the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Modeled Greenland Ice Sheet evolution constrained by ice-core-derived Holocene elevation histories
Abstract. During the Holocene, the Greenland Ice Sheet (GrIS) experienced substantial thinning, with some regions losing up to 600 meters of ice. Ice sheet reconstructions, paleoclimatic records, and geological evidence indicate that during the Last Glacial Maximum, the GrIS extended far beyond its current boundaries and was connected with the Innuitian Ice Sheet (IIS) in the northwest. We investigate these long-term geometry changes and explore several possible factors driving those changes by using the Parallel Ice Sheet Model (PISM) to simulate the GrIS thinning throughout the Holocene period, from 11.7 ka ago to the present. We perform an ensemble study of 841 model simulations in which key model parameters are systematically varied to determine the parameter values that, with quantified uncertainties, best reproduce the 11.7 ka of surface elevation records derived from ice cores, providing confidence in the modeled GrIS historical evolution. We find that since the Holocene onset, 11.7 ka ago, the GrIS mass loss has contributed 5.3±0.3 m to the mean global sea level rise, which is consistent with the ice-core-derived thinning curves spanning the time when the GrIS and the Innuitian Ice Sheet were bridged. Our results suggest that the ice bridge collapsed 4.9±0.5 ka ago and that the GrIS is still responding to these past changes today, having raised sea level by 23±26 mm SLE ka-1 in the last 500 years. Our results have implications for future mass-loss projections, which should account for this long-term, transient trend.
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Status: open (until 04 Sep 2024)
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CC1: 'Comment on egusphere-2024-2223', Tancrède Leger, 26 Jul 2024
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Dear authors,
I just wanted to point out a potential minor error in the use of the Leger et al. (2024) shapefile data.
In the preprint figure 9 panel C: the red outline is described by the authors as the "LGM extent from Leger et al. (2024)": whilst it looks more to be the outermost isochrone we mapped: the 14-13 kyr BP isochrone. This isochrone represents a less extensive GrIS than the full extent of the GrIS reached during the LGM, which occurred a few thousands years before (between 18 and 15 kyr BP): and which you can see mapped in figure 5 panel B of Leger et al (2024). In the latter figure one can see we propose two scenarios for the full LGM GrIS extent from data: due to remaining uncertainties in certain regions. Regardless of which scenario you choose (min or max), this LGM extent will most likely fit your modelled LGM better: so I would advise re-making the comparison with this LGM extent rather than the 14-13 kyr BP isochrone, which is not quite the LGM.
The shapefile for the LGM extent can be found in the PaleoGrIS database under : PaleoGrIS_1.0_isochrones\Shapefile_format\Full_Glacial_max_min_literature_review
Let me know if I've missed something and am mistaken,
Best wishes, and congrats on the work and paper which I will follow with much interest.
Tancrede LegerCitation: https://doi.org/10.5194/egusphere-2024-2223-CC1 -
CC2: 'Reply on CC1', Mikkel Lauritzen, 26 Jul 2024
reply
Dear Leger
Thanks for pointing this out and thank you for your interest in our paper. I have now updated the figure to include both your minimum and maximum LGM extent. Our modeled LGM extent is 0.9% larger than your minimum and 5.6% smaller than your maximum.
Citation: https://doi.org/10.5194/egusphere-2024-2223-CC2 -
CC3: 'Reply on CC2', Tancrède Leger, 26 Jul 2024
reply
Dear Mikkel,
Brilliant, thanks very much for your quick reply and for making these changes.
Best wishes,
Tancrede
Citation: https://doi.org/10.5194/egusphere-2024-2223-CC3
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CC3: 'Reply on CC2', Tancrède Leger, 26 Jul 2024
reply
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CC2: 'Reply on CC1', Mikkel Lauritzen, 26 Jul 2024
reply
Video supplement
Modeled Greenland Ice Sheet evolution constrained by ice-core-derived Holocene elevation histories Mikkel Lauritzen https://doi.org/10.5446/68337
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