Reconstructing the depth of the permanent thermocline through the morphology and geochemistry of the deep dwelling planktonic foraminifer Globorotalia truncatulinoides

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Abstract

Geochemical and morphological characteristics of Globorotalia truncatulinoides, a deep dwelling planktonic foraminifer, have been used since the mid-1950s to infer (paleo)oceanographic conditions of the upper ocean. The coiling ratio has been linked to different water masses and stable oxygen isotope signal of this species to changes in depth habitat and/or season. Here we show that the isotopic composition of single specimens covering Termination III of multiple size fractions of North Atlantic G. truncatulinoides<inf>sinistral</inf> is indicative of a deeper calcification depth in the water column compared to G. truncatulinoides<inf>dextral</inf> as previously indirectly inferred in a plankton tow study. Furthermore, the change in coiling ratio from dominantly G. truncatulinoides<inf>dextral</inf> (95%) to brief episodes of dominantly G. truncatulinoides<inf>sinistral</inf> (80%) gives a strong indication of deepening of the permanent thermocline during periods in which G. truncatulinoides<inf>sinistral</inf> was dominant. The position of the permanent thermocline during marine isotope stages 8 and 7 echoes the relative strength of the Atlantic meridional overturning circulation (AMOC), dominated by interglacial-glacial dynamics. We demonstrate that Glacial Heinrich (ice-rafted debris) events appear to proceed a permanent thermocline shoaling, whereas interglacial Heinrich events follow the shoaling of the permanent thermocline, likely a result of a weakened AMOC. Key Points Coiling ratio of G. truncatulinoides indicative of depth of the thermocline Single-specimen isotopes of G. truncatulinoides confirm inferred depth habitat
Original languageEnglish
Pages (from-to)1-22
JournalPaleoceanography
Volume30
Issue number1
DOIs
Publication statusPublished - 2015

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planktonic foraminifera
thermocline
geochemistry
meridional circulation
interglacial
ice-rafted debris
Heinrich event
marine isotope stage
calcification
upper ocean
habitat
water mass
oxygen isotope
plankton
stable isotope
isotopic composition
water column
dwelling
isotope

Cite this

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title = "Reconstructing the depth of the permanent thermocline through the morphology and geochemistry of the deep dwelling planktonic foraminifer Globorotalia truncatulinoides",
abstract = "Geochemical and morphological characteristics of Globorotalia truncatulinoides, a deep dwelling planktonic foraminifer, have been used since the mid-1950s to infer (paleo)oceanographic conditions of the upper ocean. The coiling ratio has been linked to different water masses and stable oxygen isotope signal of this species to changes in depth habitat and/or season. Here we show that the isotopic composition of single specimens covering Termination III of multiple size fractions of North Atlantic G. truncatulinoidessinistral is indicative of a deeper calcification depth in the water column compared to G. truncatulinoidesdextral as previously indirectly inferred in a plankton tow study. Furthermore, the change in coiling ratio from dominantly G. truncatulinoidesdextral (95{\%}) to brief episodes of dominantly G. truncatulinoidessinistral (80{\%}) gives a strong indication of deepening of the permanent thermocline during periods in which G. truncatulinoidessinistral was dominant. The position of the permanent thermocline during marine isotope stages 8 and 7 echoes the relative strength of the Atlantic meridional overturning circulation (AMOC), dominated by interglacial-glacial dynamics. We demonstrate that Glacial Heinrich (ice-rafted debris) events appear to proceed a permanent thermocline shoaling, whereas interglacial Heinrich events follow the shoaling of the permanent thermocline, likely a result of a weakened AMOC. Key Points Coiling ratio of G. truncatulinoides indicative of depth of the thermocline Single-specimen isotopes of G. truncatulinoides confirm inferred depth habitat",
author = "W. Feldmeijer and B. Metcalfe and G.J.A. Brummer and G.M. Ganssen",
year = "2015",
doi = "10.1002/2014PA002687",
language = "English",
volume = "30",
pages = "1--22",
journal = "Paleoceanography",
issn = "0883-8305",
publisher = "American Geophysical Union",
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TY - JOUR

T1 - Reconstructing the depth of the permanent thermocline through the morphology and geochemistry of the deep dwelling planktonic foraminifer Globorotalia truncatulinoides

AU - Feldmeijer, W.

AU - Metcalfe, B.

AU - Brummer, G.J.A.

AU - Ganssen, G.M.

PY - 2015

Y1 - 2015

N2 - Geochemical and morphological characteristics of Globorotalia truncatulinoides, a deep dwelling planktonic foraminifer, have been used since the mid-1950s to infer (paleo)oceanographic conditions of the upper ocean. The coiling ratio has been linked to different water masses and stable oxygen isotope signal of this species to changes in depth habitat and/or season. Here we show that the isotopic composition of single specimens covering Termination III of multiple size fractions of North Atlantic G. truncatulinoidessinistral is indicative of a deeper calcification depth in the water column compared to G. truncatulinoidesdextral as previously indirectly inferred in a plankton tow study. Furthermore, the change in coiling ratio from dominantly G. truncatulinoidesdextral (95%) to brief episodes of dominantly G. truncatulinoidessinistral (80%) gives a strong indication of deepening of the permanent thermocline during periods in which G. truncatulinoidessinistral was dominant. The position of the permanent thermocline during marine isotope stages 8 and 7 echoes the relative strength of the Atlantic meridional overturning circulation (AMOC), dominated by interglacial-glacial dynamics. We demonstrate that Glacial Heinrich (ice-rafted debris) events appear to proceed a permanent thermocline shoaling, whereas interglacial Heinrich events follow the shoaling of the permanent thermocline, likely a result of a weakened AMOC. Key Points Coiling ratio of G. truncatulinoides indicative of depth of the thermocline Single-specimen isotopes of G. truncatulinoides confirm inferred depth habitat

AB - Geochemical and morphological characteristics of Globorotalia truncatulinoides, a deep dwelling planktonic foraminifer, have been used since the mid-1950s to infer (paleo)oceanographic conditions of the upper ocean. The coiling ratio has been linked to different water masses and stable oxygen isotope signal of this species to changes in depth habitat and/or season. Here we show that the isotopic composition of single specimens covering Termination III of multiple size fractions of North Atlantic G. truncatulinoidessinistral is indicative of a deeper calcification depth in the water column compared to G. truncatulinoidesdextral as previously indirectly inferred in a plankton tow study. Furthermore, the change in coiling ratio from dominantly G. truncatulinoidesdextral (95%) to brief episodes of dominantly G. truncatulinoidessinistral (80%) gives a strong indication of deepening of the permanent thermocline during periods in which G. truncatulinoidessinistral was dominant. The position of the permanent thermocline during marine isotope stages 8 and 7 echoes the relative strength of the Atlantic meridional overturning circulation (AMOC), dominated by interglacial-glacial dynamics. We demonstrate that Glacial Heinrich (ice-rafted debris) events appear to proceed a permanent thermocline shoaling, whereas interglacial Heinrich events follow the shoaling of the permanent thermocline, likely a result of a weakened AMOC. Key Points Coiling ratio of G. truncatulinoides indicative of depth of the thermocline Single-specimen isotopes of G. truncatulinoides confirm inferred depth habitat

U2 - 10.1002/2014PA002687

DO - 10.1002/2014PA002687

M3 - Article

VL - 30

SP - 1

EP - 22

JO - Paleoceanography

JF - Paleoceanography

SN - 0883-8305

IS - 1

ER -