Diagnosing Diapycnal Mixing from Passive Tracers

Abstract Turbulent mixing across density surfaces transforms abyssal ocean waters into lighter and is vital to close the deepest branches of global overturning circulation. Over last 20 years, rates inferred from in situ microstructure profilers tracer release experiments (TREs) have provided valuable insights connection between small-scale large-scale Problematically, estimates based on TREs consistently exceed those collocated measurements. These differences been attributed a low bias that can miss strong, but rare, events. Here we demonstrate TRE suffer high bias, because approximations generally made interpret data. We first derive formulas estimate temporal growth second moment patch by extending Taylor’s celebrated formula account for both stratification variations rates. The are validated with tracers released numerical simulations turbulent flows then used discuss biases interpretation how possibly overcome them.