the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Spatial and temporal variability of sea surface temperatures and monsoon dynamics in the northwestern Arabian Sea during the last 43 kyr
Abstract. In this study, we present the first well-dated, high-resolution alkenone-based sea surface temperature (SST) record (SL167) from the northeastern Oman Margin (Gulf of Oman) in the northwestern Arabian Sea. The SST reconstructions spanning the last 43 kyr reveal fluctuations of approximately 7 °C (20.1 °C to 27.4 °C) and demonstrate a higher sensitivity to climate variations compared to similar core locations in the Arabian Sea. SSTs remained low during Heinrich events (H2, H3, H4), the Younger Dryas, early and late Holocene, and were high during Dansgaard-Oeschger interstadials (D-O 11, D-O 4 - 9, Bølling-Allerød (B-A), and mid-Holocene. SST was predominantly influenced by the SW monsoon during warmer periods and the NE monsoon during cold intervals. The dynamics of strengthening and weakening monsoon periods were likely controlled by shifts in the Intertropical Convergence Zone prompted by changes in solar radiation in the Northern Hemisphere. The last glacial maximum exhibited no intense cooling probably due to stronger NW winds and an eastward shift of the SST gradient in the Gulf of Oman, resulting in a brief and moderate cooling period. Strong SW winds during the early Holocene transported cold water masses from Oman upwelling into the Gulf of Oman, lowering SSTs. A rapid temperature increase of approx. 2 °C during the mid-Holocene was induced by an abrupt eastward shift of the SST gradient.
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RC1: 'Comment on egusphere-2024-1072', Anonymous Referee #1, 02 Jul 2024
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The article by Maier et al. presents a 43 ka-long alkenone-based SST record in the NE corner of Oman peninsula. The core location is hence potentially under the influence of the Mediterranean region, and the Asiatic and African landmasses, so many different climatic regimes could interfere, manifest, or be masked by a multitude of processes. Then it is not surprising, and very interesting, to see a SST record that look anything like what has been already published in the literature in the broader NW Indian ocean sector.
I find the authors have done a good job in interpreting their curious SST record, and I liked their choice of showcasing their record along with other alkenone-based records that are used in Figure 4 to appreciate the potential contrasted influences that surely played some role in shaping their SST record. I think the article could be published after minor revisions.
First, I suggest the authors to introduce more clearly the complexity of their SST record that comes from such a locality, and develop more on that in the conclusion. As it stands the conclusion only summarizes the main findings, but I think there is room to finish the conclusion within a broader regional context than the Arabian Sea and the Gulf of Oman only.
Other remarks:
What I found really missing was a stronger description of the age model, perhaps through adding an additional figure. Before starting to read the article the only d15N record looks so much like a series on Bond cycles for the MIS3 that I first thought that the Heinrich events were mislabeled. I had to check in the original Burdanowitz paper to be convinced by your age model, and I think it is really missing in your own article.
On your SST interpretation, with which I have no problem, it is sometimes hard to follow when you describe your curious SST record with other ones in chapters 5.1.2, 5.1.3 and 5.1.4. Particularly, for example, when you discuss the seasonality of climate patterns such as the monsoon and ITCZ along with other SST records in the northern Arabian Sea. I think the authors will find guidance if you also show the monthly SST for all individual sites that you show in Figure 4, to better highlight how changes in other SST could be partly driven by changes in seasonal/atmospheric processes that you describe. For example, the paper by Bassinot et al. (https://doi.org/10.5194/cp-7-815-2011) shows how seasonal changes in wind could enhance/dampen upwelling in regions situated in the western/eastern parts of the Arabian Sea. Even if you consider your own alkenone as being reflective of mean-annual SST I think more discussion on how seasonal features can deeply affect the regional dynamics could be more apparent in your discussion.
I liked the proposition that the Persian Gulf outflow waters could have played a role on your Holocene record. On that, perhaps you could be interested in reading the article by Naderi et al. (https://doi.org/10.1002/jqs.3614) could help having an illustration of what has been happening there and in the surrounding land.
Finally, I am not sure the whole discussion on the wavelet analysis really adds a value to your discussion. I am not sure whether the sun is something had really a discernible impact on your SST record, given the other processes you list during the discussion, but I don’t have strong recommendation to remove it either. Anyway listing the 525, 505, 493 etc. periodicities does not add something the reader will really focus on, and there is still the possibility that your sediment sampling could add wavelet artifacts on this long list of periodicities. I find it is a shame to discuss it, it dilutes your discussion.
Other minor remarks:
- There is a series of typos (and bugs at reporting the chapter numbering). Pleaser get a profound last read over the manuscript prior to submitting your revised version.
- Productivity-mediated records in your core highlighted in Figure 4 could perhaps be better used while discussing the dynamics of your core.
Citation: https://doi.org/10.5194/egusphere-2024-1072-RC1
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