Long-Term Variation in the Level of the Sea of Japan Based on Satellite Altimetry Measurements

Abstract

Long-term changes in the Sea of Japan level are estimated based on the Ssalto/Duacs satellite altimetry data. Linear sea level trends for 1993–2005 are positive for the entire sea area and average 3.3 mm/yr, which is close to the mean value for the World Ocean. Trends are weakened by 2.5 times after elimination of annual variation and intra-annual variability (low-frequency data filtering). A quasi-decadal oscillation that accounts for the in-phase rise in 1995–2000 and 2008–2013 (positive phases) and fall in 2001–2007 (negative phase) of the Sea of Japan level for the entire sea area has been observed. The positive phase in 1995–2000 is consistent with an increase in the volume transport into the Sea of Japan through the Korea (Tsushima) Strait and the negative phase is consistent with the transport decrease. Positive sea level trends have dominated in the positive phases (an average of 12.9 and 7.1 mm/yr in 1995–2000 and 2008–2013, respectively) in the entire sea and negative trends with an average of –6.4 mm/yr have been observed during the negative phase in the subtropical sea area. The strongest trends, both positive (10–20 mm/yr and more) and negative (down to –20 mm/yr) have been detected over the western Yamato Basin and near Ulleung Island in the subtropical part of the sea.