Progress in understanding of Indian Ocean circulation, variability, air–sea exchange, and impacts on biogeochemistry

Phillips, Helen E.; Tandon, Amit; Furue, Ryo; Hood, Raleigh; Ummenhofer, Caroline C.; Benthuysen, Jessica A.; Menezes, Viviane; Hu, Shijian; Webber, Ben; Sanchez-Franks, Alejandra; Cherian, Deepak; Shroyer, Emily; Feng, Ming; Wijesekera, Hemantha; Chatterjee, Abhisek; Yu, Lisan; Hermes, Juliet; Murtugudde, Raghu; Tozuka, Tomoki; Su, Danielle; Singh, Arvind; Centurioni, Luca; Prakash, Satya; Wiggert, Jerry

doi:https://doi.org/10.5194/os-17-1677-2021

Articles | Volume 17, issue 6

https://doi.org/10.5194/os-17-1677-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue:

Understanding the Indian Ocean system: past, present and future...

https://doi.org/10.5194/os-17-1677-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 17, issue 6

Review article

|

26 Nov 2021

Review article |

| 26 Nov 2021

Progress in understanding of Indian Ocean circulation, variability, air–sea exchange, and impacts on biogeochemistry

Helen E. Phillips, Amit Tandon, Ryo Furue, Raleigh Hood, Caroline C. Ummenhofer, Jessica A. Benthuysen, Viviane Menezes, Shijian Hu, Ben Webber, Alejandra Sanchez-Franks, Deepak Cherian, Emily Shroyer, Ming Feng, Hemantha Wijesekera, Abhisek Chatterjee, Lisan Yu, Juliet Hermes, Raghu Murtugudde, Tomoki Tozuka, Danielle Su, Arvind Singh, Luca Centurioni, Satya Prakash, and Jerry Wiggert

Download

Final revised paper (published on 26 Nov 2021)
Preprint (discussion started on 29 Mar 2021)

Interactive discussion

Status: closed

RC1:
'Comment on os-2021-1', Michael McPhaden, 01 Apr 2021

The comment was uploaded in the form of a supplement: https://os.copernicus.org/preprints/os-2021-1/os-2021-1-RC1-supplement.pdf

Citation: https://doi.org/10.5194/os-2021-1-RC1
- AC1: 'Reply on RC1', Helen Phillips, 13 Jul 2021
  
  The comment was uploaded in the form of a supplement: https://os.copernicus.org/preprints/os-2021-1/os-2021-1-AC1-supplement.pdf
  
  Citation: https://doi.org/10.5194/os-2021-1-AC1
RC2:
'Comment on os-2021-1', Anonymous Referee #2, 23 May 2021

This is a timely review that updates popular earlier reviews by Schott and McCreary (2001) and Schott et al. (2009). The difference is that a large group of authors wrote this review. As such, the coverage of various topics is at places uneven and the quality of the writing is variable. Sections 4.2.3 and 4.2.4 are good in coverage and readability. The discussion of biogeochemical variability helps bridge to communities beyond physical oceanography.

Major comments

The paper can benefit from better integration of different parts, possibly written different authors. A more balanced presentation among topics covered also helps, especially on climate. Here are some examples.

1. Abstract promises to bring together three major areas of research: the Indian Ocean circulation patterns, air-sea interactions, and climate variability. Reading the paper, I felt that that the emphasis was clearly on the ocean circulation while the latter topics did not receive as much attention. The Indian-western Pacific ocean capacitor (IPOC) perhaps represents an important advance in coupled ocean-atmosphere dynamics in the region but was hurried through in a single paragraph of 12 lines, including climate change, although it is a cross-basin mode (Xie et al. 2016, Adv Atmos Sci) with well-documented impacts on monsoon rainfall from India (Z. Zhou et al. 2019, GRL) to China and Japan (K. Hu et al. 2019, JC). In comparison, the text is 80 pages long, the Indian Ocean dipole (IOD) received a coverage of 4 pages and Ningaloo Niño 2 pages. This seems a lack of representation of IPOC research in the author team but a balanced approach is needed.

2. Abstract promises to discuss the role of the Indian Ocean in climate change. L80-81: “This coupling (not sure what’s this coupling) … causing a hiatus in the warming of Earth’s surface atmosphere (Section 6).” I did not see further discussion of this topics in section 6, which is entitled ”Modes of Interannual Climate Variability”.

L135-136: “The Indian Ocean accounts for 50-70% of the total anthropogenic warming in the global upper (700 m) ocean.” This seems an overstatement. Do we even know how much “the anthropogenic warming” there is in the ocean? Does this merely refer to the trends over a certain time period?

Additional comments

Figure 1 is hard to read. It’s probably from a ppt slide, which seems to include many layers of animation.

L296. “the SST variability is predominantly generated by variability in surface heat fluxes in the Seychelles-Chagos Thermocline Ridge.” Shouldn’t it first mention that intraseasonal SST variability is large in this region (e.g., Saji et al. 2006, GRL)? I understand the need to emphasize recent results but a big picture needs to be presented first.

L398-400. Is it really relevant to discuss Pacific TIWs?

L520-521. “The Agulhas variability is linked upstream to the IOD, SIOD and ENSO…” Is there a literature to back this up?

L830-832. The semi-annual cycle in the zonal wind over the equatorial Indian Ocean is well known observationally but was never explained physically. Ogata and Xie (2011, JC) showed that it’s due to the meridional advection of easterly momentum by the cross-equatorial monsoon winds.

Does Figure 13 need to show two operational products?

L1460-1461. The projection was challenged by G. Li et a. (2016, JC), a paper entitled “A robust but spurious pattern of climate change in model projections over the tropical Indian Ocean.”

Section 8 could be stronger. What happened during the 12-month period of Sept 2019-August 2020 showed that we don’t know the Indian Ocean very well as a driver of major climate anomalies in the rim countries. The period opened with a record IOD (Doi et al. 2020; Du et al. 2020, GRL) and ended with historic heavy rainfall in China and Japan that have been attributed to a strong IPOC event (Takaya et al. 2020, GRL; Zhou et al. 2021 PNAS), all without major ENSO signals in the Pacific. I don’t think we know well how this chain of events happened in the Indian Ocean but clearly we should.

Several papers were cited in the text but not in References.

L368. Zhou et al. (2017a, b)

L391. Xi et al., 2015. Is it a typo of Xie et al. (2006, JC) on orographic effects on monsoon rainfall?

L1352. De Boer et al., 2013.

L1429. Xie et al. (2009)

L1432. Zheng et al. (2013)

Citation: https://doi.org/10.5194/os-2021-1-RC2
- AC2: 'Reply on RC2', Helen Phillips, 13 Jul 2021
  
  The comment was uploaded in the form of a supplement: https://os.copernicus.org/preprints/os-2021-1/os-2021-1-AC2-supplement.pdf
  
  Citation: https://doi.org/10.5194/os-2021-1-AC2

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

AR by Helen Phillips on behalf of the Authors (13 Jul 2021) Author's response Author's tracked changes Manuscript

ED: Reconsider after major revisions (22 Jul 2021) by Hermann Bange

ED: Referee Nomination & Report Request started (23 Jul 2021) by Hermann Bange

RR by Anonymous Referee #2 (15 Aug 2021)

RR by Michael J McPhaden (19 Aug 2021)

Suggestions for revision or reasons for rejection

The authors have done an excellent job to address my concerns on the original submission of this paper. The revision is much improved both in terms of content and organization. I recommend publication subject to a few minor adjustments as described below. I do not need to see the final revised version of the paper.

General: Since the paper is so long, it might be helpful to include a table of contents at the front end with the various sections and subsections listed. That way the reader can orient with a big picture overview and, if they are interested in only a subset of topics, can navigate directly to the relevant sections.

Specifics:

Line 65. "topography". Do you mean "geography"?

Line 298. Kessler et al, 1995 and McPhaden 1999 proposed this connection before Bergman, so they should be cited as well.

Line 362-64. The juxtaposition of semi-annual with intraseasonal variability here is a little abrupt. Maybe move the reference to semi-annual variability to the section on the Wyrtki jets or provide a smoother connection at this point.

Section 3.2.2. Please point out that time scales for the MISO as for the MJO. The MJO is classically characterized by 30-60 day periods but MISOs can also occur on 10-20 day time scales (Goswami et al, 2016) and there are studies that have identified a 3-7 day time scale MISOs (e.g. Roman-Stork et al, 2020).

Section 4.4.2.1. A new paper has appeared online by Zang et al (2021) on the Somali Current/Undercurrent that might be good to cite in this section.

Lines 2081-82. There has been progress on understanding circulation at intermediate and deeper depths, at least in the equatorial band. Huang et al (2018) summarize Indian Ocean studies of deep ocean propagating features and present some new results. You could possibly fold a short discussion of this topic into section 4.3.3 if you felt is would be of benefit. But it's not necessary given how much territory you've covered already in the paper.

Line 2113-14: It might be helpful to mention marine heatwaves and their ecosystem impacts here.

A final suggestion (though I'm guessing the authors have already considering this)--some kind of acknowledgement or maybe even a dedication to the recently deceased co-author Satya Prakash.

References

Goswami, B.N., S.A. Rao, D. Sengupta, and S. Chakravorty. 2016. Monsoons to mixing in the Bay of Bengal: Multiscale air-sea interactions and monsoon predictability. Oceanography 29(2):18–27, http://dx.doi.org/10.5670/oceanog.2016.35.

Huang, K., McPhaden, M. J., Wang, D., Wang, W., Xie, Q., Chen, J., et al. (2018). Vertical propagation of middepth zonal currents associated with surface wind forcing in the equatorial Indian Ocean. Journal of Geophysical Research: Oceans, 123, 7290–7307. https://doi.org/ 10.1029/2018JC013977

Kessler, W.S., M.J. McPhaden, and K.M. Weickmann, 1995: Forcing of intraseasonal Kelvin Waves in the equatorial Pacific. J. Geophys. Res., 100, 10,613–10,631.

McPhaden, M.J., 1999: Genesis and evolution of the 1997-98 El Niño. Science, 283, 950-954.

Roman‐Stork, H. L., Subrahmanyam, B., & Trott, C. B. (2020). Monitoring
intraseasonal oscillations in the Indian Ocean using satellite observations. Journal of Geophysical Research: Oceans, 125, e2019JC015891. https://doi.org/10.1029/2019JC015891

Zang, N., Sprintall, J., Ienny, R., Wang, F., Seasonality of the Somali Current/Undercurrent System, Deep-Sea Research Part II, https://doi.org/10.1016/j.dsr2.2021.104953.

Hide

ED: Publish subject to minor revisions (review by editor) (19 Aug 2021) by Hermann Bange

AR by Helen Phillips on behalf of the Authors (10 Sep 2021) Author's response Author's tracked changes Manuscript

ED: Publish as is (15 Sep 2021) by Hermann Bange

AR by Helen Phillips on behalf of the Authors (25 Sep 2021) Manuscript

Download

The requested paper has a corresponding corrigendum published. Please read the corrigendum first before downloading the article.

Article (27154 KB)
Full-text XML

Short summary

Over the past decade, understanding of the Indian Ocean has progressed through new observations and advances in theory and models of the oceanic and atmospheric circulation. This review brings together new understanding of the ocean–atmosphere system in the Indian Ocean, describing Indian Ocean circulation patterns, air–sea interactions, climate variability, and the critical role of the Indian Ocean as a clearing house for anthropogenic heat.