Sealing the floating frames in preparation for sinking

If you want to make sure that it doesn’t rain in Kiel, take an umbrella before you leave the house. It’s a nuisance to carry the umbrella all day, but you can be certain it will stay dry.

It appears the same principle applies to ice formation in the Gullmar Fjord. We worked very hard for three days to build a system that allows to sink all our mesocosms below the sea surface in order to escape ice formation. Despite freezing temperatures since several days, however, there IS no ice formation on the fjord. In German you would call it “… das Glück des Tüchtigen”.  According to leo.de it translates to “Fortune favours the bold”.

But what is really preventing new ice to form in the fjord? Thanks to consistent north-easterly winds since last Wednesday the icy-cold, low salinity surface water was pushed out of the fjord. It was replaced by water brought up from deeper layers. The deep water is not only more saline, it is also much warmer. To be precise 5°C, warm enough to make the fjord steam on a calm and cold morning. And much too warm for ice formation, despite the freezing air temperatures. It was pure luck that this condition developed. Or was it the fact that we worked so hard on sinking the mesocosms?

When warm water hits cold air

The present weather situation is predicted to continue for at least another week. Unless fresher water will enter the fjord, we should be safe from new ice for quite some time. The new surface water is rich in nutrients and low in phytoplankton biomass, indicating that the bloom is yet to come. Ideal conditions to close the mesocosms and start the experiment. The message went out to all participants yesterday, so soon we will be the lively crowd again eager to start the experiment.

By Ulf Riebesell