Can somebody please explain exactly what is being shown he

http://tinyurl.com/rekh

I assume it shows the difference between the "current" sea surface temperatures and "normal" sea
surface temperatures.

My questions is, how do they define "normal" ?

I noticed just yesterday that the Baltic Sea was a VERY dark blue colour (about -2 deg C from
normality on the scale)
Today, the same area is predominantly a cyan colour ( ie: 0 deg C away from normal.)

Does this imply that the Baltic Sea has actually risen in temperature?
Or perhaps it has just remained the same temperature at a time when it normally should drop in
temperature.

Is "normailty" defined as the average temperature for the same date over x number of years? If so,
what is the value of x ?

Brendan