Design and results of the ice sheet model initialisation experiments initMIP-Greenland: an ISMIP6 intercomparison

Goelzer, Heiko; Nowicki, Sophie; Edwards, Tamsin; Beckley, Matthew; Abe-Ouchi, Ayako; Aschwanden, Andy; Calov, Reinhard; Gagliardini, Olivier; Gillet-Chaulet, Fabien; Golledge, Nicholas R.; Gregory, Jonathan; Greve, Ralf; Humbert, Angelika; Huybrechts, Philippe; Kennedy, Joseph H.; Larour, Eric; Lipscomb, William H.; Le clec'h, Sébastien; Lee, Victoria; Morlighem, Mathieu; Pattyn, Frank; Payne, Antony J.; Rodehacke, Christian; Rückamp, Martin; Saito, Fuyuki; Schlegel, Nicole; Seroussi, Helene; Shepherd, Andrew; Sun, Sainan; van de Wal, Roderik; Ziemen, Florian A.

doi:https://doi.org/10.5194/tc-12-1433-2018

Articles | Volume 12, issue 4

https://doi.org/10.5194/tc-12-1433-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue:

The Ice Sheet Model Intercomparison Project for CMIP6...

https://doi.org/10.5194/tc-12-1433-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 12, issue 4

Research article

|

19 Apr 2018

Research article |

| 19 Apr 2018

Design and results of the ice sheet model initialisation experiments initMIP-Greenland: an ISMIP6 intercomparison

Heiko Goelzer, Sophie Nowicki, Tamsin Edwards, Matthew Beckley, Ayako Abe-Ouchi, Andy Aschwanden, Reinhard Calov, Olivier Gagliardini, Fabien Gillet-Chaulet, Nicholas R. Golledge, Jonathan Gregory, Ralf Greve, Angelika Humbert, Philippe Huybrechts, Joseph H. Kennedy, Eric Larour, William H. Lipscomb, Sébastien Le clec'h, Victoria Lee, Mathieu Morlighem, Frank Pattyn, Antony J. Payne, Christian Rodehacke, Martin Rückamp, Fuyuki Saito, Nicole Schlegel, Helene Seroussi, Andrew Shepherd, Sainan Sun, Roderik van de Wal, and Florian A. Ziemen

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Final revised paper (published on 19 Apr 2018)
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Preprint (discussion started on 14 Jul 2017)
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Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'Review of “Design and results of the ice sheet model initialization experiments initMIP-Greenland: an ISMIP6 intercomparison”, by H. Goelzer et al.', Anonymous Referee #1, 16 Aug 2017
RC2: 'Review of Goelzer et al.: Design and results of the ice sheet model initialisation experiments initMIP-Greenland: an ISMIP6 intercomparison', Anonymous Referee #2, 18 Aug 2017
AC1: 'Response to reviewer comments', Heiko Goelzer, 09 Oct 2017

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Heiko Goelzer on behalf of the Authors (09 Oct 2017) Author's response Manuscript

ED: Reconsider after major revisions (11 Oct 2017) by G. Hilmar Gudmundsson

ED: Referee Nomination & Report Request started (10 Nov 2017) by G. Hilmar Gudmundsson

RR by Anonymous Referee #2 (21 Nov 2017)

Suggestions for revision or reasons for rejection

Thanks to the authors for their work to address previous comments (either through modifications or defence of initial text). I feel the paper is much improved, and suggest the following minor revisions prior to publication. In several cases, these address points that I made in the first revision that I feel could use still further final polishing.

-P3L28: ‘Form the target’: also, forms the majority of the validation data.

-Section 4.2, first paragraph could be edited for clarity. Some repetition occurs.

-use either ’ablation zone’ or ‘ablation area’ consistently - currently both are used.

-“discussed in context of Figure 4”
-> can it be determined why these models exhibit small ablation zones? Or is this something that is not possible within this MIP?
-> perhaps repeat reasons for exclusion at this point in the text for ease of reading

-P18L8: Suggest following change (or similar), with motivation being a clearer description of the reason for the Fig 8d plot: “For models with (unrealistically) large initial (present-day) surface areas, the ablation zones are considerably larger (Figure 9b, c), which implies dramatic mass loss. The too large ice sheet area is related to the definition of the ice sheet with respect to outlying glaciers and, more importantly, due to modelled initial conditions further from the present-day. Simply put, by design a larger ice sheet will be subject to larger rates of mass loss.” -> “For models with (unrealistically) large initial (present-day) surface areas, the prescribed ablation field generates increasingly large ablation values outside the present-day observed ice extent (Figure 9b, c). This in turn results in larger mass loss trends for the asmb experiment, as these very large ablation values cause rapid margin ice loss. Thus, as a consequence of the experimental design, models exhibiting larger initial ice sheets in the inter-comparison are in turn subject to larger rates of mass loss and therefore demonstrate a trend towards more extreme sea level contributions.”

-P194: to reiterate first-revision comments: the ratio of drift to model response is still unclear, and hidden when the model response to a change in forcing is represented as a difference between control and perturbation experiments. To alleviate this I suggest presenting a measure of the ratios of drift:perturbation (something like [asmb-ctrl]/ctrl).

-P22L4: “rendered the locally identical SMB anomaly forcing to be different on the global scale” - suggest rewording for clarity.

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RR by Anonymous Referee #1 (04 Dec 2017)

ED: Publish as is (06 Feb 2018) by G. Hilmar Gudmundsson

AR by Heiko Goelzer on behalf of the Authors (12 Feb 2018) Manuscript

Short summary

We have compared a wide spectrum of different initialisation techniques used in the ice sheet modelling community to define the modelled present-day Greenland ice sheet state as a starting point for physically based future-sea-level-change projections. Compared to earlier community-wide comparisons, we find better agreement across different models, which implies overall improvement of our understanding of what is needed to produce such initial states.