ISOW spreading and mixing as revealed by Deep‐Argo floats launched in the Charlie Gibbs Fracture Zone

Type Article
Date 2019-10
Language English
Author(s) Racape V.1, 2, Thierry VirginieORCID1, Mercier HerleORCID3, Cabanes CecileORCID2, 3
Affiliation(s) 1 : Ifremer, Univ. Brest, CNRS, IRD, Laboratoire d'Océanographie Physique et Spatiale (LOPS), IUEM Brest ,France
2 : Univ. Brest, CNRS, IRD, Unité Mixte de Service 3113, IUEM Brest ,France
3 : Univ. Brest, CNRS, Ifremer, IRD, Laboratoire d'Océanographie Physique et Spatiale (LOPS), IUEM Brest ,France
Source Journal Of Geophysical Research-oceans (2169-9275) (American Geophysical Union (AGU)), 2019-10 , Vol. 124 , N. 10 , P. 6787-6808
DOI 10.1029/2019JC015040
WOS© Times Cited 20
Keyword(s) North Atlantic Ocean, deep circulation, Deep-Argo float, mixing, North Atlantic Current, Iceland-Scotland Overflow Water

To improve our understanding of deep circulation, we deployed five Deep‐Argo floats (0–4000 m) in the Charlie Gibbs Fracture Zone (CGFZ), which channels the flow of Iceland‐Scotland Overflow Water (ISOW), a dense water mass of the North Atlantic Ocean. The floats were programmed to drift at 2750 dbar in the ISOW layer. The floats mainly moved westward in the CGFZ, although some of them followed different routes for few cycles depending on northward intrusions of the North Atlantic Current (NAC) over the CGFZ. One float revealed a direct route for ISOW from CGFZ to the Deep Western Boundary Current at Flemish Cap. In the CGFZ, oxygen data acquired by the floats revealed that the ISOW layer, characterized by salinity higher than 34.94 and density greater than 27.8 kg m‐3, was mainly composed of the highly oxygenated ISOW and the less oxygenated North East Atlantic Deep Water (NEADW), a complex water mass from the East Atlantic. In the ISOW layer, the relative contribution of ISOW was generally larger in the northern valley than in the southern valley of CGFZ. Northward intrusions of the NAC above the CGFZ increased the relative contribution of NEADW in the northern valley and favours mixing between ISOW and NEADW. The ISOW‐NEADW signal flowing westward from the CGFZ towards the DWBC was progressively diluted by Labrador Sea Water and Denmark Strait Overflow Water. Oxygen measurements from Deep‐Argo floats are essential for a better understanding and characterization of the mixing and spreading of deep water masses.

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