An Idealized Numerical Model Study of Bottom Topographic Influence on Momentum Fluxes, with Emphasis on Contrasting Prograde and Retrograde Flow

• Main Author: Slørdal, Jostein Ekker
• Format: Master Thesis
• Language: English
• Published: 2024
• Subjects: continental slope; retrograde; momentum fluxes; prograde; Arctic Ocean
• Online Access: http://hdl.handle.net/10852/112508

Given the strong topographic steering of large-scale ocean currents at high latitudes, and especially in the Artic Ocean, mesoscale eddy fluxes become of major importance as they enable communication across steep topography. These are essential to the transport of e.g. momentum, heat, salt and biochemical tracers across continental slopes between coastal- and deep ocean regions. As such, eddy fluxes do play a key part in regulating water mass transformation, altering the global overturning circulation and tuning the long term global climate evolution. Still, previous research have suggested that along-slope prograde- and retrograde flow (i.e. flow travelling in the same- and opposite direction as to topographic Rossby wave propagation, respectively) behaves quite differently. Examples of both flow regimes, which are also quite persistent, can be found throughout the Arctic Ocean. Motivated by such establishments this study investigates arising asymmetries (i.e. differences) between steady prograde- and retrograde flows. Assessments are performed using idealized high-resolution model simulations. These simulations consists of a zonally re-entrant channel, with mirrored continental slopes, which is forced by a uniform and constant wind stress. The main focus further relies on estimated lateral and vertical momentum fluxes. Still, lateral momentum fluxes receives more attention. The results of this current study are in line with previous research and seem to confirm asymmetry. However, clear similarities are also present. The flow over both slopes seem to experience strong surface trapped offshore transport of wind-momentum, which is "dumped" over the flat deep ocean. The main asymmetric signal arise as the cross-channel extent of this phenomenon appears significantly greater for retrograde flow. The retrograde flow structures do also seem to experience consistently greater alterations upon variations of different simulation parameters. Such parameters include slope-width, stratification and additional along-slope ...