Local and Downstream Relationships between Labrador Sea Water Volume and North Atlantic Meridional Overturning Circulation Variability

• Published in: Journal of climate Vol. 32; no. 13; pp. 3883 - 3898
• Main Authors: Li, Feili, Lozier, M. Susan, Danabasoglu, Gokhan, Holliday, Naomi P., Kwon, Young-Oh, Romanou, Anastasia, Yeager, Steve G., Zhang, Rong
• Format: Journal Article
• Language: English
• Published: Goddard Space Flight Center American Meteorological Society 01.07.2019
• Subjects: Atlantic Meridional Overturning Circulation (AMOC); Atmospheric models; Chemical analysis; Climate; Computer simulation; Datasets; Ice models; Meteorology And Climatology; Mixed layer; Mixed layer depth; Ocean circulation; Ocean models; Oceanic analysis; Oceans; Salinity; Sea ice; Sea ice models; Seawater; Time; Time series; Volume transport; Vortices; Water analysis; Water circulation; Labrador Sea
• ISSN: 0894-8755; 1520-0442
• DOI: 10.1175/JCLI-D-18-0735.1

While it has generally been understood that the production of Labrador Sea Water (LSW) impacts the Atlantic meridional overturning circulation (MOC), this relationship has not been explored extensively or validated against observations. To explore this relationship, a suite of global ocean–sea ice models forced by the same interannually varying atmospheric dataset, varying in resolution from non-eddy-permitting to eddy-permitting (1°–1/4°), is analyzed to investigate the local and downstream relationships between LSW formation and the MOC on interannual to decadal time scales. While all models display a strong relationship between changes in the LSW volume and the MOC in the Labrador Sea, this relationship degrades considerably downstream of the Labrador Sea. In particular, there is no consistent pattern among the models in the North Atlantic subtropical basin over interannual to decadal time scales. Furthermore, the strong response of the MOC in the Labrador Sea to LSW volume changes in that basin may be biased by the overproduction of LSW in many models compared to observations. This analysis shows that changes in LSW volume in the Labrador Sea cannot be clearly and consistently linked to a coherent MOC response across latitudes over interannual to decadal time scales in ocean hindcast simulations of the last half century. Similarly, no coherent relationships are identified between the MOC and the Labrador Sea mixed layer depth or the density of newly formed LSW across latitudes or across models over interannual to decadal time scales.