Comparison of Large Oceanic Eddies from Satellite Observations and a High-Resolution Coupled Climate Model Simulation

Abstract:

Oceanic eddies, a crucial component of ocean dynamics, play an important role in transporting water, heat, salt, and nutrients. The recently developed eddy detection schemes have enabled us to track eddies at a global scale. In this study, we examine the number of large oceanic eddies (>25 km) over the global ocean in both the satellite observation and climate model simulation during 1982-2012 using an automated approach that identifies eddies from sea surface temperature (SST) following a velocity-geometry eddy detection scheme. On average, the total number of eddies detected from AVHRR SST during 1982-2012 is ~300, and the number of anticyclonic eddies are ~14% more than that of cyclonic eddies. A significant decrease is found in the number of eddies in AVHRR SST for the past three decades, which is primarily due to the abrupt decreases in 1985 and 2007. By contrast, the model simulation, which has slightly finer resolution relative to the observation, shows substantially less eddies (~33%) as compared to the satellite observation. Moreover, in the model, the number of eddies holds steady, showing no significant decrease in recent decades.