Summer circulation variability in the South China Sea during 2006–2010

• Satellite observations of sea surface height reveal a decadal variability of summer circulation in the South China Sea.
• Unprecedented anomalous high sea level occurred in the South China Sea during 2006–2010.
• The anomalous high sea levels during 2006–2010 were associated with the Pacific decadal oscillation.

Satellite observations of sea surface height (SSH) from 1993 to 2010 reveal a decadal variability of summer circulation in the South China Sea (SCS) with three phase changes in 1998, 2001 and 2006, respectively. There appears to be a large rise during 2006–2010 contributing to unprecedented anomalous high sea levels in 2010. The first leading empirical orthogonal function (EOF) mode of SSH exhibits an anomalous anticyclonic circulation pattern in the western central SCS north of 11°N, thus weakening the northern cyclone of the summer dipole during 2006–2010. The negative phase of the Pacific decadal oscillation (PDO) may have contributed to the anomalous high sea levels and disappearance of the summer dipole pattern. These variations reflect a linkage between the circulations of the SCS and Pacific Ocean.