Sensitivity of Labrador Sea Water Formation to Changes in Model Resolution, Atmospheric Forcing, and Freshwater Input.

• Main Authors: Garcia-Quintana, Yarisbel, Courtois, Peggy, Hu, Xianmin, Pennelly, Clark, Kieke, Dagmar, Myers, Paul G.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2019
• Subjects: Atmosphere-ocean interaction; Greenland melt; Labrador Sea; Ocean models; Subduction; Greenland
• Online Access: https://era.library.ualberta.ca/items/9cafa552-bdc4-4719-b9ac-c15566f9a7cf; https://doi.org/10.7939/r3-t26e-mf92

Labrador Sea Water (LSW) is one of the main contributors to the lower limb of the Atlantic Meridional Overturning Circulation. In this study, we explore the sensitivity of LSW formation to model resolution, Greenland melt, absence of high-frequency atmospheric phenomena, and changes in precipitation. We use five numerical model simulations at both (1/4)◦ and (1/12)◦ resolutions. A kinematic subduction approach is used to obtain the LSW formation rate over the period 2004 to 2016. The control simulation, with (1/4)◦ resolution, showed a mean annual production rate of 1.9 Sv (1 Sv = 106 m3/s) in the density range of 27.68–27.80 kg/m3 for the period 2004–2016. Deep convection events that occurred during 2008, 2012, and 2014–2016 were captured. We found that with (1/4)◦ resolution the LSW formation rate is 19% larger compared with its counterpart at (1/12)◦ resolution. The presence of Greenland melt and an increase in the precipitation impact the denser LSW layer replenishment but do not decrease the overall LSW formation rate nor the maximum convection depth. A dramatic response was found when filtering the atmospheric forcing, which induced a decrease of 44% in heat loss over the Labrador Sea, strong enough to halt the deep convection and decrease the LSW formation rate by 89%. Even if our experiment was extreme, a decrease in the storms crossing the Labrador Sea with a consequent reduction in the winter heat loss might be a bigger threat to deep convection and LSW formation in the future than the expected increases in the freshwater input.