Quantifying the influence of the terrestrial biosphere on glacial–interglacial climate dynamics

Davies-Barnard, Taraka; Ridgwell, Andy; Singarayer, Joy; Valdes, Paul

doi:https://doi.org/10.5194/cp-13-1381-2017

Articles | Volume 13, issue 10

https://doi.org/10.5194/cp-13-1381-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/cp-13-1381-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 13, issue 10

Research article

|

26 Oct 2017

Research article |

| 26 Oct 2017

Quantifying the influence of the terrestrial biosphere on glacial–interglacial climate dynamics

Taraka Davies-Barnard, Andy Ridgwell, Joy Singarayer, and Paul Valdes

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Final revised paper (published on 26 Oct 2017)
Preprint (discussion started on 10 Feb 2017)

Interactive discussion

Status: closed

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

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SC1: 'Interesting simulations, but what about the real world?', Iain Colin Prentice, 17 Feb 2017
- AC1: 'Response to comment by Colin Prentice: Interesting simulations, but what about the real world?', Taraka Davies-Barnard, 09 Mar 2017
RC1: 'Review of “Quantifying the influence of the terrestrial biosphere on glacial-interglacial climate dynamics” by Takara Davies-Barnard, Andy Ridgwell, Joy Singarayer and Paul Valdes', Anonymous Referee #1, 28 Mar 2017
RC2: 'Review of „Quantifying the Influence of the Terrestrial Biosphere on Glacial-interglacial Climate Dynamics“ by Davies-Barnard et al. (2017)', Anonymous Referee #2, 31 Mar 2017

Peer-review completion

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

ED: Reconsider after major revisions (25 Apr 2017) by André Paul

AR by Taraka Davies-Barnard on behalf of the Authors (24 May 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (04 Jul 2017) by André Paul

RR by Anonymous Referee #2 (13 Jul 2017)

Suggestions for revision or reasons for rejection

I still think that the simulated vegetation cover should be compared more thoroughly with BIOME6000 data for the LGM. In particular, the following response to one of my comments does not make any sense to me:
“The climate model used in Hoogakker et al. 2016 is HadCM3B-M1 and the climate model used here is HadCM3B-M2.1. The climate between these two is virtually identical. Since the climate is the main aspect which determines the distribution of vegetation in a DGVM, the verification of Hoogakker’s work suggests that the distributions found here are also reasonable.”
I don’t understand how a validation done for the BIOME model driven by HadCM3B can be used as a replacement for a validation of the simulations presented in this study, which use the TRIFFID dynamic vegetation model coupled to HadCM3B and show a very different response of vegetation in some regions.
Regarding the tropics, the results presented in this paper show almost no change in vegetation cover between preindustrial and the LGM (Fig. 10). There is definitely evidence from the BIOME6000 dataset that the tropical rainforest area was reduced during LGM and was replaced by savannah/shrubland/grassland (e.g. Figure 3 in Prentice et al, 2011). This seems to be confirmed by at least some modelling studies (e.g. Hoogakker et al., 2016; Martin Calvo and Prentice, 2015; Prentice et al., 2011)). On the other hand a recent study suggests that some parts of the Amazon rainforest where resilient to reductions in precipitation during LGM (Wang et al., 2017). The results presented by the authors should be compared also to these data and critically discussed.
The authors also write:
“In particular, a broadleaf tree is not necessarily ‘tropical rain forest’, but equally can be a temperate broadleaf forest, or even savannah type trees.”
I don’t think that a grid cell which is covered predominantly by broadleaf trees can be considered to be savannah.

Figure 3. surface albedo is mentioned in the caption, but is not plotted in this figure.

References
Hoogakker, B. A. A., Smith, R. S., Singarayer, J. S., Marchant, R., Prentice, I. C., Allen, J. R. M., Anderson, R. S., Bhagwat, S. A., Behling, H., Borisova, O., Bush, M., Correa-Metrio, A., de Vernal, A., Finch, J. M., Fréchette, B., Lozano-Garcia, S., Gosling, W. D., Granoszewski, W., Grimm, E. C., Grüger, E., Hanselman, J., Harrison, S. P., Hill, T. R., Huntley, B., Jiménez-Moreno, G., Kershaw, P., Ledru, M.-P., Magri, D., McKenzie, M., Müller, U., Nakagawa, T., Novenko, E., Penny, D., Sadori, L., Scott, L., Stevenson, J., Valdes, P. J., Vandergoes, M., Velichko, A., Whitlock, C. and Tzedakis, C.: Terrestrial biosphere changes over the last 120 kyr, Clim. Past, 12(1), 51–73, doi:10.5194/cp-12-51-2016, 2016.
Martin Calvo, M. and Prentice, I. C.: Effects of fire and CO2 on biogeography and primary production in glacial and modern climates, New Phytol., 208(3), 987–994, doi:10.1111/nph.13485, 2015.
Prentice, I. C., Harrison, S. P. and Bartlein, P. J.: Global vegetation and terrestrial carbon cycle changes after the last ice age., New Phytol., 189(4), 988–998, doi:10.1111/j.1469-8137.2010.03620.x, 2011.
Wang, X., Edwards, R. L., Auler, A. S., Cheng, H., Kong, X., Wang, Y., Cruz, F. W., Dorale, J. A. and Chiang, H.: Hydroclimate changes across the Amazon lowlands over the past 45,000 years, Nature, 541(7636), 204–207, doi:10.1038/nature20787, 2017.

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RR by Anonymous Referee #1 (03 Aug 2017)

ED: Publish subject to minor revisions (review by Editor) (09 Aug 2017) by André Paul

AR by Taraka Davies-Barnard on behalf of the Authors (18 Aug 2017) Author's response Manuscript

ED: Publish as is (15 Sep 2017) by André Paul

AR by Taraka Davies-Barnard on behalf of the Authors (21 Sep 2017) Manuscript

Short summary

We present the first model analysis using a fully coupled dynamic atmosphere–ocean–vegetation GCM over the last 120 kyr that quantifies the net effect of vegetation on climate. This analysis shows that over the whole period the biogeophysical effect (albedo, evapotranspiration) is dominant, and that the biogeochemical impacts may have a lower possible range than typically estimated. This emphasises the temporal reliance of the balance between biogeophysical and biogeochemical effects.