Simulation of the future sea level contribution of Greenland with a new glacial system model

Calov, Reinhard; Beyer, Sebastian; Greve, Ralf; Beckmann, Johanna; Willeit, Matteo; Kleiner, Thomas; Rückamp, Martin; Humbert, Angelika; Ganopolski, Andrey

doi:10.5194/tc-12-3097-2018

Cited by 54 publications

(64 citation statements)

References 104 publications

(143 reference statements)

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“…All climate model parameter sets yield climate simulations in agreement with observations over the past 500 years (Loutre et al, 2011). Model parameter set P22 is chosen for the multi-millennial integrations because of its mid-range contribution to sea-level at 2100 AD and 2300 AD in comparison with recent studies Calov et al, 2018;Bulthuis et al, 2019; Tables S1-S2 and Figure S1). The mean annual temperature anomalies over the ice sheets for 2070-2100 relative to 1970-2005 (+4.6˚C over Greenland and +3.8 ˚C over Antarctica for 120 RCP8.5) correspond well with the mid to upper ranges of AOGCM projections over the polar regions (Fettweis et al, 2013, Barthel et al, 2019.…”

Section: Model Description and Initialisationmentioning

confidence: 83%

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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Section: Model Description and Initialisationmentioning

confidence: 83%

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

Breedam¹,

Goelzer²,

Huybrechts³

2020

Preprint

View full text Add to dashboard Cite

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“…This approach has been adopted by many ice-sheet models to represent transient past precipitation when they are not coupled to a climate model (e.g. Banderas et al, 2018;Charbit et al, 2002Charbit et al, , 2007Colleoni et al, 2014;Marshall et al, 2000;Marshall and Peltier, 2002;Marshall and Koutnik, 2006;Philippon et al, 2006;Zweck and Huybrechts, 2005). Surface ablation is calculated by the simple positive degree day (PDD) scheme (Reeh, 1989).…”

Section: Methodsmentioning

confidence: 99%

“…Properly modelling the NEGIS is a well-known prob-lem of ice-sheet models that investigate the evolution of the GrIS at large spatial scales. Most of these models underestimate the stream velocity and do not properly capture its outline (Aschwanden et al, 2016;Calov et al, 2018;Golledge and Edwards, 2019;Greve and Herzfeld, 2013;Seddik et al, 2012). Greve and Otsu (2007) succeed in reproducing a correct magnitude of its speed by increasing the basal sliding under the NEGIS by 3 orders of magnitude relative to the rest of the ice sheet, but they fail in reproducing its geometry.…”

Section: Model Performance On the Whole Grismentioning

confidence: 99%

Submarine melt as a potential trigger of the North East Greenland Ice Stream margin retreat during Marine Isotope Stage 3

et al. 2019

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The Northeast Greenland Ice Stream (NEGIS) has been suffering a significant ice mass loss during the last decades. This is partly due to increasing oceanic temperatures in the subpolar North Atlantic, which enhance submarine basal melting and mass discharge. This demonstrates the high sensitivity of this region to oceanic changes. In addition, a recent study suggested that the NEGIS grounding line was 20-40 km behind its present-day location for 15 ka during Marine Isotope Stage (MIS) 3. This is in contrast with Greenland temperature records indicating cold atmospheric conditions at that time, expected to favour ice-sheet expansion. To explain this anomalous retreat a combination of atmospheric and external forcings has been invoked. Yet, as the ocean is found to be a primary driver of the ongoing retreat of the NEGIS glaciers, the effect of past oceanic changes in their paleo evolution cannot be ruled out and should be explored in detail. Here we investigate the sensitivity of the NEGIS to the oceanic forcing during the last glacial period using a three-dimensional hybrid ice-sheet-shelf model. We find that a sufficiently high oceanic forcing could account for a NEGIS ice-margin retreat of several tens of kilometres, potentially explaining the recently proposed NEGIS groundingline retreat during Marine Isotope Stage 3.

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“…This is equivalent to applying an SMB correction (e.g. Calov and others, 2018), which is diagnosed by the model.…”

Section: Journal Of Glaciology 1025mentioning

confidence: 99%

Constraining the geothermal heat flux in Greenland at regions of radar-detected basal water

et al. 2019

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The spatial distribution of basal water critically impacts the evolution of ice sheets. Current estimates of basal water distribution beneath the Greenland Ice Sheet (GrIS) contain large uncertainties due to poorly constrained boundary conditions, primarily from geothermal heat flux (GHF). The existing GHF models often contradict each other and implementing them in numerical ice-sheet models cannot reproduce the measured temperatures at ice core locations. Here we utilize two datasets of radar-detected basal water in Greenland to constrain the GHF at regions with a thawed bed. Using the three-dimensional ice-sheet model SICOPOLIS, we iteratively adjust the GHF to find the minimum GHF required to reach the bed to the pressure melting point, GHFpmp, at locations of radar-detected basal water. We identify parts of the central-east, south and northwest Greenland with significantly high GHFpmp. Conversely, we find that the majority of low-elevation regions of west Greenland and parts of northeast have very low GHFpmp. We compare the estimated constraints with the available GHF models for Greenland and show that GHF models often do not honor the estimated constraints. Our results highlight the need for community effort to reconcile the discrepancies between radar data, GHF models, and ice core information.

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Simulation of the future sea level contribution of Greenland with a new glacial system model

Cited by 54 publications

References 104 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

Submarine melt as a potential trigger of the North East Greenland Ice Stream margin retreat during Marine Isotope Stage 3

Constraining the geothermal heat flux in Greenland at regions of radar-detected basal water

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