Statistical emulation of a perturbed basal melt ensemble of an ice sheet model to better quantify Antarctic sea level rise uncertainties

Berdahl, Mira; Leguy, Gunter; Lipscomb, William H.; Urban, Nathan M.

doi:https://doi.org/10.5194/tc-15-2683-2021

Articles | Volume 15, issue 6

https://doi.org/10.5194/tc-15-2683-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/tc-15-2683-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 15, issue 6

Research article

|

15 Jun 2021

Research article |

| 15 Jun 2021

Statistical emulation of a perturbed basal melt ensemble of an ice sheet model to better quantify Antarctic sea level rise uncertainties

Mira Berdahl, Gunter Leguy, William H. Lipscomb, and Nathan M. Urban

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Final revised paper (published on 15 Jun 2021)
Preprint (discussion started on 17 Aug 2020)

Interactive discussion

Status: closed

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

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RC1: 'Referee Comment to Statistical emulation of a perturbed basal melt ensemble of an ice sheet model to better quantify Antarctic sea level rise uncertainties', Anonymous Referee #1, 04 Sep 2020
- AC1: 'Reply on RC1', Mira Berdahl, 13 Mar 2021
RC2: 'Please see my attached review report.', Anonymous Referee #2, 20 Sep 2020
- AC2: 'Reply on RC2', Mira Berdahl, 13 Mar 2021

Peer-review completion

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

ED: Publish subject to revisions (further review by editor and referees) (29 Mar 2021) by Carlos Martin

AR by Mira Berdahl on behalf of the Authors (31 Mar 2021) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (08 Apr 2021) by Carlos Martin

RR by Anonymous Referee #1 (15 Apr 2021)

Suggestions for revision or reasons for rejection

In my opinion, the authors managed to address all concerns raised by the two reviewers in an satisfactory way. That is why I am pleased to recommend publication of the presented manuscript after technical corrections.

The only issue I see is that some of the concerns of reviewer 2 are (in my opinion) answered convincingly in the response but should be represented differently in the manuscript. Since the arguments have been presented I consider this a technicality.

The impact of missed (due to the use of smooth sigmoids) variability in the ocean melt forcing should be separated into (1) the potential cause of an bias (due to non-linearities in the model response) and (2) an increased spread in the SLR distribution. In the response the authors argue that the effect of (1) can be neglected (ref2, major point 1, a) and b)) and for me that is, for the purpose of this study, an valid argument. In fact, I believe the authors could have referred to the finding in section 4.3 of Hoffman et al. (2019) (variable melting) instead of earlier sections (variable temperature profiles) for which biases are even smaller. The bias-free noise in the SLR due to melt variability (2) is now represented by an additional uncertainty term. This separation should be made more clear in the manuscript, in fact, the current formulation (‘… the effects of
smoothing over the stochastic variability in the forcings with a sigmoidal curve is expected to be minimal (Hoffman et al., 2019). However, for completeness, autoregressive noise …’) suggests that autoregressive noise is able to represent all the neglected influences while it is (as evident by basing its magnitude solely on observations) only representing (2) and not (1).

Please also clarify what the autoregressive domain of the model is. Typically an autoregressive model at time t is a function of an earlier time-step (t-1). In my understanding the emulator has no timeseries to base this on, but only two time slices (100 and 200 years).

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RR by Anonymous Referee #2 (17 Apr 2021)

ED: Publish subject to technical corrections (04 May 2021) by Carlos Martin

AR by Mira Berdahl on behalf of the Authors (13 May 2021) Manuscript

Short summary

Antarctic ice shelves are vulnerable to warming ocean temperatures and have already begun thinning in response to increased basal melt rates. Sea level is expected to rise due to Antarctic contributions, but uncertainties in rise amount and timing remain largely unquantified. To facilitate uncertainty quantification, we use a high-resolution ice sheet model to build, test, and validate an ice sheet emulator and generate probabilistic sea level rise estimates for 100 and 200 years in the future.