The 2<sup>nd</sup> International Indian Ocean Expedition (IIOE‐2): Motivating New Exploration in a Poorly Understood Basin

Hood, Raleigh R.; Urban, Edward R.; McPhaden, Michael J.; Su, Danielle; Raes, Eric J.

doi:10.1002/lob.10149

Cited by 18 publications

(9 citation statements)

References 7 publications

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“…In December 2000, measurements in the southern Indian Ocean were carried out as preparative study for an intensive field campaign within the ELCID4 project with ship track between Reunion Islands, Amsterdam Islands, Corzet Islands and Kerguelen Islands. IO and BrO were both below the detection limit of the instrument, and hence upper limits of 4 ppt were reported for both species in the Indian Ocean (Hönninger, 2002). A field campaign in the Maldives also reported upper limits for the BrO vertical columns (3x10 14 molecules cm -2 ) (Ladstätter-Weißenmayer et al, 2007).…”

Section: Halogensmentioning

confidence: 92%

“…The strong monsoonal winds in the Indian Ocean lead to ocean upwelling, supplying nutrients to the surface layer, where they support elevated rates of primary productivity mainly in the Arabian Sea, the Somali Basin, along the Indian coast and the northern Bay of Bengal, especially during summer months. The seasonal reversals in the boundary currents of the northern Indian Ocean have important biogeochemical and ecological impacts and include seasonal switching from upwelling to downwelling circulations, and modification of primary productivity, nutrient stoichiometry, oxygen concentrations and phytoplankton species composition (Hood et al, 2017). Transient upwelling due to seasonal variations of currents and mesoscale variability can give rise to episodically high levels of primary production throughout the Indian Ocean coastal waters.…”

Section: Salinity Ssts and Productivitymentioning

confidence: 99%

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Atmospheric gas-phase composition over the Indian Ocean

Tegtmeier

Marandino

Jia

et al. 2020

Preprint

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Abstract. The Indian Ocean is coupled to atmospheric dynamics, transport and chemical composition via several unique mechanisms, such as the seasonally varying monsoon circulation. During the winter monsoon season, high pollution levels are regularly observed over the entire northern Indian Ocean, while during the summer monsoon, clean air dominates the atmospheric composition, leading to distinct chemical regimes. The changing atmospheric composition over the Indian Ocean can interact with oceanic biogeochemical cycles and impact marine ecosystems, resulting in potential climate feedbacks. Here, we review current progress in detecting and understanding atmospheric gas-phase composition over the Indian Ocean and its local and global impacts. The review takes into account results from recent Indian Ocean ship campaigns, satellite measurements, station data and information on continental and oceanic trace gas emissions. The distribution of all major pollutants and greenhouse gases shows pronounced differences between the landmass source regions and the Indian Ocean with strong gradients over the coastal areas. Surface pollution and ozone are highest during the winter monsoon over the Bay of Bengal and the Arabian Sea coastal waters due to air mass advection from the Indo-Gangetic Plain and continental outflow from Southeast Asia. We observe, however, that unusual types of wind patterns can lead to pronounced deviations of the typical trace gas distributions. For example, the ozone distribution maxima shift to different regions under different wind scenarios. The distribution of greenhouse gases over the Indian Ocean shows many similarities when compared to the pollution fields, but also some differences of the latitudinal and seasonal variations resulting from their long lifetimes and biogenic sources. Mixing ratios of greenhouse gases such as methane show positive trends over the Indian Ocean, but long-term changes of pollution and ozone, and in particular how they are driven by changing emissions and transport patterns, require further investigation in the future. Although we know that changing atmospheric composition and perturbations within the Indian Ocean affect each other, the impacts of atmospheric pollution on oceanic biogeochemistry and trace gas cycling is severely understudied. We highlight potential mechanisms, future research topics and observational requirements that need to be explored in order to fully understand interactions and feedbacks between the ocean and atmosphere in the Indian Ocean region.

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Section: Halogensmentioning

confidence: 92%

Section: Salinity Ssts and Productivitymentioning

confidence: 99%

Atmospheric gas-phase composition over the Indian Ocean

Tegtmeier

Marandino

Jia

et al. 2020

Preprint

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“…The wealth of information provided by the JGOFS expeditions has been invaluable for understanding the AS, but there has been little subsequent in situ sampling in the AS, as has been previously remarked (Hood et al, 2016). For example, in the Global Ocean Data Analysis Project v2 (GLODAP; Olsen et al, 2019) database, there are no reported observations in the AS of two important carbon variables, dissolved inorganic carbon (DIC) and total alkalinity (TA), more recent than 1998, with a similar story for pCO 2 .…”

Section: Introductionmentioning

confidence: 99%

Evaluating the Arabian Sea as a regional source of atmospheric CO<sub>2</sub>: seasonal variability and drivers

Verneil¹,

Lachkar²,

Smith³

et al. 2021

Preprint

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Abstract. The Arabian Sea (AS) was confirmed to be a net emitter of CO2 to the atmosphere during the international Joint Global Ocean Flux Study program of the 1990s, but since then little in situ data has been collected, leaving data-based methods to calculate air-sea exchange with fewer data and potentially out-of-date. Additionally, coarse-resolution models underestimate CO2 flux compared to other approaches. To address these shortcomings, we employ a high-resolution (1/24°) regional model to quantify the seasonal cycle of air-sea CO2 exchange in the AS by focusing on two main contributing factors, pCO2 and winds. We compare the model to available in situ pCO2 data and find that uncertainties in dissolved inorganic carbon (DIC) and total alkalinity (TA) lead to the greatest discrepancies. Nevertheless, the model is more successful than neural network approaches in replicating the large variability in summertime pCO2 because it captures the AS's intense monsoon dynamics. In the seasonal pCO2 cycle, temperature plays the major role in determining surface pCO2, except where DIC delivery is important in summer upwelling areas. Since seasonal temperature forcing is relatively uniform, pCO2 differences between the AS's sub-regions are mostly caused by geographic DIC gradients. We find that primary productivity during both summer and winter monsoon blooms, but also generally, is insufficient to off-set the physical delivery of DIC to the surface, resulting in limited biological control of CO2 release. The most intense air-sea CO2 exchange occurs during the summer monsoon where outgassing rates reach ~6 molCm−2 yr−1 in the upwelling regions of Oman and Somalia, but the entire AS contributes CO2 to the atmosphere. Despite a regional spring maximum of pCO2 driven by surface heating, CO2 exchange rates peak in summer due to winds, which account for ~90 % of the summer CO2 flux variability versus 6 % for pCO2 in a Reynolds decomposition. In comparison with other estimates, we find that the AS emits ~160 TgCyr−1, slightly higher than previously reported. Altogether, there is 2x variability in annual flux magnitude across methodologies considered. Future attempts to reduce the variability in estimates will likely require more in situ carbon data. Since summer monsoon winds are critical in determining flux both directly and indirectly through temperature, DIC, TA, mixing, and primary production effects on pCO2, studies looking to predict CO2 emissions in the AS with ongoing climate change will need to correctly resolve their timing, strength, and upwelling dynamics.

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“…The 2 nd International Indian Ocean Expedition program [Hood et al 2016] was launched in December 2015 on the occasion of the 50 th anniversary of the first International Indian Ocean Expedition program (1959)(1960)(1961)(1962)(1963)(1964)(1965) as a joint effort of the Scientific Committee on Oceanic Research (SCOR), the Intergovernmental Oceanographic Commission (IOC) and the Indian Ocean Global Observing System (IOGOOS). IIOE-2 was set up to advance Indian Ocean initiatives and projects addressing emerging scientific issues of the Indian Ocean in the 21 st century.…”

Section: Introductionmentioning

confidence: 99%

Anthropogenic nitrogen inputs and impacts on oceanic N2O fluxes in the northern Indian Ocean: The need for an integrated observation and modelling approach

Suntharalingam

Zamora

Bange

et al. 2019

Deep Sea Research Part II: Topical Studies in Oceanography

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Anthropogenically-derived nitrogen input to the northern Indian Ocean has increased significantly in recent decades, based on both observational and modelderived estimates This external nutrient source is supplied by atmospheric deposition and riverine fluxes, and has the potential to affect the vulnerable biogeochemical systems of the Arabian Sea and Bay of Bengal, influencing productivity and oceanic production of the greenhouse-gas nitrous-oxide (N 2 O). We summarize current estimates of this external nitrogen source to the northern Indian Ocean from observations and models, highlight implications for regional marine N 2 O emissions using model-based analyses, and make recommendations for measurement and model needs to improve current estimates and future predictions of this impact. Current observationally-derived estimates of deposition and riverine nitrogen inputs are limited by sparse measurements and uncertainties on accurate characterization of nitrogen species composition. Ocean model assessments of the impact of external nitrogen sources on regional marine N 2 O production in the northern Indian Ocean estimate potentially significant changes but also have large associated uncertainties. We recommend an integrated program of basin-wide measurements combined with high-resolution modeling and more detailed characterization of nitrogen-cycle process to address these uncertainties and improve current estimates and predictions. * Present day values derived from model simulations for period 1995-2005. ** Defined here as the ocean region north of the Equator and within the longitudinal range 42 o E-100 o E.

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The 2^nd International Indian Ocean Expedition (IIOE‐2): Motivating New Exploration in a Poorly Understood Basin

Cited by 18 publications

References 7 publications

Atmospheric gas-phase composition over the Indian Ocean

Atmospheric gas-phase composition over the Indian Ocean

Evaluating the Arabian Sea as a regional source of atmospheric CO<sub>2</sub>: seasonal variability and drivers

Anthropogenic nitrogen inputs and impacts on oceanic N2O fluxes in the northern Indian Ocean: The need for an integrated observation and modelling approach

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The 2nd International Indian Ocean Expedition (IIOE‐2): Motivating New Exploration in a Poorly Understood Basin

Cited by 18 publications

References 7 publications

Atmospheric gas-phase composition over the Indian Ocean

Atmospheric gas-phase composition over the Indian Ocean

Evaluating the Arabian Sea as a regional source of atmospheric CO&lt;sub&gt;2&lt;/sub&gt;: seasonal variability and drivers

Anthropogenic nitrogen inputs and impacts on oceanic N2O fluxes in the northern Indian Ocean: The need for an integrated observation and modelling approach

Contact Info

Product

Resources

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The 2^nd International Indian Ocean Expedition (IIOE‐2): Motivating New Exploration in a Poorly Understood Basin

Evaluating the Arabian Sea as a regional source of atmospheric CO<sub>2</sub>: seasonal variability and drivers