The Flows over the Reykjanes Ridge
The Flows over the Reykjanes Ridge
Abstract:
The Reykjanes Ridge is a major bathymetric obstacle on the way towards the Irminger Sea for both the North Atlantic Current (NAC), which carries warm and salty water of subtropical origin, and the Iceland Basin Deep Western Boundary Current, which carries ISOW. Despite the importance for climate modeling of understanding the circulation of the upper and lower branches of the Meridional Overturning Circulation in this region, estimates of transports over the Reykjanes Ride are few and divergent.
This study is based on a high spatial resolution CTD-O2/S-ADCP section carried out from 10 June to 10 July 2015 during the RREX cruise. The section extends from Iceland at 63°N to the south of the Charlie Gibbs Fracture Zone at 50°N and follows the summit of the Reykjanes Ridge. Additional observations made by deep Argo profiling floats, deployed within the framework of the NAOS project, were also analyzed. Geostrophic transports over the Reykjanes Ridge were estimated by combining S-ADCP and hydrographic data. Analysis of surface-to-bottom integrated transports reveals two main regions characterized by opposite transports. Between 53°N and Iceland, the integrated transport was directed westward, from the Iceland Basin to the Irminger Basin. Its value was estimated at 24 Sv (1Sv = 106 m3 s-1). Transport occurred in three main veins centered at 59°N, 57°N and 54°N, revealing a more complex circulation than previously thought. Between 53°N and 50°N, the transport was directed eastward and was concentrated in two branches of the NAC carrying a total of 29 Sv. We will discuss error sources associated with the transport estimates. The vertical structure of the transports will be reviewed and the contribution of the fracture zones of the Reykjanes Ridge to the transport of ISOW will be estimated. The implication of these results in terms of evolution of the Irminger Current transport, between 53°N and 63°N, will be considered.
This study is based on a high spatial resolution CTD-O2/S-ADCP section carried out from 10 June to 10 July 2015 during the RREX cruise. The section extends from Iceland at 63°N to the south of the Charlie Gibbs Fracture Zone at 50°N and follows the summit of the Reykjanes Ridge. Additional observations made by deep Argo profiling floats, deployed within the framework of the NAOS project, were also analyzed. Geostrophic transports over the Reykjanes Ridge were estimated by combining S-ADCP and hydrographic data. Analysis of surface-to-bottom integrated transports reveals two main regions characterized by opposite transports. Between 53°N and Iceland, the integrated transport was directed westward, from the Iceland Basin to the Irminger Basin. Its value was estimated at 24 Sv (1Sv = 106 m3 s-1). Transport occurred in three main veins centered at 59°N, 57°N and 54°N, revealing a more complex circulation than previously thought. Between 53°N and 50°N, the transport was directed eastward and was concentrated in two branches of the NAC carrying a total of 29 Sv. We will discuss error sources associated with the transport estimates. The vertical structure of the transports will be reviewed and the contribution of the fracture zones of the Reykjanes Ridge to the transport of ISOW will be estimated. The implication of these results in terms of evolution of the Irminger Current transport, between 53°N and 63°N, will be considered.