scholarly journals Deep water circulation in the Hunter Channel (Southwest Atlantic) in a late Pleistocene and Holocene by benthonic foraminifera

2019 ◽  
Vol 59 (1) ◽  
pp. 133-142
Author(s):  
N. P. Lukashina
Keyword(s):  
Late Pleistocene ◽  
Deep Water ◽  
Sea Water ◽  
Bottom Layer ◽  
Water Circulation ◽  
Southwest Atlantic ◽  
East Part ◽  
The North ◽  
Lower Circumpolar Deep Water ◽  
Argentine Basin

Was reconstructed deep-sea water circulation near the Hunter Channel (Rio Grande Rise – South-West Atlantic) in a late Pleistocene and Holocene (MIS 4-MIS 1) by benthonic foraminifera. Was studied three cores of bottom sediment. Now moves the upper North Atlantic deep water (NADW) through the Hunter Channel from the North to the South. The lower NADW in the same direction came in MIS 2 and in MIS 4. There was the lower Circumpolar deep water (CPDW), NADW and Antarctic bottom water (AnBW) in MIS 3 periodically. CPDW prevail in a near bottom layer and in Holocene and in the late Pleistocene before the Hunter Channel sidewise the Argentine Basin. So in the Hunter Channel and on the way to it from south side for all studied period AnBW was almost not. Dissolution of carbonates during the Holocene happens in the deepest east part of the Hunter Channel. In Ice Ages processes of dissolution amplified and affected east part of the channel. Dissolution happen and happened not at the expense of AnBW, and at the expense of NADW which becomes there aggressive in relation to a calcium carbonate.

Identification and quantification of the North Atlantic Deep Water pathways

2021 ◽  
Author(s):  
Philippe Miron ◽  
Maria J. Olascoaga ◽  
Francisco J. Beron-Vera ◽  
Kimberly L. Drouin ◽  
M. Susan Lozier
Keyword(s):  
North Atlantic ◽  
Deep Water ◽  
Sea Water ◽  
Lower Layer ◽  
North Atlantic Deep Water ◽  
Meridional Overturning Circulation ◽  
Labrador Sea ◽  
Western Boundary ◽  
The North ◽  
The North Atlantic

<p>The North Atlantic Deep Water (NADW) flows equatorward along the Deep Western Boundary Current (DWBC) as well as interior pathways and is a critical part of the Atlantic Meridional Overturning Circulation. Its upper layer, the Labrador Sea Water (LSW), is formed by open-ocean deep convection in the Labrador and Irminger Seas while its lower layers, the Iceland–Scotland Overflow Water (ISOW) and the Denmark Strait Overflow Water (DSOW), are formed north of the Greenland–Iceland–Scotland Ridge.</p><p>In recent years, more than two hundred acoustically-tracked subsurface floats have been deployed in the deep waters of the North Atlantic.  Studies to date have highlighted water mass pathways from launch locations, but due to limited float trajectory lengths, these studies have been unable to identify pathways connecting  remote regions.</p><p>This work presents a framework to explore deep water pathways from their respective sources in the North Atlantic using Markov Chain (MC) modeling and Transition Path Theory (TPT). Using observational trajectories released as part of OSNAP and the Argo projects, we constructed two MCs that approximate the lower and upper layers of the NADW Lagrangian dynamics. The reactive NADW pathways—directly connecting NADW sources with a target at 53°N—are obtained from these MCs using TPT.</p><p>Preliminary results show that twenty percent more pathways of the upper layer(LSW) reach the ocean interior compared to  the lower layer (ISOW, DSOW), which mostly flows along the DWBC in the subpolar North Atlantic. Also identified are the Labrador Sea recirculation pathways to the Irminger Sea and the direct connections from the Reykjanes Ridge to the eastern flank of the Mid–Atlantic Ridge, both previously observed. Furthermore, we quantified the eastern spread of the LSW to the area surrounding the Charlie–Gibbs Fracture Zone and compared it with previous analysis. Finally, the residence time of the upper and lower layers are assessed and compared to previous observations.</p>

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>

scholarly journals Oxygen export to the deep ocean following Labrador Sea Water formation

2021 ◽  
Author(s):  
Jannes Koelling ◽  
Dariia Atamanchuk ◽  
Johannes Karstensen ◽  
Patricia Handmann ◽  
Douglas W. R. Wallace
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
Deep Water ◽  
Sea Water ◽  
Deep Ocean ◽  
Water Layer ◽  
Labrador Sea ◽  
Boundary Current ◽  
The North ◽  
Deep Water Layer

Abstract. The Labrador Sea in the North Atlantic Ocean is one of the few regions globally where oxygen from the atmosphere can reach the deep ocean directly. This is the result of wintertime convection, which homogenizes the water column to a depth of up to 2000 m, and brings deep water undersaturated in oxygen into contact with the atmosphere. In this study, we analyze how the intense oxygen uptake during Labrador Sea Water (LSW) formation affects the properties of the outflowing deep western boundary current, which ultimately feeds the upper part of the North Atlantic Deep Water layer in much of the Atlantic Ocean. Seasonal cycles of oxygen concentration, temperature, and salinity from a two-year time series collected by sensors moored at 600 m nominal depth in the outflowing boundary current at 53° N show that LSW is primarily exported in the months following the onset of convection, from March to August. During the rest of the year, properties of the outflow resemble those of Irminger Water, which enters the basin with the boundary current from the Irminger Sea. The input of newly ventilated LSW increases the oxygen concentration from 298 μmol L−1 in January to a maximum of 306 μmol L−1 in April. As a result of this LSW input, 1.57 × 1012 mol year−1 of oxygen are added to the outflowing boundary current, mostly during summer, equivalent to 49 % of the wintertime uptake from the atmosphere in the interior of the basin. The export of oxygen from the subpolar gyre associated with this direct southward pathway of LSW is estimated to supply about 71 % of the oxygen consumed annually in the upper North Atlantic Deep Water layer in the Atlantic Ocean between the equator and 50° N. Our results show that the formation of LSW is important for replenishing oxygen to the deep oceans, meaning that possible changes in its formation rate and ventilation due to climate change could have wide-reaching impacts on marine life.

scholarly journals Water masses in the Atlantic Ocean: characteristics and distributions

Ocean Science ◽  
2021 ◽  
Vol 17 (2) ◽  
pp. 463-486
Author(s):  
Mian Liu ◽  
Toste Tanhua
Keyword(s):  
Atlantic Ocean ◽  
Deep Water ◽  
Bottom Water ◽  
Water Mass ◽  
Sea Water ◽  
Weddell Sea ◽  
Water Masses ◽  
Global Ocean ◽  
Intermediate Water ◽  
The North

Abstract. A large number of water masses are presented in the Atlantic Ocean, and knowledge of their distributions and properties is important for understanding and monitoring of a range of oceanographic phenomena. The characteristics and distributions of water masses in biogeochemical space are useful for, in particular, chemical and biological oceanography to understand the origin and mixing history of water samples. Here, we define the characteristics of the major water masses in the Atlantic Ocean as source water types (SWTs) from their formation areas, and map out their distributions. The SWTs are described by six properties taken from the biased-adjusted Global Ocean Data Analysis Project version 2 (GLODAPv2) data product, including both conservative (conservative temperature and absolute salinity) and non-conservative (oxygen, silicate, phosphate and nitrate) properties. The distributions of these water masses are investigated with the use of the optimum multi-parameter (OMP) method and mapped out. The Atlantic Ocean is divided into four vertical layers by distinct neutral densities and four zonal layers to guide the identification and characterization. The water masses in the upper layer originate from wintertime subduction and are defined as central waters. Below the upper layer, the intermediate layer consists of three main water masses: Antarctic Intermediate Water (AAIW), Subarctic Intermediate Water (SAIW) and Mediterranean Water (MW). The North Atlantic Deep Water (NADW, divided into its upper and lower components) is the dominating water mass in the deep and overflow layer. The origin of both the upper and lower NADW is the Labrador Sea Water (LSW), the Iceland–Scotland Overflow Water (ISOW) and the Denmark Strait Overflow Water (DSOW). The Antarctic Bottom Water (AABW) is the only natural water mass in the bottom layer, and this water mass is redefined as Northeast Atlantic Bottom Water (NEABW) in the north of the Equator due to the change of key properties, especially silicate. Similar with NADW, two additional water masses, Circumpolar Deep Water (CDW) and Weddell Sea Bottom Water (WSBW), are defined in the Weddell Sea region in order to understand the origin of AABW.

Characteristics of Temperature and Salinity Distribution in the Wonorejo Estuary, Surabaya, Based on Field Measurement

2017 ◽  
Vol 862 ◽  
pp. 102-106
Author(s):  
Anita Diah Pahlewi ◽  
Suntoyo ◽  
Wahyudi ◽  
Muhammad Taufik
Keyword(s):  
Fresh Water ◽  
Sea Water ◽  
Vertical Mixing ◽  
Pollutant Dispersion ◽  
Bottom Layer ◽  
Water Area ◽  
Water Circulation ◽  
Salinity Distribution ◽  
Salinity Increase ◽  
Longitudinal Position

Wonorejo waters have a significant value, both economically and socially. One of ecosystem that have close relationships with Wonorejo waters is Estuary. Temperature and salinity have role in water circulation, where the water circulation have impact to some organism distribution and pollutant dispersion. The purpose of this study is to investigate the characteristic of temperature and salinity distribution in Wonorejo Estuary body’s water. Furthermore, it can be used for determining the type of Wonorejo Estuary. The observation has been done at Wonorejo Estuary in August 2015 to measure the vertical and horizontal temperature and salinity distribution. The measurement of temperature and salinity used Conductivity, Salinity, Temperature tool by YSI. The result show that commonly the temperature and salinity vertical profile are almost similar from surface layer until the bottom layer. But they have trend where the salinity increase, while the temperature decrease to the water depth. There is no thermocline layer due to the shallow water area, it is so from the upper layer until the bottom layer still influenced by dragforce and the vertical mixing between fresh water and sea water occurs. The horizontal temperature distribution in the open sea surface tend to zonation, which is not depend to longitudinal position. The salinity value in each depth are not change obviously indicate that there is a vertical well mixed between fresh water and sea water.

scholarly journals Middle-late Pleistocene deep water circulation in the southwest subtropical Pacific

2009 ◽  
Vol 24 (4) ◽  
Author(s):  
T. Russon ◽  
M. Elliot ◽  
C. Kissel ◽  
G. Cabioch ◽  
P. De Deckker ◽  
...  
Keyword(s):  
Late Pleistocene ◽  
Deep Water ◽  
Water Circulation

scholarly journals Upwellings and water circulation of the north-western shelf of the Black Sea in the summer of 2017

2019 ◽  
pp. 105-114
Author(s):  
Yu. I. Popov ◽  
A. V. Matveev
Keyword(s):  
Black Sea ◽  
Coastal Upwelling ◽  
Sea Water ◽  
Water Circulation ◽  
Abnormal Development ◽  
The Black Sea ◽  
Landsat 8 ◽  
Summer Circulation ◽  
The North ◽  
North Western

On the basis of satellite and field atmospheric and marine observations, the water circulation processes of the north-western shelf (the NWS) of the Black Sea in the summer of 2017 were studied. The study indicated high stability of summer offshore winds of northern and north-northwest directions and 12 cases of coastal upwelling. Three cases of upwelling were instrumentally detected on the across-the-shore oceanographic sections during seasonal field works performed by the oceanographic unit of the branch “Odesa Area of State Hydrographic Service” of the state institution "State Hydrographic Service of Ukraine (SHSU)". The increase of coastal water density led to an abnormally active transfer along the coast of the Danube-Dniester interfluve area to the northernmost parts of the NWS. In 2017 a visual manifestation of anticyclonic character of summer circulation of the NWS's water could be observed. The obtained data confirm the previous conclusions on frequent cases of change in summer periods of traditional cyclonic water circulation to the anticyclonic one. The abnormal development of the summer circulation regime allowed us to record for the first time the transfer of coccolithophores phytoplankton from the open sea to the northern regions of the NWS and to reveal its intraseasonal spatial transformation and development process duration. In the seaward part of the Gulf of Odessa a frequently repeated vortex formation of cyclonic vorticity with spatial dimensions of up to 7-8 miles and orbital velocities, according to the presented data, of 0.12–0.18 m.c-1, and according to the latest field work, of over 0.30 m.c-1, was found. When analyzing the considered situations associated with transfer and vorticity of sea water a significant role was played by high-resolution visual images obtained from Sentinel-2 and Landsat-8 satellites having a spatial resolution of 10 and 30 meters respectively, as well as by similar satellites of earlier modifications.

Deep flow in the Madagascar–Mascarene Basin over the last 150000 years

2005 ◽  
Vol 363 (1826) ◽  
pp. 81-99 ◽  
Author(s):  
I. N. McCave ◽  
T. Kiefer ◽  
D. J. R. Thornalley ◽  
H. Elderfield
Keyword(s):  
Southern Ocean ◽  
Water Flow ◽  
Deep Water ◽  
Last Interglacial ◽  
Circumpolar Deep Water ◽  
The North ◽  
Bottom Waters ◽  
Lower Circumpolar Deep Water ◽  
Sw Indian Ocean ◽  
Fast Flow

The SW Indian Ocean contains at least four layers of water masses with different sources: deep Antarctic (Lower Circumpolar Deep Water) flow to the north, midwater North Indian Deep Water flow to the south and Upper Circumpolar Deep Water to the north, meridional convergence of intermediate waters at 500–1500 m, and the shallow South Equatorial Current flowing west. Sedimentation rates in the area are rather low, being less than 1 cm ka −1 on Madagascar Ridge, but up to 4 cm ka −1 at Amirante Passage. Bottom flow through the Madagascar–Mascarene Basin into Amirante Passage varies slightly on glacial–interglacial time–scales, with faster flow in the warm periods of the last interglacial and minima in cold periods. Far more important are the particularly high flow rates, inferred from silt grain size, which occur at warm–to–cold transitions rather than extrema. This suggests the cause is changing density gradient driving a transiently fast flow. Corroboration is found in the glacial–interglacial range of benthic d 18 O which is ca. 2%, suggesting water close to freezing and at least 1.2 more saline and thus more dense glacial bottom waters than present. Significant density steps are inferred in isotope stage 6, the 5e–5d, and 5a–4 transitions. Oxygen isotope data suggest little change by mixing in glacial bottom water on their northward path. Benthic carbon isotope ratios at Amirante Passage differ from glacial Southern Ocean values, due possibly to absence of a local productivity effect present in the Southern Ocean.

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.

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