Radionuclide wiggle matching reveals a nonsynchronous early Holocene climate oscillation in Greenland and western Europe around a grand solar minimum

Mekhaldi, Florian; Czymzik, Markus; Adolphi, Florian; Sjolte, Jesper; Björck, Svante; Aldahan, Ala; Brauer, Achim; Martin-Puertas, Celia; Possnert, Göran; Muscheler, Raimund

doi:https://doi.org/10.5194/cp-16-1145-2020

Articles | Volume 16, issue 4

https://doi.org/10.5194/cp-16-1145-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/cp-16-1145-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 16, issue 4

Research article

|

03 Jul 2020

Research article |

| 03 Jul 2020

Radionuclide wiggle matching reveals a nonsynchronous early Holocene climate oscillation in Greenland and western Europe around a grand solar minimum

Florian Mekhaldi, Markus Czymzik, Florian Adolphi, Jesper Sjolte, Svante Björck, Ala Aldahan, Achim Brauer, Celia Martin-Puertas, Göran Possnert, and Raimund Muscheler

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Final revised paper (published on 03 Jul 2020)
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Preprint (discussion started on 04 Nov 2019)
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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: 'Mekhaldi et al_Reviewer Comments', Anonymous Referee #1, 18 Nov 2019
- AC1: 'Final response to RC1', Florian Mekhaldi, 23 Apr 2020
RC2: 'Review of Mekhaldi et al.', Anonymous Referee #2, 30 Mar 2020
- AC2: 'Final response to RC2', Florian Mekhaldi, 23 Apr 2020

Peer-review completion

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

ED: Reconsider after major revisions (27 Apr 2020) by Hans Linderholm

AR by Florian Mekhaldi on behalf of the Authors (27 Apr 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (05 May 2020) by Hans Linderholm

RR by Richard Staff (13 May 2020)

Suggestions for revision or reasons for rejection

In their manuscript, Mekhaldi et al. present a very interesting study comparing the palaeo-environmental records of the Greenland ice-cores and the varved Meerfelder Maar (MFM) in the early Holocene. Importantly, the authors are able to align the chronologies of the respective records using Beryllium-10 (10Be) concentration data from both archives, thus demonstrating that the “11.4 ka event” (Greenland) and “Preboreal Oscillation (PBO)” (MFM) were asynchronous and therefore not, as has been previously suspected, expressions of the same underlying climatic “event”.

The manuscript is well written, based on sound science, and the final discussion is balanced and well argued. I recommend that this manuscript be accepted for publication in Climate of the Past pending very minor revisions.

Scientific questions:

L21: I do not know the term “Superepoch” – is it widely used? (Excuse my ignorance! Google also didn’t help…!)
L21: Can the term “climate events” be defined? (Perhaps not within the abstract, but below – perhaps ~L44). Would the term “oscillations” be more appropriate (in the Abstract, at least), which I think is less ‘loaded’ in terms of assumed prior synchroneity/a common ultimate trigger?)
L53: I do not understand “an event that spread over time”
L55: By “mechanisms”, do you mean ultimate causes/triggers, or propagation mechanisms (or both)?
L56-62: I would like a figure referred to here that displays what is being discussed (i.e. the common signals in 10Be and Delta14C through this period).
L107-108: please could you expand a little further upon this methodology (“The synchronization of the different radionuclide records was computed following the methodology described by Adolphi and Muscheler (2016)”).
L128: could these 14C atmospheric production rate data (from Muscheler et al. 2014) not also be included on Fig. 1? I think that this would be useful (since these data are being discussed).
L131-133: But there is also a ~40 year trough in the MFM 10Be data that is not seen in the GRIP data, rendering the ~100 year chronological offset questionable. (I.e., the signal structure is different, making it difficult to suggest that the difference is JUST one of offset chronology.)
L162-164: although “difficult to quantify objectively”, is there any covariance between any of the MFM palaeoenvironmental data and the 10Be signal (or its artefact, if primary agreement with Greenland 10Be deposition is assumed)? E.g., is there any environmental explanation for the previously noted decrease in 10Be at MFM ca. 11,290-11,250 cal BP that is not seen in the Greenland 10Be data? (N.B. the correlation matrix presented in Fig.5 is of relevance here.)
L167-168: If JUST wanting to compare between MFM and Greenland (i.e. the representation of their respective “PBO” and “11.4ka event”), is it not preferable to JUST compare the fluctuations of 10Be at the two sites directly (i.e. placing the MFM chronology on to GICC05 or vice versa)? For the purpose of assessing the synchrony/asynchrony of these climatic signals, the absolute ages are not important – you are JUST interested in the relative chronology of the two sites (MFM vs Greenland and, therefore, PBO vs 10.4ka event). Surely placing both (MFM and Greenland) separately on to IntCal creates additional unnecessary uncertainty for this purpose? (Though obviously placing on to IntCal allows for the comparison of other data too – e.g. tree-ring 14C.)
You discuss around this point above (L154-157), but opt for the modelling of both on to IntCal, rather than the direct comparison of MFM and Greenland. But wouldn’t the subsequent discussion here be (even) more robust if you just used the MFM data on GICC05 (or Greenland on MFM chronology)?
L205-208: it is probably fair to say that “When looking at the temperature proxy and varve thickness from MFM (Fig. 3d-e), we do not find any event that is coeval with the 11.4 ka event in Greenland”. However, as you go on to note subsequently, “Ticlr data (Fig. 3e) gradually decreased from ca. 11,490 years BP only to be interrupted by a small increase around 11,300 years BP. The low Ticlr data suggest less runoff probably related to drier conditions”. The structure of this Ticlr data looks visually similar to that of the Greenland accumulation anomalies (which are limited to a subset of the time range covered by the other proxies). Could it not be that this is showing some commonality in (climatic) driver, even though the isotopic signals (representing an alternative climatic variable, or subtly different combination of climatic/environmental variables) are not showing commonality through this period?
L214: it might be useful to define “grand solar minimum” for a more generalist audience (here, or at some other suitable place in the text)
L333: state when/how long the Maunder Minimum was (again for the more generalist audience)?
Fig.1: why are your new data presented with error bars, but not the previously published (Czymzik et al. MFM and Adolphi et al. Greenland) data?
Figure 5: would it be clearer to only give half the correlation matrix (since the upper left portion is the same as the lower right portion)?

Language suggestions:

LL52, 130, 249: change “chronology” to “chronological”
L116 & 118: delete “with”
L135: change to “timescale” (singular)
L169: change to “climatic proxy data”
L183: delete “of”
L202: delete “this means that”
L205: insert “…varve thickness [data]…”
L261: delete “to”
L265: change “sun” to “solar”
L285: by “boundaries” do you mean “boundary conditions”?
L307: change “is” to “are”
L342: change “of which” to “to which” (and delete subsequent “to”)
L352: change to “routinely released”
L354: change “detangle” to “disentangle”

Thank you once again for this fascinating study, and best wishes for your on-going research on this area.

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ED: Publish subject to minor revisions (review by editor) (14 May 2020) by Hans Linderholm

AR by Florian Mekhaldi on behalf of the Authors (24 May 2020) Author's response Manuscript

ED: Publish as is (03 Jun 2020) by Hans Linderholm

AR by Florian Mekhaldi on behalf of the Authors (04 Jun 2020)

Short summary

Due to chronology uncertainties within paleoclimate archives, it is unclear how climate oscillations from different records relate to one another. By using radionuclides to synchronize Greenland ice cores and a German lake record over 11 000 years, we show that two oscillations observed in these records were not synchronous but terminated and began with the onset of a grand solar minimum. Both this and changes in ocean circulation could have played a role in the two climate oscillations.