Sinking in the Labrador Sea: An Idealized Model Study

• Main Author: Van der Boog, C.G. (author)
• Other Authors: Katsman, C.A. (mentor)
• Format: Master Thesis
• Language: English
• Published: 2016
• Subjects: Sinking Eddies; AMOC; Labrador Sea; Oceanography
• Online Access: http://resolver.tudelft.nl/uuid:e5982db6-346a-49f6-b48e-6eb663558d8b

The strength of the Atlantic Meridional Overturning Circulation (AMOC) will decrease due to climate change. However, the magnitude of this decrease is still under debate, since uncertainties exist about the driving mechanisms of the sinking branch of AMOC. Conceptual models have shown that sinking is located at the lateral boundaries of the Labrador sea, and its magnitude is governed by the densification of the boundary current. However, some of the assumptions in these conceptual models are questionable in reality. These assumptions include a highly stratified density profile, constant horizontal boundary current velocity, the absence of localized eddy activity, which is present as Irminger Rings (IRs), and the seasonality of the heat flux. In this study the validity of the assumptions in the conceptual models of Spall and Pickart (2001) and Straneo (2006b) is studied in a more complex, but still idealized configuration, of the Labrador Sea. We show that the localized eddy activity and boundary current velocity influence the location and magnitude of the sinking, since the net sinking in the simulations increases from 0.4 Sv (1 Sv = 106 m3 s−1) to 1.7 Sv at 1000 m depth after the IRs were introduced. A distinction was made between friction dominated sinking and eddy dominated sinking. In friction dominated sinking, which dominates in a simulation where IRs are suppressed, the largest vertical transport region is confined to a narrow friction dominated boundary region. In this type of sinking, the validity of the conceptual models is confirmed. In eddy dominated sinking, the region with largest vertical transport moves offshore due to the presence of IRs. Our results show that the IRs affect the magnitude and location of the sinking branch of the AMOC. Civil Engineering and Geosciences Hydraulic Engineering