New insight into the formation and evolution of the East Reykjanes Ridge Current and Irminger Current

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Petit, Tillys, Mercier, Herle, Thierry, Virginie
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union (AGU) 2019
• Subjects: North-Atlantic Subpolar Gyre; Bathymetry; Oceanic circulation; Observations; Irminger Sea; Reykjanes; Iceland; north atlantic current; North Atlantic
• Online Access: https://archimer.ifremer.fr/doc/00591/70347/68407.pdf; https://archimer.ifremer.fr/doc/00591/70347/68408.eps; https://archimer.ifremer.fr/doc/00591/70347/68409.pdf; https://archimer.ifremer.fr/doc/00591/70347/68410.png; https://doi.org/10.1029/2019JC015546; https://archimer.ifremer.fr/doc/00591/70347/

The Reykjanes Ridge strongly influences the circulation of the North Atlantic Subpolar Gyre as it flows to the Irminger Sea from the Iceland Basin. The circulation is composed of two main along‐ridge currents: the southwestward East Reykjanes Ridge Current (ERRC) in the Iceland Basin and the northeastward Irminger Current (IC) in the Irminger Sea. To study their interconnection through the ridge, as well as their connections with the interior of each basin, velocity and hydrological measurements were carried out along and perpendicular to the crest of the Reykjanes Ridge in June–July 2015 as part of the RREX project. This new dataset changes our view of the ERRC and IC as it reveals undocumented along‐stream evolutions of their hydrological properties, structures and transports. These evolutions are due to flows connecting the ERRC and IC branches at specific locations set by the bathymetry of the ridge, and to significant connections with the interiors of the basins. Overall, the ERRC transport increases by 3.2 Sv between 63°N and 59.5°N and remains almost constantly southward. In the Irminger Sea, the increase in IC transport of 13.7 Sv between 56 and 59.5°N and the evolution of its properties are explained by both cross‐ridge flows and inflows from the Irminger Sea. Further north, bathymetry and cross‐ridge flows deviate the IC northwestward into the Irminger Sea. At 63°N, the IC water masses are mostly issued from the cross‐ridge flow. Plain Language Summary Along pathways in the North Atlantic Subpolar Gyre, the warm and salty water of the North Atlantic Current is densified by intense winter air‐sea buoyancy loss. This transformation preconditions this water mass for convection in the Irminger and Labrador Seas. Good knowledge of circulation in the Iceland Basin and Irminger Sea, strongly influenced by the Reykjanes Ridge, is needed to understand the along‐stream evolution of its properties. Two main conduits flow anticyclonically around the Reykjanes Ridge: the East Reykjanes Ridge Current (ERRC) in the Iceland Basin and the Irminger Current in the Irminger Sea. From in‐situ measurements carried out in the vicinity of the Reykjanes Ridge, we first investigated the along‐stream evolution of the ERRC and IC properties and structures and show their interconnections through the complex bathymetry of the Reykjanes Ridge as well as their connections with the interiors of the basins. Contrary to what has been generally thought, we found that the ERRC and IC do not flow continuously into one top‐to‐bottom current along the ridge but are composed of complex inflows and outflows that locally modify the strength and properties of the ERRC and IC.