scholarly journals Estimates of High Resolution Ventilation Age from the Equatorial Indian Ocean during Last 40 ka: Implications to Paleo Deep Water Circulation

2020 ◽  
Author(s):  
Nisha Bharti ◽  
Ravi Bhushan ◽  
M Muruganantham
Keyword(s):  
High Resolution ◽  
Indian Ocean ◽  
Deep Water ◽  
Equatorial Indian Ocean ◽  
Water Circulation

scholarly journals Deep-Water Circulation over the Last Two Glacial Cycles Reconstructed from Authigenic Neodymium Isotopes in the Equatorial Indian Ocean (Core HI1808-GPC04)

2021 ◽  
Author(s):  
Sunhwa Bang ◽  
Youngsook Huh ◽  
Boo-Keun Khim ◽  
Hiroyuki Takata ◽  
Minoru Ikehara ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Deep Water ◽  
Equatorial Indian Ocean ◽  
Weak Acid ◽  
Acid Extraction ◽  
Bulk Sediment ◽  
Glacial Cycles ◽  
Regional Effects ◽  
Neodymium Isotopes ◽  
Deep Waters

AbstractWe reconstructed the past deep-water character of the equatorial Indian Ocean using the isotope ratio of neodymium (εNd) in the Fe–Mn coating of mixed-species foraminifera. When compared with previous εNd records at the same site (ODP 758) and at another site to the west (SK 129), the three datasets were consistent and showed glacial-interglacial variations, even though the other two records were extracted from different media (cleaned foraminifera and bulk sediment leach). This confirms that while the foraminiferal coating is the preferred medium for reconstructing past bottom water εNd records, for carbonate-dominated lithologies, weak acid extraction of bulk sediment is also a viable option offering high-resolution capabilities. When the lithology includes volcanic particles or high organics, the extraction protocol may need to be adjusted to guard against detrital contamination or a slight correction may need to be applied. During glacials, the deep waters bathing the equatorial Indian Ocean had a larger AABW component and during interglacials a larger NADW component. Our HI1808-GPC04 record supplements the ODP 758 record in the interval with prominent AABW signal (MIS 6/5 transition and MIS 7) and reveals regional effects in some non-radiogenic intervals. The smaller differences between the HI1808-GPC04/ODP 758 and SK 129 records seem to reflect regional Nd input from river systems and non-radiogenic Nd from the boundaries.

Foraminiferal tracers of Indian-Atlantic interocean exchange during the last 600 kyr

2020 ◽  
Author(s):  
José N. Pérez-Asensio ◽  
Kazuyo Tachikawa ◽  
Thibault de Garidel-Thoron ◽  
Laurence Vidal ◽  
Corinne Sonzogni ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Atlantic Ocean ◽  
Deep Water ◽  
Water Circulation ◽  
Warm Water ◽  
Temperate Climate ◽  
Agulhas Current ◽  
Foraminiferal Species ◽  
The Indian Ocean ◽  
Relative Abundances

<p>The Indian-Atlantic interocean exchange (IAIE), occurring through Agulhas current and its leakage around the southern tip of Africa, is one of the return flows of global thermohaline circulation that contributes to the temperate climate in Europe. The IAIE affects the transport of heat and salt to the zone of deep-water formation in the N Atlantic, influencing the variability of Atlantic Meridional Overturning Circulation (AMOC). During the last 600 kyr, significant climatic events took place such as the Mid-Bruhnes event (MBE) (~430 ka) that marks a transition towards more intense interglacial periods.</p><p>The main objective of our study is to assess the impact of climate forcing on the strength of both surface and deep water IAIE during the last 600 kyr. For this purpose, we examined the variability of a group of warm-water planktonic foraminiferal species for tracing surface water circulation. We combined published and unpublished data from 3 cores along an Indian-Atlantic transect: two cores in the Indian Ocean, core MD96-2048 (26°10’S, 34°01’E, 660 m) in the source of the Agulhas current and our study core MD96-2077 (33º10’S, 31º14’E, 3781 m) in the middle of the Agulhas current; and one core in the Atlantic Ocean, core ODP1087 (31°27’S, 15°18’E 1372 m) recording the Agulhas leakage.</p><p>Since <em>Globorotalia menardii</em> and <em>Globorotalia tumida</em> are frequently used to trace Agulhas leakage, their variability in Agulhas current in the Indian Ocean is of our interest. Therefore, we compared the relative abundances of the warm-water planktonic <em>G. menardii</em> and <em>G. tumida</em> species with a group of warm-water planktonic foraminiferal species to record the strength of Agulhas current in core MD96-2077. Our results show that the group of warm-water planktonic species reflects increased Agulhas current strength at glacial terminations coinciding with stronger Agulhas leakage (Atlantic core ODP1087) as observed in previous studies. However, in core MD96-2077, both <em>G. menardii</em> and <em>G. tumida</em> relative abundances increase during interglacial periods. This indicates that production of these species in the Agulhas current source region is unlikely to trace Agulhas leakage in the Atlantic Ocean. The analyses of deep-water circulation proxies (Nd isotopes, benthic O and C stable isotopes) are in progress, and they will allow us to assess the response of deep circulation to changes in Agulhas current and leakage over the last 600 kyr.</p>

scholarly journals The Deep-Water Circulation of the Indian Ocean

Nature ◽  
1935 ◽  
Vol 136 (3450) ◽  
pp. 936-938 ◽  
Author(s):  
A. J. Clowes ◽  
G. E. R. Deacon
Keyword(s):  
Indian Ocean ◽  
Deep Water ◽  
Water Circulation ◽  
The Indian Ocean

scholarly journals Coherent intraseasonal oceanic variations in the eastern equatorial Indian Ocean and in the Lombok and Ombai Straits from observations and a high-resolution OGCM

2014 ◽  
Vol 119 (2) ◽  
pp. 615-630 ◽  
Author(s):  
Iskhaq Iskandar ◽  
Yukio Masumoto ◽  
Keisuke Mizuno ◽  
Hideharu Sasaki ◽  
Azhar K. Affandi ◽  
...  
Keyword(s):  
High Resolution ◽  
Indian Ocean ◽  
Equatorial Indian Ocean ◽  
Eastern Equatorial Indian Ocean

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.

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