The benefits of high-resolution models in simulating the Kuroshio Extension and its long-term changes

The Kuroshio Extension (KE) is a narrow midlatitude zonally oceanic jet-like flow, characterized by abundant mesoscale eddies and intense air-sea interaction with significant impact on the North Pacific storm track. Using two sets of coupled model simulations with FGOALS and HadGEM3, this paper evaluates the benefits of high-resolution models in simulating the climatological structure of the KE and its historical warming trend, by comparing high-resolution with low-resolution simulations from the same model. It is found that high-resolution models consistently improve the simulated KE intensity and enhanced warming trend. In low-resolution models, the warming is centered more northernly (around 40 & DEG; N) and shallower (about 300 m) compared to observations (around 35 & DEG; N). In high-resolution simulations the warming is much more concentrated, located around 35 & DEG; N with two warming centres in the vertical, one near the surface and one in the subsurface. Decadal temperature changes mainly reflect positional KE shifts, with northward movement resulting in a warming and southward movement resulting in cooling. Heat budget analysis shows the temperature advection term was the major contributor to the Kuroshio Extension enhanced warming, suggesting a possible intensification of the western boundary circulation.

Automated summary

This study evaluates the benefits of high-resolution models in simulating the Kuroshio Extension (KE) and its warming trend, and finds that high-resolution models improve the simulated KE intensity and enhanced warming trend. The results highlight the importance of KE changes on the North Pacific storm track.