Greenland temperature and precipitation over the last 20&thinsp;000 years using data assimilation

Badgeley, Jessica A.; Steig, Eric J.; Hakim, Gregory J.; Fudge, Tyler J.

doi:https://doi.org/10.5194/cp-16-1325-2020

CP | Articles | Volume 16, issue 4

Clim. Past, 16, 1325–1346, 2020
https://doi.org/10.5194/cp-16-1325-2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

CP | Articles | Volume 16, issue 4

Research article 28 Jul 2020

Research article | 28 Jul 2020

Greenland temperature and precipitation over the last 20 000 years using data assimilation

Jessica A. Badgeley et al.

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Final revised paper (published on 28 Jul 2020)
Supplement to the final revised paper
Preprint (discussion started on 20 Jan 2020)
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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', Anonymous Referee #1, 30 Jan 2020
- AC1: 'Reply to Referees #1 and #2', Jessica Badgeley, 06 Mar 2020
RC2: 'Review of manuscript cp-2019-164', Anonymous Referee #2, 12 Feb 2020
- AC2: 'For the reply, please see Author Comment #1 (AC1)', Jessica Badgeley, 06 Mar 2020
RC3: 'Review of Badgeley et al.: Greenland temperature and precipitation over the last 20,000 years using data assimilation', Anonymous Referee #3, 12 Mar 2020
- AC3: 'Reply to Referee #3', Jessica Badgeley, 07 Apr 2020

Peer review completion

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

ED: Reconsider after major revisions (14 Apr 2020) by Amaelle Landais

AR by Jessica Badgeley on behalf of the Authors (26 May 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (03 Jun 2020) by Amaelle Landais

RR by Anonymous Referee #1 (05 Jun 2020)

RR by Anonymous Referee #3 (18 Jun 2020)

Suggestions for revision or reasons for rejection

Review of the revised version of Badgeley et al: Greenland temperature and precipitation over the last 20,000 years using data assimilation

The authors have done an extremely detailed and comprehensive overhaul of their paper in response to the reviewer comments. I wish all authors were as responsive to reviewer reports!

They address most of my comments and remarks satisfactorily – in many cases actually going much beyond what I would have thought necessary.

I have a few minor comments that I would like the authors to address, after which the work is suitable for publication.

Regarding seasonality:

The authors clarified my confusion on this issue well. I had expected the approach to give seasonal temperatures in some way, which it does not. I think it would be important to emphasize this in the abstract and conclusion, by stating that they are reconstructing *annual mean* temperature and precipitation. Particularly for issues like the HTM (which I think of as a summer signal) this distinction is important. Suggested changes:

Line 6: We avoid these limitations by using paleoclimate data assimilation to create independent reconstructions of *annual mean* temperature and precipitation for the last 20,000 years.

Line 630: Our approach, combining ice-core records with a climate-model simulation, provides complete spatial reanalyses of both *annual mean* temperature and precipitation covering the last 20,000 years.

Regarding abrupt climate change:

One of my main concerns was the spatial pattern of abrupt climate change, and the authors have done a great job of both visualizing this, and providing the patterns in the supplementary tables. Thanks for this. The additional tests in Section 4.2 clearly show that the water isotopes want to push the N-S abrupt climate change spatial pattern in the opposite direction from the d15N.

I think the section could use a stronger discussion at the end of this section.

As I stated before, all GCM studies I am aware of agree with the d15N pattern. Their suggestion that this is an artifact of the GCM forcing is somewhat unfair – I am not aware of a single model study that has the largest abrupt D-O magnitude in North Greenland (and I’ve looked at a many). The paper that they cite as an example of an alternative forcing (Obase and Abe-Ouchi 2019) actually has the largest abrupt temperature change in South Greenland also (See their fig 4a, lower right panel. The colors are saturated in red, but the contour lines clearly show that the abrupt warming is greatest over the N-Atlantic, and that the largest abrupt Greenland warming occurs in the south).

I would encourage just a simple statement of the fact that the spatial abrupt change pattern of the reanalysis does not match that seen in d15N or in climate models simulations. Based on the reliability of d15N as an abrupt climate change proxy, and the overwhelming GCM agreement on this point, I think it would be fair to state that this single aspect of the d18O-based reanalysis is probably unreliable.

And yes, another ice core in South Greenland would be highly desirable.

Figures S12 and S13 are identical, as far as I can tell.

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ED: Publish subject to minor revisions (review by editor) (22 Jun 2020) by Amaelle Landais

AR by Jessica Badgeley on behalf of the Authors (26 Jun 2020) Author's response Manuscript

ED: Publish as is (30 Jun 2020) by Amaelle Landais

AR by Jessica Badgeley on behalf of the Authors (02 Jul 2020) Author's response Manuscript

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Greenland temperature and precipitation over the last 20 000 years using data assimilation

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