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Atlantic Deep-water Response to the Early Pliocene Shoaling of the Central American Seaway.

Bell DB, Jung SJ, Kroon D, Hodell DA, Lourens LJ, Raymo ME - Sci Rep (2015)

Bottom Line: We find that NADW formation was vigorous prior to 4.7 Ma and showed limited subsequent change.Hence, the overall structure of the deep Atlantic was largely unaffected by the early Pliocene CAS shoaling, corroborating other evidence that indicates larger changes in NADW resulted from earlier and deeper shoaling phases.This finding implies that the early Pliocene shoaling of the CAS had no profound impact on the evolution of climate.

View Article: PubMed Central - PubMed

Affiliation: School of Geosciences, University of Edinburgh, Edinburgh, UK.

ABSTRACT
The early Pliocene shoaling of the Central American Seaway (CAS), ~4.7-4.2 million years ago (mega annum-Ma), is thought to have strengthened Atlantic Meridional Overturning Circulation (AMOC). The associated increase in northward flux of heat and moisture may have significantly influenced the evolution of Pliocene climate. While some evidence for the predicted increase in North Atlantic Deep Water (NADW) formation exists in the Caribbean and Western Atlantic, similar evidence is missing in the wider Atlantic. Here, we present stable carbon (δ(13)C) and oxygen (δ(18)O) isotope records from the Southeast Atlantic-a key region for monitoring the southern extent of NADW. Using these data, together with other δ(13)C and δ(18)O records from the Atlantic, we assess the impact of the early Pliocene CAS shoaling phase on deep-water circulation. We find that NADW formation was vigorous prior to 4.7 Ma and showed limited subsequent change. Hence, the overall structure of the deep Atlantic was largely unaffected by the early Pliocene CAS shoaling, corroborating other evidence that indicates larger changes in NADW resulted from earlier and deeper shoaling phases. This finding implies that the early Pliocene shoaling of the CAS had no profound impact on the evolution of climate.

No MeSH data available.


Related in: MedlinePlus

Dissolved oxygen concentration maps of the Atlantic at different depths (modified from the WOCE Atlantic Ocean Atlas 26 to show features of deep-water circulation and the locations of all sites referred to in the text), reflecting aspects of the chemical structure of the deep-Atlantic.Arrows depict general NADW circulation patterns and blue ovals indicate areas of NADW formation. Sites are displayed on maps according to their relevant depth (Table 1). Sites with isotopic data presented in Figs 4, 5, 6 plotted with a red circle, while other sites mentioned in the text are plotted with a red square. Site 999 is situated at 2828 m in the Caribbean, but is expected to record deep-waters entering across the Atlantic-Caribbean sills at ~1600–1900 m depth. High oxygen concentrations result from recent and prolonged contact with the atmosphere, while low oxygen concentrations result from microbial respiration of organic matter over time. NADW, with high oxygen concentrations, is a well “ventilated” water mass, in contrast with deep-waters entering the Atlantic from the south. These maps outline the modern dominance of NADW and highlight the importance of bathymetric constraints and deep-water pathways (e.g. the Deep Western Boundary Current versus interior pathways) in setting gradients in water-mass properties within the Atlantic.
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f3: Dissolved oxygen concentration maps of the Atlantic at different depths (modified from the WOCE Atlantic Ocean Atlas 26 to show features of deep-water circulation and the locations of all sites referred to in the text), reflecting aspects of the chemical structure of the deep-Atlantic.Arrows depict general NADW circulation patterns and blue ovals indicate areas of NADW formation. Sites are displayed on maps according to their relevant depth (Table 1). Sites with isotopic data presented in Figs 4, 5, 6 plotted with a red circle, while other sites mentioned in the text are plotted with a red square. Site 999 is situated at 2828 m in the Caribbean, but is expected to record deep-waters entering across the Atlantic-Caribbean sills at ~1600–1900 m depth. High oxygen concentrations result from recent and prolonged contact with the atmosphere, while low oxygen concentrations result from microbial respiration of organic matter over time. NADW, with high oxygen concentrations, is a well “ventilated” water mass, in contrast with deep-waters entering the Atlantic from the south. These maps outline the modern dominance of NADW and highlight the importance of bathymetric constraints and deep-water pathways (e.g. the Deep Western Boundary Current versus interior pathways) in setting gradients in water-mass properties within the Atlantic.

Mentions: Based on the original interpretation of surface water changes in the Caribbean, many studies have marked the early Pliocene as a key interval in the CAS closure history and linked it to proxy records that indicate an enhancement in NADW345819212425. However, the evidence for NADW changes during the early Pliocene is mainly limited to the Caribbean Sea and deep equatorial Western Atlantic (Fig. 2). As both bathymetric constraints from major ocean ridges and differences between water mass advection within the Deep Western Boundary Current (DWBC) and interior pathways are markedly influential in setting up gradients and pathways within the Atlantic262728 (Fig. 3), it is straightforward to envisage scenarios whereby regional changes in water mass prevalence are not representative of large-scale changes in the wider deep Atlantic. Indeed, important regional differences in Pleistocene deep-water circulation have been shown previously2930313233, reinforcing the need to consider previously documented changes in a wider spatial context.


Atlantic Deep-water Response to the Early Pliocene Shoaling of the Central American Seaway.

Bell DB, Jung SJ, Kroon D, Hodell DA, Lourens LJ, Raymo ME - Sci Rep (2015)

Dissolved oxygen concentration maps of the Atlantic at different depths (modified from the WOCE Atlantic Ocean Atlas 26 to show features of deep-water circulation and the locations of all sites referred to in the text), reflecting aspects of the chemical structure of the deep-Atlantic.Arrows depict general NADW circulation patterns and blue ovals indicate areas of NADW formation. Sites are displayed on maps according to their relevant depth (Table 1). Sites with isotopic data presented in Figs 4, 5, 6 plotted with a red circle, while other sites mentioned in the text are plotted with a red square. Site 999 is situated at 2828 m in the Caribbean, but is expected to record deep-waters entering across the Atlantic-Caribbean sills at ~1600–1900 m depth. High oxygen concentrations result from recent and prolonged contact with the atmosphere, while low oxygen concentrations result from microbial respiration of organic matter over time. NADW, with high oxygen concentrations, is a well “ventilated” water mass, in contrast with deep-waters entering the Atlantic from the south. These maps outline the modern dominance of NADW and highlight the importance of bathymetric constraints and deep-water pathways (e.g. the Deep Western Boundary Current versus interior pathways) in setting gradients in water-mass properties within the Atlantic.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4507445&req=5

f3: Dissolved oxygen concentration maps of the Atlantic at different depths (modified from the WOCE Atlantic Ocean Atlas 26 to show features of deep-water circulation and the locations of all sites referred to in the text), reflecting aspects of the chemical structure of the deep-Atlantic.Arrows depict general NADW circulation patterns and blue ovals indicate areas of NADW formation. Sites are displayed on maps according to their relevant depth (Table 1). Sites with isotopic data presented in Figs 4, 5, 6 plotted with a red circle, while other sites mentioned in the text are plotted with a red square. Site 999 is situated at 2828 m in the Caribbean, but is expected to record deep-waters entering across the Atlantic-Caribbean sills at ~1600–1900 m depth. High oxygen concentrations result from recent and prolonged contact with the atmosphere, while low oxygen concentrations result from microbial respiration of organic matter over time. NADW, with high oxygen concentrations, is a well “ventilated” water mass, in contrast with deep-waters entering the Atlantic from the south. These maps outline the modern dominance of NADW and highlight the importance of bathymetric constraints and deep-water pathways (e.g. the Deep Western Boundary Current versus interior pathways) in setting gradients in water-mass properties within the Atlantic.
Mentions: Based on the original interpretation of surface water changes in the Caribbean, many studies have marked the early Pliocene as a key interval in the CAS closure history and linked it to proxy records that indicate an enhancement in NADW345819212425. However, the evidence for NADW changes during the early Pliocene is mainly limited to the Caribbean Sea and deep equatorial Western Atlantic (Fig. 2). As both bathymetric constraints from major ocean ridges and differences between water mass advection within the Deep Western Boundary Current (DWBC) and interior pathways are markedly influential in setting up gradients and pathways within the Atlantic262728 (Fig. 3), it is straightforward to envisage scenarios whereby regional changes in water mass prevalence are not representative of large-scale changes in the wider deep Atlantic. Indeed, important regional differences in Pleistocene deep-water circulation have been shown previously2930313233, reinforcing the need to consider previously documented changes in a wider spatial context.

Bottom Line: We find that NADW formation was vigorous prior to 4.7 Ma and showed limited subsequent change.Hence, the overall structure of the deep Atlantic was largely unaffected by the early Pliocene CAS shoaling, corroborating other evidence that indicates larger changes in NADW resulted from earlier and deeper shoaling phases.This finding implies that the early Pliocene shoaling of the CAS had no profound impact on the evolution of climate.

View Article: PubMed Central - PubMed

Affiliation: School of Geosciences, University of Edinburgh, Edinburgh, UK.

ABSTRACT
The early Pliocene shoaling of the Central American Seaway (CAS), ~4.7-4.2 million years ago (mega annum-Ma), is thought to have strengthened Atlantic Meridional Overturning Circulation (AMOC). The associated increase in northward flux of heat and moisture may have significantly influenced the evolution of Pliocene climate. While some evidence for the predicted increase in North Atlantic Deep Water (NADW) formation exists in the Caribbean and Western Atlantic, similar evidence is missing in the wider Atlantic. Here, we present stable carbon (δ(13)C) and oxygen (δ(18)O) isotope records from the Southeast Atlantic-a key region for monitoring the southern extent of NADW. Using these data, together with other δ(13)C and δ(18)O records from the Atlantic, we assess the impact of the early Pliocene CAS shoaling phase on deep-water circulation. We find that NADW formation was vigorous prior to 4.7 Ma and showed limited subsequent change. Hence, the overall structure of the deep Atlantic was largely unaffected by the early Pliocene CAS shoaling, corroborating other evidence that indicates larger changes in NADW resulted from earlier and deeper shoaling phases. This finding implies that the early Pliocene shoaling of the CAS had no profound impact on the evolution of climate.

No MeSH data available.


Related in: MedlinePlus