Lidar attenuation coefficient in the global oceans: insights from ICESat-2 mission

The attenuation coefficient of natural waters plays a significant role in our understanding of hydrology from both the oceanographic and biological point of view. The advent of near-continuous observations by sophisticated space-based lidars now offers an unprecedented opportunity to characterize attenuation coefficients over open oceans on global and regional scales. At present, however, literature reports of lidar-derived attenuation coefficient estimates (k(lidar), m(-1)) in oceanic waters are very limited. In this study, we present a global survey of k(lidar) derived from ATLAS/ICESat-2 nighttime measurements. Our results augment the existing passive sensor ocean color data set with a new diurnal component and extend the record to now include previously unavailable polar nighttime observations. The values of ATLAS measured k(lidar) at 532 nm are between 0.045 and 0.39m(-1) with the higher values (>0.15m(-1)) correlated with coastal waters and sea ice covered oceans. The average k(lidar) in clearest oligotrophic ocean gyres is similar to 0.058 +/- 0.012m(-1) at 532 nm. The results reported here demonstrate the feasibility of using ATLAS/ICESat-2 lidar measurements for global k(lidar) studies, which will in turn provide critical insights that enable climate models to correctly describe the amount of light present under sea ice, and for heat deposition studies in the upper ocean. (c) 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement