Frigatebirds Monitor Planetary Boundary Layer Dynamics Across Multiple Ocean Environments

Planetary boundary layer (PBL) dynamics over the ocean are not well-studied outside of coastal regions, and establishing baseline measurements in both coastal and pelagic areas could be helpful to assess key differences and inform how to best observe and model PBL dynamics in the future. One novel and low-cost method to measure and track PBL dynamics is to use animals-as-sensors of the environment, who can observe ambient conditions in remote regions. We previously identified that a seabird, the great frigatebird, tracks PBL dynamics via diel ascending and descending flights in atmospheric thermals and cumulus clouds; a process that can take them from the sea surface up to >4000 m high. Building on our previous study at Palmyra Atoll in the central Pacific Ocean, we analyzed additional telemetry data from three coastal frigatebird populations (Caribbean; French Guiana; Gulf of California) and three pelagic populations (Ascension Island, Atlantic; Europa Island, Mozambique Channel, Indian Ocean; Galapagos, eastern Pacific). Our objectives were to 1) establish frigatebird relationships with PBL dynamics in these regions; and 2) compare frigatebird dynamics across regions that experience different oceanographic and atmospheric processes. Frigatebirds tracked PBL dynamics across all regions, such that peak flight heights were consistent with the long-term climatology of each region’s PBL height, and peak flight heights were significantly different between frigatebird populations. Differences in wind, convection, and temperature gradients between pelagic and coastal regions could contribute to differences in PBL dynamics and frigatebird behaviors that we observed. Frigatebirds demonstrate that biologging is a useful and novel tool for tracking differences in oceanographic and atmospheric processes throughout the world ocean and can help inform future data collection and modeling schemes of the PBL.