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

Abstract

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.

Seasonal Structure and Interannual Variation of the South Equatorial Current in the Indian Ocean

“…The South Equatorial Current (SEC) is a key current in the tropical SIO (Phillips et al., 2021; see also the schematics in the sixth panel of Figure 1). Ship‐drift (e.g., Cutler & Swallow, 1984) and drifters data (Shenoi et al., 1999) have shown that the SEC is a band of westward flow between 10°S and 20°S extending across the SIO basin.…”

Comparison in the phylogenetic pattern of Java eel (Anguilla bicolor bicolor) from Java to Western Indian Ocean: Monophyletic fact and migration loop possibility

“…Even though ocean current patterns and circulations are mostly similar all-around years, the Indian Ocean circulation pattern varies by inter-annual variability (Schott et al, 2009 andPhillips et al, 2021). The simulation year of 2015 noticed that the peak current can reach more than 80 cm.s -1 in some months.…”

Atmospheric gas-phase composition over the Indian Ocean

“…The physical oceanography of the northern Indian Ocean reflects the seasonal changes in the monsoon cycle, including impacts on currents, thermohaline circulation, sea surface temperature (SST), salinity, and upwelling events, while the equatorial and southern Indian Ocean does not experience this influence. For more details about general Indian Ocean physical processes, please see Schott et al (2009) and references therein, Phillips et al (2021) from this issue, and Sect. S2.…”