Dear Dr. Balaji,

thank you very much for responding to the reviewers' reports and outlying how the manuscript would be revised to address their concerns. My assessment is that the manuscript can be revised towards an eventual publication. I would, however, also advice you to pay special attention to some of the comments of reviewer #2 concerning the link between SST and upwelling at long timescales and the confounding influence of the glacial-interglacial cycles, and the comment on the link between upwelling and precipitation. Your responses to those points, though indicative of the possible revisions of the manuscript, appear somewhat unclear in my reading.

The recommendation of 'major revisions' is motivated to allow the reviewers a second round of review of the revised version.

I am looking forward to the revised manuscript.

Sincerely,

Eduardo Zorita

Dear Dr. Balaji

The last version of your manuscript has now been evaluated by three reviewers. As you probably remember from our last email exchange, this version had been sent out for review to two reviewers, who expressed a contradictory opinion on the merits or the manuscript. Therefore, I decided to send the manuscript to a third reviewer, and this has been the reason for the protracted evaluation processes of the manuscript.

This third reviewer also acknowledges the positive aspects of the manuscript, but agrees with the more critical reviewer that some aspects of the manuscript are unclear and not totally substantiated, in particular that the connection between Somali-upwelling and Monsoon precipitation . I am therefore returning the manuscript to you for some revisions.

The manuscript has already undergone two rounds of revisions. Therefore, I would emphatically ask you to pay attention to the critical comments of all reviewers, but in particular of reviewer #2. This reviewer has recommended the rejection of the present version of the manuscript, with possible re-submission of a revised version. The criticism is therefore, substantial, although my interpretation is that the required revisions are mainly directed to the structure of the manuscript and the clarity of some of the sections, and not so much to the results themselves. Reviewer #3 also agrees that some sections of the manuscript should be more clearly reformulated. For instance, both reviewers express their difficulties to understand the sedimentation rate that has been assumed to date the core. Another connected point is that the Ca/Mg record may be reflecting not only upwelling intensity but more generally variations in the SSTs caused by changes in the global external forcing (glacial-interglacial transition).
I am aware that the interpretation of proxy records is usually prone to uncertainties, and that these cannot be always resolved. However, the manuscript should at a minimum clearly discuss these uncertainties and present a fair view to the reader of the strengths, weaknesses and author's interpretation of these records, so that the readers themselves can reach their own evaluation of the results presented in the manuscript.

Sincerely,

Eduardo Zorita

Dear Dr. Balaji,

Thank you very much for submitting the revised version of the manuscript now entitled 'Variations of the Somali upwelling since 18.5 ka BP and its relationship with southwest monsoon rainfall'

The three previewers that evaluated the previous version did not wish to evaluate the revised version again. Two of them had suggested minor revisions, whereas a third reviewer was more critical and had recommended a fresh re-submission. From the scientific point of view, I would tend to align with the two more positive reviewers. However, when going through the manuscript again, I could spot numerous grammatical issues, some of them also structural, that still need your attention. There may be more of them. Therefore, I am returning the manuscript to you once more so that you can revise those aspects of the manuscript. I may remind you that, although all manuscripts are copy-edited by the editorial office, major editorial revisions may delay the publication of the manuscript even more, and thus it is convenient for you and your authors to submit a manuscript as close to a publishable form as possible.

I have included a list of suggestions, but I would strongly recommend that you also carefully reside the text, perhaps with the help of a native English speaker.

Best regards

Eduardo Zorita


- In the abstract you mention ' upwelling during the last glacial period (18.5-15 ka BP) and strengthened upwelling during the Bølling-Allerød (15-12.9 ka BP) ..' Although later in the text you explain the term Last Glacial period in the context of Somali upwelling, a reader will be strongly suprised that the Last Glacial period is defined as 18.5-15 ka BP. I would recommend not to mentio last Glacial Period it is clearly defined in the text.


- Tiwari et al., 2010). Most of these previous studies were based on the foraminifera shell abundance or it’s chemistry.

its chemistry


- Siliceous productivity in the study area being restricted to the southwest monsoon season can serve as a better proxy for upwelling. The variations in siliceous productivity in the western Arabian Sea thus has direct implications to the upwelling
strength during the past.

thus have direct implication

- In the introduction (page 3, line 64) you mention ' in the present record'. However, 'this record' has not been previously mentioned in the text. It is only later mentioned in the last paragraph of the introduction, when the aims of the study are summarized.
My suggestion is to move this last paragraph ('The present study thus aims..') ti line 44 in the introduction, just before the paragraph starting with 'The surface waters...'). It is perhaps not an ideal solution, but it would avoid more drastic reorganizations of the introduction. Ideally, it would be better to state the aims of the study earlier in the introduction, possibly in the first or second paragraph, but I have not identified a suitable place without further extensive re-phrasing.

- regions, where upwelled nutrient-rich water causes high primary production (Koning et al., 2001). The ocean is under saturated

undersaturated, as a single word






- increased at the bottom of the mixed layer at the core location, whereas, significant increase in silicate concentration occurs

Delete comma after 'whereas'

- only at depths of thermocline. During the onset of SWM upwelling, nitrate and phosphate rich waters surfaced more compared
to silicate due to the upwelling of shallow waters.


more nitrate and phosphate than silicate reach the surface..

- High silicate content and depletion of micro-nutrients to sustain excessive nutrient utilization results in siliceous productivity and subsequent biogenic silica flux to the sediments

that sustain excessive nutrient utlization


biogenic silica flux to the sediments (Fig. 1; Koning et al., 2001). Initially, this upwelled deep water surfaced at Somali coastal upwelling zone and transported towards the mouth of Gulf of Aden (core location) through the Socotra channel i.e. between the Socotra Island and Somalia (Young and Kindle, 1994).

was transported

135
The uncertainties associated with the biogenic silica concentration (B.Si) is estimated from the error in Aluminium and Silicon concentration based on repeat measurements of standard material. The maximum error in biogenic silica concentration is

aluminum and silicon (not capitalized)



- upwelling (Broccoli, 2000; Dahl and Oppo, 2006). While, the biogenic silica flux has been controlled by the SWM upwelling signal since it is produced during the southwest monsoon season and preserves upwelling signal.

However, the biogenic silica flux is controlled by the SWM upwelling after its production during the southwest Monsoon season, and therefore preserves the upwelling signal.

- The variations in biogenic
silica fluxes during the 18.5 ka are shown in Fig.5 and the data is presented in table 1.

during the last 18.5 ka

- No definitive relation can be observed between biogenic silica flux and SST records on temporal scale.

on temporal scale -> 'over time'

-The SST using different proxies show inconsistent changes in the studied time span, the TEX86 SST is always higher than Mg/Ca SST (Fig.
6&8).

the TEX86 SST always being higher that Mg/Ca SST

- However, during the last 11.7 ka the Mg/Ca based SST shows a strong anti-correlation with biogenic silica flux record, indicating variation in of influence of on the seasonal signal for of different proxies (Fig. 8).

indicating variation in the influence of the seasonal sgnal.

However, I cannot see how this firm conclusion can be derived from the strong anticorrelation.


- indicating the strong influence of pacific SST anomalies on monsoon. It was also suggested that Arabian Sea SST modulates

Pacific


- that delivers rainfall to the western part of the Indian sub-continent. Though, the upwelling-rainfall connection is not fully

However, the upwelling-rainfall...

- Sea SST during SWM) and SWM rainfall. Both Somali upwelling and SWM rainfall being caused by southwest monsoonal winds during SWM season, hence their anti-correlation indicates a negative feed-back within the system.

I do not think that negative feedback is the right word here. Negative feedback would indicate that a given variable reacts to oppose the initial perturbation. Here, the text just shows there is an anticorrelation between upwelling and rainfall, but there is not reaction of any of the variables to oppose the influence of a driver.. Also, the word 'system' is ambiguous. Which system ? it has not been defined before.

- Though, there are no observational study on the relation between upwelling strength and there are rainfall in Oman, a comparison is made to give a preliminary assessment. Since records are from different regions and have irregular temporal resolution, only long-term trends have been examined.

However, there is no observation studies...


- from the Western Ghats caused by high SWM rainfall, during the B/A (Fig. 7c).

Delete comma




- Sea during the early Holocene (11.7 to 8 ka BP; Fig. 10a) could have reduced the IOWP expanse during the SWM season,

the IOWP eextension


-last 8 ka suggesting reduction in SWM rainfall (Fig. 10b). The hiatus in Oman speleothem record at 2 ka BP coincides with the strengthened Somali upwelling, however, is difficult to explain (Fig. 10a & b). The SK-17 record (Anand et al., 2008)

However, it is difficult to explain. Please be more specific. What is difficult to explain ?


- The last two conclusions are very speculative, and I do not think they can be derived from the results. The result section itself indicates that a change in the source of moisture could explain the change in the correlation between upwelling and rainfall, but this is just one plausible explanation. I do not think it can be listed as one firm conclusion of the study.

Also, the last conclusion is rather a recommendation for future studies, but at least for modelling studies it is not really useful. Climate models simulate by themselves any variations in the precipitation source. Modellers do not need to incorporate them ad-hoc..

Both, latitudinal shifts in the Intertropical Convergence Zone (ITCZ) and changes in moisture source region act as causative factors for the reversal in the relationship between upwelling and southwest monsoon rainfall.

Future observational and modelling studies on southwest monsoon rainfall reconstruction and prediction should incorporate variations in the moisture source region.

Dear Dr. Balaji,

thank you very much for revising the manuscript according to my last suggestions.
I am now happy to recommend its publication in Climate of the Past.

Sincerely,

Eduardo Zorita