estimated contributions, especially for the earlier decades. The authors propose the following: thermal expansion simulated by climate models may previously have been underestimated because of their not including volcanic forcing in their control state; the rate of glacier mass loss was larger than previously estimated and was not smaller in the first half than in the second half of the century; the Greenland ice sheet could have made a positive contribution throughout the century; and groundwater depletion and reservoir impoundment, which are of opposite sign, may have been approximately equal in magnitude. It is possible to reconstruct the time series of GMSLR from the quantified contributions, apart from a constant residual term, which is small enough to be explained as a long-term contribution from the Antarctic ice sheet. The reconstructions account for the observation that the rate of GMSLR was not much larger during the last 50 years than during the twentieth century as a whole, despite the increasing anthropogenic forcing. Semiempirical methods for projecting GMSLR depend on the existence of a relationship between global climate change and the rate of GMSLR, but the implication of the authors' closure of the budget is that such a relationship is weak or absent during the twentieth century.

scholarly journals Is there a 60-year oscillation in global mean sea level?

2012 ◽  
Vol 39 (18) ◽  
Author(s):  
Don P. Chambers ◽  
Mark A. Merrifield ◽  
R. Steven Nerem
Keyword(s):  
Sea Level ◽  
Mean Sea Level ◽  
Global Mean Sea Level ◽  
Global Mean

A 25-Year Satellite Altimetry-Based Global Mean Sea Level Record

2017 ◽  
pp. 187-210 ◽  
Author(s):  
R. Steven Nerem ◽  
Michaël Ablain ◽  
Anny Cazenave ◽  
John Church ◽  
Eric Leuliette
Keyword(s):  
Sea Level ◽  
Satellite Altimetry ◽  
Mean Sea Level ◽  
Global Mean Sea Level ◽  
Global Mean
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