Deep water composition and water mass mixing in the Paleogene North Atlantic; Results from the Newfoundland ridges

2014 ◽  
Vol 31 ◽  
pp. 193-194
Author(s):  
Howie D. Scher
Keyword(s):  
North Atlantic ◽  
Deep Water ◽  
Water Mass ◽  
Water Composition

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 Tracking water masses using passive-tracer transport in NEMO v3.4 with NEMOTAM: application to North Atlantic Deep Water and North Atlantic Subtropical Mode Water

2019 ◽  
Author(s):  
Dafydd Stephenson ◽  
Simon Müller ◽  
Florian Sévellec
Keyword(s):  
North Atlantic ◽  
Deep Water ◽  
Water Mass ◽  
North Atlantic Deep Water ◽  
The Arctic ◽  
Global Ocean ◽  
Passive Tracer ◽  
Tracer Transport ◽  
Mode Water ◽  
Subtropical Mode Water

Abstract. Water mass ventilation provides an important link between the atmosphere and the global ocean circulation. In this study, we present a newly developed, probabilistic tool for offline water mass tracking. In particular, NEMOTAM, the tangent-linear and adjoint counterpart to the NEMO ocean general circulation model, is modified to allow passive-tracer transport. By terminating dynamic feedbacks in NEMOTAM, tagged water can be tracked forward and backwards in time as a passive dye, producing a probability distribution of pathways and origins, respectively. Upon contact with the surface, the tracer is removed from the system, and a record of ventilation is produced. Two test cases are detailed, examining the creation and fate of North Atlantic Subtropical Mode Water (NASMW) and North Atlantic Deep Water (NADW) in a 2&degree; configuration of NEMO run with repeated annual forcing for up to 400 years. NASMW is shown to have an expected age of 4.5 years, and is predominantly eradicated by internal processes. A bed of more persistent NASMW is detected below the mixed layer with an expected age of 8.7 years It is shown that while model NADW has two distinct outcrops (in the Arctic and North Atlantic), its formation primarily takes place in the subpolar Labrador and Irminger seas. Its expected age is 112 years.

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 Tracking water masses using passive-tracer transport in NEMO v3.4 with NEMOTAM: application to North Atlantic Deep Water and North Atlantic Subtropical Mode Water

2020 ◽  
Vol 13 (4) ◽  
pp. 2031-2050
Author(s):  
Dafydd Stephenson ◽  
Simon A. Müller ◽  
Florian Sévellec
Keyword(s):  
North Atlantic ◽  
Deep Water ◽  
Water Mass ◽  
North Atlantic Deep Water ◽  
The Arctic ◽  
Global Ocean ◽  
Passive Tracer ◽  
Tracer Transport ◽  
Mode Water ◽  
Subtropical Mode Water

Abstract. Water mass ventilation provides an important link between the atmosphere and the global ocean circulation. In this study, we present a newly developed, probabilistic tool for offline water mass tracking. In particular, NEMOTAM, the tangent-linear and adjoint counterpart to the NEMO ocean general circulation model, is modified to allow passive-tracer transport. By terminating dynamic feedbacks in NEMOTAM, tagged water can be tracked forward and backward in time as a passive dye, producing a probability distribution of pathways and origins, respectively. To represent surface (re-)ventilation, we optionally decrease the tracer concentration in the surface layer and track this concentration removal to produce a ventilation record. Two test cases are detailed, examining the creation and fate of North Atlantic Subtropical Mode Water (NASMW) and North Atlantic Deep Water (NADW) in a 2∘ configuration of NEMO run with repeated annual forcing for up to 400 years. Model NASMW is shown to have an expected age of 4.5 years and is predominantly eradicated by internal processes. A bed of more persistent NASMW is detected below the mixed layer with an expected age of 8.7 years. It is shown that while model NADW has two distinct outcrops (in the Arctic and North Atlantic), its formation primarily takes place in the subpolar Labrador and Irminger seas. Its expected age is 112 years.

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