Abstract's details
Rafting behavior of Scopoli’s shearwaters: a proxy to describe surface currents in the western Mediterranean Sea?
CoAuthors
Event: 2017 Ocean Surface Topography Science Team Meeting
Session: Science III: Mesoscale and sub-mesoscale oceanography
Presentation type: Type Poster
Contribution: PDF file
Abstract:
The relatively recent development of miniaturized bio-logging devices has allowed the study of fine-scale distribution and behavior of seabirds while they are traveling, feeding or searching for food at sea. However, most of the studies presently available in literature are based on the analysis of long range flights, where birds are travelling at high velocities during long time periods. Conversely, rafting behavior of seabirds has been poorly investigated.
In this work we assess feasibility of rafting behavior of Scopoli’s shearwaters to estimate surface currents in the western Mediterranean Sea. These birds habitually rest on the sea surface during their foraging trips along the eastern Spanish mainland coasts, the Balearic Islands coasts and the Balearic Sea in between tending to be passive drifters. The final goal of this work is to contribute to the understanding of marine system’s dynamics and their spatio-temporal evolution.
We compare the satellite-derived velocity pattern in the western Mediterranean Sea with the paths followed by Scopoli’s shearwaters when they are resting on the sea surface in an attempt to determine whether animal-borne GPS data can be used as a proxy to estimate sea surface currents in the area. Moreover, the outputs of the Cross-Calibrated Multi Platform version 2 (CCMPv2) gridded surface L3 ocean vector wind analysis product are used to investigate both the slippage and Ekman drift of the tracked seabirds. The method uses a speed filter to identify rafting behavior outside of 5 km of the breeding colonies and distinguishes between four different rafting patterns according to the prevailing driving force of the tracks: the local wind, the surface currents, a mixture of both driving forces, or none of the above mentioned.
We found that 76 % of the trajectories (306 drifts) were visually associated with the combined effects of slippage & Ekman drift and/or surface drag; almost 59% of them (180 drifts) were directly driven by the sea surface currents. Therefore, shearwaters were likely to be passively transported by these driving forces while resting. These tracks consistently reconstructed some parts of the mesoscale features observed from satellite data and identified through an eddy-tracker tool.
In this work we assess feasibility of rafting behavior of Scopoli’s shearwaters to estimate surface currents in the western Mediterranean Sea. These birds habitually rest on the sea surface during their foraging trips along the eastern Spanish mainland coasts, the Balearic Islands coasts and the Balearic Sea in between tending to be passive drifters. The final goal of this work is to contribute to the understanding of marine system’s dynamics and their spatio-temporal evolution.
We compare the satellite-derived velocity pattern in the western Mediterranean Sea with the paths followed by Scopoli’s shearwaters when they are resting on the sea surface in an attempt to determine whether animal-borne GPS data can be used as a proxy to estimate sea surface currents in the area. Moreover, the outputs of the Cross-Calibrated Multi Platform version 2 (CCMPv2) gridded surface L3 ocean vector wind analysis product are used to investigate both the slippage and Ekman drift of the tracked seabirds. The method uses a speed filter to identify rafting behavior outside of 5 km of the breeding colonies and distinguishes between four different rafting patterns according to the prevailing driving force of the tracks: the local wind, the surface currents, a mixture of both driving forces, or none of the above mentioned.
We found that 76 % of the trajectories (306 drifts) were visually associated with the combined effects of slippage & Ekman drift and/or surface drag; almost 59% of them (180 drifts) were directly driven by the sea surface currents. Therefore, shearwaters were likely to be passively transported by these driving forces while resting. These tracks consistently reconstructed some parts of the mesoscale features observed from satellite data and identified through an eddy-tracker tool.