The causes of sea-level rise since 1900

Global-mean sea level (GMSL) has been rising unsteadily by about 1.5 mm/yr since 1900, but the underlying causes of this trend and the multi-decadal variations are still poorly understood. Over the last few years, updated estimates of the underlying contributing processes have become available, notably for the contributions from glaciers, terrestrial water storage, the Greenland Ice Sheet, and thermal expansion. In parallel, 20th-century GMSL estimates have been revised downward as a result of improved reconstruction approaches, spatial bias correction schemes, and the inclusion of estimates of local vertical land motion at tide-gauge locations. Together, both developments now necessitate the re-evaluation of the GMSL budget to determine whether the observed sea-level rise since 1900 can be reconciled with the estimated sum of contributing processes.&#160;Here we present a probabilistic framework to reconstruct and budget sea level with independent observations considering their inherent uncertainties. We find that the sum of thermal expansion, ice-mass loss and terrestrial water storage changes is consistent with the trends and multi-decadal variability in observed sea level on both global and basin scales, which we reconstruct from tide-gauge records.&#160;Glacier-dominated cryospheric mass loss has caused twice as much sea-level rise as thermal expansion since 1900. Glacier and Greenland Ice Sheet mass loss well explains the high rates typically seen in global sea-level reconstructions during the 1930s, while a sharp increase in water impoundment by artificial reservoirs has been the dominant contributor to lower-than-average rates during the 1970s. The acceleration since the 1970s is caused by both thermal expansion and increased Greenland mass loss. No additional large-scale deep ocean warming or additional mass loss from Antarctica are needed to explain 20th-century changes in global-mean sea level. This assessment reconciles the magnitude of observed global-mean sea-level rise since 1900 with estimates of underlying processes.

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Coupled ice-climate simulation of future Greenland ice sheet evolution: mechanisms, thresholds and feedbacks for accelerated mass loss

10.5194/egusphere-egu2020-19692 ◽

2020 ◽

Author(s):

Miren Vizcaino ◽

Laura Muntjewerf ◽

Raymond Sellevold ◽

Carolina Ernani da Silva ◽

Michele Petrini ◽

...

Keyword(s):

Global Warming ◽

Mass Loss ◽

Sea Level Rise ◽

Sea Level ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Mean Sea Level ◽

Model Version ◽

Global Mean Sea Level ◽

Global Mean

The Greenland ice sheet (GrIS) has been losing mass in the last several decades, with a current contributing of around 0.7 mm per year to global mean sea level rise (SLR). Projections of future melt rates are often derived from standalone ice sheet models, forced by data from global or regional climate models. In many cases, the surface mass balance parameterization relies on simplified schemes that relate melt with surface temperature.In this study, we present a mass and energy conserving, 350-year simulation with the Community Earth System Model version 2.1 (CESM2.1) bidirectionally coupled to the Community Ice Sheet Model version 2.1 (CISM2.1). In this simulation, the carbon dioxide concentration is initially increasing by 1% per year&#160; from pre-industrial levels (287 ppmv), to a quadrupling (1140 ppmv) and stabilization after year 140. The model simulates a global warming of 5.3 K and 8.5 K with respect to preindustrial by years 131-150 and 331-150, respectively, and a strong decline in the North Atlantic Meridional Overturning Circulation that is initiated before GrIS runoff substantially increases. 91% of the total GrIS contribution to global mean sea level rise (SLR, 1140 mm) is simulated in the two centuries following CO2 stabilization, as the mass loss increases from 2.2 mm SLR per year in 131-150 to 6.6 mm SLR per year in 331-351. This increase is caused by melt acceleration as the ablation areas expand, and Greenland summer surface temperatures predominantly approach melt conditions when the global warming exceeds a certain threshold (around 4.2 K).&#160; This enhances the albedo and turbulent heat fluxes contribution to total melt energy. &#160;

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

Journal of Climate ◽

10.1175/jcli-d-12-00319.1 ◽

2013 ◽

Vol 26 (13) ◽

pp. 4476-4499 ◽

Cited By ~ 136

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.

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An ensemble approach to quantify global mean sea-level rise over the 20th century from tide gauge reconstructions

Environmental Research Letters ◽

10.1088/1748-9326/abdaec ◽

2021 ◽

Author(s):

Matthew D Palmer ◽

Catia M. Domingues ◽

Aimée B.A. Slangen ◽

Fabio Boeira Dias

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

20Th Century ◽

Tide Gauge ◽

Mean Sea Level ◽

Ensemble Approach ◽

Global Mean Sea Level ◽

Global Mean

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The rate and acceleration of the global mean sea level revisited

10.5194/egusphere-egu2020-4643 ◽

2020 ◽

Author(s):

Lorena Moreira ◽

Anny Cazenave ◽

Denise Cáceres ◽

Hindumathi Palanisamy ◽

Habib Dieng

Keyword(s):

Thermal Expansion ◽

Global Warming ◽

Sea Level Rise ◽

Interannual Variability ◽

Sea Level ◽

Water Storage ◽

Mean Sea Level ◽

Global Mean Sea Level ◽

Land Water ◽

Global Mean

Since nearly 3 decades, high-precision satellite altimetry allows us to precisely measure the mean sea level evolution at global and regional scales. In terms of global mean, sea level is rising at a mean rate of 3.2 mm/yr. The altimetry record is also suggesting that the global mean sea level rise is accelerating. However, the exact value of the acceleration and even its mere existence are still debated. Determination of the global warming-related sea level rate and acceleration are somewhat hindered by the interannual signal caused by natural climate variability. During the recent years, several studies have shown that at interannual time scale, the global mean sea level is mostly due to ENSO-driven land water storage variations. But thermal expansion fluctuations may also contribute. Thus, to isolate the global warming signal in the global mean sea level, we need to remove the ENSO-related interannual variability. For that purpose we use the Water Gap Global Hydrological model developed by the University of Frankfurt for land water storage as well as GRACE space gravimetry data on land and empirical models based on ENSO indices. We also extract the ENSO-related signal in thermal expansion. After removing the total interannual variability signal due to both mass and steric components, we compute the evolution with time of the &#8216;residual&#8217; rate of sea level rise over successive 5-year moving windows, as well as the associated acceleration. Using time series of thermal expansion and ice sheet mass balances, we also estimate the respective contributions of each component to the global mean sea level acceleration.

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

Journal of Climate ◽

10.1175/jcli-d-17-0110.1 ◽

2017 ◽

Vol 30 (21) ◽

pp. 8539-8563 ◽

Cited By ~ 23

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.

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A new assessment of global mean sea level from altimeters highlights a reduction of global trend from 2005 to 2008

Ocean Science Discussions ◽

10.5194/osd-6-31-2009 ◽

2009 ◽

Vol 6 (1) ◽

pp. 31-56 ◽

Cited By ~ 3

Author(s):

M. Ablain ◽

A. Cazenave ◽

G. Valladeau ◽

S. Guinehut

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Tide Gauge ◽

Mean Sea Level ◽

Error Budget ◽

Isostatic Adjustment ◽

Global Trend ◽

Tide Gauge Measurements ◽

Global Mean Sea Level ◽

Global Mean

Abstract. A new error budget assessment of the global Mean Sea Level (MSL) determined by TOPEX/Poseidon and Jason-1 altimeter satellites between January 1993 and June 2008 is presented. We discuss all potential errors affecting the calculation of the global MSL rate. We also compare altimetry-based sea level with tide gauge measurements over the altimetric period. This allows us to provide a realistic error budget of the MSL rise measured by satellite altimetry. These new calculations highlight a reduction in the rate of sea level rise since 2005, by ~2 mm/yr. This represents a 60% reduction compared to the 3.3 mm/yr sea level rise (glacial isostatic adjustment correction applied) measured between 1993 and 2005. Since November 2005, MSL is accurately measured by a single satellite, Jason-1. However the error analysis performed here indicates that the recent reduction in MSL rate is real.

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Effects of Sea-Level Rise and Subsidence on Deltas

Deltas and Humans ◽

10.1093/oso/9780199764174.003.0010 ◽

2016 ◽

Author(s):

Thomas S. Bianchi

Keyword(s):

Thermal Expansion ◽

Global Warming ◽

Sea Level Rise ◽

Sea Level ◽

Sea Level Change ◽

Mean Sea Level ◽

Level Change ◽

Global Mean Sea Level ◽

Global Sea Level ◽

Global Mean

As I briefly mentioned in Chapter 3, the global mean sea level, as deduced from the accumulation of paleo-sea level, tide gauge, and satellite-altimeter data, rose by 0.19 m (range, 0.17–0.21 m) between 1901 and 2010 (see Figure 3.3). Global mean sea level represents the longer-term global changes in sea level, without the short-term variability, and is also commonly called eustatic sea-level change. On an annual basis, global mean sea-level change translates to around 1.5 to 2 mm. During the last century, global sea level rose by 10 to 25 cm. Projections of sea-level rise for the period from 2000 to 2081 indicate that global mean sea-level rise will likely be as high as 0.52 to 0.98 m, or 8 to 16 mm/ yr, depending on the greenhouse gas emission scenarios used in the models. Mean sea-level rise is primarily controlled by ocean thermal expansion. But there is also transfer of water from land to ocean via melting of land ice, primarily in Greenland and Antarctica. Model predictions indicate that thermal expansion will increase with global warming because the contribution from glaciers will decrease as their volume is lost over time. (Take a look at Figure 5.1 if you have doubts about glaciers melting.) And remember our discussion in Chapter 2 about the role of the oceans in absorbing carbon dioxide (CO2) and the resultant ocean acidification in recent years. The global ocean also absorbs about 90% of all the net energy increase from global warming as well, which is why the ocean temperature is increasing, which in turn results in thermal expansion and sea-level rise. To make things even more complicated, the expansion of water will vary with latitude because expansion of seawater is greater with increasing temperature. In any event, sea level is expected to rise by 1 to 3 m per degree of warming over the next few millennia.

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

Journal of Climate ◽

10.1175/jcli3881.1 ◽

2006 ◽

Vol 19 (18) ◽

pp. 4576-4591 ◽

Cited By ~ 59

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.

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