Tracking Irminger Rings’ properties using a sub-mesoscale ocean model

• Published in: Progress in Oceanography
• Main Authors: Pennelly, Clark, Myers, Paul G.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2022
• Subjects: Greenland; Labrador Sea
• Online Access: https://oceanrep.geomar.de/id/eprint/56984/; https://oceanrep.geomar.de/id/eprint/56984/1/Pennelly.pdf; https://doi.org/10.1016/j.pocean.2021.102735

A 1/60° numerical simulation is carried out within the Labrador Sea to investigate eddies produced along the western coast of Greenland. These eddies, known as Irminger Rings, carry relatively buoyant water from the West Greenland Current system into the interior Labrador Sea. These eddies can survive for up to 2 years; we detect and track 232 eddies produced within our 14 year simulation to investigate how they evolve during their lifetime. Irminger Rings start with a significant layer of freshwater (median 4.4 m) that quickly erodes during the convective winter. The freshwater layer, as opposed to the warm Irminger Water layer, constitutes the majority of the stratification within each eddy. Eddies generally travel southwestwards after formation, and eddies whose trajectory is close to the continental slope tend to have a reduced lifespan and quicker speed than those which drift into the interior deep basin. We find that eddies which spawn further north are more likely to end up influenced by the boundary currents, while those which form to the south are more likely to live longer and enter the deep interior basin. While the formation rate of eddies is generally uniform across our 2005–2018 simulation, Irminger Rings are far more likely to decay during the convective wintertime. We find that most eddies quickly decay within a few months, although some survive long enough to endure two convective winters. All Irminger Rings increase the local stratification in the Labrador Sea, limiting convection. However, the eddies which endure some part of two winters experience a significant buoyancy loss over a long time span such that they may produce Labrador Sea Water within their core during their second winter. This constitutes a small but non-negligible volume of Labrador Sea Water (0.02 to 0.09 Sv) and updates our understanding of Irminger Ring’s role on stratifying the Labrador Sea.