Research ReportDiurnal global ocean surface CO and air-sea CO flux reconstructed from spaceborne LiDAR data.

The ocean absorbs a significant amount of carbon dioxide (CO) from the atmosphere, helping regulate Earth's climate. However, our knowledge of ocean CO sink levels remains limited. This research focused on assessing daily changes in ocean CO sink levels and air-sea CO exchange, using a new technique. We used LiDAR technology, which provides continuous measurements during day and night, to estimate global ocean CO absorption over 23 years. Our model successfully reproduced sea surface partial pressure of CO data. The results suggest the total amount of CO absorbed by oceans is higher at night than during the day. This difference arises from a combination of factors like temperatures, winds, photosynthesis, and respiration. Understanding these daily fluctuations can improve predictions of ocean CO uptake. It may also help explain why current carbon budget calculations are not fully balanced-an issue scientists have grappled with. Overall, this pioneering study highlights the value of LiDAR's unique day-night ocean data coverage. The findings advance knowledge of ocean carbon cycles and their role in climate regulation. They underscore the need to incorporate day-night variability when assessing the ocean's carbon sink capacity.