scholarly journals Mean circulation and EKE distribution in the Labrador Sea Water level of the subpolar North Atlantic

2018 ◽  
Author(s):  
Jürgen Fischer ◽  
Johannes Karstensen ◽  
Marilena Oltmanns ◽  
Sunke Schmidtko
Keyword(s):  
Flow Field ◽  
North Atlantic ◽  
Sea Water ◽  
Labrador Sea ◽  
Mean Flow ◽  
Southern Boundary ◽  
Mapping Algorithms ◽  
Iceland Basin ◽  
Irminger Sea ◽  
Labrador Sea Water

Abstract. A long term mean flow field for the subpolar North Atlantic region with a horizontal resolution of approximately 25 km is created by gridding Argo-derived velocity vectors using two different topography following interpolation schemes. The 10-d float displacements in the typical drift depths of 1000 m to 1500 m represent the flow in the Labrador Sea Water density range. Both mapping algorithms separate the flow field into potential vorticity (PV) conserving, i.e. topography following contribution and a deviating part, which we define as the eddy contribution. To verify the significance of the separation, we compare the mean flow and the eddy kinetic energy (EKE), derived from both mapping algorithms, with those obtained from multiyear mooring observations. The PV-conserving mean flow is characterized by stable boundary currents along all major topographic features including shelf breaks and basin-interior topographic ridges such as the Reykjanes Ridge or the Rockall Plateau. Mid-basin northward advection pathways from the northeastern Labrador Sea into the Irminger Sea and from the Mid Atlantic Ridge region into the Iceland basin are well-resolved. An eastward flow is present across the southern boundary of the subpolar gyre near 52° N, the latitude of the Charlie Gibbs Fracture Zone. The mid-depth EKE field resembles most of the satellite-derived surface EKE field. However, noticeable differences exist along the northward advection pathways in the Irminger Sea and the Iceland basin, where the deep EKE exceeds the surface EKE field. Further, the ratio between mean flow and the square root of the EKE, the Peclet Number, reveals distinct advection-dominated regions as well as basin interior regimes in which mixing is prevailing.

scholarly journals Mean circulation and EKE distribution in the Labrador Sea Water level of the subpolar North Atlantic

Ocean Science ◽  
2018 ◽  
Vol 14 (5) ◽  
pp. 1167-1183 ◽  
Author(s):  
Jürgen Fischer ◽  
Johannes Karstensen ◽  
Marilena Oltmanns ◽  
Sunke Schmidtko
Keyword(s):  
Flow Field ◽  
North Atlantic ◽  
Sea Water ◽  
Labrador Sea ◽  
Mean Flow ◽  
Southern Boundary ◽  
Mapping Algorithms ◽  
Iceland Basin ◽  
Irminger Sea ◽  
Labrador Sea Water

Abstract. A long-term mean flow field for the subpolar North Atlantic region with a horizontal resolution of approximately 25 km is created by gridding Argo-derived velocity vectors using two different topography-following interpolation schemes. The 10-day float displacements in the typical drift depths of 1000 to 1500 m represent the flow in the Labrador Sea Water density range. Both mapping algorithms separate the flow field into potential vorticity (PV) conserving, i.e., topography-following contribution and a deviating part, which we define as the eddy contribution. To verify the significance of the separation, we compare the mean flow and the eddy kinetic energy (EKE), derived from both mapping algorithms, with those obtained from multiyear mooring observations. The PV-conserving mean flow is characterized by stable boundary currents along all major topographic features including shelf breaks and basin-interior topographic ridges such as the Reykjanes Ridge or the Rockall Plateau. Mid-basin northward advection pathways from the northeastern Labrador Sea into the Irminger Sea and from the Mid-Atlantic Ridge region into the Iceland Basin are well-resolved. An eastward flow is present across the southern boundary of the subpolar gyre near 52∘ N, the latitude of the Charlie Gibbs Fracture Zone (CGFZ). The mid-depth EKE field resembles most of the satellite-derived surface EKE field. However, noticeable differences exist along the northward advection pathways in the Irminger Sea and the Iceland Basin, where the deep EKE exceeds the surface EKE field. Further, the ratio between mean flow and the square root of the EKE, the Peclet number, reveals distinct advection-dominated regions as well as basin-interior regimes in which mixing is prevailing.

scholarly journals Ventilation variability of Labrador Sea Water and its impact on oxygen and anthropogenic carbon: a review

2017 ◽  
Vol 375 (2102) ◽  
pp. 20160321 ◽  
Author(s):  
Monika Rhein ◽  
Reiner Steinfeldt ◽  
Dagmar Kieke ◽  
Ilaria Stendardo ◽  
Igor Yashayaev
Keyword(s):  
Time Scales ◽  
North Atlantic ◽  
Sea Water ◽  
Meridional Overturning Circulation ◽  
Labrador Sea ◽  
Southern Boundary ◽  
Rate Of Increase ◽  
Anthropogenic Carbon ◽  
Warming World ◽  
Labrador Sea Water

Ventilation of Labrador Sea Water (LSW) receives ample attention because of its potential relation to the strength of the Atlantic Meridional Overturning Circulation (AMOC). Here, we provide an overview of the changes of LSW from observations in the Labrador Sea and from the southern boundary of the subpolar gyre at 47° N. A strong winter-time atmospheric cooling over the Labrador Sea led to intense and deep convection, producing a thick and dense LSW layer as, for instance, in the early to mid-1990s. The weaker convection in the following years mostly ventilated less dense LSW vintages and also reduced the supply of oxygen. As a further consequence, the rate of uptake of anthropogenic carbon by LSW decreased between the two time periods 1996–1999 and 2007–2010 in the western subpolar North Atlantic. In the eastern basins, the rate of increase in anthropogenic carbon became greater due to the delayed advection of LSW that was ventilated in previous years. Starting in winter 2013/2014 and prevailing at least into winter 2015/2016, production of denser and more voluminous LSW resumed. Increasing oxygen signals have already been found in the western boundary current at 47° N. On decadal and shorter time scales, anomalous cold atmospheric conditions over the Labrador Sea lead to an intensification of convection. On multi-decadal time scales, the ‘cold blob’ in the subpolar North Atlantic projected by climate models in the next 100 years is linked to a weaker AMOC and weaker convection (and thus deoxygenation) in the Labrador Sea. This article is part of the themed issue ‘Ocean ventilation and deoxygenation in a warming world’.

scholarly journals Upper Labrador Sea Water in the Irminger Sea during a weak convection period (2002–2006)

2009 ◽  
Vol 6 (3) ◽  
pp. 2085-2113 ◽  
Author(s):  
E. Louarn ◽  
H. Mercier ◽  
P. Morin ◽  
E. de Boisseson ◽  
S. Bacon
Keyword(s):  
North Atlantic ◽  
Sea Water ◽  
Labrador Sea ◽  
Subpolar Gyre ◽  
Chemical Tracers ◽  
The North ◽  
Irminger Sea ◽  
North Atlantic Subpolar Gyre ◽  
Physical And Chemical ◽  
Labrador Sea Water

Abstract. Four cruises between 2002 and 2006 sampled physical and chemical tracers in the southern Irminger Sea during the period of weak convection in the North Atlantic Subpolar Gyre. The upper Labrador Sea Water (uLSW) shows complex and time variable patterns reflecting different formation sites: Irminger Sea, South Greenland and Labrador Sea.

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.

Spreading of Labrador Sea Water in the eastern North Atlantic

1998 ◽  
Vol 103 (C5) ◽  
pp. 10223-10239 ◽  
Author(s):  
Jérôme Paillet ◽  
Michel Arhan ◽  
Michael S. McCartney
Keyword(s):  
North Atlantic ◽  
Sea Water ◽  
Labrador Sea ◽  
Eastern North Atlantic ◽  
Labrador Sea Water

scholarly journals Cold-water corals in the Subpolar North Atlantic Ocean exposed to aragonite undersaturation if Paris 2 ºC is not met

2021 ◽  
Author(s):  
Maribel I. García-Ibáñez ◽  
Nicholas R. Bates ◽  
Dorothee C.E. Bakker ◽  
Marcos Fontela ◽  
Antón Velo
Keyword(s):  
Atlantic Ocean ◽  
Water Column ◽  
North Atlantic ◽  
Cold Water ◽  
Sea Water ◽  
North Atlantic Ocean ◽  
Labrador Sea ◽  
Entire Water Column ◽  
Intermediate Waters ◽  
Labrador Sea Water

<p>The uptake of carbon dioxide (CO<sub>2</sub>) from the atmosphere is changing the ocean’s chemical state. Such changes, commonly known as ocean acidification, include reduction in pH and the carbonate ion concentration ([CO<sub>3</sub><sup>2-</sup>]), which in turn lowers oceanic saturation states (Ω) for calcium carbonate (CaCO<sub>3</sub>) minerals. The Ω values for aragonite (Ω<sub>aragonite</sub>; one of the main CaCO<sub>3</sub> minerals formed by marine calcifying organisms) influence the calcification rate and geographic distribution of cold-water corals (CWCs), important for biodiversity. In this work we use high-quality data of inorganic carbon measurements, collected on thirteen cruises along the same track during 1991–2018, to determine the long-term trends in Ω<sub>aragonite</sub> in the Irminger and Iceland Basins of the North Atlantic Ocean, providing the first trends of Ω<sub>aragonite</sub> in the deep waters of these basins. The entire water column of both basins showed significant negative Ω<sub>aragonite</sub> trends between -0.0015 ± 0.0002 and -0.0061 ± 0.0016 per year. The decrease in Ω<sub>aragonite</sub> in the intermediate waters, where nearly half of the CWC reefs of the study region are located, caused the Ω<sub>aragonite</sub> isolines to migrate upwards rapidly at a rate between 6 and 34 m per year. The main driver of the observed decline in Ω<sub>aragonite</sub> in the Irminger and Iceland Basins was the increase in anthropogenic CO<sub>2</sub>. But this was partially offset by increases in salinity (in Subpolar Mode Water), enhanced ventilation (in upper Labrador Sea Water) and increases in alkalinity (in classical Labrador Sea Water, cLSW; and overflow waters). We also found that water mass aging reinforced the Ω<sub>aragonite</sub> decrease in cLSW. Based on the observed Ω<sub>aragonite</sub> trends, we project that the entire water column of the Irminger and Iceland Basins will likely be undersaturated for aragonite when in equilibrium with an atmospheric mole fraction of CO<sub>2</sub> (xCO<sub>2</sub>) of ~860 ppmv, corresponding to climate model projections for the end of the century based on the highest CO<sub>2</sub> emission scenarios. However, intermediate waters will likely be aragonite undersaturated when in equilibrium with an atmospheric xCO<sub>2</sub> of ~600 ppmv, an xCO<sub>2</sub> level slightly above that corresponding to 2 ºC warming, thus exposing CWCs inhabiting the intermediate waters to undersaturation for aragonite.</p>

Instabilities in the Labrador Sea water mass structure during the last climatic cycle

2000 ◽  
Vol 37 (5) ◽  
pp. 795-809 ◽  
Author(s):  
Claude Hillaire-Marcel ◽  
Guy Bilodeau
Keyword(s):  
North Atlantic ◽  
Water Mass ◽  
Sea Water ◽  
Labrador Sea ◽  
Benthic Species ◽  
Globigerina Bulloides ◽  
Neogloboquadrina Pachyderma ◽  
The North ◽  
The North Atlantic ◽  
Labrador Sea Water

In the modern Labrador Sea, the North Atlantic deep water components are found below the ~2 km deep, intermediate Labrador Sea water (LSW) mass, which is renewed locally through winter convective mixing. This water mass structure remained relatively stable since ~9.5 14C ka BP, as indicated by isotopic studies of foraminifer assemblages from deep-sea cores. Almost constant differences in δ18O values are observed between major species. These average -0.5‰ between the epipelagic species Globigerina bulloides and the mesopelagic species Neogloboquadrina pachyderma, left coiled, and -1‰ between Neogloboquadrina pachyderma and the benthic species Cibicides wuellerstorfi, after correction for Cibicides wuellerstorfi specific fractionation. These isotopic compositions represent thermohaline conditions in surface waters, in the pycnocline with the LSW, and in the deep component of the North Atlantic deep water, respectively. A drastically different structure characterized the glacial Labrador Sea. Differences in δ18O values of ~ -2 to -2.5‰ are then observed between Globigerina bulloides and benthic species, indicative of a strong halocline between the corresponding water masses, thus for reduced production of intermediate waters. During the same interval, Neogloboquadrina pachyderma shows 13C and 18O fluctuations of 1 to 1.5‰ amplitude, in phase with Heinrich-Bond events and higher frequency climate oscillations. The δ18O values in Neogloboquadrina pachyderma vary between those of Globigerina bulloides and of benthic foraminifers, suggesting large amplitude bathymetric fluctuations of the halo-thermocline above and below the bathymetric range occupied by Neogloboquadrina pachyderma. Minimum δ18O values in Neogloboquadrina pachyderma match intervals of maximum ice rafting deposition, such as the late Heinrich events, thus intervals with a deeper, more dilute buoyant surface water layer.

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