Ice Stream Slowdown Will Drive Long‐Term Thinning of the Ross Ice Shelf, With or Without Ocean Warming

As time series observations of Antarctic change proliferate, it is imperative that mathematical frameworks through which they are understood keep pace. Here we present a new method of interpreting remotely sensed change using spatial statistics and apply it to the specific case of thickness change on the Ross Ice Shelf. First, a numerical model of ice shelf flow is used together with empirical orthogonal function analysis to generate characteristic patterns of response to specific forcings. Because they are continuous and scalable in space and time, the patterns allow short duration observations to be placed in a longer time series context. Second, focusing only on changes that are statistically significant, the synthetic response surfaces are used to extract magnitude and timing of past events from the observational data. Slowdown of Kamb and Whillans Ice Streams is clearly detectable in remotely sensed thickness change. Moreover, those past events will continue to drive thinning into the future. Plain Language Summary The Ross Ice Shelf (RIS) is an important gateway through which climate change will come to West Antarctica. Satellite observations indicate that RIS is changing slowly now, but it is not known if this is due to contemporary climate change, events in the past, or both. This research develops and applies a quantitative method for uniquely fingerprinting sources of change on RIS. We will be able to say what happened, when it happened, and what it means for the future. Once tested, the approach can be applied to other regions. Key Points A new physics‐based, empirical method identifies drivers of contemporary thickness change on RIS Response surface analysis finds physics‐based synthetic modes of variability in observational data Past tributary flux changes will continue to thin the RIS by several meters over the next century