Fundamental Modes and Abrupt Changes in North Atlantic Circulation and Climate over the last 60 ky — Concepts, Reconstruction and Numerical Modeling

Sarnthein, Michael; Stattegger, Karl; Dreger, Derek; Erlenkeuser, Helmut; Grootes, Pieter Meiert; Haupt, Bernd J.; Jung, Simon; Kiefer, Thorsten; Kuhnt, Wolfgang; Pflaumann, Uwe; Schäfer-Neth, Christian; Schulz, Hartmut; Schulz, Michael; Seidov, Dan; Simstich, Johannes; Kreveld, Shirley van; Vogelsang, E.; Völker, Antje H. L.; Weinelt, Mara

doi:10.1007/978-3-642-56876-3_21

Cited by 172 publications

(172 citation statements)

References 181 publications

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“…The Heinrich 1 melt water event has previously been recorded off North Iceland by Voelker et al (1998) and by Sarnthein et al (1999), and a strong pre-Bølling Irminger Current into this area has also previously been described by Voelker et al (1998) and by Eiríksson et al (2000a). The present study clearly supports the idea of an anti-phase temperature relationship between the North Icelandic shelf and the eastern North Atlandic during pre-Bølling time (see also Sarnthein et al, 1995).…”

Section: Comparison and Discussionmentioning

confidence: 78%

“…Boyle and Keigwin, 1987;Kroon et al, 1997 andKroon, 2001), a change which corresponds to the end of the Heinrich 1 event in the North Atlantic. Grousset et al (2001) dated the end of the Heinrich 1 event to about 13400 14 C years BP (15700 cal yr BP), while Sarnthein et al (1999) found that the end of the Heinrich 1 melt water and IRD signals occurred between 13000 and 13400 14 C years BP. According to the GRIP ice-core record, the age of the transition between GS-2 and GI-le (the Bølling Interstadial) is considerably younger than recorded in the North Iceland shelf cores, i.e.…”

Section: Comparison and Discussionmentioning

confidence: 99%

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Environmental changes off North Iceland during the deglaciation and the Holocene: foraminifera, diatoms and stable isotopes

Knudsen

Jiang

Jansen

et al. 2004

Marine Micropaleontology

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A combined study of foraminifera, diatoms and stable isotopes in marine sediments off North Iceland records major changes in sea surface conditions since about 15800 cal years (yr) BP. Results are presented from two gravity cores obtained at about 400 m water depth from two separate sedimentary basins on each side of the submarine Kolbeinsey Ridge. The chronology of the sedimentary record is based partly on AMS 14 C dates, partly on the Vedde and the Saksunarvatn tephra markers, as well as the historical Hekla AD 1104 tephra. During the regional deglaciation, the planktonic foraminiferal assemblages are characterised by consistently high percentages of sinistrally coiled Neogloboquadrina pachyderma. However, major environmental variability is reflected by changes in stable isotope values and diatom assemblages. Low 18 O values indicate a strong freshwater peak as well as possible brine formation by sea-ice freezing during a pre-Bølling interval (Greenland Stadial 2), corresponding to the Heinrich 1 event. The foraminifera suggest a strong concurrent influence of relatively warm and saline Atlantic water, and both the foraminifera and the diatoms suggest mixing of cold and warm water masses. Similar but weaker environmental signals are observed during the Younger Dryas (Greenland Stadial 1) around the level of the Vedde Ash. Each freshwater peak is succeeded by an interval of severe cooling both at the beginning of the Bølling-Allerød Interstadial Complex (Greenland Interstadial 1) and during the Preboreal, presumably associated with the onset of intense deep water formatiom in the Nordic Seas. The Holocene thermal optimum, between 10200 and about 7000 cal years (yr) BP, is interrupted by a marked cooling of the surface waters around 8200 cal yr BP. This cold event is clearly expressed by a pronounced increase in the percentages of sinistrally coiled N. pachyderma, corresponding to a temperature decrease of about 3°C. A general cooling in the area is indicated after 7000-6000 cal yr BP, both by the diatom data and by the planktonic foraminiferal data. After a severe cooling around 6000 cal yr BP, the planktonic foraminiferal assemblages suggest a warmer interval between 5500 and 4500 cal yr BP. Minor temperature fluctuations are reflected both in the foraminiferal and in the diatom data in the upper part of the record, but the time resolution of the present data is not high enough to pick up details in environmental changes through the late Holocene.

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Section: Comparison and Discussionmentioning

confidence: 78%

Section: Comparison and Discussionmentioning

confidence: 99%

Environmental changes off North Iceland during the deglaciation and the Holocene: foraminifera, diatoms and stable isotopes

Knudsen

Jiang

Jansen

et al. 2004

Marine Micropaleontology

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“…A set of experiments was performed in which Heinrich events are mimicked by periodic freshwater pulses with 0.15 and 0.45 Sv am- plitude. The duration of these sawtoothlike pulses 4 is chosen to be 300 yr and their periodicity is 8000 yr, resembling approximately the spacing between subsequent Heinrich events (e.g., Sarnthein et al 2001). Furthermore, the oceanic boxes are subjected to a stochastic freshwater component of 0.06 Sv amplitude.…”

Section: The Bond Cycle: a Coupled Ocean-cryosphere Oscillationmentioning

confidence: 99%

Coherent Resonant Millennial-Scale Climate Oscillations Triggered by Massive Meltwater Pulses

Timmermann¹,

Gildor²,

Schulz³

et al. 2003

J. Climate

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131

140

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The role of mean and stochastic freshwater forcing on the generation of millennial-scale climate variability in the North Atlantic is studied using a low-order coupled atmosphere-ocean-sea ice model. It is shown that millennial-scale oscillations can be excited stochastically, when the North Atlantic Ocean is fresh enough. This finding is used in order to interpret the aftermath of massive iceberg surges (Heinrich events) in the glacial North Atlantic, which are characterized by an excitation of Dansgaard-Oeschger events. Based on model results, it is hypothesized that Heinrich events trigger Dansgaard-Oeschger cycles and that furthermore the occurrence of Heinrich events is dependent on the accumulated climatic effect of a series of Dansgaard-Oeschger events. This scenario leads to a coupled ocean-ice sheet oscillation that shares many similarities with the Bond cycle. Further sensitivity experiments reveal that the timescale of the oscillations can be decomposed into stochastic, linear, and nonlinear deterministic components. A schematic bifurcation diagram is used to compare theoretical results with paleoclimatic data.

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“…We reconstruct specific successions of paleoceanographic changes for each of the last five glacial terminations, and deduce important evidence for a better understanding of the suite of oceanographic and climatic changes that governed deglacial and peak interglacial times. The changes include vertical mixing, full reversals in meridional overturning, and short-term strong increases in nutrient inventories in a major highlatitude region of the global ocean [Sigman et al, 2004;Sarnthein et al, 2001Sarnthein et al, , 2007.…”

Section: Introductionmentioning

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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Fundamental Modes and Abrupt Changes in North Atlantic Circulation and Climate over the last 60 ky — Concepts, Reconstruction and Numerical Modeling

Cited by 172 publications

References 181 publications

Environmental changes off North Iceland during the deglaciation and the Holocene: foraminifera, diatoms and stable isotopes

Environmental changes off North Iceland during the deglaciation and the Holocene: foraminifera, diatoms and stable isotopes

Coherent Resonant Millennial-Scale Climate Oscillations Triggered by Massive Meltwater Pulses

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

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