Deepwater source variations during the last climatic cycle and their impact on the global deepwater circulation

Duplessy, Jean‐Claude; Shackleton, Nicholas J; Fairbanks, Richard G.; Labeyrie, Laurent D; Oppo, Delia W; Kallel, Néjib

doi:10.1029/pa003i003p00343

Cited by 1,034 publications

(684 citation statements)

References 39 publications

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“…Since these cha nges are respo nsible for only a minor part of the shift. the glacial/intergla cial S 13C-cycles are probably a function of mainly global changes in ocea n prod uctivity, nutrient and bottom Water mass d istribut ion (Curry et al, 1988;Duplessy et al, 1988 The diffe rence in 6 U e values of the bemhlc for aminifer E. exigua of abo ut 0.9°/00 be tween th e last glacial and late Holocen e time falls in th e same ran ge as calculated by Curry er al. (1988) for C. wuellersrorji £rom South Atlant ic co res (26°· 44°S).…”

Section: Mater Lal and Methodssupporting

confidence: 64%

Stable Isotope Record and Late Quaternary Sedimentation Rates at the Antarctic Continental Margin

Grobe

Mackensen

Hubberten

et al. 1990

Geological History of the Polar Oceans: Arctic Versus Antarctic

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2UIliversjtal BremenFachbereiJ:h Geowisseruchaften, ·280Bremen, F.R GemllllfJABST RACT. Four cores Irorn the Ant arcti c conliDC ntaJ margin tcceted between .50 and 200 Icm Irc m the present-day iee·~elf edge, were setected ror sed ime nlologiea l aDd mass spectroeterer analyses..The rU"Sl sta~isotope records of lhe Sou thc:rn Polar Ocean can be correlaled in delail with global isotope st raligra pby. Toget her wiLb magncl OSlratigraphi c, sed ime ntGlogical and micropaleon loklgical dala, the record provides stratigrapbic and paleoceanographic information back 10 lhe JaramiUo Subehron (910 ka). A1tboug.b the isotope values have been alte red by diagenetic processes in the sedi meats, which are poor in c:arbonale , an interpretalion i5 possib le using eorretauoe with the scdirnenlologicaJ parameters, Oxygen isotope data give indicalions ror a meltwat er spike at tbe begi nning of inlerglacial!, when largẽ Ie melting or parts or the ice-shelves took place. The syndrroDous record of lhe ben lhK:and planktit.: 6 C signaJs re£ka oontin uous bottom waler rorm ation also during gbcials.Primary productivity was 5UictJy red uced during glacials due 10 coettescus ice CO\oc rage in lbe Wcddcll Sea. The climatic improwcmenl al the begin ning of an interglacia l is lISSOci:llcd with peak values in biologk adi\;ty lasting Ior about I Styr.During oee climatic cycle , mean sedimentation rates at the continental margin decrease with increasing dislance Irom the continent from S.2 to 13 cm/kyr. Maximum sed imentation rates or 25 cm/kyr at the beginn ing or an intergl acial and minimum .sedime ntation rates of 0.6 cm /kyr during glacial periods have been calcula ted . Th ese rates are main ly controll ed by movements of the ice-shelf edge and ice-rafting. IntroductionThe An tarcric circumpolar ocean with its extens ive ice-shelves in the WeddeU and Ross Seas, is one of the Earth's prin cipal sources of ocea nic bottom waters and strongly influe nces the global clima te (Foster & Middletcn, 1980 540shelf edge, the sea ice distribution, and oceanographic and biologic processes, related to global climatic changes (Pudsey et aJ., 1988; Futt erer et al., 1988). On the eastern continental margin o f the Wedde U Sea. distinct cycles in the sedimentary environment main ly reflect cha nges in the hydrographic regim e in response 10 the retreat and adva nce of iceshe lves an d sea ice (Grebe, 1986) . Pri or to this study, sedi me nts fro m so uth o f th e present-da y Antarctic Polar Front have not been included in th e co nstr uctio n of Quaternary isotope stratigraphy. because of the paucity of biogenic carbonate (Hays eJ al., 1976; Shackleton, 1977; Imbrie et al ., 1984;Pisias et al., 1984; Prell et al., 1986; Mart inson et al., 1987; Williams er al., 1988). All interpretations of southern high latitude glacial and inlerglacial paleoenvironments to dale (e.g. G robe, 1986; Ledbetter & Ciesielski, 1986; Burekle & Abrams, 1987;Pudsey et al., 1988;Fanerer et al .• 1988) have therefore suffered fro m the lack of detailed, worldwide correla...

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Section: Mater Lal and Methodssupporting

confidence: 64%

Stable Isotope Record and Late Quaternary Sedimentation Rates at the Antarctic Continental Margin

Grobe

Mackensen

Hubberten

et al. 1990

Geological History of the Polar Oceans: Arctic Versus Antarctic

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“…A secular effect of 0.3% for interglacial-to-glacial changes in preformed nutrients [Duplessy et al, 1988] was not reproducible in later reconstructions of Atlantic epibenthic d 13 C variations from glacial-to-interglacial times [Sarnthein et al, 1994].…”

Section: Tracers Of Nutrient Concentration and Bottom Water Ventilationmentioning

confidence: 99%

Paleonutrient and productivity records from the subarctic North Pacific for Pleistocene glacial terminations I to V

Gebhardt¹,

Sarnthein²,

et al. 2008

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[1] Our study addresses fundamental questions of the mode and timing of orbital and millennial-scale changes in the meridional overturning circulation (MOC) of the subarctic North Pacific. Particular concerns are the vertical mixing, the present and past abundance of nutrients in surface waters despite strong stratification, and the North Pacific-North Atlantic seesaw of oscillations in sea surface temperature (SST). We do this by generating and interpreting multiple records for glacial terminations I-V down two long piston cores, one each from the western and eastern subarctic Pacific. Chlorins and biogenic opal are proxies for surface water productivity; d 13 C of epibenthic foraminifera is a record of deepwater ventilation; and the d 13 C of N. pachyderma sin. is a tracer of nutrients in subsurface waters that extend up to the sea surface during times of vertical mixing. The degree of mixing is traced by pairing SST and d 18 O records of planktic surface and subsurface (pycnocline) dwellers. Tight age control is deduced from a suite of age-calibrated 14 C plateau boundaries for Termination I and benthic d 18 O and geomagnetic events for the last 800 ka. Carbon 14 paleoreservoir ages record the ages of surface and deep waters to uncover short-term changes in MOC over Termination I. We have defined a standard sequence of short-term productivity events for Termination I, also evident during terminations II to V and subsequent interglacials over the last 450 ka. The peak glacial regime of stable stratification and low productivity terminated, together with the end of ice rafting and melting, near 17 ka, $2000 years after the onset of Termination I. Pulses of vertical mixing and incursion of warm surface waters from the subtropics followed. Convected young water masses finally penetrated down to 3600-m water depth at 17.0 to less than 14.5 ka, significantly improving bottom water ventilation through the late deglacial and earliest interglacial. Mixing with upwelled nutrients from the pycnocline induced short-term maxima in algal production of chlorins and biogenic opal near 17-15 and 15-12 ka, respectively. Deglacial meltwater incursions in the Aleutian Current and silica input from North American rivers also promoted East Pacific productivity after 15.5 ka. Productivity decreased during the late deglacial and early interglacial, coeval with an exceptional peak in CaCO 3 preservation caused by both low organic flux and well-ventilated deepwater. Subsequently, low salinity and cool surface waters and in turn, stratification were gradually restored. A second, opaldominated productivity maximum marked the ends of interglacials. The deglacial pulses of vertical mixing around 17-11 ka imply an important contribution of the North Pacific to the coeval release of oceanic CO 2 into the atmosphere and support the east-west seesaw model of climate change.Citation: Gebhardt, H., M. Sarnthein, P. M. Grootes, T. Kiefer, H. Kuehn, F. Schmieder, and U. Röhl (2008), Paleonutrient and productivity records from the subarctic North ...

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“…[15] An alternative interpretation of these data by Duplessy et al [1988] suggests intermediate water was formed in the North Atlantic, and then spread out into all other oceans except the Southern Ocean (an intermediate sinking state, ISS). There it is proposed AABW formation occurred, which spread into the deep levels of the other oceans.…”

Section: Climate Modelmentioning

confidence: 99%

Sensitivity of the glacial ocean to Heinrich events from different iceberg sources, as modeled by a coupled atmosphere‐iceberg‐ocean model

2008

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[1] We introduce explicit icebergs from a dynamic and thermodynamic iceberg model into an intermediate complexity climate model, which includes the coupled atmosphere-ocean system. This modeling approach allows iceberg meltwater to be injected into the ocean on the basis of thermodynamical considerations along the iceberg trajectories. Icebergs are seeded from known ice sheets in both hemispheres. Adding icebergs to the present-day climate model has a minimal impact, but during the Last Glacial Maximum (LGM), Atlantic overturning strength is reduced by a third, while producing a model state that is consistent with a steady state climate. We test the sensitivity of the model at the LGM to additional Heinrich event-scale fluxes of icebergs from three possible sources: Hudson Strait, the Gulf of Saint Lawrence, and the Norwegian Channel Ice Stream (NCIS). The sensitivity of the ocean is similar for all locations, with differences dominated by the length of the iceberg meltwater pathways to the main ocean convection region. The NCIS events result in more variability and a distinctly different, more northerly, salinity anomaly. We compare these results to a more typical modeling approach, whereby meltwater is injected directly into the ocean at the iceberg source locations, and find that these floods overestimate the oceanic response compared to the iceberg events. Our results suggest that 0.3-0.4 Sv of additional freshwater flux, either as icebergs or freshwater, is required to shut down the North Atlantic meridional overturning, a larger freshwater flux than sometimes suggested because of the localized nature of the release of the freshwater.Citation: Levine, R. C., and G. R. Bigg (2008), Sensitivity of the glacial ocean to Heinrich events from different iceberg sources, as modeled by a coupled atmosphere-iceberg-ocean model, Paleoceanography, 23, PA4213,

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Deepwater source variations during the last climatic cycle and their impact on the global deepwater circulation

Cited by 1,034 publications

References 39 publications

Stable Isotope Record and Late Quaternary Sedimentation Rates at the Antarctic Continental Margin

Stable Isotope Record and Late Quaternary Sedimentation Rates at the Antarctic Continental Margin

Paleonutrient and productivity records from the subarctic North Pacific for Pleistocene glacial terminations I to V

Sensitivity of the glacial ocean to Heinrich events from different iceberg sources, as modeled by a coupled atmosphere‐iceberg‐ocean model

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