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 ◽  
...  

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.

Author(s):  
Thomas S. Bianchi

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.


2006 ◽  
Vol 19 (18) ◽  
pp. 4576-4591 ◽  
Author(s):  
J. M. Gregory ◽  
J. A. Lowe ◽  
S. F. B. Tett

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.


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 ◽  
...  

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.


2014 ◽  
Vol 11 (1) ◽  
pp. 123-169 ◽  
Author(s):  
T. Howard ◽  
J. Ridley ◽  
A. K. Pardaens ◽  
R. T. W. L. Hurkmans ◽  
A. J. Payne ◽  
...  

Abstract. Climate change has the potential to locally influence mean sea level through a number of processes including (but not limited to) thermal expansion of the oceans and enhanced land ice melt. These lead to departures from the global mean sea level change, due to spatial variations in the change of water density and transport, which are termed dynamic sea level changes. In this study we present regional patterns of sea-level change projected by a global coupled atmosphere–ocean climate model forced by projected ice-melt fluxes from three sources: the Antarctic ice sheet, the Greenland ice sheet and small glaciers and ice caps. The largest ice melt flux we consider is equivalent to almost 0.7 m of global sea level rise over the 21st century. Since the ice melt is not constant, the evolution of the dynamic sea level changes is analysed. We find that the dynamic sea level change associated with the ice melt is small, with the largest changes, occurring in the North Atlantic, contributing of order 3 cm above the global mean rise. Furthermore, the dynamic sea level change associated with the ice melt is similar regardless of whether the simulated ice fluxes are applied to a simulation with fixed or changing atmospheric CO2.


Science ◽  
1997 ◽  
Vol 275 (5303) ◽  
pp. 1049i-1053 ◽  
Author(s):  
R. S. Nerem

2020 ◽  
Author(s):  
Lorena Moreira ◽  
Anny Cazenave ◽  
Denise Cáceres ◽  
Hindumathi Palanisamy ◽  
Habib Dieng

<p>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 ‘residual’ 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.</p>


1999 ◽  
Vol 26 (19) ◽  
pp. 3005-3008 ◽  
Author(s):  
R. S. Nerem ◽  
D. P. Chambers ◽  
E. W. Leuliette ◽  
G. T. Mitchum ◽  
B. S. Giese

2019 ◽  
Vol 11 (10) ◽  
pp. 1176
Author(s):  
Yongcun Cheng ◽  
Qing Xu ◽  
Le Gao ◽  
Xiaofeng Li ◽  
Bin Zou ◽  
...  

Sea State Bias (SSB) contributes to global mean sea level variability and it needs cm-level range adjustment due to the instrumental drift over time. To investigate its variations and correct the global and regional sea level trend precisely, we calculate the temporal and spatial variability of the SSB correction in TOPEX, Jason-1, Jason-2 and Jason-3 missions, separately, as well as in the combined missions over the period 1993–2017. The long-term trend in global mean operational 2D non-parametric SSB correction is about −0.03 ± 0.03 mm/yr, which accounts for 1% of current global mean sea level change rate during 1993–2016. This correction contributes to sea level change rates of −1.27 ± 0.21 mm/yr and −0.26 ± 0.13 mm/yr in TOPEX-A and Jason-2 missions, respectively. The global mean SSB varies up to 7–10 mm during the very strong ENSO events in 1997–1998 and 2015–2016. Furthermore, the TOPEX SSB trend, which is consistent with recently reported sea level trend drift during 1993–1998, may leak into the determined global sea level trend in the period. Moreover, the Jason-1/2 zonal SSB variability is highly correlated with the significant wave height (SWH). On zonal average, SSB correction causes about 1% uncertainty in mean sea level trend. At high SWH regions, the uncertainties grow to 2–4% near the 50°N and 60°S bands. This should be considered in the study of regional sea level variability.


2005 ◽  
Vol 79 (9) ◽  
pp. 532-539 ◽  
Author(s):  
J. L. Chen ◽  
C. R. Wilson ◽  
B. D. Tapley ◽  
J. S. Famiglietti ◽  
Matt Rodell

Ocean Science ◽  
2014 ◽  
Vol 10 (3) ◽  
pp. 485-500 ◽  
Author(s):  
T. Howard ◽  
J. Ridley ◽  
A. K. Pardaens ◽  
R. T. W. L. Hurkmans ◽  
A. J. Payne ◽  
...  

Abstract. Climate change has the potential to influence global mean sea level through a number of processes including (but not limited to) thermal expansion of the oceans and enhanced land ice melt. In addition to their contribution to global mean sea level change, these two processes (among others) lead to local departures from the global mean sea level change, through a number of mechanisms including the effect on spatial variations in the change of water density and transport, usually termed dynamic sea level changes. In this study, we focus on the component of dynamic sea level change that might be given by additional freshwater inflow to the ocean under scenarios of 21st-century land-based ice melt. We present regional patterns of dynamic sea level change given by a global-coupled atmosphere–ocean climate model forced by spatially and temporally varying projected ice-melt fluxes from three sources: the Antarctic ice sheet, the Greenland Ice Sheet and small glaciers and ice caps. The largest ice melt flux we consider is equivalent to almost 0.7 m of global mean sea level rise over the 21st century. The temporal evolution of the dynamic sea level changes, in the presence of considerable variations in the ice melt flux, is also analysed. We find that the dynamic sea level change associated with the ice melt is small, with the largest changes occurring in the North Atlantic amounting to 3 cm above the global mean rise. Furthermore, the dynamic sea level change associated with the ice melt is similar regardless of whether the simulated ice fluxes are applied to a simulation with fixed CO2 or under a business-as-usual greenhouse gas warming scenario of increasing CO2.


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