School of Natural and Environmental Sciences

Projects

MILAN: Sea-surface MIcroLAyer functioning during the Night

Wadden Sea area
Location of the MILAN experiment in the coastal North Sea. The dashed line indicates the approximate area of sampling.

Thin Surface Layer of the Oceans influences Climate

An international team of marine and climate researchers will meet on March 27th at the ICBM (Institute for Chemistry and Biology of the Marine Environment, University of Oldenburg). In an interdisciplinary approach this team of experts will conduct an, as yet, unprecedented experiment: they will investigate the extremely delicate marine surface layer at night. This sea surface microlayer influences the gaseous exchange at the ocean-atmosphere boundary and hence climatic developments.

A major part of the oceans is covered with thin natural films, so-called marine surface layers. They are enriched with organic com-pounds of biological origin and form a turbulence-free boundary layer at the sea surface. These layers decelerate the gaseous exchange between ocean and atmosphere. And, frequently, they provide ideal environmental conditions for microorganisms, which may actively influence this exchange as well. These delicate pellicles may react in a different manner in the darkness of the night, the scientists of the project team presume: Solar irradiation, for example, makes microalgae produce oxygen (O2) during daylight – after all, the oceans account for about one half of the oxygen on earth. Moreover, they absorb about one third of the greenhouse gas carbon dioxide (CO2), produced by man. Especially during night, as an assumption, breathing microorganisms might dominate the boundary layer, which generate CO2 as well.

At the Jade bay in the two weeks to come these are important questions in particular: Are there appreciable intraday fluctuations in composition and metabolic activity of microbial assemblages? And do they really affect significantly the gas exchange of O2 and CO2 across the marine surface layer? Moreover the scientists want to know, to what extent biological, physical and (photo-) chemical-processes shape the amount and properties of delicate particulate material (aerosols) above the sea surface – this also affects cloud formation.

“This is the first time that sea surface layers will be investigated during night, moreover, in an international and interdisciplinary approach. This is going to be a special challenge, as work at night on sea is difficult in any case“, explains Dr Mariana Ribas Ribas, oceanographer of the research group Sea Surfaces at the ICBM. She initiated the project, together with her colleague Dr Christian Stolle, who furthermore does research at the Leibniz Institute for Baltic Sea Research (IOW). The idea for “MILAN” (sea-surface microlayer functioning during the night) occurred to the scientists on the brink of an expert conference in an unconventional manner. "Normally, one has to procure the funding first and then starts the project. In this case it went the other way round", continues Ribas Ribas. Together with her international colleagues she wants to expand MILAN to a European-scale project.

Researchers from Costa Rica, Denmark, Great Britain, Italy, Croatia, Poland, Sweden and Spain currently constitute the team. Besides project instigators Ribas Ribas and Stolle as well as the Head of the European Research Council (ERC Starting Grants) funded Sea Surfaces Research Group, Dr Oliver Wurl, there participate further scientists from the University of Oldenburg, the GEOMAR Helmholtz Centre for Ocean Research Kiel, the Leibniz Centre for Tropical Marine Research (ZMT, Bremen) and the Leibniz-Institute for Tropospheric Research (TROPOS) in Leipzig.

The project team has the research cutter “Senckenberg” of the Wilhelmshaven Senckenberg Institute at their disposal. The scientists are going to deploy a special sensor-equipped drifting buoy as well as a remotely operated research catamaran of the ICBM research group sea surfaces from aboard the vessel. The catamaran collects major amounts of the surface layer for lab investigations. Moreover, delimited earmarked university funds permit the use of ICBM research boat “Otzum”.

MILAN starts on March 27th and will end for now on April 13th. Those who are interested in more information may follow the project via social media: a blog will be installed under http://icbm-auf-see.uni-oldenburg.de/category/home/fs-senckenberg/, and Dr Mariana Ribas Ribas is going to inform the public via Twitter (#MILANProject) after the project has started.