Changes in surface salinity of the North Atlantic Ocean during the last deglaciation

Duplessy, Jean‐Claude; Labeyrie, Laurent D; Arnold, Maurice; Paterne, Martine; Duprat, J.; Weering, Tj.C.E. van

doi:10.1038/358485a0

Cited by 290 publications

(191 citation statements)

References 25 publications

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“…While in the model they are only slightly warmer than the present interglacial, the reconstructions suggest that previous interglacials were warmer by about 4 • C (Jouzel et al, 2007). Much warmer conditions in Antarctica during previous interglacials can be attributed to the disappearance of the West Antarctic ice sheet (Holden et al, 2010) and the initial temperature overshoot due to the mechanism of the bipolar seesaw (Ganopolski and Roche, 2009). The first mechanism is not taken into account in our simulations since we did not include changes in the Antarctic ice sheet.…”

Section: Model Description and Experimental Setupmentioning

confidence: 93%

“…For the earlier part of the modeled period, reliable reconstructions of global ice volume are lacking, and the benthic δ 18 O c stack by Lisiecki and Raymo (2005) was used for comparison. Since benthic δ 18 O c is not an accurate proxy for ice volume, we computed the model's equivalent of δ 18 O c from the simulated global ice volume and deep ocean temperature using a simple relationship between the three (Duplessy et al, 1991). In addition, based on the results of simulations of the Antarctic ice sheet evolution during the last glacial cycle (Huybrechts, 2002), we assume that the Southern Hemisphere contributed an additional 10 % to global ice volume variations.…”

Section: Model Description and Experimental Setupmentioning

confidence: 99%

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The role of orbital forcing, carbon dioxide and regolith in 100 kyr glacial cycles

2011

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Abstract. The origin of the 100 kyr cyclicity, which dominates ice volume variations and other climate records over the past million years, remains debatable. Here, using a comprehensive Earth system model of intermediate complexity, we demonstrate that both strong 100 kyr periodicity in the ice volume variations and the timing of glacial terminations during past 800 kyr can be successfully simulated as direct, strongly nonlinear responses of the climate-cryosphere system to orbital forcing alone, if the atmospheric CO 2 concentration stays below its typical interglacial value. The existence of long glacial cycles is primarily attributed to the North American ice sheet and requires the presence of a large continental area with exposed rocks. We show that the sharp, 100 kyr peak in the power spectrum of ice volume results from the long glacial cycles being synchronized with the Earth's orbital eccentricity. Although 100 kyr cyclicity can be simulated with a constant CO 2 concentration, temporal variability in the CO 2 concentration plays an important role in the amplification of the 100 kyr cycles.

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Section: Model Description and Experimental Setupmentioning

confidence: 93%

Section: Model Description and Experimental Setupmentioning

confidence: 99%

The role of orbital forcing, carbon dioxide and regolith in 100 kyr glacial cycles

2011

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“…Variations in d sw arise from: the waxing and waning of ice sheets (i.e., changes in global ice volumes); changes in the balance of evaporation and precipitation (e.g., Duplessy et al, 1991Duplessy et al, , 1992; changes in the balance between advection and mixing between water masses (e.g., Curry and Oppo, 1997); and changes in the processes and intensity of deep-water formation, where varying contributions of melt-water, entrained water, and brine to the newly formed deep waters may impose regional d sw anomalies. For example, pore-water d sw measurements are different in the deep Pacific, and northern and southern Atlantic between the LGM and today ; the inferred changes suggest a large freshwater imbalance in the northern convecting regions during the LGM, with an important role for increased sea-ice formation and export.…”

Section: The Global D 18 O:sea-level/ice-volume Relationshipmentioning

confidence: 99%

Differences between the last two glacial maxima and implications for ice-sheet, δ18O, and sea-level reconstructions

Rohling

Hibbert

Williams

et al. 2017

Quaternary Science Reviews

100

115

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Arctic ice shelf Last Interglacial Glacioisostatic adjustment a b s t r a c t Studies of past glacial cycles yield critical information about climate and sea-level (ice-volume) variability, including the sensitivity of climate to radiative change, and impacts of crustal rebound on sealevel reconstructions for past interglacials. Here we identify significant differences between the last and penultimate glacial maxima (LGM and PGM) in terms of global volume and distribution of land ice, despite similar temperatures and radiative forcing. Our analysis challenges conventional views of relationships between global ice volume, sea level, seawater oxygen isotope values, and deep-sea temperature, and supports the potential presence of large floating Arctic ice shelves during the PGM. The existence of different glacial 'modes' calls for focussed research on the complex processes behind ice-age development. We present a glacioisostatic assessment to demonstrate how a different PGM ice-sheet configuration might affect sea-level estimates for the last interglacial. Results suggest that this may alter existing last interglacial sea-level estimates, which often use an LGM-like ice configuration, by several metres (likely upward).

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“…They were corrected for changes in global ice volume [Labeyrie et al, 1987] and normalized for SST changes, following the techniques proposed by Duplessy et al [1991a] and assuming that 1% d 18 O is equal to 3.57°C and 2.75 psu in local SSS [Keigwin, 1998]. …”

Section: Sea Surface Temperature and Sea Surface Salinitymentioning

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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Changes in surface salinity of the North Atlantic Ocean during the last deglaciation

Cited by 290 publications

References 25 publications

The role of orbital forcing, carbon dioxide and regolith in 100 kyr glacial cycles

The role of orbital forcing, carbon dioxide and regolith in 100 kyr glacial cycles

Differences between the last two glacial maxima and implications for ice-sheet, δ18O, and sea-level reconstructions

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

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