Evolution of the neodymium isotopic signature of neritic seawater on a northwestern Pacific margin: new constrains on possible end-members for the composition of deep-water masses in the Late Cretaceous ocean

2013 ◽  
Vol 356 ◽  
pp. 160-170 ◽  
Author(s):  
Mathieu Moiroud ◽  
Emmanuelle Pucéat ◽  
Yannick Donnadieu ◽  
Germain Bayon ◽  
Kazuyoshi Moriya ◽  
...  
Keyword(s):  
Late Cretaceous ◽  
Deep Water ◽  
Isotopic Signature ◽  
Water Masses ◽  
Northwestern Pacific ◽  
Pacific Margin ◽  
End Members

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).

Late Cretaceous climatic trends, faunas, and hydrography in Britain and Ireland

1976 ◽  
Vol 113 (2) ◽  
pp. 115-128 ◽  
Author(s):  
R. E. H. Reid
Keyword(s):  
Late Cretaceous ◽  
Upper Cretaceous ◽  
Water Masses ◽  
Relative Distribution ◽  
Isotopic Data ◽  
Climatic Trends

SummaryChanges in the Upper Cretaceous faunas of northeastern Ireland point to rising Cenomanian temperatures, and to progressive falls in temperatures from early Santonian to Maastrichtian times. At first sight, these changes fit the Cretaceous climatic trends claimed from isotopic data; but comparison with faunas seen in England suggests that this fit is illusory. It is suggested that faunas were more directly controlled by the influence of contrasting Atlanto-West Tethyan and Russo-Germanic water masses, and by changes in their relative distribution. Changes seen through the Irish Senonian may reflect the progressive submergence of a Scotland—Pennines barrier, permitting an increasing westward spread of the Russo—Germanic (‘boreal’) water and fauna.

scholarly journals Assessment of the structure and variability of Weddell Sea water masses in distinct ocean reanalysis products

Ocean Science ◽  
2014 ◽  
Vol 10 (3) ◽  
pp. 523-546 ◽  
Author(s):  
T. S. Dotto ◽  
R. Kerr ◽  
M. M. Mata ◽  
M. Azaneu ◽  
I. Wainer ◽  
...  
Keyword(s):  
Deep Water ◽  
Sea Water ◽  
Horizontal Resolution ◽  
Weddell Sea ◽  
Water Masses ◽  
Ocean Reanalysis ◽  
In Situ Data ◽  
Ocean Data Assimilation ◽  
Sea Bottom ◽  
Warm Deep Water

Abstract. We assessed and evaluated the performance of five ocean reanalysis products in reproducing essential hydrographic properties and their associated temporal variability for the Weddell Sea, Antarctica. The products used in this assessment were ECMWF ORAS4 (European Centre for Medium-Range Weather Forecasts Ocean Reanalysis System 4), CFSR (Climate Forecast System Reanalysis), MyOcean UR025.4 (University of Reading), ECCO2 (Estimating the Circulation and Climate of the Ocean, Phase II) and SODA (Simple Ocean Data Assimilation). The present study focuses on the Weddell Sea deep layer, which is composed of the following three main water masses: Warm Deep Water (WDW), Weddell Sea Deep Water (WSDW) and Weddell Sea Bottom Water (WSBW). The MyOcean UR025.4 product provided the most accurate representation of the structure and thermohaline properties of the Weddell Sea water masses when compared with observations. All the ocean reanalysis products analyzed exhibited limited capabilities in representing the surface water masses in the Weddell Sea. The CFSR and ECCO2 products were not able to represent deep water masses with a neutral density ≥ 28.40 kg m−3, which was considered the WSBW's upper limit throughout the simulation period. The expected WDW warming was only reproduced by the SODA product, whereas the ECCO2 product was able to represent the trends in the WSDW's hydrographic properties. All the assessed ocean reanalyses were able to represent the decrease in the WSBW's density, except the SODA product in the inner Weddell Sea. Improvements in parameterization may have as much impact on the reanalyses assessed as improvements in horizontal resolution primarily because the Southern Ocean lacks in situ data, and the data that are currently available are summer-biased. The choice of the reanalysis product should be made carefully, taking into account the performance, the parameters of interest, and the type of physical processes to be evaluated.

scholarly journals Middle Holocene expansion of Pacific Deep Water into the Southern Ocean

2019 ◽  
Vol 117 (2) ◽  
pp. 889-894
Author(s):  
Torben Struve ◽  
David J. Wilson ◽  
Tina van de Flierdt ◽  
Naomi Pratt ◽  
Kirsty C. Crocket
Keyword(s):  
Southern Ocean ◽  
Ocean Circulation ◽  
Deep Water ◽  
Water Masses ◽  
Ocean Dynamics ◽  
Global Ocean ◽  
Circulation System ◽  
The Holocene ◽  
Middle Holocene ◽  
Deep Mixing

The Southern Ocean is a key region for the overturning and mixing of water masses within the global ocean circulation system. Because Southern Ocean dynamics are influenced by the Southern Hemisphere westerly winds (SWW), changes in the westerly wind forcing could significantly affect the circulation and mixing of water masses in this important location. While changes in SWW forcing during the Holocene (i.e., the last ∼11,700 y) have been documented, evidence of the oceanic response to these changes is equivocal. Here we use the neodymium (Nd) isotopic composition of absolute-dated cold-water coral skeletons to show that there have been distinct changes in the chemistry of the Southern Ocean water column during the Holocene. Our results reveal a pronounced Middle Holocene excursion (peaking ∼7,000–6,000 y before present), at the depth level presently occupied by Upper Circumpolar Deep Water (UCDW), toward Nd isotope values more typical of Pacific waters. We suggest that poleward-reduced SWW forcing during the Middle Holocene led to both reduced Southern Ocean deep mixing and enhanced influx of Pacific Deep Water into UCDW, inducing a water mass structure that was significantly different from today. Poleward SWW intensification during the Late Holocene could then have reinforced deep mixing along and across density surfaces, thus enhancing the release of accumulated CO2 to the atmosphere.

scholarly journals The impact of African aridity on the isotopic signature of Atlantic deep waters across the Middle Pleistocene Transition

2012 ◽  
Vol 77 (1) ◽  
pp. 182-191 ◽  
Author(s):  
Bruno Malaizé ◽  
Elsa Jullien ◽  
Amandine Tisserand ◽  
Charlotte Skonieczny ◽  
E. Francis Grousset ◽  
...  
Keyword(s):  
Deep Water ◽  
Benthic Foraminifera ◽  
Environmental Changes ◽  
Phase Relationship ◽  
Isotopic Signature ◽  
Middle Pleistocene ◽  
Time Interval ◽  
Deep Waters ◽  
Time Period ◽  
The Impact

A high resolution analysis of benthic foraminifera as well as of aeolian terrigenous proxies extracted from a 37 m-long marine core located off the Mauritanian margin spanning the last ~ 1.2 Ma, documents the possible link between major continental environmental changes with a shift in the isotopic signature of deep waters around 1.0–0.9 Ma, within the so-called Mid-Pleistocene Transition (MPT) time period. The increase in the oxygen isotopic composition of deep waters, as seen through the benthic foraminifera δ18O values, is consistent with the growth of larger ice sheets known to have occurred during this transition. Deep-water mass δ13C changes, also estimated from benthic foraminifera, show a strong depletion for the same time interval. This drastic change in δ13C values is concomitant with a worldwide 0.3‰ decrease observed in the major deep oceanic waters for the MPT time period. The phase relationship between aeolian terrigeneous signal increase and this δ13C decrease in our record, as well as in other paleorecords, supports the hypothesis of a global aridification amongst others processes to explain the deep-water masses isotopic signature changes during the MPT. In any case, the isotopic shifts imply major changes in the end-member δ18O and δ13C values of deep waters.

Deep water circulation patterns in the Atlantic during MISs 12-11

2020 ◽  
Author(s):  
Jasmin M. Link ◽  
Norbert Frank
Keyword(s):  
North Atlantic ◽  
Deep Water ◽  
Glacial Maximum ◽  
Water Circulation ◽  
Water Masses ◽  
Overturning Circulation ◽  
The Past ◽  
The North ◽  
Circulation Patterns ◽  
The North Atlantic

<p>Glacial Termination V is one of the most extreme glacial-interglacial transitions of the past 800 ka [1]. However, the changes in orbital forcing from Marine Isotope Stage (MIS) 12 to 11 are comparatively weak. In addition, MIS 11c is exceptionally distinct compared to other interglacials with for example a longer duration [2] and a higher-than-present sea level [3] despite a relative low incoming insolation. Therefore, the term “MIS 11 paradox” was coined [4]. However, only little is known about the Atlantic overturning circulation during this time interval [e.g. 5,6].</p><p>Here, we present Atlantic-wide deep water circulation patterns spanning the glacial maximum of MIS 12, Termination V, and MIS 11. Therefore, sediment cores throughout the Atlantic were analyzed regarding their Nd isotopic composition of authigenic coatings to reconstruct the provenance of the prevailing bottom water masses.</p><p>During the glacial maximum of MIS 12, the deep Atlantic Ocean was bathed with a higher amount of southern sourced water compared to the following interglacial. Termination V is represented by a sharp transition in the high-accumulating sites from the North Atlantic with a switch to northern sourced water masses. MIS 11 is characterized through an active deep water formation in the North Atlantic with active overflows from the Nordic Seas, only disrupted by a short deterioration. A strong export of northern sourced water masses to the South Atlantic points to an overall strong overturning circulation.</p><p> </p><p>[1] Lang and Wolff 2011, Climate of the Past 7: 361-380.</p><p>[2] Candy et al. 2014, Earth-Science Reviews 128: 18-51.</p><p>[3] Dutton et al. 2015, Science 349: aaa4019.</p><p>[4] Berger and Wefer 2003, Geophysical Monograph 137: 41-60.</p><p>[5] Dickson et al. 2009, Nature Geoscience 2: 428-433.</p><p>[6] Vázquez Riveiros et al. 2013, EPSL 371-372: 258-268.</p>

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