scholarly journals Antarctic bottom and lower circumpolar deep water circulation in the eastern Indian Ocean

2006 ◽  
Vol 111 (C2) ◽  
Author(s):  
Bernadette M. Sloyan
Keyword(s):  
Indian Ocean ◽  
Deep Water ◽  
Water Circulation ◽  
Eastern Indian Ocean ◽  
Circumpolar Deep Water ◽  
Lower Circumpolar Deep Water

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 We combined published and unpublished data from 3 cores along an Indian-Atlantic transect: two cores in the Indian Ocean, core MD96-2048 (26°10’S, 34°01’E, 660 m) in the source of the Agulhas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 Deep water circulation in the Hunter Channel (Southwest Atlantic) in a late Pleistocene and Holocene by benthonic foraminifera

2019 ◽  
Vol 59 (1) ◽  
pp. 133-142
Author(s):  
N. P. Lukashina
Keyword(s):  
Late Pleistocene ◽  
Deep Water ◽  
Sea Water ◽  
Bottom Layer ◽  
Water Circulation ◽  
Southwest Atlantic ◽  
East Part ◽  
The North ◽  
Lower Circumpolar Deep Water ◽  
Argentine Basin

Was reconstructed deep-sea water circulation near the Hunter Channel (Rio Grande Rise – South-West Atlantic) in a late Pleistocene and Holocene (MIS 4-MIS 1) by benthonic foraminifera. Was studied three cores of bottom sediment. Now moves the upper North Atlantic deep water (NADW) through the Hunter Channel from the North to the South. The lower NADW in the same direction came in MIS 2 and in MIS 4. There was the lower Circumpolar deep water (CPDW), NADW and Antarctic bottom water (AnBW) in MIS 3 periodically. CPDW prevail in a near bottom layer and in Holocene and in the late Pleistocene before the Hunter Channel sidewise the Argentine Basin. So in the Hunter Channel and on the way to it from south side for all studied period AnBW was almost not. Dissolution of carbonates during the Holocene happens in the deepest east part of the Hunter Channel. In Ice Ages processes of dissolution amplified and affected east part of the channel. Dissolution happen and happened not at the expense of AnBW, and at the expense of NADW which becomes there aggressive in relation to a calcium carbonate.

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 Bottom water warming along the pathway of lower circumpolar deep water in the Pacific Ocean

2006 ◽  
Vol 33 (23) ◽  
Author(s):  
Takeshi Kawano ◽  
Masao Fukasawa ◽  
Shinya Kouketsu ◽  
Hiroshi Uchida ◽  
Toshimasa Doi ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Deep Water ◽  
Bottom Water ◽  
Circumpolar Deep Water ◽  
The Pacific ◽  
Lower Circumpolar Deep Water ◽  
The Pacific Ocean

Nd and Pb isotope evolution of deep water masses in the eastern Indian Ocean during the past 33 Myr

2006 ◽  
Vol 226 (3-4) ◽  
pp. 264-279 ◽  
Author(s):  
Martin Frank ◽  
Nicholas Whiteley ◽  
Tina van de Flierdt ◽  
Ben C. Reynolds ◽  
Keith O'Nions
Keyword(s):  
Indian Ocean ◽  
Deep Water ◽  
Water Masses ◽  
Eastern Indian Ocean ◽  
Pb Isotope ◽  
The Past

Deep flow in the Madagascar–Mascarene Basin over the last 150000 years

2005 ◽  
Vol 363 (1826) ◽  
pp. 81-99 ◽  
Author(s):  
I. N. McCave ◽  
T. Kiefer ◽  
D. J. R. Thornalley ◽  
H. Elderfield
Keyword(s):  
Southern Ocean ◽  
Water Flow ◽  
Deep Water ◽  
Last Interglacial ◽  
Circumpolar Deep Water ◽  
The North ◽  
Bottom Waters ◽  
Lower Circumpolar Deep Water ◽  
Sw Indian Ocean ◽  
Fast Flow

The SW Indian Ocean contains at least four layers of water masses with different sources: deep Antarctic (Lower Circumpolar Deep Water) flow to the north, midwater North Indian Deep Water flow to the south and Upper Circumpolar Deep Water to the north, meridional convergence of intermediate waters at 500–1500 m, and the shallow South Equatorial Current flowing west. Sedimentation rates in the area are rather low, being less than 1 cm ka −1 on Madagascar Ridge, but up to 4 cm ka −1 at Amirante Passage. Bottom flow through the Madagascar–Mascarene Basin into Amirante Passage varies slightly on glacial–interglacial time–scales, with faster flow in the warm periods of the last interglacial and minima in cold periods. Far more important are the particularly high flow rates, inferred from silt grain size, which occur at warm–to–cold transitions rather than extrema. This suggests the cause is changing density gradient driving a transiently fast flow. Corroboration is found in the glacial–interglacial range of benthic d 18 O which is ca. 2%, suggesting water close to freezing and at least 1.2 more saline and thus more dense glacial bottom waters than present. Significant density steps are inferred in isotope stage 6, the 5e–5d, and 5a–4 transitions. Oxygen isotope data suggest little change by mixing in glacial bottom water on their northward path. Benthic carbon isotope ratios at Amirante Passage differ from glacial Southern Ocean values, due possibly to absence of a local productivity effect present in the Southern Ocean.

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