Contrasting lateral stirring regimes along line P modulated by intermittent mesoscale eddies
Date
2025
Authors
Talbot, Lauryn
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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, $\theta^{*}$, 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 $k^{0.2}$, with more high wavenumber variance than many previously reported values, but less than predicted by Surface Quasi-Geostrophy (SQG). Offshore, tracer spectra vary with eddy activity: slopes follow $k^0$ during active periods and $k^{1/3}$ during quieter phases, consistent with Kolmogorov scaling. Large-scale temporal 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 model is analyzed. Simulation-derived temperature variability diverges from glider observations across multiple spatial scales, including the mesoscale (e.g., eddies), and submesoscale (<80 km). These discrepancies suggest deficiencies in the model’s physical representation and parameterizations of lateral stirring.
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Keywords
Turbulence, Oceanography, Lateral stirring, Ocean gliders, Model comparison