  The main properties of the climate of waves in the seasonally ice-covered
Baltic Sea and its decadal changes since 1990 are estimated from satellite
altimetry data. The data set of significant wave heights (SWH) from all
existing nine satellites, cleaned and cross-validated against in situ
measurements, shows overall a very consistent picture. A comparison with visual
observations shows a good correspondence with correlation coefficients of
0.6-0.8. The annual mean SWH reveals a tentative increase of 0.005 m yr-1, but
higher quantiles behave in a cyclic manner with a timescale of 10-15 yr.
Changes in the basin-wide average SWH have a strong meridional pattern: an
increase in the central and western parts of the sea and decrease in the east.
This pattern is likely caused by a rotation of wind directions rather than by
an increase in the wind speed.
