Slip‐Event Timing and Ice Velocity Vary at Long‐Period Ocean Tidal Frequencies at Whillans Ice Plain, West Antarctica

Abstract Whillans Ice Plain (WIP), a region of West Antarctica flowing into the southern Ross Sea, lurches forward 0.2–0.6 m over 30–60 min once or twice per diurnal ocean tidal cycle. Combining 11 years (2008–2019) of 30 s or better resolution Global Navigation Satellite System (GNSS) data from past field campaigns is necessary to provide insight into WIP dynamics by connecting individual slip events to decadal velocity trends. We processed GNSS data from 48 stations and used a linear least squares residual thresholding algorithm to automatically detect 5150 slip events during the 11‐year observational period. Event frequency decreased over the 11‐year record, due to an increased prevalence of one‐slip diurnal ocean tidal cycles over two‐slip cycles. Slip‐event frequency varies at fortnightly, monthly, and semiannual ocean tidal periods, but does not explain the overall decrease in events. Combining the full complexity of the regional barotropic tides with secular changes over decadal timescales is necessary to interpret observed ice‐stream dynamics.