Suomenlahti

I did not realize it had been such a mild winter. On a "normal" winter (ten years ago) I would expect to see ice cover all the way to the outer islands -- except for the ship route right there of course.

do you know if this is an unusually warm year or is it part of a larger trend (global warming)? do you know if anyone has systematically monitored these things?

The onset of this winter was late, but after that the temperatures were close to what would be expected.

The ice cover, admittedly, is a poor metric. It is tremendously variable from year to year. Some examples from a single decade can be seen here:
http://www.fimr.fi/en/tietoa/jaa/jaatalvi/en_GB/jaatalvi/

This pretty much demolishes my comment; there is effectively no "normal" year for ice cover.

Temperatures have been tracked at many locations for a longish while now. This the last image on this page shows some records.
http://www.fmi.fi/ilmastonmuutos/suomessa_17.html

For the Helsinki dataset the urbanisation has been discounted in the thinner red line; upward trend still shows.