Labrador Sea Water in the Eastern North Atlantic. Part I: A Synoptic Circulation Inferred from a Minimum in Potential Vorticity

1995 ◽  
Vol 25 (4) ◽  
pp. 649-665 ◽  
Author(s):  
Stuart A. Cunningham ◽  
Thomas W. N. Haine
Keyword(s):  
North Atlantic ◽  
Potential Vorticity ◽  
Sea Water ◽  
Labrador Sea ◽  
Eastern North Atlantic ◽  
Synoptic Circulation ◽  
Labrador Sea Water

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 Changes in the CFC Inventories and Formation Rates of Upper Labrador Sea Water, 1997–2001

2006 ◽  
Vol 36 (1) ◽  
pp. 64-86 ◽  
Author(s):  
Dagmar Kieke ◽  
Monika Rhein ◽  
Lothar Stramma ◽  
William M. Smethie ◽  
Deborah A. LeBel ◽  
...  
Keyword(s):  
North Atlantic ◽  
Large Scale ◽  
Sea Water ◽  
North Atlantic Ocean ◽  
Formation Rate ◽  
Labrador Sea ◽  
The North ◽  
The Mean ◽  
Eastern North Atlantic ◽  
Labrador Sea Water

Abstract Chlorofluorocarbon (component CFC-11) and hydrographic data from 1997, 1999, and 2001 are presented to track the large-scale spreading of the Upper Labrador Sea Water (ULSW) in the subpolar gyre of the North Atlantic Ocean. ULSW is CFC rich and comparatively low in salinity. It is located on top of the denser “classical” Labrador Sea Water (LSW), defined in the density range σΘ = 27.68–27.74 kg m−3. It follows spreading pathways similar to LSW and has entered the eastern North Atlantic. Despite data gaps, the CFC-11 inventories of ULSW in the subpolar North Atlantic (40°–65°N) could be estimated within 11%. The inventory increased from 6.0 ± 0.6 million moles in 1997 to 8.1 ± 0.6 million moles in 1999 and to 9.5 ± 0.6 million moles in 2001. CFC-11 inventory estimates were used to determine ULSW formation rates for different periods. For 1970–97, the mean formation rate resulted in 3.2–3.3 Sv (Sv ≡ 106 m3 s−1). To obtain this estimate, 5.0 million moles of CFC-11 located in 1997 in the ULSW in the subtropical/tropical Atlantic were added to the inventory of the subpolar North Atlantic. An estimate of the mean combined ULSW/LSW formation rate for the same period gave 7.6–8.9 Sv. For the years 1998–99, the ULSW formation rate solely based on the subpolar North Atlantic CFC-11 inventories yielded 6.9–9.2 Sv. At this time, the lack of classical LSW formation was almost compensated for by the strongly pronounced ULSW formation. Indications are presented that the convection area needed in 1998–99 to form this amount of ULSW exceeded the available area in the Labrador Sea. The Irminger Sea might be considered as an additional region favoring ULSW formation. In 2000–01, ULSW formation weakened to 3.3–4.7 Sv. Time series of layer thickness based on historical data indicate that there exists considerable variability of ULSW and classical LSW formation on decadal scales.

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 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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