The North Equatorial Counter Current (NECC) is an eastward-flowing surface current that transports a significant amount of water from the warm pool in the western Pacific to the east. Variations in the NECC exert profound effects on the tropical Pacific climate and need to be better understood. Recent work of Shuwen Tan and Dr. Hui Zhou conduct statistical analyses and ocean model experiments to show that different flavors of El Niño can displace the NECC location and alter its intensity in distinct ways.

The NECC shifts southward and intensifies during the developing phase of El Niño, but the variations are confined in the central-eastern Pacific for the EP type and the western-central Pacific for the CP type. The cause and the physical mechanisms behind the distinct impacts are identified and verified using specific El Niño events of each flavor. It is found that the wind stress anomalies during the two El Niño types are of comparable amplitude but have different spatial structures, which results in significant and distinct variations in the NECC. Also, these differences can be attributed to modulations in equatorial Kelvin wave and tropical Rossby wave propagation as well as Ekman pumping. The findings reported in this study contribute to advance our understanding of El Niño diversity and its impacts on the circulation and variability of the Pacific Ocean.

These results are recently published online in Geophysical Research Letters. This work was supported by the Qingdao National Laboratory for Marine Science and Technology. Grant Number: 2016ASKJ12; NSFC. Grant Numbers: 41376032, 41720104008, 41421005, 41876009

Citation: Tan, S., & Zhou, H^*. (2018). The observed impacts of the two types of El Niño on the North Equatorial Countercurrent in the Pacific Ocean. Geophysical Research Letters, 45. https://doi.org/10.1029/2018GL079273