Transport of Nordic Seas overflow water into and within the Irminger Sea: An eddy‐resolving simulation and observations

Abstract

[1] Results from a climatologically forced, eddy-resolving (1/12°) Atlantic simulation using the Hybrid Coordinate Ocean Model help clarify some presently unresolved connections between volume transports of Nordic Seas overflow water at key locations in the northernmost North Atlantic Ocean. The model results demonstrate that, in addition to the known westward flow through the Charlie Gibbs Fracture Zone (CGFZ), some Iceland Scotland overflow water (ISOW) flows westward through gaps in the Reykjanes Ridge north of the CGFZ into the Irminger Sea, and some flows southward along the eastern flank of the Mid-Atlantic Ridge into the West European Basin. These results provide insights into the well-known inconsistency between observed westward transport of ISOW through the CGFZ (2.4 Sv) and the transports upstream at Southeast of Iceland section (3.2 Sv) and downstream in the western Irminger Sea (4.5 Sv). Although the portion of the simulated ISOW that flows through CGFZ is about 500 m deeper than observed, the model results also show two ISOW pathways of this flow into the Irminger Sea, one northward along the western flank of the Reykjanes Ridge and the other westward before turning north-eastward on the western side of the Irminger Basin. Comparisons with the long-term moored instrument database in the Irminger Sea show that the model-based mean circulation is in reasonable agreement with observed volume transports of overflow water and that it gives approximately correct temperature and salinity characteristics.

Water mass distributions and transports for the 2014 GEOVIDE cruise in the North Atlantic

“…1), as reported in previous studies (e.g. Fleischmann et al, 2001;LeBel et al, 2008;Xu et al, 2010;Zou et al, 2017).…”

“…This distribution of ISOW is consistent with its circulation from the Iceland-Scotland sills, across the Iceland Basin along the eastern flank of the Reykjanes Ridge, crossing the Charlie-Gibbs Fracture Zone (CGFZ) (Dickson and Brown, 1994;Saunders, 2001), flowing cyclonically in the Irminger Sea and joining the DWBC (e.g. Price and Baringer, 1994;Rudels et al, 2002;Tanhua et al, 2008), and then flowing cyclonically in the Labrador Sea (Xu et al, 2010). The eastward extension of ISOW into the West European Basin may result from a fraction of ISOW bypassing the CGFZ (Fig.…”

Mechanisms for decadal scale variability in a simulated Atlantic meridional overturning circulation

“…The main areas of entrainment into the ODW are downstream of the Denmark Strait and the Faroe-Shetland Channel, where the layer situated at the bottom changes rapidly downstream. The same areas of entrainment are also found in Dickson and Brown (1994) and Xu et al (2010). The decrease in density of the DW as a consequence of the entrainment south of the ridge can be seen in Fig.…”

Overturning in the Subpolar North Atlantic Program: A New International Ocean Observing System

“…The DWBC has traditionally been considered the sole conduit for the lower limb of the AMOC. However, this assumption has been challenged by observational and modeling studies that reveal the importance of interior, and boundary, pathways (e.g., Bower et al 2009;Holliday et al 2009;Stramma et al 2004;Xu et al 2010;Lozier et al 2013).…”