ICESat‐2 Elevation Retrievals in Support of Satellite‐Derived Bathymetry for Global Science Applications

Bathymetry retrievals from 2D, multispectral imagery, referred to as Satellite‐Derived Bathymetry (SDB), afford the potential to obtain global, nearshore bathymetric data in optically clear waters. However, accurate SDB depth retrievals are limited in the absence of “seed depths.” The Ice, Cloud, and land Elevation Satellite‐2 (ICESat‐2) space‐based altimeter has proven capable of accurate bathymetry, but methods of employing ICESat‐2 bathymetry for SDB retrievals over broad spatial extents are immature. This research aims to establish and test a baseline methodology for generating bathymetric surface models using SDB with ICESat‐2. The workflow is operationally efficient (17–37 min processing time) and capable of producing bathymetry of sufficient vertical accuracy for many coastal science applications, with RMSEs of 0.96 and 1.54 m when using Sentinel‐2 and Landsat 8, respectively. The highest priorities for further automation have also been identified, supporting the long‐range goal of global coral reef habitat change analysis using ICESat‐2‐aided SDB. Plain Language Summary Mapping the underwater surface in coastal areas is important for understanding our changing climate and how it impacts the nearshore environment. Space‐based imagers are critical to underwater mapping, given their global coverage and wide spatial extent, but require reference depth measurements to inform accurate bathymetric retrievals. Laser altimetry from ICESat‐2 has the potential to address the reference measurement need. This work establishes a foundational technical approach for combining the data and producing a nearshore bathymetric product that is efficient, accurate and informs new research opportunities. Key Points Satellite‐derived bathymetry using passive sensors, requires elevation “seed points” to yield physically meaningful seafloor elevations. NASA ICESat‐2 laser altimetry provides a vertical reference for satellite‐derived bathymetry products. Operationally efficient ICESat‐2‐aided satellite‐derived bathymetry workflows hold promise for global assessment of benthic habitat change.