I believe noise here just refers to high frequency variation in atmospheric forcing. The ocean can be thought of as adding inertia to the climate system like a massive flywheel. This means it reacts slowly to change. This paper is arguing the ocean is becoming quicker to respond to changes it sees (or that’s my interpretation after a first read)

This paper is tangentially related https://onlinelibrary.wiley.com/doi/10.1111/j.2153-3490.1976...