# Slowing planetary rotation influences ocean nutrient cycling and oxygenation

## TL;DR

Slower planetary rotation can boost ocean productivity and oxygen levels, improving conditions for marine life on Earth and similar exoplanets.

## Contribution

This study reveals how slowing planetary rotation enhances ocean nutrient cycling and oxygenation through Earth system modeling.

## Key findings

- Slower rotation increases wind-driven upwelling and global ocean circulation.
- Enhanced circulation improves nutrient recycling and photosynthetic productivity.
- Slower rotation can increase oxygen fluxes from ocean to atmosphere under low atmospheric oxygen.

## Abstract

Marine habitability for complex life on Earth and Earth-like planets requires bioavailable nutrients and dissolved oxygen. The cycling of nutrients and oxygen is controlled by physical ocean circulation. However, our understanding of how circulation has varied through time and space is incomplete for Earth and unconstrained for Earth-like exoplanets. Earth’s rotation has slowed over time, affecting ocean circulation by modifying the Coriolis effect. We use a three-dimensional Earth system model to explore how slowing planetary rotation influences ocean circulation and biogeochemistry. We show that slower rotation enhances wind-driven upwelling and global circulation. Nutrient recycling is consequently more efficient, increasing photosynthetic productivity. Additionally, enhanced ocean oxygenation improves habitability for aerobic life under a well-oxygenated atmosphere. However, under a poorly oxygenated atmosphere, slowing rotation increases oxygen fluxes from the ocean to the atmosphere. Therefore, Earth’s rotational history may have been a long-term background control on surface oxygenation and the evolution of animals.

Slowing rotation (longer days) may improve marine biospheric productivity and oxygenation on Earth and Earth-like exoplanets.