Satellite Evidence for Strengthened M <sub>2</sub> Internal Tides in the Past 30 Years
Zhongxiang Zhao
Abstract
Abstract Satellite altimetry sea surface height measurements from 1993 to 2022 are used to show the strengthened mode‐1 M 2 internal tides in the past 30 years. Two mode‐1 M 2 internal tide models M9509 and M1019 are constructed using the data in 1995–2009 and 2010–2019, respectively. The results show that the global mean M 2 internal tides strengthened by 6% in energy. However, the internal tide strengthening is spatially inhomogeneous. Significantly strengthened internal tides are observed in a number of regions including the Aleutian Ridge and the Madagascar‐Mascarene region. Weakened internal tides are observed in the central Pacific. On global average, M1019 leads M9509 by about 10° (20 min in time), suggesting that the propagation speed of M 2 internal tides increased. M9509 and M1019 are evaluated using independent altimetry data. The results show that M9509 and M1019 perform better for the data in 1993–1994 and 2020–2022, respectively.