scholarly journals A statistical protocol for a holistic adjustment of global sea level budget

2020 ◽  
Vol 10 (1) ◽  
pp. 1-6
Author(s):  
H. Bâki Iz ◽  
C. K. Shum
Keyword(s):  
Sea Level ◽  
Science Studies ◽  
The Other ◽  
Error Statistics ◽  
Intergovernmental Panel ◽  
Mean Sea Level ◽  
Global Mean Sea Level ◽  
Global Sea Level ◽  
Global Mean ◽  
Assessment Reports

AbstractCurrent studies in global mean sea level, GMSL, studies assess the closure/misclosure of the GMSL budget components and their uncertainties. Because Earth’s hydrosphere conserves water, a closed global mean sea level budget with a consistent set of estimates and their statistics is necessary. An unclosed budget means that there are problems to be addressed such as biases in the budget components, unreliable error statistics about the estimates, unknown or known but unmodeled budget components. In a misclosed global mean sea level budget, as practiced in recent studies, the trend estimates for the budget components and their errors account only for the anomalies of each budget component in isolation. On the other hand, the trend of each series must consider the trends of the other series in tandem such that the global mean sea level budget is closed for a holistic assessment, which can only be achieved by adjusting global mean sea level budget components simultaneously. In this study, we demonstrate a statistical protocol to ameliorate this deficiency, which potentially have implications for future sea level science studies, including the future Intergovernmental Panel on Climate Change (IPCC) Assessment Reports, and the US Climate Assessment Reports.

scholarly journals Year by year closure adjustment of global mean sea level budget, inclusive of lumped snow, water vapor, and permafrost mass components

2020 ◽  
Vol 10 (1) ◽  
pp. 83-90
Author(s):  
H. Bâki Iz ◽  
C. K. Shum
Keyword(s):  
Water Vapor ◽  
Sea Level ◽  
Satellite Altimetry ◽  
Linear Trend ◽  
The Other ◽  
Mean Sea Level ◽  
Lump Sum ◽  
Snow Water ◽  
Global Mean Sea Level ◽  
Global Mean

AbstractGlobal mean sea level budget is rigorously adjusted during the period 2005–2015 with an emphasis on closing the budget on a year by year basis as opposed to using linear trends of global mean sea level components. The adjustment also accounts for the effect of snow, water vapor, and permafrost mass components as a lump sum. The approach provides better resolution for evaluating individual contribution of each budget component year by year in tandem with the other components. Year by year budget misclosures and the confidence intervals of the year by year adjusted budget components are suggestive of an increasing non-linearity in satellite altimetry derived global mean sea level measurements starting in 2012, which are not present in the other components. The solution also generates time series iteratively for the lumped snow, water vapor, and permafrost mass components as well as an estimate for its linear trend, 0.06±0.59 mm/yr. Nonetheless, its standard error is markedly large because of the un-modeled variability in satellite altimetry observed yearly averaged global mean sea level anomalies.

scholarly journals The certitude of a global sea level acceleration during the satellite altimeter era

2020 ◽  
Vol 10 (1) ◽  
pp. 29-40
Author(s):  
H. Bâki İz ◽  
C.K. Shum
Keyword(s):  
Sea Level ◽  
Satellite Altimetry ◽  
Mean Sea Level ◽  
Sea Level Acceleration ◽  
Kinematic Models ◽  
Sea Level Variations ◽  
Global Mean Sea Level ◽  
Global Sea Level ◽  
Omission Errors ◽  
Global Mean

AbstractRecent studies reported a uniform global sea level acceleration during the satellite altimetry era (1993–2017) by analyzing globally averaged satellite altimetry measurements. Here, we discuss potential omission errors that were not thoroughly addressed in detecting and estimating the reported global sea level acceleration in these studies. Our analyses results demonstrate that the declared acceleration in recent studies can also be explained equally well by alternative kinematic models based on previously well-established multi-decadal global mean sea level variations of various origins, which suggests prudence before declaring the presence of an accelerating global mean sea level with confidence during the satellite altimetry era.

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.

scholarly journals Kinematics of global mean thermosteric sea level during 1993–2019

2021 ◽  
Vol 11 (1) ◽  
pp. 75-82
Author(s):  
H. Bâki İz
Keyword(s):  
Time Series ◽  
Sea Level ◽  
Temperature Gradients ◽  
Sea Surface ◽  
Sea Level Changes ◽  
Mean Sea Level ◽  
Mean Sea Surface ◽  
Global Mean Sea Level ◽  
Global Sea Level ◽  
Global Mean

Abstract Because oceans cover 71% of Earth’s surface, ocean warming, consequential for thermal expansion of sea water, has been the largest contributor to the global mean sea level rise averaged over the 20 th and the early 21 st century. This study first generates quasi-observed monthly globally averaged thermosteric sea level time series by removing the contributions of global mean sea level budget components, namely, Glaciers, Greenland, Antarctica, and Terrestrial Water Storage from satellite altimetry measured global sea level changes during 1993–2019. A baseline kinematic model with global mean thermosteric sea level trend and a uniform acceleration is solved to evaluate the performance of a rigorous mixed kinematic model. The model also includes coefficients of monthly lagged 60 yearlong cumulative global mean sea surface temperature gradients and control variables of lunisolar origins and representations for first order autoregressive disturbances. The mixed kinematic model explains 94% (Adjusted R 2)1 of the total variability in quasi-observed monthly and globally averaged thermosteric time series compared to the 46% of the baseline kinematic model’s Adjusted R 2. The estimated trend, 1.19±0.03 mm/yr., is attributed to the long-term ocean warming. Whereas eleven statistically significant (α = 0.05) monthly lagged cumulative global mean sea surface temperature gradients each having a memory of 60 years explain the remainder transient global mean thermosteric sea level changes due to the episodic ocean surface warming and cooling during this period. The series also exhibit signatures of a statistically significant contingent uniform global sea level acceleration and periodic lunisolar forcings.

scholarly journals Climate-change–driven accelerated sea-level rise detected in the altimeter era

2018 ◽  
Vol 115 (9) ◽  
pp. 2022-2025 ◽  
Author(s):  
R. S. Nerem ◽  
B. D. Beckley ◽  
J. T. Fasullo ◽  
B. D. Hamlington ◽  
D. Masters ◽  
...  
Keyword(s):  
Climate Change ◽  
Sea Level Rise ◽  
Sea Level ◽  
Altimeter Data ◽  
Intergovernmental Panel ◽  
Mean Sea Level ◽  
Simple Extrapolation ◽  
Global Mean Sea Level ◽  
Satellite Altimeter Data ◽  
Global Mean

Using a 25-y time series of precision satellite altimeter data from TOPEX/Poseidon, Jason-1, Jason-2, and Jason-3, we estimate the climate-change–driven acceleration of global mean sea level over the last 25 y to be 0.084 ± 0.025 mm/y2. Coupled with the average climate-change–driven rate of sea level rise over these same 25 y of 2.9 mm/y, simple extrapolation of the quadratic implies global mean sea level could rise 65 ± 12 cm by 2100 compared with 2005, roughly in agreement with the Intergovernmental Panel on Climate Change (IPCC) 5th Assessment Report (AR5) model projections.

Effects of Sea-Level Rise and Subsidence on Deltas

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.

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

scholarly journals The effect of lateral variations in Earth structure on Last Interglacial sea level

2021 ◽  
Author(s):  
Jacqueline Austermann ◽  
Mark Hoggard ◽  
Konstantin Latychev ◽  
Fred Richards ◽  
Jerry Mitrovica
Keyword(s):  
Sea Level ◽  
Earth Structure ◽  
Last Interglacial ◽  
Level Indicator ◽  
Mean Sea Level ◽  
Mineral Physics ◽  
Shear Wave Speed ◽  
Global Mean Sea Level ◽  
Lateral Variations ◽  
Global Mean

It is generally agreed that the Last Interglacial (LIG; ~130-115ka) was a time when global average temperatures and global mean sea level were higher than they are today. However, the exact timing, magnitude, and spatial pattern of ice melt is much debated. One difficulty in extracting past global mean sea level from local observations is that their elevations need to be corrected for glacial isostatic adjustment (GIA), which requires knowledge of Earth’s internal viscoelastic structure. While this structure is generally assumed to be radially symmetric, evidence from seismology, geodynamics, and mineral physics indicates that large lateral variations in viscosity exist within the mantle. In this study, we construct a new model of Earth’s internal structure by converting shear wave speed into viscosity using parameterisations from mineral physics experiments and geodynamical constraints on Earth’s thermal structure. We use this 3D Earth structure, which includes both variations in lithospheric thickness and lateral variations in viscosity, to calculate the first 3D GIA prediction for LIG sea level. We find that the difference between predictions with and without lateral Earth structure can be meters to 10s of meters in the near field of former ice sheets, and up to a few meters in their far field. We demonstrate how forebulge dynamics and continental levering are affected by laterally varying Earth structure, with a particular focus on those sites with prominent LIG sea level records. Results from three 3D GIA calculations show that accounting for lateral structure acts to increase local sea level by up to ~1.5m at the Seychelles and minimally decrease it in Western Australia. We acknowledge that this result is only based on a few simulations, but if robust, this shift brings estimates of global mean sea level from these two sites into closer agreement with each other. We further demonstrate that simulations with a suitable radial viscosity profile can be used to locally approximate the 3D GIA result, but that these radial profiles cannot be found by simply averaging viscosity below the sea level indicator site.

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