Polar Bear Continuous Time-Correlated Random Walk (CTCRW) Location Data Derived from Satellite Location Data, Chukchi and Beaufort Seas, July-November 1985-2017

Raw tracking data were obtained through the Argos System (www.argos-system.org) or the Iridium satellite system (Iridium Satellite Communications, McLean, VA, USA).

All polar bear satellite locations collected between 1985–2003 were Doppler-shift derived and estimated by the Argos system (CLS; https://www.argos-system.org/manual/ ). We performed an initial filter to remove implausible Doppler locations using the Douglas Argos-filter (DAF) algorithm (Douglas et al. 2012). DAF retained all standard-quality locations (Argos location classes 3, 2, and 1), and auxiliary location classes (0, A, B and Z) when corroborated by a consecutive location within a 10 km radius, or when movement rates were <10 km hr-1 and the internal angles (α, in degrees) formed by preceding and subsequent vectors (of lengths d1 and d2 km) were not suspiciously acute (α > -25 + β × ln[minimum (d1,d2)], where β = 15). We assigned β = 15 because it performed well for our specific tracking data across seasons and regions. Most polar bear locations collected after 2003 were derived by on-board global positioning system (GPS) receivers whose horizontal accuracy has been estimated as 30 m (Adams et al 2013). Argos locations collected after 2003 were also filtered as described above. To standardize location intervals across all annual tracking data subsets, we used continuous time-correlated random walk (CTCRW) model to estimate a single location every 6 hr at 00:00, 06:00, 12:00, and 18:00 Coordinated Universal Time (UTC) based on the filtered Argos and GPS locations. The CTCRW model further provides standard error estimates for the average estimated locations based on the estimated error for Argos Location Classes and GPS locations, and the elapsed time differences between the sequential empirical tracking locations.