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Glacial-interglacial productivity contrasts along the eastern Arabian Sea:Dominance of convective mixing over upwelling

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Geoscience Frontiers 2015年第6期6卷 913-925页

作者： Kumar Avinash busnur r.manjunath P.John Kurian Earth System Science Organization National Centre for Antarctic and Ocean ResearchMinistry of Earth Sciences Department of Marine Geology Mangalore University

The western continental margin of India is one of the highly productive regions in the global *** productivity is induced by upwelling and convective mixing during the southwest and northeast monsoons *** the importance of high primary productivity,a sediment core was collected below the current oxygen minimum zone（OMZ） from the southwestern continental margin of *** was dated by AMS radiocarbon and as many as 60 paleoclimate/paceoceanographic proxies,such as particle size,biogenic components,major,trace and rare earth elements（rEEs） which were measured for the first time to determine sources of sediment,biogeochemical processes operating in the water column and their variations since the last glacial cycle.r-mode factor analysis of comprehensive data indicates that the dominant regulator of paleoproductivity is the southwest monsoon wind induced *** paleoproductivity related factors identified are the marine biogenic component and biogenic detritus（as an exported component from the water column added to the bottom sediment）.All paleoproductivity components increased significantly during the marine isotope stage-1（MIS-1）compared to those accumulated from MIS-4 to *** second group of factors identified are the terrigenous sediments with heavy minerals like zircon and *** terrigenous sediment,in particular,increased during MIS-2 when the sea-level was lower;however,the heavy mineral component fluctuated over time implying pulsed inputs of *** diagenetic fraction and reducing component are the third group of factors identified which varied with time with increased accumulation during the MIS *** primary productivity along the southwestern continental margin of India seems to have been controlled principally by the upwelling during the southwest monsoon season that was weaker from MIS-4 to MIS-2,as relative to that during the *** contrast,increased glacial productivity noticed in se

关键词： Paleoproductivity Upwelling Convective mixing Terrigenous sedimentation Western continental margin of India

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The response of Geopotential Height Anomalies to El Niño and La Niña Conditions and Their Implications to Seasonal rainfall Variability over the Horn of Africa

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Atmospheric and Climate Sciences 2022年第2期12卷 475-492页

作者： Solomon Gunta Hejamady Gangadhara Bhat busnur rachotappa manjunatha Department of Physics College of Natural and Computational Sciences Wolaita Sodo University Wolaita Sodo Ethiopia remote Sensing and Geo-Informatics Division Department of Marine Geology Faculty of Science and Technology Mangalore University Karnataka India

In this study, we unveil atmospheric circulation anomalies associated with the large-scale tropical teleconnections using National Center for Environmental Prediction (NCEP) reanalysis dataset. Composite analyses have been performed to know the impact of large-scale tropical circulations on the Horn of Africa. The composite analysis performed at the geopotential height of 850 Mb and 200 Mb, and precipitation rate (mm/day) during six strong El Niño and La Niña episodes revealed that the large-scale tropical variability induced climate anomalies in space and time. A substantial decrease in upper-level height (200 Mb) has been observed in the study area during El Niño composite years as compared to the La Niña years. During El Niño conditions, the upper-level divergence initiates low-level vertical motion, thereby enhancing convection, however, during La Niña composite years, nearly contrasting situations are noticed in Belg (February to May) season in Ethiopia. However, geopotential height anomalies at 850 Mb are above-normal during the strong El Niño years, suggesting suppressed convection due to vertical shrinking and enhancement of divergence at the lower level. Compared to the Belg (February to May), geopotential anomalies were generally positive during the Kiremt (June to September) season, thereby suppressing the rainfall, particularly in Southern Ethiopia and Northern Part of Kenya. In contrast, an increase in rainfall was observed during the Belg season (February to May).

关键词： Geopotential Height Composite Analysis ENSO Atmospheric Circulations NCEP reanalysis Tropical SST Anomalies Teleconnections Belg Kiremt

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