Weakening Trend of Luzon Strait Overflow Transport in the Past Two Decades

The Luzon Strait overflow is a deep current of dense water flowing persistently into the South China Sea (SCS) from the Pacific. It is the primary driving force of the deep SCS circulation and potentially influenced by ocean mass changes. Limited by the lengths of in situ observations, long‐term changes in the Luzon Strait overflow transport (LSOT) have not been ascertained. Based on 14 years of satellite‐based ocean bottom pressure (OBP) time series, here we provide an evidence of a weakening of the LSOT by −0.43 Sv decade−1 between 2003 and 2016. Moreover, both OBP data and mooring time series reveal a large annual cycle in the LSOT. The weakening trend in the LSOT may profoundly influence the deep SCS circulation, as well as heat and mass fluxes between the SCS and surrounding oceans. Plain Language Summary Deep ocean circulation has been changed for recent decades. Limited by in situ observations, long‐term changes in the Luzon Strait overflow transport (LSOT) is unknown yet. However, it is of great importance as the LSOT is the main driving force of the deep South China Sea circulation. Based on 14‐year ocean bottom pressure data, here we initially provide a satellite‐based evidence on the LSOT changes and reveal a robust weakening trend of −0.43 Sv decade−1 in the LSOT over the past two decades. Key Points A satellite‐based evidence on changes in the Luzon Strait overflow transport (LSOT) is initially provided and validated by mooring data Changes in ocean bottom pressure reveal a robust weakening trend of −0.43 Sv decade−1 in the LSOT over the past two decades Annual variation is the dominant component in the LSOT and regulated by bottom pressure difference along and across the Luzon Strait