The middle Miocene climatic transition: East Antarctic ice sheet development, deep ocean circulation and global carbon cycling

1994 ◽  
Vol 108 (3-4) ◽  
pp. 537-555 ◽  
Author(s):  
Benjamin P. Flower ◽  
James P. Kennett
Keyword(s):  
Carbon Cycling ◽  
Ocean Circulation ◽  
Middle Miocene ◽  
Ice Sheet ◽  
Deep Ocean ◽  
Antarctic Ice Sheet ◽  
Climatic Transition ◽  
Deep Ocean Circulation ◽  
Global Carbon ◽  
Middle Miocene Climatic Transition

scholarly journals The role of eastern Tethys seaway closure in the Middle Miocene Climatic Transition (ca. 14 Ma)

2013 ◽  
Vol 9 (6) ◽  
pp. 2687-2702 ◽  
Author(s):  
N. Hamon ◽  
P. Sepulchre ◽  
V. Lefebvre ◽  
G. Ramstein
Keyword(s):  
General Circulation ◽  
Middle Miocene ◽  
Ice Sheet ◽  
Water Source ◽  
Meridional Overturning Circulation ◽  
Oceanic Circulation ◽  
Climatic Transition ◽  
The Impact ◽  
Final Closure ◽  
Middle Miocene Climatic Transition

Abstract. The Middle Miocene Climatic Transition (MMCT, approximately 14 Ma) is a key period in Cenozoic cooling and cryospheric expansion. Despite being well documented in isotopic record, the causes of the MMCT are still a matter of debate. Among various hypotheses, some authors suggested that it was due the final closure of the eastern Tethys seaway and subsequent oceanic circulation reorganisation. The aim of the present study is to quantify the impact of varying Tethys seaway depths on middle Miocene ocean and climate, in order to better understand its role in the MMCT. We present four sensitivity experiments with a fully coupled ocean-atmosphere general circulation model. Our results indicate the presence of a warm and salty water source in the northern Indian Ocean when the eastern Tethys is deep open (4000 or 1000 m), which corresponds to the Tethyan Indian Saline Water (TISW) described on the basis of isotopic studies. This water source is absent in the experiments with shallow (250 m) and closed Tethys seaway, inducing strong changes in the latitudinal density gradient and ultimately the reinforcement of the Antarctic Circumpolar Current (ACC). Moreover, when the Tethys seaway is shallow or closed, there is a westward water flow in the Gibraltar Strait that strengthens the Atlantic Meridional Overturning Circulation (AMOC) compared to the experiments with deep-open Tethys seaway. Our results therefore suggest that the shoaling and final closure of the eastern Tethys seaway played a major role in the oceanic circulation reorganisation during the middle Miocene. The results presented here provide new constraints on the timing of the Tethys seaway closure and particularly indicate that, prior to 14 Ma, a deep-open Tethys seaway should have allowed the formation of TISW. Moreover, whereas the final closure of this seaway likely played a major role in the reorganisation of oceanic circulation, we suggest that it was not the main driver of the global cooling and Antarctica ice-sheet expansion during the MMCT. Here we propose that the initiation of the MMCT was caused by an atmospheric pCO2 drawdown and that the oceanic changes due to the Tethys seaway closure amplified the response of global climate and East Antarctic Ice Sheet.

scholarly journals The rise to dominance of lanternfishes (Teleostei: Myctophidae) in the oceanic ecosystems: a paleontological perspective

Paleobiology ◽  
2021 ◽  
pp. 1-18
Author(s):  
Werner Schwarzhans ◽  
Giorgio Carnevale
Keyword(s):  
Ocean Circulation ◽  
Evolutionary History ◽  
Middle Miocene ◽  
Middle Eocene ◽  
Food Resource ◽  
Deep Ocean ◽  
Early Oligocene ◽  
Diatom Abundance ◽  
Deep Ocean Circulation ◽  
Upper Slope

AbstractLanternfishes currently represent one of the dominant groups of mesopelagic fishes in terms of abundance, biomass, and diversity. Their otolith record dominates pelagic sediments below 200 m in dredges, especially during the entire Neogene. Here we provide an analysis of their diversity and rise to dominance primarily based on their otolith record. The earliest unambiguous fossil myctophids are known based on otoliths from the late Paleocene and early Eocene. During their early evolutionary history, myctophids were likely not adapted to a high oceanic lifestyle but occurred over shelf and upper-slope regions, where they were locally abundant during the middle Eocene. A distinct upscaling in otolith size is observed in the early Oligocene, which also marks their earliest occurrence in bathyal sediments. We interpret this transition to be related to the change from a halothermal deep-ocean circulation to a thermohaline regime and the associated cooling of the deep ocean and rearrangement of nutrient and silica supply. The early Oligocene myctophid size acme shows a remarkable congruence with diatom abundance, the main food resource for the zooplankton and thus for myctophids and whales. The warmer late Oligocene to early middle Miocene period was characterized by an increase in disparity of myctophids but with a reduction in their otolith sizes. A second and persisting secular pulse in myctophid diversity (particularly within the genusDiaphus) and increase in size begins with the “biogenic bloom” in the late Miocene, paralleled with diatom abundance and mysticete gigantism.

scholarly journals The role of East-Tethys seaway closure in the middle Miocene climatic transition (ca. 14 Ma)

2013 ◽  
Vol 9 (2) ◽  
pp. 2115-2152
Author(s):  
N. Hamon ◽  
P. Sepulchre ◽  
V. Lefebvre ◽  
G. Ramstein
Keyword(s):  
Middle Miocene ◽  
Ice Sheet ◽  
Circulation Model ◽  
Water Source ◽  
Meridional Overturning Circulation ◽  
Oceanic Circulation ◽  
Climatic Transition ◽  
The Impact ◽  
Final Closure ◽  
Middle Miocene Climatic Transition

Abstract. The middle Miocene climatic transition (MMCT, approximately 14 Ma) is a key period in Cenozoic cooling and cryospheric expansion. Despite it is well documented in isotopic record, the causes of the MMCT are still a matter of debate. Among various hypotheses, some authors suggested that it was linked with the final closure of the East-Tethys seaway and subsequent oceanic circulation reorganisation. The aim of the present study is to quantify the impact of varying East-Tethys seaway depths on middle Miocene ocean and climate, in order to better understand its role in the MMCT. We present four sensitivity experiments with a fully coupled ocean-atmosphere generalized circulation model. Our results indicate the presence of a warm and salty water source in the northern Indian Ocean when the East-Tethys is deep-open (4000 or 1000 m), which corresponds to the Tethyan Indian Saline Water (TISW) described on the basis of isotopic studies. This water source is absent in the experiments with shallow (250 m) and closed East-Tethys, inducing strong changes in the latitudinal density gradient and ultimately the reinforcement of the Antarctic Circumpolar Current (ACC). Moreover, when the East-Tethys seaway is shallow or closed, there is a westward water flow in the Gibraltar Strait that strengthens the Atlantic meridional overturning circulation (AMOC) compared to the experiments with deep-open East-Tethys. Our results therefore suggest that the shoaling and final closure of the East-Tethys seaway played a major role in the oceanic circulation reorganisation during the middle Miocene. The results presented here provide new constraints on the timing of the East-Tethys seaway closure, and particularly indicate that, prior to 14 Ma, a deep-open East-Tethys should have allow the formation of TISW. Moreover, whereas the final closure of this seaway likely played a major role in the MMCT, we suggest that it was not the only driver of the global cooling and Antarctica ice sheet growth. Here, we propose that the initiation of the MMCT may have been an atmospheric pCO2 drawdown and that the oceanic Changes due to the East-Tethys seaway closure amplified the response of global climate and East-Antarctic Ice Sheet.

Tracking ice-sheet dynamics by detrital feldspar Pb-isotope and 87Rb/87Sr dating during the Middle Miocene Climatic Transition, Weddell Sea, Antarctica

2021 ◽  
Author(s):  
Roland Neofitu ◽  
Chris Mark ◽  
Suzanne O'Connell ◽  
Samuel Kelley ◽  
Delia Rösel ◽  
...  
Keyword(s):  
Deep Sea ◽  
Middle Miocene ◽  
Ice Sheet ◽  
Weddell Sea ◽  
Provenance Analysis ◽  
Pb Isotope ◽  
Iceberg Calving ◽  
Climatic Transition ◽  
The Antarctic ◽  
Middle Miocene Climatic Transition

<p>Antarctic ice-sheet instability is recorded by ice-rafted debris (IRD) in mid- to high-latitude marine sediment, especially throughout climate transitions. The middle Miocene climatic transition (MMCT), 14.2 to 13.8 Ma, which marks the end of a significant warm period during the mid-Miocene, saw a rapid cooling of ca. 6-7 °C in the high-latitude Southern Ocean. This climatic shift was also accompanied by a global δ<sup>18</sup>O excursion of ca. 1‰, indicating a time of global cooling and significant Antarctic ice expansion (Shevenell et al., 2004). The MMCT is recorded by numerous IRD-rich sediment horizons in deep-sea sediment cores around the Antarctic margin, reflecting iceberg calving during times of ice-sheet instability. Resolving the locations of iceberg calving sites by detrital provenance analysis during the MMCT will be an important tool for forecasting effects of anthropogenic climate change.</p><p>Here we present results of a multi-proxy provenance study by using K- and plagioclase feldspar, selected due to their relative abundance in clastic sediment, and tendency to incorporate Rb (Kfs only), Pb, and Sr at analytically useful concentrations, thus enabling source-terrane fingerprinting. While Pb-isotope fingerprinting is an established method for provenance analysis of glaciogenic sediment (Flowerdew et al., 2012), combining in-situ Sr-isotope fingerprinting with <sup>87</sup>Rb/<sup>87</sup>Sr dating is a novel approach. These techniques are applied to deep-sea core ODP113-694, which was recovered from the Weddell Sea; as this is located ca. 750 km from the continental rise, in 4671.3 m of water. This location is ideal, as it acts as a major iceberg graveyard making it a key IRD depocenter (Barker, Kennett et al., 1988). Within the core, several IRD layers were identified and analysed with preliminary depositional ages of 14 to 14.4 Ma.</p><p>We discuss the implications of our results in terms of location of active iceberg calving sites and further consider the viability of our multi-proxy provenance approach to the Antarctic offshore.</p><p>Barker, P.F., Kennett, J.P., et al., 1988, Proc. Init. Repts. (Pt. A): ODP, 113, College Station, TX (Ocean Drilling Program).</p><p>Flowerdew, M.J., et al., 2012, Chemical Geology, v. 292–293, p. 88–102, doi: 10.1016/j.chemgeo.2011.11.006.</p><p>Shevenell, A.E., et al., 2004, Science, v. 305, p. 1766-1770, doi: 10.1126/science.1100061.</p>

scholarly journals Eccentricity-paced atmospheric carbon-dioxide variations across the middle Miocene climate transition

2020 ◽  
Author(s):  
Markus Raitzsch ◽  
Jelle Bijma ◽  
Torsten Bickert ◽  
Michael Schulz ◽  
Ann Holbourn ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Middle Miocene ◽  
Ice Sheet ◽  
Deep Ocean ◽  
Rapid Expansion ◽  
Atmospheric Co2 ◽  
High Eccentricity ◽  
Antarctic Ice Sheet ◽  
Organic Carbon Burial ◽  
Climate Transition

Abstract. The middle Miocene climate transition ~ 14 Ma marks a fundamental step towards the current “icehouse” climate, with a ~ 1 ‰ δ18O increase and a ~ 1 ‰ transient δ13C rise in the deep ocean, indicating rapid expansion of the East Antarctic Ice Sheet associated with a change in the operation of the global carbon cycle. The variation of atmospheric CO2 across the carbon-cycle perturbation has been intensely debated as proxy records of pCO2 for this time interval are sparse and partly contradictory. Using boron isotopes (δ11B) in planktonic foraminifers from drill site ODP 1092 in the South Atlantic, we show that long-term pCO2 variations between ~ 14.3 and 13.2 Ma were paced by 400 k.y. eccentricity cycles, with decreasing pCO2 at high eccentricity and vice versa. Our data support results from a carbon-cycle model study, according to which increased monsoon intensity at high eccentricity enhanced weathering and river fluxes in the tropics, resulting in increasing carbonate and organic carbon burial and hence decreasing atmospheric CO2. In this scenario, a combination of the eccentricity-driven climatic cycle and enhanced meridional deep-ocean circulation during Antarctic ice-sheet expansion may have both contributed to the pCO2 rise following Antarctic glaciation, acting as a negative feedback on the progressing glaciation and helping to stabilize the climate system on its way to the late Cenozoic “icehouse” world.

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