Sea Turtle Beaching Probability Index (BPI) in the Northern Gulf of America from 2017-01-01 to present

This dataset contains the sea turtle beaching probability index (BPI) for the northern Gulf of America region since 2017-01-01. The data files are in CSV and JPEG formats. The daily CSV files contain beaching probability indexes with latitudes, longitudes, total accumulations, and stranding density log scaled radii (for plotting). The yearly CSV files contain daily accumulated BPI for the nine predefined regions. The daily JPEG files are BPI spatial distribution plots for these regions.

The BPI describes the likelihood that dead or debilitated sea turtles floating at the sea surface will be deposited on shore based on prevailing wind and currents. BPI is an indicator of favorable beaching conditions, that is, if there are drifting carcasses, they will be more likely to beach if BPI is high. This relationship between strandings and environmental conditions is relevant to understanding causes of stranding as well as the degree to which at-sea mortality may be represented by animals found on shore. The BPI applies velocity and direction of surface currents and wind from the American Seas Ocean Model (AMSEAS) of the Regional Navy Coastal Ocean Model (NCOM) to predict and describe the probability that floating turtles will be brought into shore. Within the BPI simulation, surface currents and winds from AMSEAS were used to push particles for an 8 day period based on lab and field studies of decomposition and persistence of sea turtle carcasses in the environment. Each day, at 0 h GMT, new particles were seeded onto a starting grid of 84,044 points spaced 1 nautical mile apart. This uniform grid extended from the coast to 60 nautical miles offshore, which is the furthest distance sea turtle carcasses were likely to drift based on observations. The system maintained a running tally such that on any given day all objects that are still in motion and less than 8 days old were pushed forward. Particles that encountered shallow water (<25 cm depth) stopped moving and were counted as "beached". The leeway value, the amount of "push" the wind gives a floating object was set to 3.5%, a value applicable to sea turtles or any other floating object which has about 50% of its area exposed above the sea surface.