PRINCESS AND THE PEA: THE IMPACT OF ROUGH TOPOGRAPHY ON DYNAMICS OF LARGE-SCALE SURFACE CIRCULATION PATTERNS

The circulation of the upper ocean has a critical role in the climate regulation of the Earth by redistribution of heat, nutrients and momentum across five basins. Large-scale gyres in these basins are driven by wind stress and planetary rotation. However, the interaction between these forces and unresolved bottom topography is poorly understood and not properly represented in coarse-resolution models. This study investigates how ocean floor roughness, at the kilometer scale, influences the double-gyre circulation by utilizing a two-layer quasi-geostrophic model. Using Radko’s sandpaper theory, bottom drag is parameterized to capture the momentum loss due to bathymetric features. Simulations are conducted across various topographic heights, viscosities and wind stress. Diagnostics include absolute velocity, eddy kinetic energy (EKE), mean kinetic energy (MKE) and the D-function to quantify shear and energy redistribution. Similarly, this research explores how subtle roughness at the ocean floor can influence the structure energetics of surface circulation. Results reveal that bottom roughness damps deep-layer velocity and EKE while the surface-layer gyre structure is preserved. The sandpaper model is validated for coarse-grid simulations as it aligns with the resolved topographic cases. Viscosity and wind-forcing set the energy response while topography amplifies dissipation under higher viscosity and dampens wind-driven energy input.

Department dc:contributor.department

Oceanography (OC)

Grantor dc:publisher

Monterey, CA; Naval Postgraduate School

Year dc:date.issued

2025

Author dc:creator

• Mountain, Nicole D.

Advisors dc:contributor.advisor

• Radko, Timour
• Brown, Justin M.

Statement dc:rights

• This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.

Handle dc:identifier.uri

https://hdl.handle.net/10945/74847

OAI identifier oai:identifier

oai:calhoun.nps.edu:10945/74847