This repository is for updating the "Bifurcation Index" presented in Malick et al. (2017). The BI indexes the north-south position of the bifurcation of the North Pacific Current into the northward flowing Alaska Current and the southward flowing California Current. The BI is calculated from drifter simulations that are run via the OSCURS model https://oceanview.pfeg.noaa.gov/oscurs/. For each year, a grid of drifters are simulated in the North Pacific from February 1 to June 30 and the index is calculated as the percentage of the simulated drifters that ended south of their starting latitude. Thus, the index is bound between 0 and 1 with higher values indicating a more northern bifurcation and lower values indicating a more southern bifurcation.
A downloadable version of the index is available in the share directory.
Malick, M.J., et al. 2017. Effects of the North Pacific Current on the productivity of 163 Pacific salmon stocks. Fisheries Oceanography 26:268--281. https://doi.org/10.1111/fog.12190
Land mask used to truncate drifters when they hit land was the GHRSST 1 km land sea mask downloaded from: https://www.ghrsst.org/ghrsst-data-services/tools/