Amundsen Gulf, located in the southeastern Beaufort Sea, is an important gateway connecting the western Arctic Ocean with the Canadian Arctic Archipelago and ultimately the Labrador Sea. Using time series of velocity and hydrographic observations from a mooring deployed at the western entrance of Amundsen Gulf from October 2012 to September 2013, we identify an anomalous warming and salinification of the water column during March when there is full ice cover. Concurrently, the boundary current reaches its record-long maximum strength and flows eastward out of the gulf, despite exhibiting no significant relationship with local wind forcing or surface stress. Instead, strong correlations between the mooring velocity and wind are observed farther west in the vicinity of Mackenzie Canyon, with a lag of approximately 24 hours. These results suggest that remotely generated shelf waves propagate from the west and induce the upwelling of warm subsurface water at the western entrance of Amundsen Gulf.