noun

• (hydrology) A short-term standing wave oscillation of the water level in a lake, or other confined body of water such as a fjord, characteristic of its geometry.
  "In September 2023, we detected the start of a 9-day-long, global . . . very-long-period seismic signal, originating from East Greenland. . . .this event started with a glacial thinning-induced rock-ice avalanche of 25 million cubic meters plunging into Dickson Fjord, triggering a 200-meter-high tsunami. Simulations show that the tsunami stabilized into a 7-meter-high long-duration seiche with a frequency. . .and slow amplitude decay that were nearly identical to the seismic signal. An oscillating, fjord-transverse single force . . . reproduced the seismic amplitudes and their radiation pattern relative to the fjord, demonstrating how a seiche directly caused the 9-day-long seismic signal."