North Atlantic surface-ocean control of Pleistocene deep-ocean circulation

doi:10.1016/0012-821X(85)90072-X

Earth and Planetary Science Letters

Volume 73, Issues 2–4, May 1985, Pages 231-243

https://doi.org/10.1016/0012-821X(85)90072-X Get rights and content

Abstract

Deep basins of the North Atlantic were occupied by a cold¹³C-depleted (nutrient-rich) water mass during glaciations, and a warmer¹³C-enriched (nutrient-poor) water mass (modern NADW) during interglaciations. This mode of deep-water variability is related directly to migration of the North Atlantic Polar Front. Down-core stable isotope records from the Atlantic and Antarctic suggest that¹³C depletion of the glacial North Atlantic may reflect higher preformed nutrients (due to bottom-water formation under sea and/or shelf ice) and increased residence time of northern-source water, rather than replacement of NADW with AABW.

References (40)

ShackletonN.J. et al.
Oxygen and carbon isotope record of East Pacific core V19–30: implications for the formation of deep water in the late Pleistocene North Atlantic
Earth Planet. Sci. Lett.
(1983)
CurryW.B. et al.
Carbon isotopic changes in benthic foraminifera from the western South Atlantic: reconstruction of glacial abyssal circulation patterns
Quat. Res.
(1982)
ShackletonN.J. et al.
Oxygen isotope and paleomagnetic stratigraphy of equatorial Pacific core V28–238: oxygen isotope temperatures and ice volumes on a 10⁵ and 10⁶ year scale
Quat. Res.
(1973)
DuplessyJ.C. et al.
Carbon-13 record of benthic foraminifera in the last interglacial ocean: implications for the carbon cycle and the global deepwater circulation
Quat. Res.
(1984)
BelangerP.E. et al.
Core-top evaluation of benthic foraminiferal isotopic ratios for paleo-oceanographic interpretations
Palaeogeogr., Palaeoclimatol., Palaeoecol.
(1981)
WeissR.F. et al.
Geochemical studies of the Weddell Sea
Deep-Sea Res.
(1979)
KroopnickP.
The distribution of¹³C in the Atlantic Ocean
Earth Planet. Sci. Lett.
(1980)
MorleyJ.J.
Identification of density-stratified waters in the late-Pleistocene North Atlantic: a faunal derivation
Quat. Res.
(1983)
McIntyreA. et al.
Seasonal reconstructions of the earth's surface at the last glacial maximum
Geol. Soc. Am., Map Chart Ser. MC-36
(1981)
ShackletonN.J.
Tropical rainforest history and the equatorial Pacific carbonate dissolution cycles

BroeckerW.S.

Glacial to interglacial changes in ocean chemistry

Progr. Oceanogr.

(1981)

BoyleE.A. et al.

Deep circulation of the North Atlantic during the last 150,000 years: geochemical evidence

Science

(1982)

CurryW.B. et al.

Reduced advection into Atlantic Ocean deep eastern basins during last glaciation maximum

Nature

(1984)

DuplessyJ.C. et al.

Deep water formation in the North Atlantic Ocean during the last ice age

Nature

(1980)

DuplessyJ.C.

Circulation des eaux profondes Nord Atlantiques au cours du dernier cycle climatique

Bull. Inst. Geol. Bassin d'Aquitaine

(1982)

N.J. Shackleton and N.G. Pisias, Atmospheric carbon dioxide, orbital forcing, and climate, in: Natural Variations in...

ImbrieJ. et al.

The orbital theory of Pleistocene climate: support from a revised chronology of the marine 180 record

JenkinsG.M. et al.

Spectral Analysis and Its Applications

(1968)

ShackletonN.J.

Attainment of isotopic equilibrium between ocean water and the benthonic foraminifera genus Uvigerina: isotopic changes in the ocean during the last glacial

Colloq. Int. Cent. Rech. Sci.

(1974)

GrahamD.W. et al.

Carbon and oxygen isotopic disequilibria of recent deep-sea foraminifera

Mar. Micropaleontol.

(1982)

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The long-term orbital-scale sea surface temperature (SST) variability in the tropics is thought to be mainly driven by greenhouse gases (GHG) forcing. However, few studies have investigated the drivers of such variability in the tropical Atlantic. Given the evidence of orbital-scale changes in Atlantic Meridional Overturning Circulation (AMOC) strength, one can hypothesize that AMOC variability also modulates the long-term tropical Atlantic SST through the bipolar seesaw mechanism. According to this mechanism, under weak [strong] AMOC conditions, the Southern Hemisphere is expected to warm up [cool down], while the Northern Hemisphere cools down [warms up]. Here, we investigate the long-term SST variability of the western tropical South Atlantic (WTSA), i.e., along the main pathway of the upper AMOC branch towards the equator, using a new 300 thousand years (kyr)-long Mg/Ca-based SST record. Our SST record shows glacial-interglacial variability superimposed by four remarkable long-term warm events during the three recorded glacial periods. These glacial warm events occurred between ca. 280–260, 160–143, 75–60, and 40–24 ka before present. Our results support the notion that atmospheric GHG plays a leading role in modulating the glacial-interglacial SST variability in the WTSA. However, it does not explain the occurrence of glacial warm events. Our study supports that the glacial warm events were caused by an orbital-scale bipolar seesaw mechanism operating in the Atlantic due to changes in the AMOC strength. These warm events may have been amplified by annual mean insolation driven by obliquity. Finally, we suggest that the long-term bipolar seesaw warmed the western tropical (South) Atlantic during the MIS 5/4 transition when the Earth's climate was cooling off.
Glacial expansion of carbon-rich deep waters into the Southwestern Indian Ocean over the last 630 kyr
2023, Global and Planetary Change
Oceanic carbon storage is one of the main sinks for atmospheric CO₂, and thought to be the major contributing factor for CO₂ drawdown during past glacial periods. Both physical and biogeochemical processes control the capacity of carbon storage in the ocean. During glacial periods of the Pleistocene the larger volume of deep-water masses of Southern Hemisphere origin in the Atlantic has been shown to promote carbon storage in the Southern Ocean. However, the latitudinal extension of this water mass in the Indian Ocean has been scarcely studied. In this study, we combine foraminiferal ε_Nd and benthic δ¹³C of two sediment cores in the southwest Indian Ocean (MD96–2077, 33°S, 3781 m water depth; MD96–2052, 19°S, 2627 m water depth), to reconstruct the spatial and temporal evolution of glacial carbon-rich deep waters in the SW Indian over the last 630 kyr. The combined use of foraminiferal ε_Nd and benthic δ¹³C allows to distinguish δ¹³C changes related to water mass mixing and from respired carbon accumulation within the water masses. Nutrient-rich deep waters, which cannot be explained by the enhanced proportion of southern-sourced waters, were present at core sites deeper than 2700 m during glacial periods and extended at least until 33°S into the SW Indian Ocean. From Marine Isotope Stage (MIS) 14 to MIS 10, glacial carbon storage increased gradually until reaching its highest capacity during the extreme glacial periods MIS 12 and 10. Orbital forcing (100-kyr eccentricity, 41-kyr obliquity), restricted air-sea exchange and enhanced ocean stratification, fostered higher carbon storage during periods of relatively lower eccentricity and obliquity. Furthermore, after MIS 10, a progressive transition was observed from 100-kyr eccentricity to 41-kyr obliquity cycles in benthic δ¹³C and δ¹⁸O records of core MD96–2077 and sea-ice cover changes derived from ice-rafted debris of the Agulhas Plateau composite core site.
North Atlantic Deep Water during Pleistocene interglacials and glacials
2021, Quaternary Science Reviews
Citation Excerpt :
Interglacial peaks are characterized by lower εNd and higher benthic δ13C values, consistent with the strong presence of nutrient-depleted NASW in the deep North Atlantic, and glacial peaks show higher εNd and lower benthic δ13C values, both consistent with increased presence of nutrient-rich SSW (Fig. 5a). Comparisons of coeval data points of the new εNd data at Site 607 with its published benthic δ13C records (Boyle and Keigwin, 1985; Mix and Fairbanks, 1985; Raymo et al., 1990; Ruddiman et al., 1989) show good negative correlations (r2 = 0.45, n = 82, for all εNd data generated in this study with available coeval δ13C; r2 = 0.55, n = 51, when only the interglacial and glacial peaks are considered) (Fig. S3). The εNd-benthic δ13C correlation is disrupted around MIS 26 (961 ka), just prior to the MPT-AMOC crisis, when benthic δ13C shows a shift toward a stronger SSW-like signal but the εNd-value is unusually negative for a glacial (Fig. 5).
The global ocean overturning circulation is a major means of distributing heat around the Earth, and an important trigger or amplifier of climate change. This study presents a 1.5-Myr-long neodymium (Nd) isotope record of Deep Sea Drilling Project Site 607, in the core of present-day North Atlantic Deep Water (NADW), the water mass that drives the overturning circulation and its Atlantic end-member (Broecker, 1991; Gordon, 1991), in order to document its composition through time. This time interval is marked by major changes in fundamental aspects of the Earth's climate, including the Mid-Pleistocene Transition (MPT) from ∼41-kyr to ∼100-kyr interglacial-glacial cycles and more intense glacials. The new record, mainly focusing on interglacial and glacial peaks, shows a pattern that mimics the record of benthic foraminiferal δ¹⁸O (Lisiecki and Raymo, 2005) in that the magnitude of interglacial-glacial Nd isotope shifts were smaller in the 41-kyr world than in the 100-kyr world. During the “900 ka event” (Clark et al., 2006), between ∼960 and 860 ka, marking the first 100-kyr interglacial-glacial cycle, the Nd isotope ratios shift abruptly to higher values, consistent with increased incursion of Southern Ocean water masses into the deep North Atlantic. This pattern was previously observed in the South Atlantic over the same time interval and interpreted as a weakened presence of NADW signal that reflected a period of disrupted deep ocean overturning circulation, termed the “MPT-AMOC crisis” (Pena and Goldstein, 2014). The Site 607 data support this interpretation and show the effects to be basin-wide. Following the disruption, an enhanced southern-sourced Nd isotope signature remained for ∼200 kyr during the period of “lukewarm interglacials” (Howe and Piotrowski, 2017; Jaccard et al., 2013), consistent with weaker overturning circulation. With the exception of this “MPT-AMOC crisis and recovery” interval, the Nd isotope ratios during interglacial peaks have been similar to present-day NADW, indicating similar interglacial North Atlantic ocean circulation dynamics both before and after the MPT. This contrasts with the pattern during glacial periods of the 100-kyr world, during which Nd isotopes have continued to follow the pattern of the 900-kyr event indicating a strong southern water mass signal, interpreted as intensified incursions of Southern Ocean water into the deep North Atlantic and consistent with a generally weaker overturning circulation during glacials.
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The important changes that took place in the glacial cycle at the termination, from the Last Glacial Maximum to the present interglacial, deserve an examination of ocean sedimentary records that document past productivity, carbon fluxes, and carbonate preservation. In this study, we analyzed coccoliths, alkenones, and foraminifers in core HU2008–029-004 PC (61.46°N and 58.04°W, water depth = 2,674 m) from the northwestern Labrador Sea to document linkages between hydrographic conditions, biogenic carbonate fluxes to the seafloor, and their preservation/dissolution during the last 25,000 years. Large changes in coccolith and foraminifer concentrations are recorded, with sediments from the last glacial interval containing significantly less carbonate microfossils (9.5 ± 3.9 × 10⁵ coccoliths g⁻¹ and 2,860 ± 580 planktonic foraminifers g⁻¹) than sediments from the deglacial and postglacial intervals (up to 3.1 × 10⁸ coccoliths g⁻¹ and 2.9 × 10⁴ foraminifers g⁻¹). Three foraminifer-based calcite dissolution indices were used to evaluate biogenic carbonate preservation: the planktonic foraminifer fragmentation index, the ratio of benthic-to-planktonic foraminifers (B/P), and the ratio of organic linings to benthic foraminifers (OL/B). Fragmentation remained low throughout the postglacial (mean of 4%) but reached up to 8% in the deglacial and peaked at 16% in samples from the Bølling-Allerød of the late glacial interval. Samples from the Bølling-Allerød and the deglacial interval also display a slightly elevated B/P index (>0.15), which suggests that some dissolution may have occurred. In contrast, with the exception of the Bølling-Allerød and the deglacial interval, near zero OL/B values characterize most of the sequence, suggesting good biogenic carbonate preservation, which implies that the low biogenic carbonate and coccolith content in sediments of the glacial stage mirror low productivity of calcifying organisms. The elevated fragmentation of foraminifers during the Bølling-Allerød and the deglacial interval, a time of elevated productivity and low percentages of ice-rafted debris, may indicate the development of calcite undersaturated porewaters and consequent dissolution resulting from oxic remineralization of sedimentary organic matter. We also identify a significant decoupling of coccolith and alkenone concentrations throughout the core. Colder-than-expected U^K₃₇-SST estimates from the alkenones of the glacial interval rule out possible allochthonous inputs from lower-latitude locations. Instead, our records imply that at least during the glacial interval, alkenones were produced by non-calcifying haptophytes that may not follow the canonical U^K₃₇-based temperature calibrations.
Eastern Atlantic deep-water circulation and carbon storage inferred from neodymium and carbon isotopic compositions over the past 1.1 million years
2021, Quaternary Science Reviews
Citation Excerpt :
The new binary mixing curve would be formed above the initial one with a general shift towards higher εNd values (Fig. 7a: the black triangles, circles and diamonds indicate the binary mixing trends when the Nd sources to the North Atlantic are more radiogenic with an increase of +2, +4 and + 6 ε-units, respectively). If the δ13C-DIC values of NSW and SSW decrease because of accumulation of remineralised organic matter in relation to slow ventilation and/or restricted air-sea exchange (Mix and Fairbanks, 1985; Gebbie, 2014), a new mixing curve would be formed below the initial one (Fig. 7a). These features are used to evaluate the above-mentioned hypothesis.
The Mid-Pleistocene transition (MPT; 1200 to 800 thousand years, kyr) is marked by the shift from 41-kyr to 100-kyr interglacial-glacial cyclicity without substantial change in the astronomical forcing. This change in climate response relied on internal feedback processes including interaction between ice sheet/sea ice, ocean circulation and the carbon cycle. It was suggested that a major perturbation of global oceanic carbon chemistry occurred at around 900 ka (Marine Isotope Stage, MIS, 24–22) although the mechanism responsible for the change is still to be elucidated. To investigate the link between the Atlantic Meridional Overturning Circulation (AMOC) and oceanic carbon storage for the past 1100 kyr, we combined neodymium isotopic composition (¹⁴³Nd/¹⁴⁴Nd or ε_Nd) recorded in foraminiferal authigenic fractions with epibenthic foraminiferal δ¹³C and δ¹⁸O from two cores in the North- and South-east Atlantic Ocean. Glacial/interglacial ε_Nd amplitude is smaller before the 900-ka event than after the event. The 900-ka event is marked by increase in seawater ε_Nd at both sites. These observations are consistent with previous studies, suggesting basin-wide ε_Nd changes. Combined with existing data, these new results reveal a persistent meridional gradient of seawater ε_Nd in the Atlantic Ocean over the past 1100 kyr. By comparing the reconstructions with numerical modelling results, we propose that weaker AMOC and changes in Nd sources to the North Atlantic were the main reasons for the observed ε_Nd shift at the 900-ka event in relation to the evolution of the Northern hemisphere cryosphere. The influence of enhanced Southern Ocean overturning circulation on ε_Nd values was estimated to be minor_. Seawater ε_Nd and benthic δ¹³C relationship for the whole study period indicates the presence of carbon-rich glacial deep water (>3000 m) in the North and the South Atlantic, in particular at MIS 22 and 24. This suggests that, in addition to weaker AMOC, reduction of deep-water ventilation and/or air-sea exchange in the Southern Ocean could have been responsible for the observed low benthic δ¹³C values. Together with increased biological productivity due to iron fertilization in the Southern Ocean, the physical process significantly contributed to the deep Atlantic carbon storage during the 900-ka event and the subsequent glacial periods.
Evolution of the Global Overturning Circulation since the Last Glacial Maximum based on marine authigenic neodymium isotopes
2020, Quaternary Science Reviews
Citation Excerpt :
Consistent with these requirements, carbonate system parameters suggest greater accumulation of remineralized carbon in the glacial deep ocean (Broecker et al., 2004; Burke and Robinson, 2012; Chalk et al., 2019; Rae et al., 2018), and inverse methods suggest lower preformed δ13C of glacial SSW (Gebbie, 2014; Oppo et al., 2018). A two-layer structure of glacial NSWs is also possible, in which a high preformed δ13C intermediate-to-mid depth NSW (<2500 m; Glacial North Atlantic Intermediate Water/GNAIW) formed through open-ocean convection with strong air-sea gas exchange, and a low preformed δ13C bottom NSW (>2500 m; Glacial North Atlantic Bottom Water/GNABW) formed under sea ice with limited air-sea gas exchange (Howe et al., 2016a; Keigwin and Swift, 2017; Mix and Fairbanks, 1985; Zhao et al., 2019) (Fig. 13A). Such a glacial NSW division is not yet fully resolved by εNd data (Fig. 9A), but this εNd-δ13C comparison speaks to the importance of the multi-proxy approach to circulation reconstruction (Gu et al., 2020; Lippold et al., 2016; Muglia et al., 2018; Ng et al., 2018; Piotrowski et al., 2005; Skinner et al., 2013), taking advantage of the differing mechanisms that control various circulation tracers.
The Global Overturning Circulation is linked to climate change on glacial-interglacial and multi-millennial timescales. The understanding of past climate-circulation links remains hindered by apparent conflicts among proxy measures of circulation. Here we reconstruct circulation changes since the Last Glacial Maximum (LGM) based on a global synthesis of authigenic neodymium isotope records (ε_Nd). We propose the bottom-up framework of interpreting seawater and authigenic ε_Nd considering not only conservative watermass mixing, but also the preformed properties and the non-conservative behavior of ε_Nd, both subject to sedimentary influences. We extract the major spatial-temporal modes of authigenic ε_Nd using Principal Component Analysis, and make a first-order circulation reconstruction with budget-constrained box model simulations. We show that during the LGM, the source region of North Atlantic overturning shifted southward, which led to more radiogenic preformed ε_Nd of glacial Northern Source Water (NSW). Considering this preformed effect, we infer that glacial deep Atlantic had a similar proportion of NSW as today, although the overall strength of glacial circulation appears reduced from both North Atlantic and Southern Ocean sources, which increased the relative importance of non-conservative behavior of ε_Nd and may have facilitated accumulation of respired carbon in the deep ocean. During the deglaciation, we find that Southern Ocean overturning increased, which offset suppressed North Atlantic overturning and resulted in a net stronger global abyssal circulation. Faster global scale deglacial circulation reduced the relative importance of non-conservative effects, resulting in Atlantic-Pacific convergence of abyssal ε_Nd signatures. Variations of Southern Ocean overturning likely drove a significant fraction of deglacial changes in atmospheric CO₂ and oceanic heat budget.

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^*: Present address: College of Oceanography, Oregon State University, Corvallis, OR 97331-5503, U.S.A.

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North Atlantic surface-ocean control of Pleistocene deep-ocean circulation

Abstract

Earth Planet. Sci. Lett.

Quat. Res.

Quat. Res.

Quat. Res.

Palaeogeogr., Palaeoclimatol., Palaeoecol.

Deep-Sea Res.

Earth Planet. Sci. Lett.

Quat. Res.

Seasonal reconstructions of the earth's surface at the last glacial maximum

Geol. Soc. Am., Map Chart Ser. MC-36

Tropical rainforest history and the equatorial Pacific carbonate dissolution cycles

Glacial to interglacial changes in ocean chemistry

Progr. Oceanogr.

Deep circulation of the North Atlantic during the last 150,000 years: geochemical evidence

Science

Reduced advection into Atlantic Ocean deep eastern basins during last glaciation maximum

Nature

Deep water formation in the North Atlantic Ocean during the last ice age

Nature

Circulation des eaux profondes Nord Atlantiques au cours du dernier cycle climatique

Bull. Inst. Geol. Bassin d'Aquitaine

The orbital theory of Pleistocene climate: support from a revised chronology of the marine 180 record

Spectral Analysis and Its Applications

Attainment of isotopic equilibrium between ocean water and the benthonic foraminifera genus Uvigerina: isotopic changes in the ocean during the last glacial

Colloq. Int. Cent. Rech. Sci.

Carbon and oxygen isotopic disequilibria of recent deep-sea foraminifera

Mar. Micropaleontol.