Charting the ocean's hidden dimension: Lidar advancements in quantifying marine ecosystems and the carbon cycle

Public summary

* Ocean life and carbon cycles occur in deep water, hidden from traditional surface-viewing satellites.

* Spaceborne high-spectral-resolution lidar (HSRL) accurately maps this hidden vertical structure.

* Combining HSRL, satellite imagers, and Biogeochemical-Argo (BGC-Argo) floats creates a 3D view.

* These data build an ocean digital twin to predict climate responses and guide sustainable management.

Abstract

Most of the ocean's life and biogeochemical activity is hidden from our satellite view, occurring in a vast vertical dimension that fundamentally governs marine ecosystems, the global carbon cycle, and Earth’s climate. For decades, oceanography from space has been limited to a 2D surface perspective, with early light detection and ranging (lidar) offering tantalizing but quantitatively flawed glimpses into the ocean’s interior. Here, we review the significant advancement driven by high-spectral-resolution lidar (HSRL), a technology that resolves this long-standing uncertainty. By directly measuring depth-resolved optical properties, HSRL transitions ocean profiling from estimation to quantitative measurement. The recent launches of the first spaceborne HSRL systems mark a major development in this new era. This technological step enables a “virtual constellation” in which HSRL provides the vertical backbone, hyperspectral sensors add biological complexity, and the Biogeochemical-Argo (BGC-Argo) network provides in situ biogeochemical context. This synergistic system is paving the way for 4D (3D space + time) ocean monitoring, providing the essential data streams to build a predictive “ocean digital twin”—a critical tool to advance our understanding of the ocean’s response to climate change and to support global efforts in sustainable development.