Flight paths of seabirds soaring over the ocean surface enable measurement of fine-scale wind speed and direction

Abstract

Ocean surface winds are an essential factor in understanding the physical interactions between the atmosphere and the ocean. Surface winds measured by satellite scatterometers and buoys cover most of the global ocean; however, there are still spatial and temporal gaps and finer-scale variations of wind that may be overlooked, particularly in coastal areas. Here, we show that flight paths of soaring seabirds can be used to estimate fine-scale (every 5 min, ∼5 km) ocean surface winds. Fine-scale global positioning system (GPS) positional data revealed that soaring seabirds flew tortuously and ground speed fluctuated presumably due to tail winds and head winds. Taking advantage of the ground speed difference in relation to flight direction, we reliably estimated wind speed and direction experienced by the birds. These birdbased wind velocities were significantly correlated with wind velocities estimated by satellite-borne scatterometers. Furthermore, extensive travel distances and flight duration of the seabirds enabled a wide range of high-resolution wind observations, especially in coastal areas. Our study suggests that seabirds provide a platform from which to measure ocean surface winds, potentially complementing conventional wind measurements by covering spatial and temporal measurement gaps.biologging | dynamic soaring | satellite scatterometer | GPS | meteorology R ecently, remote-sensing systems used to record atmospheric circulation have been developed. Satellite-borne scatterometers estimate ocean surface wind velocities each day covering the majority of the global ocean. These wide-range wind data in combination with refined ocean models are used in numerical weather predictions and describe the oceanographic features more accurately (1-3). Buoys scattered over the ocean also measure fine-time resolution in situ surface winds and are used in validating remote-sensing measurements and are assimilated into model analyses (4, 5). However, because wind data are only acquired twice per day by each satellite and buoys have limited spatial coverage, finer-scale changes of hours to days in local wind conditions could be overlooked. In addition, in coastal areas, where high biological productivity is associated with ocean and atmosphere circulation patterns (6), wind data are lacking due to variations in wind and wave caused by complex topographic effects that satellites have difficulty measuring (5,7,8). Obtaining in situ high-resolution atmospheric and oceanographic data to fill these spatial and temporal observation gaps would deepen our understanding of physical processes relevant to interactions between the atmosphere and ocean, contribute to improved atmospheric and ocean model analyses (7,8), and reveal detailed structure that remains unresolved by using conventional methods (9).The recent development of miniaturized animal-borne data loggers presented a capability to use animals as indicators of environmental variables. The extensive movement range and locomotion ability of marine mammals and seabirds ena...

Acoustic activity across a seabird colony reflects patterns of within‐colony flight rather than nest density

“…While the temporal resolution of our tracking data was too coarse (4-to 12-min intervals between GPS locations) to identify fine-scale details of these flight paths, the highly consistent distribution of tracks across years suggests that persistent flight paths do occur. The literature suggests that social information exchange is most likely to be the driver of the consistency in the flight paths observed here; however, other factors such as avoidance of topographical features or olfactory cues may also influence these distributions (Pollonara et al 2015, Yonehara et al 2016. One other possible reason for increased flight through this area is that the west coast of the island faces the Atlantic Ocean.…”

Flight speed and performance of the wandering albatross with respect to wind

“…There appear to be examples of both diagonal upwind flight and direct upwind flight by tacking. Further analysis of high temporal resolution tracks could provide details of fine-scale dynamic soaring flight maneuvers, estimates of fine-scale wind velocities [37], and more accurate airspeed and ground speed polars.…”

“…This same assumption was used as a basis to calculate fine-scale estimates of wind velocity from high resolution GPS measurements of the dynamic soaring maneuvers of seabirds [37]. Specifically, we modeled ground speed (magnitude of ground velocity) as a linear function of the component of wind velocity in the direction of ground velocity, W cos θ , where W is the wind speed at a reference height of 5 m (the median height of albatrosses observed near Bird Island) and θ is the relative angle between wind velocity and ground velocity [8].…”

Ocean Observations in Support of Studies and Forecasts of Tropical and Extratropical Cyclones

“…Flight and drift paths of sea birds soaring and floating over the ocean surface enable measurement of fine-scale winds and currents. Yonehara et al (2016) and Goto et al (2017) found out that fine-scale flight trajectories by recording one position per second and minute provide 5-min to 1-h interval surface wind direction and speed along the trajectories. The birdestimated wind directions showed good agreement with those from satellite, although wind speeds were slower than satellite winds because sea birds flew at lower altitudes than 10 m at which satellite winds were calibrated.…”