An update on the thermosteric sea level rise commitment to global warming

Hieronymus, Magnus

doi:10.1088/1748-9326/ab1c31

Cited by 17 publications

(12 citation statements)

References 23 publications

(26 reference statements)

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“…At the end of the 21st century, the global glacier volume is projected to decrease by between 21 % (MMCP2.6) and 24 % (MMCP8.5) of its current value. The contribution to GMSL from glaciers and ice caps melting generally corroborates the findings by Hock et al (2019), who found that by the end of the 21st century mountain glaciers and ice caps lose between 11 %-25 % (RCP2.6) and 25 %-47 % (RCP8.5) of their volume. For scenario MMCP8.5, our results are below the average estimates at the end of the 21st century because of the rather low climate sensitivity in LOVECLIM.…”

Section: Discussionsupporting

confidence: 88%

“…Glaciers and ice caps are the second-largest contributor to present-day GMSL rise (after the thermosteric component) and will continue to be a major source of sea-level rise during the next century (Huss and Hock, 2015;Hock et al, 2019;Marzeion et al, 2020). At the end of the 21st century, the global glacier volume is projected to decrease by between 21 % (MMCP2.6) and 24 % (MMCP8.5) of its current value.…”

Section: Discussionmentioning

confidence: 99%

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Semi-equilibrated global sea-level change projections for the next 10 000 years

2020

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Abstract. The emphasis for informing policy makers on future sea-level rise has been on projections by the end of the 21st century. However, due to the long lifetime of atmospheric CO2, the thermal inertia of the climate system and the slow equilibration of the ice sheets, global sea level will continue to rise on a multi-millennial timescale even when anthropogenic CO2 emissions cease completely during the coming decades to centuries. Here we present global sea-level change projections due to the melting of land ice combined with steric sea effects during the next 10 000 years calculated in a fully interactive way with the Earth system model of intermediate complexity LOVECLIMv1.3. The greenhouse forcing is based on the Extended Concentration Pathways defined until 2300 CE with no carbon dioxide emissions thereafter, equivalent to a cumulative CO2 release of between 460 and 5300 GtC. We performed one additional experiment for the highest-forcing scenario with the inclusion of a methane emission feedback where methane is slowly released due to a strong increase in surface and oceanic temperatures. After 10 000 years, the sea-level change rate drops below 0.05 m per century and a semi-equilibrated state is reached. The Greenland ice sheet is found to nearly disappear for all forcing scenarios. The Antarctic ice sheet contributes only about 1.6 m to sea level for the lowest forcing scenario with a limited retreat of the grounding line in West Antarctica. For the higher-forcing scenarios, the marine basins of the East Antarctic Ice Sheet also become ice free, resulting in a sea-level rise of up to 27 m. The global mean sea-level change after 10 000 years ranges from 9.2 to more than 37 m. For the highest-forcing scenario, the model uncertainty does not exclude the complete melting of the Antarctic ice sheet during the next 10 000 years.

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Section: Discussionsupporting

confidence: 88%

Section: Discussionmentioning

confidence: 99%

Semi-equilibrated global sea-level change projections for the next 10 000 years

2020

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“…Levermann et al (2013) identified a similar linear relation between thermal expansion and global mean temperatures of 0.2 to 0.63 m per °C. Hieronymus (2019) assessed several coupled climate models and found an updated sensitivity of 0.51 to 0.83 m per ˚C of surface warming. The higher sensitivity is present in climate models that show an increase in AMOC strength.…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, the higher sensitivity reported by Hieronymus (2019) might be an overestimation in future scenarios where the ice sheets will melt strongly, due to the neglect of ice sheet-ocean interactions.…”

mentioning

confidence: 94%

Semi-equilibrated global sea-level change projections for the next 10 000 years

Breedam¹,

Goelzer²,

Huybrechts³

2020

Preprint

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The emphasis for informing policy makers on future sea-level rise has been on projections by the end of the 21 st century. However, due to the long lifetime of atmospheric CO2, the thermal inertia of the climate system and the slow equilibration of the ice sheets, global sea level will continue to rise on a multi-millennial timescale even when anthropogenic CO2 emissions cease completely during the coming decades to centuries. Here we present global sea-level change projections 25 due to melting of land ice combined with steric sea effects during the next 10,000 years calculated in a fully interactive way with the Earth System Model of Intermediate Complexity LOVECLIMv1.3. The climate forcing is based on the Extended Concentration Pathways defined until 2300 AD with no carbon dioxide emissions thereafter and the inclusion of a methaneemission feedback for the highest forcing scenario, equivalent to a cumulative CO2 release of around 460 to 5800 GtC. After 10,000 years, the sea-level change rate drops below 0.05 m per century and a semi-equilibrated state is reached. The Greenland 30 ice sheet is found to nearly disappear for all forcing scenarios. The Antarctic ice sheet contributes only about 1.6 m to sea level for the lowest forcing scenario with a limited retreat of the grounding line in West Antarctica. For the higher forcing scenarios, the marine basins of the East Antarctic ice sheet also become ice free, resulting in a sea-level rise of up to 27 m. The global mean sea-level change after 10,000 years ranges from 9.2 m to more than 37 m. The projections of multi-millennial semiequilibrated sea-level rise for a given CO2 forcing are shown to be in good agreement with geological archives. 35 45 from 10,000 years for accumulation rate changes to up to 100,000 years for temperature changes for the Antarctic ice sheet (Alley and Whillans, 1984).On a multi-millennial timescale, changes in land ice volume (mass contribution) together with ocean density changes from thermal expansion (thermosteric contribution) and haline contraction (halosteric contribution) are the main components contributing to global sea-level change (Miller et al., 2005). The mass contribution comes from melting or growing of the 50 Antarctic ice sheet, the Greenland ice sheet and glaciers and ice caps. The steric contribution is the expansion of ocean water when it gets warmer and less saline or conversely, the contraction when water is cooling and gets more salty (Feistel, 2010).The magnitude of thermal expansion depends on the climatic temperature forcing and on the rate of oceanic heat uptake.Because of the large mass and slow turnover time of the deep ocean, the oceanic heat content (and hence thermal expansion) will continue to rise in the ocean for centuries to millennia, even when surface warming has halted. Haline contraction -or 55 expansion of ocean water due to freshening -is a smaller, though not negligible component of steric sea-level rise. Physicallybased models have been used to study the different components contributing to g...

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“…To link the CDF for GMST increase by CP16 to global mean sea level (GMSL) rise, one needs a functional relationship between the two parameters. A linear relationship between GMST and GMSL has been found to hold on time scales of millennia [22,23]; however, for end of the current century projections, it is not evident what to use. Figure 9 (top) shows the GMSL projections (median and likely range) for RCPs 2.6, 4.5 and 8.5 relative to 1986-2005 from [1] plotted against the corresponding projected GMST increase relative to preindustrial from [24].…”

Section: Probabilities For a Baseline Scenariomentioning

confidence: 99%

Nonlinear Interactions and Some Other Aspects of Probabilistic Sea Level Projections

Hieronymus

2020

Water

Self Cite

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Probabilistic sea level projections are frequently used to characterise the uncertainty in future sea level rise. Here, it is investigated how different modelling assumptions and process estimates affect such projections using two process-based models that add up the sea level contributions from different processes such as thermosteric expansion and ice sheet melt. A method is applied to estimate the direct contributions from the different processes as well as that of nonlinear interactions between the processes to the projections. In general, the nonlinear interaction terms are found to be small compared to the direct contributions from the processes, and only a few interaction terms give significant contributions to the projections. Apart from the process estimates, probabilistic models often also incorporate some expert judgements that inflate the uncertainty compared with that derived from climate and ice-sheet models, and the effects of some such judgements are also evaluated and found to have a considerable influence on the projections. Lastly, sea level projections are most often given contingent on representative concentration pathways for atmospheric greenhouse gases. Here, we generalize this approach by also providing projections for a probabilistic baseline scenario.

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An update on the thermosteric sea level rise commitment to global warming

Cited by 17 publications

References 23 publications

Semi-equilibrated global sea-level change projections for the next 10 000 years

Semi-equilibrated global sea-level change projections for the next 10 000 years

Semi-equilibrated global sea-level change projections for the next 10 000 years

Nonlinear Interactions and Some Other Aspects of Probabilistic Sea Level Projections

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