Ventilation history of Nordic Seas overflows during the last (de)glacial period revealed by species-specific benthic foraminiferal 
            14C dates

Mohamed M. Ezat; Tine L. Rasmussen; David J. R. Thornalley; Jesper Olsen; Luke C. Skinner; Barbel Honisch; Jeroen Groeneveld

doi:10.1002/2016PA003053

Ventilation history of Nordic Seas overflows during the last (de)glacial period revealed by species-specific benthic foraminiferal ¹⁴C dates

Mohamed M. Ezat^*
, Tine L. Rasmussen
, David J. R. Thornalley
, Jesper Olsen
, Luke C. Skinner
, Barbel Honisch
, Jeroen Groeneveld

^*Corresponding author for this work

Department of Physics and Astronomy

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaper › Journal article › Research › peer-review

35 Citations (Scopus)

Abstract

Formation of deep water in the high-latitude North Atlantic is important for the global meridional ocean circulation, and its variability in the past may have played an important role in regional and global climate change. Here we study ocean circulation associated with the last (de)glacial period, using water-column radiocarbon age reconstructions in the Faroe-Shetland Channel, southeastern Norwegian Sea, and from the Iceland Basin, central North Atlantic. The presence of tephra layer Faroe Marine Ash Zone II, dated to ~26.7 ka, enables us to determine that the middepth (1179 m water depth) and shallow subsurface reservoir ages were ~1500 and 1100 ¹⁴C years, respectively, older during the late glacial period compared to modern, suggesting substantial suppression of the overturning circulation in the Nordic Seas. During the late Last Glacial Maximum and the onset of deglaciation (~20–18 ka), Nordic Seas overflow was weak but active. During the early deglaciation (~17.5–14.5 ka), our data reveal large differences between ¹⁴C ventilation ages that are derived from dating different benthic foraminiferal species: Pyrgo and other miliolid species yield ventilation ages >6000 ¹⁴C years, while all other species reveal ventilation ages <2000 ¹⁴C years. These data either suggest subcentennial, regional, circulation changes or that miliolid-based ¹⁴C ages are biased due to taphonomic or vital processes. Implications of each interpretation are discussed. Regardless of this “enigma,” the onset of the Bølling-Allerød interstadial (14.5 ka) is clearly marked by an increase in middepth Nordic Seas ventilation and the renewal of a stronger overflow.

Original language	English
Journal	Paleoceanography
Volume	32
Issue	2
Pages (from-to)	172-181
Number of pages	10
ISSN	0883-8305
DOIs	https://doi.org/10.1002/2016PA003053
Publication status	Published - Feb 2017

Keywords

ARCTIC-OCEAN
CARBON-DIOXIDE
CIRCULATION
DEEP
DEGLACIATION
GLACIAL PERIOD
ICE-CORE
NORTH-ATLANTIC
SEDIMENTS
WATERS
Nordic Seas
deglaciation
last glacial
radiocarbon
ocean ventilation

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Cite this

@article{7685acac32bf46b1bd836c85b32c7f39,

title = "Ventilation history of Nordic Seas overflows during the last (de)glacial period revealed by species-specific benthic foraminiferal 14C dates",

abstract = "Formation of deep water in the high-latitude North Atlantic is important for the global meridional ocean circulation, and its variability in the past may have played an important role in regional and global climate change. Here we study ocean circulation associated with the last (de)glacial period, using water-column radiocarbon age reconstructions in the Faroe-Shetland Channel, southeastern Norwegian Sea, and from the Iceland Basin, central North Atlantic. The presence of tephra layer Faroe Marine Ash Zone II, dated to \textasciitilde{}26.7 ka, enables us to determine that the middepth (1179 m water depth) and shallow subsurface reservoir ages were \textasciitilde{}1500 and 1100 14C years, respectively, older during the late glacial period compared to modern, suggesting substantial suppression of the overturning circulation in the Nordic Seas. During the late Last Glacial Maximum and the onset of deglaciation (\textasciitilde{}20–18 ka), Nordic Seas overflow was weak but active. During the early deglaciation (\textasciitilde{}17.5–14.5 ka), our data reveal large differences between 14C ventilation ages that are derived from dating different benthic foraminiferal species: Pyrgo and other miliolid species yield ventilation ages >6000 14C years, while all other species reveal ventilation ages <2000 14C years. These data either suggest subcentennial, regional, circulation changes or that miliolid-based 14C ages are biased due to taphonomic or vital processes. Implications of each interpretation are discussed. Regardless of this “enigma,” the onset of the B{\o}lling-Aller{\o}d interstadial (14.5 ka) is clearly marked by an increase in middepth Nordic Seas ventilation and the renewal of a stronger overflow.",

keywords = "ARCTIC-OCEAN, CARBON-DIOXIDE, CIRCULATION, DEEP, DEGLACIATION, GLACIAL PERIOD, ICE-CORE, NORTH-ATLANTIC, SEDIMENTS, WATERS, Nordic Seas, deglaciation, last glacial, radiocarbon, ocean ventilation",

author = "Ezat, \{Mohamed M.\} and Rasmussen, \{Tine L.\} and Thornalley, \{David J. R.\} and Jesper Olsen and Skinner, \{Luke C.\} and Barbel Honisch and Jeroen Groeneveld",

year = "2017",

month = feb,

doi = "10.1002/2016PA003053",

language = "English",

volume = "32",

pages = "172--181",

journal = "Paleoceanography",

issn = "0883-8305",

publisher = "John Wiley \& Sons Inc.",

number = "2",

}

Ventilation history of Nordic Seas overflows during the last (de)glacial period revealed by species-specific benthic foraminiferal ¹⁴C dates. / Ezat, Mohamed M.; Rasmussen, Tine L.; Thornalley, David J. R. et al.
In: Paleoceanography, Vol. 32, No. 2, 02.2017, p. 172-181.

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaper › Journal article › Research › peer-review

TY - JOUR

T1 - Ventilation history of Nordic Seas overflows during the last (de)glacial period revealed by species-specific benthic foraminiferal 14C dates

AU - Ezat, Mohamed M.

AU - Rasmussen, Tine L.

AU - Thornalley, David J. R.

AU - Olsen, Jesper

AU - Skinner, Luke C.

AU - Honisch, Barbel

AU - Groeneveld, Jeroen

PY - 2017/2

Y1 - 2017/2

N2 - Formation of deep water in the high-latitude North Atlantic is important for the global meridional ocean circulation, and its variability in the past may have played an important role in regional and global climate change. Here we study ocean circulation associated with the last (de)glacial period, using water-column radiocarbon age reconstructions in the Faroe-Shetland Channel, southeastern Norwegian Sea, and from the Iceland Basin, central North Atlantic. The presence of tephra layer Faroe Marine Ash Zone II, dated to ~26.7 ka, enables us to determine that the middepth (1179 m water depth) and shallow subsurface reservoir ages were ~1500 and 1100 14C years, respectively, older during the late glacial period compared to modern, suggesting substantial suppression of the overturning circulation in the Nordic Seas. During the late Last Glacial Maximum and the onset of deglaciation (~20–18 ka), Nordic Seas overflow was weak but active. During the early deglaciation (~17.5–14.5 ka), our data reveal large differences between 14C ventilation ages that are derived from dating different benthic foraminiferal species: Pyrgo and other miliolid species yield ventilation ages >6000 14C years, while all other species reveal ventilation ages <2000 14C years. These data either suggest subcentennial, regional, circulation changes or that miliolid-based 14C ages are biased due to taphonomic or vital processes. Implications of each interpretation are discussed. Regardless of this “enigma,” the onset of the Bølling-Allerød interstadial (14.5 ka) is clearly marked by an increase in middepth Nordic Seas ventilation and the renewal of a stronger overflow.

AB - Formation of deep water in the high-latitude North Atlantic is important for the global meridional ocean circulation, and its variability in the past may have played an important role in regional and global climate change. Here we study ocean circulation associated with the last (de)glacial period, using water-column radiocarbon age reconstructions in the Faroe-Shetland Channel, southeastern Norwegian Sea, and from the Iceland Basin, central North Atlantic. The presence of tephra layer Faroe Marine Ash Zone II, dated to ~26.7 ka, enables us to determine that the middepth (1179 m water depth) and shallow subsurface reservoir ages were ~1500 and 1100 14C years, respectively, older during the late glacial period compared to modern, suggesting substantial suppression of the overturning circulation in the Nordic Seas. During the late Last Glacial Maximum and the onset of deglaciation (~20–18 ka), Nordic Seas overflow was weak but active. During the early deglaciation (~17.5–14.5 ka), our data reveal large differences between 14C ventilation ages that are derived from dating different benthic foraminiferal species: Pyrgo and other miliolid species yield ventilation ages >6000 14C years, while all other species reveal ventilation ages <2000 14C years. These data either suggest subcentennial, regional, circulation changes or that miliolid-based 14C ages are biased due to taphonomic or vital processes. Implications of each interpretation are discussed. Regardless of this “enigma,” the onset of the Bølling-Allerød interstadial (14.5 ka) is clearly marked by an increase in middepth Nordic Seas ventilation and the renewal of a stronger overflow.

KW - ARCTIC-OCEAN

KW - CARBON-DIOXIDE

KW - CIRCULATION

KW - DEEP

KW - DEGLACIATION

KW - GLACIAL PERIOD

KW - ICE-CORE

KW - NORTH-ATLANTIC

KW - SEDIMENTS

KW - WATERS

KW - Nordic Seas

KW - deglaciation

KW - last glacial

KW - radiocarbon

KW - ocean ventilation

UR - https://www.scopus.com/pages/publications/85013382096

U2 - 10.1002/2016PA003053

DO - 10.1002/2016PA003053

M3 - Journal article

SN - 0883-8305

VL - 32

SP - 172

EP - 181

JO - Paleoceanography

JF - Paleoceanography

IS - 2

ER -