In September 2023, a bizarre global seismic signal was observed which appeared every 90 seconds over nine days – and was then repeated a month later. Almost a year later, two scientific studies proposed that the cause of these seismic anomalies were two mega tsunamis which were triggered in a remote East Greenland fjord by two major landslides which occurred due to warming of an unnamed glacier. The waves were thought to have become trapped in the fjord system, forming standing waves (or seiches) that undulated back and forth, causing the mystery signals.
However, up to now no observations of these seiches existed to confirm this theory. Even a Danish military vessel which visited the fjord three days into the first seismic event did not observe the wave which was shaking the Earth.
Professor Thomas Adcock is co-author (with lead author DPhil candidate Thomas Monahan) of a new study led by the University of Oxford, which has finally confirmed the theory that the cause of the extraordinary global tremors in September and October 2023 was indeed two mega tsunamis in Greenland that became trapped standing waves.
Using a brand-new type of satellite altimetry, the researchers provide the first observations to confirm the existence of these waves, whose behaviour is entirely unprecedented.
The findings were published in June in Nature Communications. Lay readers can learn more about the significance of the findings in this BBC article.
Prof Adcock said, ‘This study is an example of how the next generation of satellite data can resolve phenomena that have remained a mystery in the past. We will be able to get new insights into ocean extremes such as tsunamis, storm surges, and freak waves. However, to get the most out of these data, we will need to innovate and use both machine learning and our knowledge of ocean physics to interpret our new results.’
About Prof Adock
Prof Adcock is Fellow and Tutor in Engineering Science at St Peter’s College and Professor of Engineering Science at the University of Oxford. He tutors students in structures and dynamics at St Peter’s and Exeter College. His research group examines how engineers understand the ocean environment and how this interacts with offshore and coastal infrastructure. The main application of his work is offshore renewable energy. Prof Adcock first joined St Peter’s College as an undergraduate studying Engineering Science in 2001. He then went on to complete a doctorate in Engineering Science at New College, University of Oxford. After working in a number of post-doctoral and industry positions, he returned to St Peter’s as a Fellow in 2012 and has since then served in a handful College Officer roles and as Associate Head of the Engineering Science department. In 2024-2025, Prof Adcock served as Senior Proctor at the University of Oxford.