Contrasting deeper ocean responses around the Kuroshio-Oyashio Extension in high and low-resolution coupled climate models

How much heat is pumped into the interior of the oceans directly affects projected future warmings of the atmosphere and surface climate, with both global and regional implications. Kuroshio-Oyashio Extension region (KOE) influences the local marine ecosystems and is part of the North Pacific decadal variation systems, it also tele-connects with the North American weather and is a key projection indicator for the marine heatwaves. For a more reliable understanding and future projection of the future climate and extreme events in the North Pacific, it is important to predict potential future spatial and temporal warming patterns in KOE more accurately. The future KOE warming pattern and warming mechanisms are analysed, with future scenario simulation by skillful high-resolution coupled model FGOALS-f3-H, compared with low-resolution model FGOALS-f3-L. Results show that high-resolution models simulate a future deep, strong warming reaching 600 m in the Kuroshio-Oyashio region, while the warming in low-resolution models is only above 300 m. Deep warming includes two spatial parts, one in the south of Kuroshio, which is contributed by heaving, and one in the north around Oyashio which is contributed by the northward movement of the subtropical gyre. The skill of high-resolution models to simulate future deep warming is co-contribute by the improvements in the ability to realistically capture the Kuroshio Extension current, with its meridional position, sharp front as well as large horizontal current speed, and mixed layer depth with mesoscale eddies effects.