The impact of interannual climate variability on a deep marginal sea under climate change is examined using an idealized numerical model. The results show that the interannual variability (specifically, the occurrence of cold winters) leads to a maximum water age located distinctly above the seafloor, resembling observed features in certain marginal seas such as the Sea of Japan. The interannual variability is also shown to be crucial for the appearance of the warming trend at depth, shortly after the onset of the warming trend at the surface. This mechanism may make such marginal seas early indicators of global climate change.

Overturning circulation,Deep-water property,Climate change,Climate variability,Sea of Japan,Numerical modeling