scholarly journals Changes in productivity and intermediate circulation in the northern Indian Ocean since the last deglaciation: new insights from benthic foraminiferal Cd /thinsp;Ca records and benthic assemblage analyses

2020 ◽  
Author(s):  
Ruifang Ma ◽  
Sophie Sépulcre ◽  
Laetitia Licari ◽  
Frédéric Haurine ◽  
Franck Bassinot ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Primary Productivity ◽  
Arabian Sea ◽  
Bottom Water ◽  
Geochemical Data ◽  
Intermediate Water ◽  
Last Deglaciation ◽  
Northern Indian Ocean ◽  
Surface Productivity ◽  
The Last Deglaciation

Abstract. We have measured Cd / Ca ratios of several benthic foraminiferal species and studied benthic foraminiferal assemblages on two cores from the northern Indian Ocean (Arabian Sea and northern Bay of Bengal, BoB), in order to reconstruct variations in intermediate water circulation and paleo-nutrient content since the last deglaciation. Intermediate water Cdw records estimated from the benthic Cd / Ca reflect past changes in surface productivity and/or intermediate-bottom water ventilation. The benthic foraminiferal assemblages are consistent with the geochemical data. These results suggest that during the last deglaciation, the Heinrich Stadial 1 and Younger Dryas (HS1 and YD, respectively) millennial-scale events were marked by a decrease in Cdw values, indicating an enhanced ventilation of intermediate-bottom water masses. Benthic foraminifer assemblages indicate that surface primary productivity was low during the early Holocene (from 10 to 6 cal kyr BP), resulting in low intermediate water Cdw at both sites. From ~ 5.2 to 2.4 cal kyr BP, the benthic foraminiferal assemblages indicate meso- to eutrophic intermediate water conditions, which correspond to high surface productivity. This is consistent with a significant increase in the intermediate water Cdw in the southeastern Arabian Sea and the northeastern BoB. The comparison of intermediate water Cdw records with previous reconstructions of past Indian monsoon evolution during the Holocene suggests a direct control of intermediate water Cdw by monsoon-induced changes in upper water stratification and surface primary productivity.

Antarctic Intermediate Water penetration into the Northern Indian Ocean during the last deglaciation

2018 ◽  
Vol 500 ◽  
pp. 67-75 ◽  
Author(s):  
Zhaojie Yu ◽  
Christophe Colin ◽  
Ruifang Ma ◽  
Laure Meynadier ◽  
Shiming Wan ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Intermediate Water ◽  
Last Deglaciation ◽  
Northern Indian Ocean ◽  
Water Penetration ◽  
Antarctic Intermediate Water ◽  
The Last Deglaciation

scholarly journals A multi-proxy analysis of Late Quaternary ocean and climate variability for the Maldives, Inner Sea

2017 ◽  
Vol 13 (12) ◽  
pp. 1791-1813 ◽  
Author(s):  
Dorothea Bunzel ◽  
Gerhard Schmiedl ◽  
Sebastian Lindhorst ◽  
Andreas Mackensen ◽  
Jesús Reolid ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Indian Ocean ◽  
Organic Carbon ◽  
Sea Level ◽  
Benthic Foraminifera ◽  
Arabian Sea ◽  
Bottom Water ◽  
Winter Monsoon ◽  
Intermediate Water ◽  
Combined Effects

Abstract. As a natural sediment trap, the marine sediments of the sheltered central part of the Maldives Inner Sea represent an exceptional archive for paleoenvironmental and climate changes in the equatorial Indian Ocean. To evaluate the complex interplay between high-latitude and monsoonal climate variability, related dust fluxes, and regional oceanographic responses, we focused on Fe ∕ Al, Ti ∕ Al and Si ∕ Ca ratios as proxies for terrigenous sediment delivery and total organic carbon (TOC) and Br XRF counts as proxies for marine productivity. Benthic foraminiferal fauna distributions, grain size and stable δ18O and δ13C data were used for evaluating changes in the benthic ecosystem and changes in the intermediate water circulation, bottom water current velocity and oxygenation. Our multi-proxy data record reveals an enhanced dust supply during the glacial intervals, causing elevated Fe ∕ Al and Si ∕ Ca ratios, an overall coarsening of the sediment and an increasing amount of agglutinated benthic foraminifera. The enhanced dust fluxes can be attributed to higher dust availability in the Asian desert and loess areas and its transport by intensified winter monsoon winds during glacial conditions. These combined effects of wind-induced mixing of surface waters and dust fertilization during the cold phases resulted in an increased surface water productivity and related organic carbon fluxes. Thus, the development of highly diverse benthic foraminiferal faunas with certain detritus and suspension feeders was fostered. The difference in the δ13C signal between epifaunal and deep infaunal benthic foraminifera reveals intermediate water oxygen concentrations between approximately 40 and 100 µmol kg−1 during this time. The precessional fluctuation pattern of oxygen changes resembles that from the deep Arabian Sea, suggesting an expansion of the oxygen minimum zone (OMZ) from the Arabian Sea into the tropical Indian Ocean with a probable regional signal of strengthened winter-monsoon-induced organic matter fluxes and oxygen consumption further controlled by the varying inflow intensity of the Antarctic Intermediate Water (AAIW). In addition, the bottom water oxygenation pattern of the Maldives Inner Sea reveals a long phase of reduced ventilation during the last glacial period. This process is likely linked to the combined effects of generally enhanced oxygen consumption rates during high-productivity phases, reduced AAIW production and the restriction of upper bathyal environments in the Inner Sea during sea-level lowstands. Thus, our multi-proxy record reflects a close linkage between the Indian monsoon oscillation, intermediate water circulation, productivity and sea-level changes on orbital timescale.

scholarly journals A multi-proxy analysis of late Quaternary Indian monsoon dynamics for the Maldives, Inner Sea

2017 ◽  
Author(s):  
Dorothea Bunzel ◽  
Gerhard Schmiedl ◽  
Sebastian Lindhorst ◽  
Andreas Mackensen ◽  
Jesús Reolid ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Organic Carbon ◽  
Arabian Sea ◽  
Bottom Water ◽  
Indian Monsoon ◽  
Late Quaternary ◽  
Intermediate Water ◽  
Combined Effects ◽  
Proxy Data ◽  
Data Record

Abstract. We present a detailed multi-proxy data record to reveal the late Quaternary changes in marine sedimentation and biogeochemical processes of the upper bathyal Maldives (equatorial Indian Ocean) and how they are related to the benthic ecosystem dynamics. We investigated the sediment core SO-236-052-4 from the central part of the Inner Sea, Maldives, focusing on Fe / Ca and Si / Ca ratios as proxies for terrigenous sediment delivery, as well as Total Organic Carbon (TOC) and Ba / Ca ratios as proxies for marine productivity. Benthic foraminiferal fauna distributions, sortable silt records and stable oxygen and carbon isotope analyses were used for reconstructing the past ecosystem, as well as changes in the intermediate water circulation, bottom water current velocity and oxygenation. This multi-proxy data record shows an enhanced dust supply during the glacial intervals, represented by increased Fe / Ca and Si / Ca ratios, an overall coarsening of the sediment and increasing amount of agglutinated benthic foraminifera. The enhanced dust fluxes can be attributed to higher dust availability in the Asian desert and loess areas and its transport by intensified winter monsoon winds during glacial conditions. These combined effects of wind-induced mixing of surface waters and dust fertilisation during the cold phases resulted in increased surface water productivity and related organic carbon fluxes. Thus, the development of highly diverse benthic foraminiferal faunas and the distribution of certain detritus and suspension feeders were fostered. The difference in the stable carbon isotope signal between epifaunal and deep infaunal benthic foraminifera reveals intermediate water oxygen concentrations between approximately 40 and 100 μmol kg−1. The pattern of oxygen changes resembles that from the deep Arabian Sea suggesting an expansion of the Oxygen Minimum Zone (OMZ) from the Arabian Sea into the tropical Indian Ocean, further controlled by the inflow of the Antarctic Intermediate Water (AAIW). The precessional circulation pattern of the bottom water oxygenation is overprinted by glacial-/interglacial changes resulting in a long phase of reduced ventilation during the last glacial period. The latter process is likely linked to the combined effects of generally enhanced oxygen consumption rates during high-productivity phases, reduced AAIW production and restriction of bathyal environments of the Inner Sea of the Maldives during sea-level lowstands. Thus, this multi-proxy record provide a close linkage between the Indian monsoon oscillation, intermediate water circulation, productivity and sea-level changes on orbital time-scale.

Relationships between primary productivity and bottom-water oxygenation off northwest Africa during the last deglaciation

2011 ◽  
Vol 26 (4) ◽  
pp. 448-456 ◽  
Author(s):  
Helena L. Filipsson ◽  
Oscar E. Romero ◽  
Jan-Berend W. Stuut ◽  
Barbara Donner
Keyword(s):  
Primary Productivity ◽  
Bottom Water ◽  
Last Deglaciation ◽  
Northwest Africa ◽  
The Last Deglaciation

OSTRACOD-BASED RECONSTRUCTION OF BOTTOM WATER CONDITIONS IN THE INNER SEA OF THE MALDIVES DURING THE PLEISTOCENE (IODP SITE U1467, NORTHERN INDIAN OCEAN)

2017 ◽  
Author(s):  
Carlos A. Alvarez Zarikian ◽  
◽  
Chimnaz Nadiri ◽  
Montserrat Alonso-Garcia ◽  
Loren Petruny ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Bottom Water ◽  
Northern Indian Ocean ◽  
Water Conditions

scholarly journals Wind-Driven Response of the Northern Indian Ocean to Climate Extremes*

2007 ◽  
Vol 20 (13) ◽  
pp. 2978-2993 ◽  
Author(s):  
Tommy G. Jensen
Keyword(s):  
Indian Ocean ◽  
Ocean Circulation ◽  
Bay Of Bengal ◽  
El Niño ◽  
Arabian Sea ◽  
El Nino ◽  
Ocean Model ◽  
La Niña ◽  
Northern Indian Ocean ◽  
La Nina

Abstract Composites of Florida State University winds (1970–99) for four different climate scenarios are used to force an Indian Ocean model. In addition to the mean climatology, the cases include La Niña, El Niño, and the Indian Ocean dipole (IOD). The differences in upper-ocean water mass exchanges between the Arabian Sea and the Bay of Bengal are investigated and show that, during El Niño and IOD years, the average clockwise Indian Ocean circulation is intensified, while it is weakened during La Niña years. As a consequence, high-salinity water export from the Arabian Sea into the Bay of Bengal is enhanced during El Niño and IOD years, while transport of low-salinity waters from the Bay of Bengal into the Arabian Sea is enhanced during La Niña years. This provides a venue for interannual salinity variations in the northern Indian Ocean.

Distant origin of circulation changes in the Indian Ocean during the last deglaciation

2006 ◽  
Vol 243 (1-2) ◽  
pp. 244-251 ◽  
Author(s):  
C WAELBROECK ◽  
C LEVI ◽  
J DUPLESSY ◽  
L LABEYRIE ◽  
E MICHEL ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Last Deglaciation ◽  
The Indian Ocean ◽  
The Last Deglaciation ◽  
Circulation Changes

Millennial-scale changes of surface and bottom water conditions in the northwestern Pacific during the last deglaciation

2017 ◽  
Vol 154 ◽  
pp. 33-43 ◽  
Author(s):  
Sunghan Kim ◽  
Boo-Keun Khim ◽  
Ken Ikehara ◽  
Takuya Itaki ◽  
Akihiko Shibahara ◽  
...  
Keyword(s):  
Bottom Water ◽  
Northwestern Pacific ◽  
Last Deglaciation ◽  
Water Conditions ◽  
The Last Deglaciation ◽  
Millennial Scale
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