51³Ô¹Ï

Topic

Contrasting Lateral Stirring Regimes Along Line P Modulated by Intermittent Mesoscale Eddies

School of Earth and Ocean Sciences

Date & location

• Friday, July 18, 2025
• 10:00 A.M.
• Clearihue Building, Room B019

Examining Committee

Supervisory Committee

• Dr. Jody Klymak, School of Earth and Ocean Sciences, 51³Ô¹Ï (Co-Supervisor)
• Dr. Tetjana Ross, School of Earth and Ocean Sciences, UVic (Co-Supervisor)
• Dr. Guoqi Han, School of Earth and Ocean Sciences, UVic (Member)

External Examiner

• Dr. Dhruv Balwada, Columbia Climate School, Columbia University

Chair of Oral Examination

• Dr. Colin Macleod, Department of Philosophy, UVic

Abstract

Lateral stirring is a key process shaping the physical and biogeochemical state of the ocean, yet it remains under-sampled and poorly understood, particularly at submesoscales (1–100 km). Along Line P in the Northeast Pacific, lateral stirring was characterized using 15 glider transects at 3 km horizontal resolution, collected from September 2019 to December 2024. Normalized isopycnal temperature anomalies, 𝜃^∗, equivalent to normalized spice anomalies, reveal significant spatial and temporal variability in lateral variance across meso- and submesoscale ranges. Nearshore tracer spectra follow a power-law slope of 𝑘^0.2—bluer than many previously reported values, but redder than the slope predicted by Surface Quasi-Geostrophy (SQG). Offshore, tracer spectra vary with eddy activity: slopes flatten to 𝑘⁰ during active periods and steepen to 𝑘^1/3 during quieter phases, consistent with Kolmogorov scaling. Large-scale spatial changes are also evident, marked by shifts in water mass structure and temperature range, though the driving mechanisms remain uncertain. To contextualize these observations, a regional NEMO-based simulation—the Northeast Pacific Ocean Model (NEPOM)—is analyzed. NEPOM-derived temperature variability diverges from glider observations across multiple spatial scales, including super-mesoscale (e.g., Alaska Gyre), mesoscale (e.g., eddies), and submesoscale (<80 km). These discrepancies suggest deficiencies in the model’s physical representation and parameterizations of lateral stirring.