the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
29 Mar 2021
29 Mar 2021
Progress in understanding of Indian Ocean circulation, variability, air-sea exchange and impacts on biogeochemistry
- 1Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, 7005, Australia
- 2Australian Antarctic Program Partnership, University of Tasmania, Hobart, 7005, Australia
- 3Department of Mechanical Engineering, College of Engineering, University of Massachusetts Dartmouth, 02747, USA
- 4APL/JAMSTEC, Yokohama, Japan
- 5University of Maryland Center for Environmental Science, Horn Point Laboratory, Cambridge, 21613, USA
- 6Department of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, 02543, USA
- 7ARC Centre of Excellence for Climate Extremes, University of New South Wales, Sydney, Australia
- 8Australian Institute of Marine Science, Indian Ocean Marine Research Centre, Crawley, Australia
- 9Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- 10School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UK
- 11National Oceanography Centre, Southampton, UK
- 12National Center for Atmospheric Research, Boulder, USA
- 13College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, 97331, USA
- 14CSIRO Oceans and Atmosphere, Indian Ocean Marine Research Centre, Crawley, Australia
- 15Centre for Southern Hemisphere Oceans Research, Hobart, Australia
- 16U.S. Naval Research Laboratory, Washington, 20032, USA
- 17Indian National Centre for Ocean Information Services, Ministry of Earth Sciences, Hyderabad, India
- 18South African Environmental Observation Network, Cape Town, South Africa
- 19Department of Atmospheric and Oceanic Science, University of Maryland, College Park, 20742, USA
- 20Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Tokyo, Japan
- 21Sorbonne Universités, UPMC Université Paris 06, CNRS, UMR 7159 LOCEAN-IPSL, Paris, France
- 22Physical Research Laboratory, Ahmedabad, India
- 23Scripps Institution of Oceanography, University of California San Diego, La Jolla, 92093, USA
- 24University of Southern Mississippi, Hattiesburg, 399406, USA
- 1Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, 7005, Australia
- 2Australian Antarctic Program Partnership, University of Tasmania, Hobart, 7005, Australia
- 3Department of Mechanical Engineering, College of Engineering, University of Massachusetts Dartmouth, 02747, USA
- 4APL/JAMSTEC, Yokohama, Japan
- 5University of Maryland Center for Environmental Science, Horn Point Laboratory, Cambridge, 21613, USA
- 6Department of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, 02543, USA
- 7ARC Centre of Excellence for Climate Extremes, University of New South Wales, Sydney, Australia
- 8Australian Institute of Marine Science, Indian Ocean Marine Research Centre, Crawley, Australia
- 9Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- 10School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UK
- 11National Oceanography Centre, Southampton, UK
- 12National Center for Atmospheric Research, Boulder, USA
- 13College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, 97331, USA
- 14CSIRO Oceans and Atmosphere, Indian Ocean Marine Research Centre, Crawley, Australia
- 15Centre for Southern Hemisphere Oceans Research, Hobart, Australia
- 16U.S. Naval Research Laboratory, Washington, 20032, USA
- 17Indian National Centre for Ocean Information Services, Ministry of Earth Sciences, Hyderabad, India
- 18South African Environmental Observation Network, Cape Town, South Africa
- 19Department of Atmospheric and Oceanic Science, University of Maryland, College Park, 20742, USA
- 20Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Tokyo, Japan
- 21Sorbonne Universités, UPMC Université Paris 06, CNRS, UMR 7159 LOCEAN-IPSL, Paris, France
- 22Physical Research Laboratory, Ahmedabad, India
- 23Scripps Institution of Oceanography, University of California San Diego, La Jolla, 92093, USA
- 24University of Southern Mississippi, Hattiesburg, 399406, USA
Abstract. Over the past decade, our understanding of the Indian Ocean has advanced through concerted efforts toward measuring the ocean circulation and its water properties, detecting changes in water masses, and linking physical processes to ecologically important variables. New circulation pathways and mechanisms have been discovered, which control atmospheric and oceanic mean state and variability. This review brings together new understanding of the ocean-atmosphere system in the Indian Ocean since the last comprehensive review, describing the Indian Ocean circulation patterns, air-sea interactions and climate variability. The second International Indian Ocean Expedition (IIOE-2) and related efforts have motivated the application of new technologies to deliver higher-resolution observations and models of Indian Ocean processes. As a result we are discovering the importance of small scale processes in setting the large-scale gradients and circulation, interactions between physical and biogeochemical processes, interactions between boundary currents and the interior, and between the surface and the deep ocean. In the last decade we have seen rapid warming of the Indian Ocean overlaid with extremes in the form of marine heatwaves. These events have motivated studies that have delivered new insight into the variability in ocean heat content and exchanges in the Indian Ocean, and climate variability on interannual to decadal timescales.This synthesis paper reviews the advances in these areas in the last decade.
Helen E. Phillips et al.
Status: final response (author comments only)
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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
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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
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AC1: 'Reply on RC1', Helen Phillips, 13 Jul 2021
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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)
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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
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AC2: 'Reply on RC2', Helen Phillips, 13 Jul 2021
Helen E. Phillips et al.
Helen E. Phillips et al.
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