For our June cruise we were planning to locate a methane or chlorophyll anomaly in the German Bight and measure its extension, shape and possibly development over two days using two ships. The first question we have to ask ourselves is how to locate an anomaly. We were lucky enough that the days before our cruise had only few clouds over the North Sea, which made satellite data, or more precisely, ocean color data, the first choice. Several chlorophyll images from three satellites for the past three days were available. On the evening before the cruise we would sit down together with the team and analyze these images. Another contribution to answer the “where” question comes from plots that show methane measurement results from earlier cruises. Methane and chlorophyll are not necessarily related, but the recent satellite data and the old measurements both pointed us to approximately the same location southeast of Helgoland. We decided to head toward this spot, both vessels cruising in approximately two to three kilometers distance from each other, running our underway sensors and waiting to find “the patch”.
Once we hit the spot the plan was to sail right through it, measure its extension and then have one ship go North-South transects through the patch and the other one East-West ones. For the next day we would then study output from a computer model that forecasts ocean drift and use this information to find the patch again and take water samples and analyze the anomaly in more detail.
Having been in the field quite a few times, you know that reality isn’t always what you expect – we’ll see how this one plays out…
(Text and picture: Holger Brix, HZG)