11:00 AM - 11:15 AM
[ACG38-02] Long-term variability of sea level along the coast of Japan during the 20th century reproduced by an eddy resolving model
Keywords:coastal sea level rise, Kuroshio/Kuroshio Extension, Eddy resolving model
Long-term changes in sea level along the coast of Japan during the 20th century are characterized by decadal variations: a peak in the 1950s and a decline in the 1980s, followed by a consistent upward trend since 1980s. There are also weak fluctuations of sea level with a period of 10 to 20 years. In order to elucidate the mechanism of these coastal sea level variations, we drive an ocean general circulation model that can reproduce the Kuroshio/Kuroshio Extension and coastal trapped waves (CTWs) using multiple reanalysis data for the 20th century. This is the first experiment that uses an eddy-resolving model forced by reanalysis data for the entire 20th century. Since the effect of adjustment by longshore trapped waves is important in coastal areas, we also condust ideal experiments on CTWs. Although the ocean model is based on the Boussinesq approximation, the sea level rise due to thermal expansion of seawater can be diagnosed by its global mean because its local contribution spreads rapidly around the world. This global average sea level rise has been a major contributor to rising coastal sea levels since the 1980s. Prior to the 1980s, the contribution of the thermal expansion was small, with variations due to the change in wind stress curl dominating. The high coastal sea levels in the 1950s, with similar amplitudes along the northern coast of Honshu and Hokkaido, are found to be caused by the arrival of high sea level anomaly on the eastern coast of Hokkaido and their adjustment by CTWs. Since the 1980s, the sea level variation around Hokkaido is smaller than that of Honshu, except for the contribution of thermal expansion, suggesting that the sea level change around Japan was largely related to the path variability of the Kuroshio Current.