Ok, then that narrows it down to sparse/noisy underlying data and some issues with interpolation. If you look at something like the NOAA bathymetry viewer you can see where we have either multi- or singlebeam sounding data. Generally in the area you're looking at we have very few tracks, so the bathymetry is going to be primarily from satellite gravity data (e.g., this). This is a sparse dataset, and one that I would expect to broadly have issues at the poles especially.

At the end of the day, these are clearly a data artifact and anyone who works with gridded topographic/bathymetric data immediately recognizes it as such, but given the available data, it's better than nothing.