scholarly journals Deep-water mass source and dynamic associated with rapid climatic variations during the last glacial stage in the North Atlantic: A multiproxy investigation of the detrital fraction of deep-sea sediments

2006 ◽  
Vol 7 (2) ◽  
pp. n/a-n/a ◽  
Author(s):  
M. Ballini ◽  
C. Kissel ◽  
C. Colin ◽  
T. Richter
Keyword(s):  
North Atlantic ◽  
Deep Water ◽  
Deep Sea ◽  
Water Mass ◽  
Mass Source ◽  
Climatic Variations ◽  
The North ◽  
Glacial Stage ◽  
The North Atlantic ◽  
The Last Glacial

Climatic Record of the Past 130,000 Years in North Atlantic Deep-Sea Core V23-82: Correlation with the Terrestrial Record

1973 ◽  
Vol 3 (1) ◽  
pp. 110-116 ◽  
Author(s):  
Constance Sancetta ◽  
John Imbrie ◽  
N.G. Kipp
Keyword(s):  
North Atlantic ◽  
Deep Sea ◽  
Planktonic Foraminifera ◽  
Linear Interpolation ◽  
Stratigraphic Correlation ◽  
Last Glacial ◽  
The Past ◽  
The North ◽  
The North Atlantic ◽  
The Last Glacial

AbstractQuantitative paleo-environmental analyses of planktonic foraminifera in 182 samples covering the past 130,000 years in North Atlantic deep-sea core V23-82 yield time series interpreted in terms of changing surface-water conditions. An absolute chronology is estimated by linear interpolation between levels dated by 14C or by stratigraphic correlation with other radiometrically dated climatic records. Significant events include: (1) rapid warming at 127,000 YBP, marking the start of the penultimate North Atlantic and European interglacial; (2) 124,000 YBP temperature maximum (Eemian); (3) 109,000 YBP cooling, correlated with the beginning of the last European glaciation (Würm), and representing a temporary cooling of the North Atlantic; (4) severe cooling 73,000 YBP, marking the start of the last full glacial regime in the North Atlantic; (5) short warm intervals within the last glacial regime dated at 59,000 YBP, 48,000 YBP, and 31,000 YBP; (6) rapid termination of the last glacial interval at 11,000 YBP; (7) a 6000 YBP hypsi-saline, followed by lowering salinity values presumably associated with decreasing flux of Gulf Stream waters over the core site.

scholarly journals Changes in the geometry and strength of the Atlantic Meridional Overturning Circulation during the last glacial (20–50 ka)

2016 ◽  
Author(s):  
Pierre Burckel ◽  
Claire Waelbroeck ◽  
Yiming Luo ◽  
Didier Roche ◽  
Sylvain Pichat ◽  
...  
Keyword(s):  
Flow Rate ◽  
North Atlantic ◽  
Deep Water ◽  
Water Mass ◽  
Atlantic Meridional Overturning Circulation ◽  
Meridional Overturning Circulation ◽  
Overturning Circulation ◽  
The North ◽  
Meridional Overturning ◽  
The North Atlantic

Abstract. We reconstruct the geometry and strength of the Atlantic Meridional Overturning Circulation during Heinrich Stadial 2 and three Greenland interstadials of the 20–50 ka period based on the comparison of new and published sedimentary 231Pa/230Th data with simulated sedimentary 231Pa/230Th. We show that the deep Atlantic circulation during these interstadials was very different from that of the Holocene. Northern-sourced waters likely circulated above 2500 m depth, with a flow rate lower than that of the present day North Atlantic Deep Water (NADW). Southern-sourced deep waters most probably flowed northwards below 4000 m depth into the North Atlantic basin, and then southwards as a return flow between 2500 and 4000 m depth. The flow rate of this southern-sourced deep water was likely larger than that of the modern Antarctic Bottom Water (AABW). At the onset of Heinrich Stadial 2, the structure of the AMOC significantly changed. The deep Atlantic was probably directly affected by a southern sourced water mass below 2500 m depth, while a slow southward flowing water mass originating from the North Atlantic likely influenced depths between 1500 and 2500 m down to the equator.

North Atlantic deep water sources and export since MIS3: implications from Nd isotopes

2020 ◽  
Author(s):  
Patrick Blaser ◽  
Frerk Pöppelmeier ◽  
Martin Frank ◽  
Marcus Gutjahr ◽  
Jörg Lippold
Keyword(s):  
North Atlantic ◽  
Deep Water ◽  
Water Mass ◽  
Deep Ocean ◽  
Source Rocks ◽  
Nd Isotopes ◽  
Nordic Seas ◽  
Last Glacial ◽  
The North ◽  
The Last Glacial

<p><span>Deep water formation in the North Atlantic represents an integral link between the atmosphere, cryosphere, and the deep ocean: heat loss </span><span>from</span><span> warm surface waters supplies moisture to the high latitudes and the</span><span>ir</span><span> subsequent sinking ventilates the deep ocean and sequesters greenhouse gases from the atmosphere. This moisture supply supported the formation of immense ice sheets in the region during the last glacial, which in turn affect</span><span>ed</span><span> climate. While many studies have improved our understanding of these processes for past glacials, a comprehensive </span><span>picture</span><span> including the significance and variation of deep water export from the Nordic Seas is still missing. Furthermore, recent </span><span><span>observations suggested the export of a previously unknown bottom water mass from the glacial </span></span><span><span>subpolar</span></span><span><span> North Atlantic.</span></span></p><p><span><span>In this study we investigate the distribution and sourcing of water masses in the </span></span><span><span>subpolar</span></span><span><span> Nort</span></span><span>h Atlantic since MIS3 with the help of authigenic Nd isotopes. This method benefits from the large heterogeneity in Nd isotopic compositions of source rocks in this region, but the post-depositional dissolution of detritus within the sediments can also impede interpretations of individual records. We thus compare several Nd isotope records from the subpolar North Atlantic and Nordic Seas in order to define </span><span>distinct</span><span> deep water mass end members and estimate their prevalence </span><span>and mixing</span><span> in the subpolar North Atlantic during the last 30 ka. Our observations suggest that Nordic Seas deep water overflowing the Greenland-Scotland Ridge during MIS2 reached into the deep subpolar North Atlantic. Furthermore, its spatial distribution implies that overflow across Denmark Strait into the Irminger Basin was more pronounced than overflow into the Iceland Basin further south. The hydrographic configuration during the Last Glacial Maximum thus appears </span><span>to have been </span><span>more complex and more similar to today than previously thought.</span></p>

scholarly journals On the effect of the North Atlantic Oscillation on temperature and salinity of the subpolar North Atlantic intermediate and deep waters

2009 ◽  
Vol 66 (7) ◽  
pp. 1448-1454 ◽  
Author(s):  
Artem Sarafanov
Keyword(s):  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Deep Water ◽  
Water Mass ◽  
General Mechanism ◽  
The North ◽  
Deep Waters ◽  
Mass Properties ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract Sarafanov, A. 2009. On the effect of the North Atlantic Oscillation on temperature and salinity of the subpolar North Atlantic intermediate and deep waters. – ICES Journal of Marine Science, 66: 1448–1454. The close relationship between the observed water mass properties and the winter North Atlantic Oscillation (NAO) index (1950–2000s; r2 ≈ 0.65) implies that changes in the NAO-related atmospheric forcing may account for up to two-thirds of thermohaline changes at the intermediate and deep levels in the subpolar North Atlantic on a decadal time-scale. Persistent NAO decline (amplification) results in increase (decrease) in temperature and salinity in the intermediate–deep water column. A general mechanism explaining the close link between the NAO and coherent decadal changes in the intermediate and deep-water temperature and salinity in the region is inferred from the observed changes in the regional circulation and water mass properties. Two factors dominate this link: (i) intensity of convection in the Labrador Sea controlling injection of relatively cold freshwater into the intermediate layer, and (ii) zonal extension of the Subpolar Gyre that regulates the relative contribution of cold fresh subpolar water and warm saline subtropical water to the deep-water formation.

scholarly journals Changes in the geometry and strength of the Atlantic meridional overturning circulation during the last glacial (20–50 ka)

2016 ◽  
Vol 12 (11) ◽  
pp. 2061-2075 ◽  
Author(s):  
Pierre Burckel ◽  
Claire Waelbroeck ◽  
Yiming Luo ◽  
Didier M. Roche ◽  
Sylvain Pichat ◽  
...  
Keyword(s):  
Flow Rate ◽  
North Atlantic ◽  
Deep Water ◽  
Water Mass ◽  
Atlantic Meridional Overturning Circulation ◽  
Meridional Overturning Circulation ◽  
Overturning Circulation ◽  
The North ◽  
Meridional Overturning ◽  
The North Atlantic

Abstract. We reconstruct the geometry and strength of the Atlantic meridional overturning circulation during the Heinrich stadial 2 and three Greenland interstadials of the 20–50 ka period based on the comparison of new and published sedimentary 231Pa / 230Th data with simulated sedimentary 231Pa / 230Th. We show that the deep Atlantic circulation during these interstadials was very different from that of the Holocene. Northern-sourced waters likely circulated above 2500 m depth, with a flow rate lower than that of the present-day North Atlantic deep water (NADW). Southern-sourced deep waters most probably flowed northwards below 4000 m depth into the North Atlantic basin and then southwards as a return flow between 2500 and 4000 m depth. The flow rate of this southern-sourced deep water was likely larger than that of the modern Antarctic bottom water (AABW). Our results further show that during Heinrich stadial 2, the deep Atlantic was probably directly affected by a southern-sourced water mass below 2500 m depth, while a slow, southward-flowing water mass originating from the North Atlantic likely influenced depths between 1500 and 2500 m down to the equator.

scholarly journals Surface and deep water circulation in late Cretaceous North Atlantic greenhouse ocean

2009 ◽  
Author(s):  
◽  
Carolina Isaza Londoño
Keyword(s):  
Ocean Circulation ◽  
Late Cretaceous ◽  
North Atlantic ◽  
Deep Water ◽  
Water Mass ◽  
Deep Ocean ◽  
Water Circulation ◽  
Regional Warming ◽  
The North ◽  
The North Atlantic

This research provides the first of its kind empirical data regarding the evolution of Maastrichtian surface to deep ocean circulation in the North Atlantic. Differences in foraminiferal abundances and oxygen and carbon isotopic ratios of bulk carbonate and foraminifera between two Ocean Drilling Program Sites in the subtropical North Atlantic indicate a sharp water mass boundary was a relatively stable and persistent feature of the Maastrichtian North Atlantic despite significant regional warming across the interval. Neodymium isotopes of fish debris, on the other hand, indicate significant changes in intermediate and deep water circulation through the Late Cretaceous and especially during the Maastrichtian. During the Cenomanian-Campanian interval at least three different deep water masses were active in the North Atlantic including one formed by downwelling of warm saline waters in the Demerara Rise region. During the Campanian-Maastrichtian, low-latitude-sourced waters seem to have reached abyssal depths, but from the mid-Maastrichtian on, this water mass seems to have declined in importance. From the mid-Danian on, we found evidence for only one water mass (plausibly sourced in the northern North Atlantic, as it is today) at bathyal and abyssal depths in the North Atlantic. Our data demonstrate that surface and, especially, intermediate and deep water circulation patterns are an important (and measurable) variable that helps determine greenhouse temperature distributions on regional and global scales.

scholarly journals Simulated stability of the AMOC during the Last Glacial Maximum under realistic boundary conditions

2020 ◽  
Author(s):  
Frerk Pöppelmeier ◽  
Jeemijn Scheen ◽  
Aurich Jeltsch-Thömmes ◽  
Thomas F. Stocker
Keyword(s):  
Boundary Conditions ◽  
North Atlantic ◽  
Deep Water ◽  
Bering Strait ◽  
Deep Water Formation ◽  
The North ◽  
Water Formation ◽  
The North Atlantic ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. The response of the Atlantic Meridional Overturning Circulation (AMOC) to freshwater perturbations critically depends on its mean-state. Large swaths of icebergs melting in the North Atlantic during the last deglaciation constituted such perturbations, and thus can provide important constraints on the stability of the AMOC. Yet, the mean AMOC state during the Last Glacial Maximum (LGM), preceding the rapid disintegration of the ice-sheets during the deglaciation, as well as its response to these perturbations remain debated. Here we investigate the evolution of the AMOC responding to freshwater perturbations under improved LGM boundary conditions in the Bern3D intermediate complexity model. Particularly, we consider the effect of an open versus a closed Bering Strait. The vigorous and deep AMOC under these glacial boundary conditions, consistent with previous simulations with different models, reacts more strongly to North Atlantic freshwater forcings than under pre-industrial conditions. This increased sensitivity is mostly related to the closed Bering Strait that cuts off the freshwater escape route through the Arctic into the Pacific, thus facilitating faster accumulation of freshwater in the North Atlantic halting deep water formation. Proxy reconstructions of the LGM AMOC instead indicate a weaker and possibly shallower AMOC than today, in conflict with the particularly strong and deep circulation states coherently simulated with ocean circulation models for the LGM. Simulations with reduced North Atlantic deep water formation, as a consequence of potentially increased continental runoff from ice-sheet melt and imposed changes in the hydrological cycle, more closely resemble the overturning circulation inferred from proxies. These circulation states also show bistable behavior, where the AMOC does not recover after North Atlantic freshwater hosing. However, no AMOC states are found here that either comprise an extreme shoaling or vigorous and concurrent shallow overturning as previously proposed based on paleoceanographic data.

Late Quaternary palaeo-oceanography of the Denmark Strait overflow pathway, South-East Greenland margin

1998 ◽  
Vol 180 ◽  
pp. 163-167
Author(s):  
Antoon Kuijpers ◽  
Jørn Bo Jensen ◽  
Simon R . Troelstra ◽  
And shipboard scientific party of RV Professor Logachev and RV Dana
Keyword(s):  
North Atlantic ◽  
Deep Water ◽  
Deep Convection ◽  
Conveyor Belt ◽  
Water Masses ◽  
Labrador Sea ◽  
Greenland Sea ◽  
The North ◽  
Denmark Strait ◽  
The North Atlantic

Direct interaction between the atmosphere and the deep ocean basins takes place today only in the Southern Ocean near the Antarctic continent and in the northern extremity of the North Atlantic Ocean, notably in the Norwegian–Greenland Sea and Labrador Sea. Cooling and evaporation cause surface waters in the latter region to become dense and sink. At depth, further mixing occurs with Arctic water masses from adjacent polar shelves. Export of these water masses from the Norwegian–Greenland Sea (Norwegian Sea Overflow Water) to the North Atlantic basin occurs via two major gateways, the Denmark Strait system and the Faeroe– Shetland Channel and Faeroe Bank Channel system (e.g. Dickson et al. 1990; Fig.1). Deep convection in the Labrador Sea produces intermediate waters (Labrador Sea Water), which spreads across the North Atlantic. Deep waters thus formed in the North Atlantic (North Atlantic Deep Water) constitute an essential component of a global ‘conveyor’ belt extending from the North Atlantic via the Southern and Indian Oceans to the Pacific. Water masses return as a (warm) surface water flow. In the North Atlantic this is the Gulf Stream and the relatively warm and saline North Atlantic Current. Numerous palaeo-oceanographic studies have indicated that climatic changes in the North Atlantic region are closely related to changes in surface circulation and in the production of North Atlantic Deep Water. Abrupt shut-down of the ocean-overturning and subsequently of the conveyor belt is believed to represent a potential explanation for rapid climate deterioration at high latitudes, such as those that caused the Quaternary ice ages. Here it should be noted, that significant changes in deep convection in Greenland waters have also recently occurred. While in the Greenland Sea deep water formation over the last decade has drastically decreased, a strong increase of deep convection has simultaneously been observed in the Labrador Sea (Sy et al. 1997).

scholarly journals Evidence for strong relations between the upper Tagus loess formation (central Iberia) and the marine atmosphere off the Iberian margin during the last glacial period

2021 ◽  
pp. 1-30
Author(s):  
Daniel Wolf ◽  
Thomas Kolb ◽  
Karolin Ryborz ◽  
Susann Heinrich ◽  
Imke Schäfer ◽  
...  
Keyword(s):  
North Atlantic ◽  
Moisture Transfer ◽  
Sea Temperature ◽  
Last Glacial ◽  
Atmospheric Circulation Patterns ◽  
The North ◽  
Terrestrial Environments ◽  
The North Atlantic ◽  
Iberian Margin ◽  
The Last Glacial

Abstract During glacial times, the North Atlantic region was affected by serious climate changes corresponding to Dansgaard-Oeschger cycles that were linked to dramatic shifts in sea temperature and moisture transfer to the continents. However, considerable efforts are still needed to understand the effects of these shifts on terrestrial environments. In this context, the Iberian Peninsula is particularly interesting because of its close proximity to the North Atlantic, although the Iberian interior lacks paleoenvironmental information so far because suitable archives are rare. Here we provide an accurate impression of the last glacial environmental developments in central Iberia based on comprehensive investigations using the upper Tagus loess record. A multi-proxy approach revealed that phases of loess formation during Marine Isotope Stage (MIS) 2 (and upper MIS 3) were linked to utmost aridity, coldness, and highest wind strengths in line with the most intense Greenland stadials also including Heinrich Events 3–1. Lack of loess deposition during the global last glacial maximum (LGM) suggests milder conditions, which agrees with less-cold sea surface temperatures (SST) off the Iberian margin. Our results demonstrate that geomorphological system behavior in central Iberia is highly sensitive to North Atlantic SST fluctuations, thus enabling us to reconstruct a detailed hydrological model in relation to marine–atmospheric circulation patterns.

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