Cold anticyclonic eddies and warm cyclonic eddies in the ocean

Mesoscale eddies are ubiquitous features of the global ocean circulation. Tradiontally, anticyclonic eddies are thought to be associated with positive temperature anomalies while cyclonic eddies are associated with negative temperature anomalies. However, our recent study found that about one-fifth of the eddies identified from altimeter data are surface cold-core anticyclonic eddies (CAEs) and warm-core cyclonic eddies (WCEs). Idealized numerical model experiments highlight the role of relative wind-stress-induced Ekman pumping, surface mixed layer depth, and vertical entrainment in the formation and seasonal cycle of these unconventional eddies. The abundance of CAEs and WCEs in the global ocean calls for further research on this topic.