Review of manuscript by Zhang et al. entitled “Effects of melting ice sheets and orbital forcing on the early Holocene warming in the extratropical Northern Hemispheres”.
The manuscript by Zhang et al. has greatly improved since the previous version and now presents a study that is both interesting and readable. There are still a number of small questions that remain as well as several technical comments. When those are taken care of I recommend this manuscript for publication in Climate of the Past.
Minor comments:
Throughout the manuscript different the present and past tense are often mixed. Please read the manuscript carefully to be consistent in the usage of the different tenses.
Throughout the manuscript the word ‘the’ is often used when it should not, or missing where it should have been used. For example line 4 on page 9 ‘of FIS’ should be ‘of the FIS’ and use ‘ORBGHG’ or ‘the ORBGHG simulation’.
Throughout the manuscript ‘N’ is used to indicate ‘North’ or ‘Northern’, perhaps a personal preference, but consider writing out the whole word.
Throughout the manuscript be consistent and clear in the use of PI or preindustrial or present or 0ka.
Throughout the manuscript I find the usage of ‘ka’ as ‘ka BP’ a little confusing because then, strictly speaking, you also use for instance °C (ka BP)-1. Consider using ‘ky’ instead of ‘ka’, for instance °C ky-1.
Lines 12-17 page 1: Consider mentioning in the first paragraph what has previously been found in proxy-based studies, as to introduce the importance of your results presented in the remainder of the abstract. For instance something like ‘Proxy-based temperature reconstructions suggest a Northern Hemisphere warming, but also indicate important regional differences. Here we show what forcings and feedbacks can underlie these regional differences…’. If for instance Alaska and Northern Canada are mentioned, then the focus on these two specific regions in the remainder of the abstract doesn’t seem so arbitrary anymore.
Lines 29-31 page 5: So the ice sheet reconstruction that is used is solely based on geological constraints, not on ice-sheet modelling?
Lines 11-12 page 6: How can an equilibrium meltwater forcing match estimates for the early Holocene?
Section 2.3: It is still not clear to me how the two freshwater forcing scenarios are different. Is their initial value the same or different? Is the rate of change the same or different. Please clarify in the text.
The results sections could become a little more clear if you write them all following the same structure. Such a structure could be to first present the summer results, then winter and finally annual mean. Then the reader knows what to expect and where to look for a certain result.
Lines 24 page 12: Shortly introduce the stacks of Shakun et al. (2012) and Marcott et al. (2013).
Line 32 page 12: Is this bias found for specific regions and how does this compare to the 30-90N model-data comparison that is performed here?
Line 34 page 12: CP does not have a page limit, as far as I know, as long as the content is relevant.
Line 12 page 13: And how did they interpret this result and how does it connect to the work presented here? Shortly elaborate.
Line 30 page 13: Explain what causes a southward migration of the tundra under a warming climate.
Lines 31-33 page 13: They counterbalanced, but still led to a substantially cooler climate? Please explain.
Lines 1-3 page 15: Does this part discuss the results of FWF-v1 or FWF-v2? Or both? If the latter, perhaps move to earlier part of the manuscript.
Line 15 page 15: Perhaps shortly repeat the differences between the two freshwater scenario and how they can explain the AMOC differences.
Line 27 page 15: Perhaps shortly mention future plans: comparison with previously performed transient deglacial/early Holocene experiments etc.
Technical comments:
Line 2 page 2: illustrate
Line 1-3 page 2: This is a little hard to read, consider rewording. Moreover, it would be good to say that this kind of work has the potential to constrain the uncertainties in ice sheet reconstructions.
Line 2 page 2: configuration instead of deglaciation?
Line 14 page 2: Consider “a couple degrees of warming (Vinther et al., 2009).
Line 21 page 2: ‘in planktonic’.
Line 24 page 2: ‘drivers of climate’.
Line 28 page 2: consider removing ‘critical’.
Lines 2-6 page 3: Difficult to read, please rewrite.
Line 20 page 3: Consider removing ‘particular’.
Line 20 page 3: “influence of the decay of the LIS..”.
Line 26 page 3: ‘renamed to’.
Lines 28-29: Consider removing this sentence since it is very obvious.
Line 34 page 3: Not sure if ‘in preparation’ is allowed in CP, I’ll leave it to the editor.
Line 5 page 4: Consider removing “in the present study”.
Line 22 page 4: ‘the ice sheet evolution and GHGs where prescribed’
Line 2 page 5: Younger Dryas strictly speaking not an example of a Holocene study.
Line 7 page 5: It is preferable to use ‘that’ instead of ‘which’.
Line 26 page 5: PMIP3 protocol up to 11.5ka?
Line 1 page 6: The average thickness?
Line 27 page 6: Was instead of were.
Line 28 page 6: Why mention experiments that are not presented in the manuscript?
Line 12 page 7: cold instead of cooler.
Line 18 page 7: PI simulations, with a maximum
Lines 18-19 page 7: in the central parts of the Northern Hemisphere continents
Lines 19-20 page 7: than that over the continents.
Lines 26-28 page 7: Please rephrase.
Line 30 page 7: ‘southern regions’, where is that?
Line 8 page 8: Additionally, SSTs where also
Lines 7-10 page 8: Please rephrase.
Line 29 page 8: overall cooling of about
Lines 29-30 page 8: Too obvious, consider removing.
Line 32 page 8: of ORBGHG ……of the Holocene
Lines 2-3 page 9: It was …..further. Consider removing whole sentence.
Line 4 page 9: the FIS
Line 8 page 9: insolation anomalies.
Line 9 page 9: by the demise in the orbital forcing.
Line 11 page 9: indicates
Line 14 page 9: Please rephrase.
Line 22 page 9: The ORBGHG simulation
Lines 27-29 page 9: Isn’t this part of the equilibrium response?
Line 31 page 9: temperature rise
Line 15 page 10: remove ‘up’.
Line 26 page 10: remove ‘climate’.
Line 32 page 10: higher instead of warmer.
Line 6 page 11: Alaskan temperature trend.
Lines 8, 9 and 14 page 11: temperatures
Line 32 page 11: and slightly lower SSTs
Line 5 page 12: The only
Lines 6-7 page 12: suggest similar early Holocene summer temperature anomalies compared to the present
Line 9 page 12: palaeotemperature proxy?
Line 18 page 12: which indicates warmer
Line 19 page 12: temperatures
Line 20 page 12: challenged instead of changed?
Line 22 page 12: is instead of was?
Line 4 page 13: variations are
Line 8 page 13: Geopotential with a capital letter?
Line 16 page 13: and overwhelms the warming
Line 17 page 13: partly be……..by enhanced albedo
Line 23 page 13: which caused locally cooler conditions.
Line 23 page 14: use either ‘net’ or ‘overall’.
Line 23 page 14: the climate
Section 4.3: Perhaps the description of AMOC changes in section 3.2 could be moved to section 4.3?
Line 27 page 14: around 10 degrees?
Line 32 page 14: Perhaps ‘with a further AMOC weakening’.
Line 32 page 14: 1-2Sv compared to?
Line 2 page 16: The temperature anomalies at 11.5ka relative to PI were….
Line 3 page 16: higher? Do you mean positive?
Line 15 page 16: in promoting these cold conditions.
Lines 17-18 page 16: heat transport and sea-ice feedbacks.
Line 21 page 16: at 11.5 ka over central Siberia can be….
Line 24 page 16: The dominant factors driving the climate in the eastern Arctic Ocean were
Line 2 page 7: This sounds a little double.
Lines 10-11 page 17: can potentially be constrained by applying different deglacial scenarios and compare them with networks of proxy-records.
Line 14 page 17: Perhaps mention that this also helps in understanding the differences between proxy-records.
Table 2: What is FWF? FWF_v1 or FWF_v2 or are those also the same for 11.5ka?
Caption figure 3: Define ones (in the main manuscript or in a figure caption) what is meant with summer and winter (JJA and DJF?).
Figures in general: When figures include a clear legend than the meaning of the different colours does not need to be repeated in the caption.
Figure 2: present? PI, 0ka?
Figure 4: why is the shaded bar only shown for the top panel?
Figure 4: On basis of which scenario are these slopes calculated?
Figure 8: mention the start and end of this shorter period for completeness.
Figure 9: Perhaps the proxy data for the modern period can be removed since no human induced warming is included in the simulations.
Figure 10: Wind vectors could perhaps give a clearer picture of the changes in atmospheric circulation.
Figure 12: Consider giving the maximum AMOC strength for the different panels for illustration.
Figure 14: Some units have an asterisks in them, like 10E+12*, perhaps a latex issue?
Figure S2: include colour scale.
Figure S4: why 10ka? |