Turbulent kinetic energy dissipation rates at Station Aloha: Possible influences of eddies, wind, internal tides, and seasonality

Abstract

Turbulent kinetic energy (TKE) dissipation rates provide valuable insight into ocean mixing andits effect on biogeochemical processes, such as nutrient supply to the lower euphotic zone. This study investigates the conditions that lead to elevated TKE dissipation rates at Station ALOHA, focusing on the roles of mesoscale eddies, wind forcing, internal tides, and seasonal patterns. Using data from a lowered acoustic Doppler current profiler (LADCP), CTD casts, and shipboard ADCP (SADCP) collected during HOT cruises 299–328 (January 2018–March 2021), dissipation rates were calculated for each profile. Results show that dissipation rates are typically higher during winter months and lower in summer, suggesting seasonal influence. Elevated mixing frequently coincided with the presence of anticyclonic eddies, though a notable exception occurred during a cyclonic eddy event. These findings highlight the complex interplay of physical drivers influencing mixing, with implications for nutrient transport and the strength of the biological pump in the North Pacific Subtropical Gyre.