Comparison of Radiolarian/Planktonic Foraminiferal Paleoceanography of the Subantarctic Indian Ocean

A detailed paleoceanographic history of the Subantarctic region for the last million years was determined using paleomagnetic stratigraphy, radiolarian and planktonic foraminiferal biostratigraphy, and the oxygen isotope record from stages 1 to 13 (0.5 MY) in a deep-sea core (E45-74) from the southern Indian Ocean. Changes in the abundances of Antarctissa strelkovi and Neogloboquadrina pachyderma record 12 glacial/interglacial cycles. The paleoceanographic events based on the combined results of these siliceous and calcareous indexes agree with changes in the global ice-volume record. Calcium carbonate dissolution selectively alters the planktonic foraminiferal fauna and causes test fragmentation and increased numbers of benthic foraminifera and radiolarians. Intense periods of calcium carbonate dissolution are associated principally with glacial episodes and are probably related to increased Antarctic bottom-water activity as well as changes in surface-water mass positions.

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Contrasts in calcium carbonate dissolution above the lysocline in the equatorial Indian Ocean over the last ~40 ka

Marine Geology ◽

10.1016/j.margeo.2021.106717 ◽

2021 ◽

pp. 106717

Author(s):

Ramanand Yadav ◽

Sushant S. Naik ◽

Pothuri Divakar Naidu

Keyword(s):

Calcium Carbonate ◽

Indian Ocean ◽

Equatorial Indian Ocean ◽

Carbonate Dissolution ◽

Calcium Carbonate Dissolution

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Pteropods from the Caribbean Sea: variations in calcification as an indicator of past ocean carbonate saturation

Biogeosciences ◽

10.5194/bg-9-309-2012 ◽

2012 ◽

Vol 9 (1) ◽

pp. 309-315 ◽

Cited By ~ 23

Author(s):

D. Wall-Palmer ◽

M. B. Hart ◽

C. W. Smart ◽

R. S. J. Sparks ◽

A. Le Friant ◽

...

Keyword(s):

Ocean Acidification ◽

Sediment Cores ◽

Caribbean Sea ◽

Global Changes ◽

Ice Volume ◽

Global Ice Volume ◽

Global Signal ◽

Oxygen Isotope Record ◽

Isotope Record ◽

The Caribbean

Abstract. The aragonite shell-bearing thecosome pteropods are an important component of the oceanic plankton. However, with increasing pCO2 and the associated reduction in oceanic pH (ocean acidification), thecosome pteropods are thought to be particularly vulnerable to shell dissolution. The distribution and preservation of pteropods over the last 250 000 years have been investigated in marine sediment cores from the Caribbean Sea close to the island of Montserrat. Using the Limacina Dissolution Index (LDX), fluctuations in pteropod calcification through the most recent glacial/interglacial cycles are documented. By comparison to the oxygen isotope record (global ice volume), we show that pteropod calcification is closely linked to global changes in pCO2 and pH and is, therefore, a global signal. These data are in agreement with the findings of experiments upon living pteropods, which show that variations in pH can greatly affect aragonitic shells. The results of this study provide information which may be useful in the prediction of future changes to the pteropod assemblage caused by ocean acidification.

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Oxygen-Isotope Analyses and Pleistocene Ice Volumes

Quaternary Research ◽

10.1016/0033-5894(84)90085-1 ◽

1984 ◽

Vol 21 (1) ◽

pp. 1-20 ◽

Cited By ~ 123

Author(s):

Alan C. Mix ◽

William F. Ruddiman

Keyword(s):

Isotopic Composition ◽

Oxygen Isotope ◽

Volume Change ◽

Past History ◽

Model Parameters ◽

Ice Volume ◽

Oxygen Isotope Record ◽

Isotope Record ◽

History Of ◽

Selective Preservation

The oxygen-isotope record from fossil foraminifera in deep-sea sediments is commonly used as a proxy for global ice volume. The linkage between δ18O and ice volume, however, is probably nonlinear. We have developed a simple numerical model of the isotopic response of the oceans to ice-volume change. The major features it simulates are (1) the changing mean isotopic composition of snow as a function of ice volume (colder snow temperatures forced by climate change and higher-elevation accumulation areas imply more negative mean δ18O); (2) the nonequilibrium isotopic composition of ice sheets (the past history of an ice sheet is integrated into its mean isotopic composition, which introduces a lag of isotopic “ice volume,” i.e., the measured δ18O record, scaled to ice-volume units, behind true ice volume); (3) selective preservation of isotopically more negative (colder, higher-latitude) ice (this geographic effect can selectively amplify or dampen the isotopic response to the ice-volume signal). We illustrate the response of our model to simple hypothetical ice-volume transitions of ice growth and ice decay. Sensitivity tests are illustrated for all model parameters. The results suggest that oxygen-isotope records reproduce the general patterns of ice-volume change fairly accurately. The foraminiferal isotope record, however, may misrepresent the true amplitude of the ice-volume signal and lag true ice volume by 1000 to 3000 yr.

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