# Ocean transit times: from basin to planetary scales

## TL;DR

The paper explores how ocean currents and eddies affect the time it takes for water to travel across large ocean regions.

## Contribution

The study reveals how multiscale processes, including throughflow currents and eddy dispersion, shape Lagrangian transit times in the ocean.

## Key findings

- Mesoscale eddies increase dispersion and widen transit-time distributions.
- Ocean gyres cause tortuous paths and multimodal transit-time distributions.
- Trapping within gyres leads to complex transit-time patterns.

## Abstract

Lagrangian transit times on basin to planetary scales are controlled by the interplay of multiscale processes. The primary advective time scale is set by throughflow currents, such as interhemispheric western boundary currents. Dispersion by mesoscale eddies introduces fluctuations that erase memory and enhance dispersion, widening the transit-time distribution. The tortuous paths of Lagrangian parcels, particularly within ocean gyres, significantly enhance dispersion beyond the levels attributed to mesoscale eddies alone. Additionally, trapping by ocean gyres leads to multimodal distributions of Lagrangian transit times. These processes are illustrated in three complementary contexts: eddy-permitting ocean state estimates, simplified spatially extended three-dimensional flows and diffusively coupled two-dimensional pipe models.