scholarly journals Solicited review of Parvathi et al., " Positive Indian Ocean Dipole events prevent anoxia along the west coast of India"

2016 ◽  
Author(s):  
Anonymous
Keyword(s):  
Indian Ocean ◽  
West Coast ◽  
Indian Ocean Dipole ◽  
The West ◽  
West Coast Of India ◽  
Positive Indian Ocean Dipole

scholarly journals Positive Indian Ocean Dipole events prevent anoxia off the west coast of India

2017 ◽  
Vol 14 (6) ◽  
pp. 1541-1559 ◽  
Author(s):  
Parvathi Vallivattathillam ◽  
Suresh Iyyappan ◽  
Matthieu Lengaigne ◽  
Christian Ethé ◽  
Jérôme Vialard ◽  
...  
Keyword(s):  
Indian Ocean ◽  
West Coast ◽  
Indian Ocean Dipole ◽  
Boreal Summer ◽  
Low Oxygen ◽  
The West ◽  
Easterly Wind ◽  
West Coast Of India ◽  
Positive Indian Ocean Dipole ◽  
Subsurface Waters

Abstract. The seasonal upwelling along the west coast of India (WCI) brings nutrient-rich, oxygen-poor subsurface waters to the continental shelf, favoring very low oxygen concentrations in the surface waters during late boreal summer and fall. This yearly-recurring coastal hypoxia is more severe during some years, leading to coastal anoxia that has strong impacts on the living resources. In the present study, we analyze a 1/4° resolution coupled physical–biogeochemical regional oceanic simulation over the 1960–2012 period to investigate the physical processes influencing the oxycline interannual variability off the WCI, that being a proxy for the variability on the shelf in our model. Our analysis indicates a tight relationship between the oxycline and thermocline variations in this region on both seasonal and interannual timescales, thereby revealing a strong physical control of the oxycline variability. As in observations, our model exhibits a shallow oxycline and thermocline during fall that combines with interannual variations to create a window of opportunity for coastal anoxic events. We further demonstrate that the boreal fall oxycline fluctuations off the WCI are strongly related to the Indian Ocean Dipole (IOD), with an asymmetric influence of its positive and negative phases. Positive IODs are associated with easterly wind anomalies near the southern tip of India. These winds force downwelling coastal Kelvin waves that propagate along the WCI and deepen the thermocline and oxycline there, thus preventing the occurrence of coastal anoxia. On the other hand, negative IODs are associated with WCI thermocline and oxycline anomalies of opposite sign but of smaller amplitude, so that the negative or neutral IOD phases are necessary but not the sufficient condition for coastal anoxia. As the IODs generally start developing in summer, these findings suggest some predictability to the occurrence of coastal anoxia off the WCI a couple of months ahead.

scholarly journals A biological Indian Ocean Dipole event in 2019

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Wei Shi ◽  
Menghua Wang
Keyword(s):  
Biological Activity ◽  
Indian Ocean ◽  
Indian Ocean Dipole ◽  
Infrared Imaging ◽  
Equatorial Indian Ocean ◽  
The West ◽  
Indian Ocean Dipole Event ◽  
Chl A ◽  
Positive Indian Ocean Dipole ◽  
Dipole Response

AbstractThe 2019 positive Indian Ocean Dipole (IOD) event in the boreal autumn was the most serious IOD event of the century with reports of significant sea surface temperature (SST) changes in the east and west equatorial Indian Ocean. Observations of the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-orbiting Partnership (SNPP) between 2012 and 2020 are used to study the significant biological dipole response that occurred in the equatorial Indian Ocean following the 2019 positive IOD event. For the first time, we propose, identify, characterize, and quantify the biological IOD. The 2019 positive IOD event led to anomalous biological activity in both the east IOD zone and west IOD zone. The average chlorophyll-a (Chl-a) concentration reached over ~ 0.5 mg m−3 in 2019 in comparison to the climatology Chl-a of ~ 0.3 mg m−3 in the east IOD zone. In the west IOD zone, the biological activity was significantly depressed. The depressed Chl-a lasted until May 2020. The anomalous ocean biological activity in the east IOD zone was attributed to the advection of the higher-nutrient surface water due to enhanced upwelling. On the other hand, the dampened ocean biological activity in the west IOD zone was attributed to the stronger convergence of the surface waters than that in a normal year.

English Private Trade on the West Coast of India, c. 1680–c. 1740

Itinerario ◽  
2014 ◽  
Vol 38 (2) ◽  
pp. 51-73 ◽  
Author(s):  
Timothy Davies
Keyword(s):  
Indian Ocean ◽  
West Coast ◽  
Western Indian Ocean ◽  
East India Company ◽  
The West ◽  
Trade Networks ◽  
West Coast Of India ◽  
The Indian Ocean ◽  
English East India Company ◽  
Indian Ocean World

This article explores the private trade networks of English East India Company merchants on the west coast of India during the first half of the eighteenth century. Existing studies of English private trade in the Indian Ocean have almost exclusively focused on India's eastern seaboard, the Coromandel Coast and the Bay of Bengal regions. This article argues that looking at private trade from the perspective of the western Indian Ocean provides a different picture of this important branch of European trade. It uses EIC records and merchants' private papers to argue against recent metropolitan-centred approaches to English private trade, instead emphasising the importance of more localised political and economic contexts, within the Indian Ocean world, for shaping the conduct and success of this commerce.

NAKHUDAS AND NAUVITTAKAS: SHIP-OWNING MERCHANTS IN THE WEST COAST OF INDIA (C. AD 1000-1500)

2000 ◽  
Vol 43 (1) ◽  
pp. 34-64 ◽  
Author(s):  
Ranabir Chakravarti
Keyword(s):  
Indian Ocean ◽  
West Coast ◽  
Coastal Areas ◽  
Religious Toleration ◽  
Western India ◽  
The West ◽  
West Coast Of India ◽  
Cultural Activities ◽  
The Indian Ocean

AbstractAmong the diverse types of merchants active in India during the first half of the second millennium, the ship-owning merchants occupy a prominent position in the coastal areas of western India (especially at ports). These merchants are given distinct epithets nakhuda and nauvittaka, the two terms being occasionally used as interchangeable ones and also in their abbreviated forms in official documents. Known from the medieval Jewish letters of 'India Traders', copper plates, a bilingual inscription, Arabic accounts and epitaphs and Jaina carita (biographical) texts, nakudas and nauvittkas of different religious leanings (Jewish, Muslim and Hindu) illustrate remarkable co-operation and social amity and religious toleration, which underline their importance in the Indian Ocean maritime network prior to AD 1500. Possessing considerable wealth, these ship-owning merchants can be considered as elites in the ports of coastal western India and were also known for their patronage to religious and cultural activities. The paper is presented as a tribute to the memory of Professor Ashin Das Gupta who immensely enlightened us on the ship-owners of coastal western India between 1500-1800.

scholarly journals Impact of the Strong Downwelling (Upwelling) on Small Pelagic Fish Production during the 2016 (2019) Negative (Positive) Indian Ocean Dipole Events in the Eastern Indian Ocean off Java

Climate ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 29
Author(s):  
Jonson Lumban-Gaol ◽  
Eko Siswanto ◽  
Kedarnath Mahapatra ◽  
Nyoman Metta Nyanakumara Natih ◽  
I Wayan Nurjaya ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Indian Ocean Dipole ◽  
Pelagic Fish ◽  
Eastern Indian Ocean ◽  
Fish Production ◽  
Small Pelagic Fish ◽  
Field Surveys ◽  
Chl A ◽  
Positive Indian Ocean Dipole ◽  
The Impact

Although researchers have investigated the impact of Indian Ocean Dipole (IOD) phases on human lives, only a few have examined such impacts on fisheries. In this study, we analyzed the influence of negative (positive) IOD phases on chlorophyll a (Chl-a) concentrations as an indicator of phytoplankton biomass and small pelagic fish production in the eastern Indian Ocean (EIO) off Java. We also conducted field surveys in the EIO off Palabuhanratu Bay at the peak (October) and the end (December) of the 2019 positive IOD phase. Our findings show that the Chl-a concentration had a strong and robust association with the 2016 (2019) negative (positive) IOD phases. The negative (positive) anomalous Chl-a concentration in the EIO off Java associated with the negative (positive) IOD phase induced strong downwelling (upwelling), leading to the preponderant decrease (increase) in small pelagic fish production in the EIO off Java.

scholarly journals Two-year consecutive concurrences of positive Indian Ocean Dipole and Central Pacific El Niño preconditioned the 2019/2020 Australian “black summer” bushfires

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Guojian Wang ◽  
Wenju Cai
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
Indian Ocean Dipole ◽  
El Nino ◽  
Greenhouse Warming ◽  
Central Pacific ◽  
Central Pacific El Niño ◽  
Positive Indian Ocean Dipole ◽  
The Future ◽  
Rainfall Anomalies

Abstract The 2019/20 Australian black summer bushfires were particularly severe in many respects, including its early commencement, large spatial coverage, and large number of burning days, preceded by record dry and hot anomalies. Determining whether greenhouse warming has played a role is an important issue. Here, we examine known modes of tropical climate variability that contribute to droughts in Australia to provide a gauge. We find that a two-year consecutive concurrence of the 2018 and 2019 positive Indian Ocean Dipole and the 2018 and 2019 Central Pacific El Niño, with the former affecting Southeast Australia, and the latter influencing eastern and northeastern Australia, may explain many characteristics of the fires. Such consecutive events occurred only once in the observations since 1911. Using two generations of state-of-the-art climate models under historical and a business-as-usual emission scenario, we show that the frequency of such consecutive concurrences increases slightly, but rainfall anomalies during such events are stronger in the future climate, and there are drying trends across Australia. The impact of the stronger rainfall anomalies during such events under drying trends is likely to be exacerbated by greenhouse warming-induced rise in temperatures, making such events in the future even more extreme.

Myanmar Coastal Area Field Survey after the December 2004 Indian Ocean Tsunami

2006 ◽  
Vol 22 (3_suppl) ◽  
pp. 285-294 ◽  
Author(s):  
Tint Lwin Swe ◽  
Kenji Satake ◽  
Than Tin Aung ◽  
Yuki Sawai ◽  
Yukinobu Okamura ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Real Time ◽  
West Coast ◽  
Coastal Area ◽  
Field Survey ◽  
Indian Ocean Tsunami ◽  
Sumatra Earthquake ◽  
The West ◽  
Tide Level ◽  
The Indian Ocean

A post-tsunami survey was conducted along the Myanmar coast two months after the 2004 Great Sumatra earthquake ( Mw=9.0) that occurred off the west coast of Sumatra and generated a devastating tsunami around the Indian Ocean. Visual observations, measurements, and a survey of local people's experiences with the tsunami indicated some reasons why less damage and fewer casualties occurred in Myanmar than in other countries around the Indian Ocean. The tide level at the measured sites was calibrated with reference to a real-time tsunami datum, and the tsunami tide level range was 2–3 m for 22 localities in Myanmar. The tsunami arrived three to four hours after the earthquake.

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