Dynamic Sea Level Variability Due to Seasonal River Discharge: A Preliminary Global Ocean Model Study

Abstract

River discharge R is an important driver of the coastal ocean circulation. However, the influence of variable R effects on large-scale sea level 𝜁 related to ocean dynamics is not well understood. We perform numerical experiments using a coarse (~ °) global ocean state estimate to quantify R effects on the seasonal cycle in dynamic 𝜁 over the global ocean. Forcing by R drives substantial dynamic 𝜁 signals (1 cm) on regional scales around major rivers (e.g., Amazon, Ganges, Brahmaputra, Irrawaddy, Ob, Lena, and Yenisei). Modeled 𝜁 changes largely reflect halosteric (salinity) effects, which are partly affected by transport processes involving planetary waves and advection. The modeled 𝜁 response to R is informative for interpreting 𝜁 observations from satellite altimetry and tide gauges, explaining 10–20% of the regional-scale seasonal data variance around some major rivers. Future 𝜁 studies should consider finer-resolution models and R forcing on nonseasonal time scales of relevance to climate.