scholarly journals Aluminium in the North Atlantic Ocean and the Labrador Sea (GEOTRACES GA01 section): roles of continental inputs and biogenic particle removal

2018 ◽  
Vol 15 (16) ◽  
pp. 5271-5286 ◽  
Author(s):  
Jan-Lukas Menzel Barraqueta ◽  
Christian Schlosser ◽  
Hélène Planquette ◽  
Arthur Gourain ◽  
Marie Cheize ◽  
...  
Keyword(s):  
Surface Water ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Aerosol Deposition ◽  
Labrador Sea ◽  
Particle Removal ◽  
Ice Melt ◽  
The North ◽  
Glacial Flour ◽  
The North Atlantic

Abstract. The distribution of dissolved aluminium (dAl) in the water column of the North Atlantic and Labrador Sea was studied along GEOTRACES section GA01 to unravel the sources and sinks of this element. Surface water dAl concentrations were low (median of 2.5 nM) due to low aerosol deposition and removal by biogenic particles (i.e. phytoplankton cells). However, surface water dAl concentrations were enhanced on the Iberian and Greenland shelves (up to 30.9 nM) due to continental inputs (rivers, glacial flour, and ice melt). Dissolved Al in surface waters scaled negatively with chlorophyll a and biogenic silica (opal) concentrations. The abundance of diatoms exerted a significant (p<0.01) control on the surface particulate Al (pAl) to dAl ratios by decreasing dAl levels and increasing pAl levels. Dissolved Al concentrations generally increased with depth and correlated strongly with silicic acid (R2>0.76) west of the Iberian Basin, suggesting net release of dAl at depth during remineralization of sinking opal-containing particles. Enrichment of dAl at near-bottom depths was observed due to the resuspension of sediments. The highest dAl concentrations (up to 38.7 nM) were observed in Mediterranean Outflow Waters, which act as a major source of dAl to mid-depth waters of the eastern North Atlantic. This study clearly shows that the vertical and lateral distributions of dAl in the North Atlantic differ when compared to other regions of the Atlantic and global oceans. Responsible for these large inter- and intra-basin differences are the large spatial variabilities in the main Al source, atmospheric deposition, and the main Al sink, particle scavenging by biogenic particles.

scholarly journals Aluminium in the North Atlantic Ocean and the Labrador Sea (GEOTRACES GA01 section): roles of continental inputs and biogenic particle removal

2018 ◽  
Author(s):  
Jan-Lukas Menzel Barraqueta ◽  
Christian Schlosser ◽  
Hélène Planquette ◽  
Arthur Gourain ◽  
Marie Cheize ◽  
...  
Keyword(s):  
Surface Water ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Aerosol Deposition ◽  
Global Ocean ◽  
Labrador Sea ◽  
Particle Removal ◽  
Biogenic Opal ◽  
The North ◽  
The North Atlantic

Abstract. The distribution of dissolved aluminium (dAl) in the water column of the North Atlantic and Labrador Sea was studied along GEOTRACES section GA01 to unravel the sources and sinks of this element. Surface water dAl concentrations were low (median of 2.5 nM) due to low aerosol deposition and removal by phytoplankton. However, surface water dAl concentrations were enhanced on the Iberian and Greenland shelves (up to 30.9 nM) due to continental inputs (rivers, glacial flour and ice melt). A negative correlation was observed between dAl in surface waters and primary production, phytoplankton community structure and biogenic opal production. The abundance of diatoms exerted a significant (p  0.76) west of the Iberian Basin, suggesting net release of dAl at depth during remineralization of sinking biogenic opal containing particles. Enrichment of dAl at near-bottom depths was observed due to resuspension of sediments near the sediment-water interface. The highest dAl (up to 38.7 nM) concentrations were observed in Mediterranean Overflow Waters which act as a major source of dAl to mid depth waters of the eastern North Atlantic. This study clearly shows that the vertical and lateral distribution of dAl in the North Atlantic differs when compared to other regions of the North Atlantic and global ocean due to the large spatial differences both in the main source of Al, atmospheric deposition, and the main sink for Al, particle scavenging, between different oceanic regions.

scholarly journals Dissolved iron in the North Atlantic Ocean and Labrador Sea along the GEOVIDE section (GEOTRACES section GA01)

2018 ◽  
Author(s):  
Manon Tonnard ◽  
Hélène Planquette ◽  
Andrew R. Bowie ◽  
Pier van der Merwe ◽  
Morgane Gallinari ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
Sea Water ◽  
North Atlantic Ocean ◽  
Deep Convection ◽  
Labrador Sea ◽  
Intermediate Water ◽  
The North ◽  
Irminger Sea ◽  
The North Atlantic

Abstract. Dissolved Fe (DFe) samples from the GEOVIDE voyage (GEOTRACES GA01, May–June 2014) in the North Atlantic Ocean were analysed using a SeaFAST-picoTM coupled to an Element XR HR-ICP-MS and provided interesting insights on the Fe sources in this area. Overall, DFe concentrations ranged from 0.09 ± 0.01 nmol L−1 to 7.8 ± 0.5 nmol L−1. Elevated DFe concentrations were observed above the Iberian, Greenland and Newfoundland Margins likely due to riverine inputs from the Tagus River, meteoric water inputs and sedimentary inputs. Air-sea interactions were suspected to be responsible for the increase in DFe concentrations within subsurface waters of the Irminger Sea due to deep convection occurring the previous winter, that provided iron-to-nitrate ratios sufficient to sustain phytoplankton growth. Increasing DFe concentrations along the flow path of the Labrador Sea Water were attributed to sedimentary inputs from the Newfoundland Margin. Bottom waters from the Irminger Sea displayed high DFe concentrations likely due to the dissolution of Fe-rich particles from the Denmark Strait Overflow Water and the Polar Intermediate Water. Finally, the nepheloid layers were found to act as either a source or a sink of DFe depending on the nature of particles.

scholarly journals The silicon stable isotope distribution along the GEOVIDE section (GEOTRACES GA-01) of the North Atlantic Ocean

2018 ◽  
Vol 15 (18) ◽  
pp. 5663-5676 ◽  
Author(s):  
Jill N. Sutton ◽  
Gregory F. de Souza ◽  
Maribel I. García-Ibáñez ◽  
Christina L. De La Rocha
Keyword(s):  
Stable Isotope ◽  
Atlantic Ocean ◽  
North Atlantic ◽  
Deep Water ◽  
North Atlantic Ocean ◽  
Water Masses ◽  
Labrador Sea ◽  
The North ◽  
The North Atlantic ◽  
Eastern North Atlantic

Abstract. The stable isotope composition of dissolved silicon in seawater (δ30SiDSi) was examined at 10 stations along the GEOVIDE section (GEOTRACES GA-01), spanning the North Atlantic Ocean (40–60∘ N) and Labrador Sea. Variations in δ30SiDSi below 500 m were closely tied to the distribution of water masses. Higher δ30SiDSi values are associated with intermediate and deep water masses of northern Atlantic or Arctic Ocean origin, whilst lower δ30SiDSi values are associated with DSi-rich waters sourced ultimately from the Southern Ocean. Correspondingly, the lowest δ30SiDSi values were observed in the deep and abyssal eastern North Atlantic, where dense southern-sourced waters dominate. The extent to which the spreading of water masses influences the δ30SiDSi distribution is marked clearly by Labrador Sea Water (LSW), whose high δ30SiDSi signature is visible not only within its region of formation within the Labrador and Irminger seas, but also throughout the mid-depth western and eastern North Atlantic Ocean. Both δ30SiDSi and hydrographic parameters document the circulation of LSW into the eastern North Atlantic, where it overlies southern-sourced Lower Deep Water. The GEOVIDE δ30SiDSi distribution thus provides a clear view of the direct interaction between subpolar/polar water masses of northern and southern origin, and allow examination of the extent to which these far-field signals influence the local δ30SiDSi distribution.

The mid-Cretaceous succession of Orphan Knoll (northwest Atlantic): micropalaeontology and palaeo-oceanographic implications

1976 ◽  
Vol 13 (10) ◽  
pp. 1411-1421 ◽  
Author(s):  
Malcolm B. Hart
Keyword(s):  
Surface Water ◽  
Atlantic Ocean ◽  
North Atlantic ◽  
World Wide ◽  
North Atlantic Ocean ◽  
Water Circulation ◽  
Northwest Atlantic ◽  
The North ◽  
The North Atlantic

Micropalaeontological investigation of the mid-Cretaceous succession (Albian–Cenomanian) of Orphan Knoll (northwest Atlantic Ocean) has allowed direct stratigraphic comparison with successions of a similar age elsewhere in the area of the North Atlantic Ocean. The microfaunal evidence presently available suggests a major world-wide eustatic change in the mid-Cenomanian, together with associated changes in the surface water circulation of the Cretaceous North Atlantic Ocean.

scholarly journals Temperature domination of AMOC weakening due to freshwater hosing in two GCMs

2019 ◽  
Vol 54 (1-2) ◽  
pp. 273-286 ◽  
Author(s):  
Rosalind K. Haskins ◽  
Kevin I. C. Oliver ◽  
Laura C. Jackson ◽  
Richard A. Wood ◽  
Sybren S. Drijfhout
Keyword(s):  
North Atlantic ◽  
Climate Models ◽  
North Atlantic Ocean ◽  
Global Climate ◽  
Mixed Layer Depth ◽  
Global Climate Models ◽  
Meridional Overturning Circulation ◽  
Ice Melt ◽  
The North ◽  
The North Atlantic

Abstract Anthropogenic climate change is projected to lead to a weakening of the Atlantic meridional overturning circulation (AMOC). One of the mechanisms contributing to this is ice melt leading to a freshening of the North Atlantic Ocean. We use two global climate models to investigate the role of temperature and salinity in the weakening of the AMOC resulting from freshwater forcing. This study finds that freshwater hosing reduces the strength of the AMOC, but in some situations it is not through reduced density from freshening, but a reduction in density from subsurface warming. When the freshwater is mixed down it directly reduces the density of the North Atlantic, weakening the strength of the AMOC. As the AMOC weakens, the mixed layer depth reduces and surface properties are less effectively mixed down. A buoyant surface cap forms, blocking atmospheric fluxes. This leads to the development of a warm anomaly beneath the surface cap, which becomes the primary driver of AMOC weakening. We found that the mean North Atlantic salinity anomaly can be used as a proxy for AMOC weakening because it describes the extent of this surface cap.

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