In the surface layers of the oceans (euphotic zone) planktonic biomass through photosynthesis results in production of organic compounds into the surrounding seawater. Some of these volatile species (VOCs) with low Henrys Law coefficients are able to escape to the atmosphere, where some of the species can have a significant influence on the photochemistry of the atmosphere, particularly unsaturated hydrocarbons (such as isoprene:2-methyl-1,3 butadiene, or light alkenes) and carbon monoxide (CO) which have a strong impact on the OH radical and ozone budget as well as on the formation of organic aerosols. The dramatic reduction of sea ice in the Arctic will not only alter the current air-sea gas exchange but will have additional consequences on the species distribution and the occurrence of phytoplankton blooms. Thus it is important to conduct simultaneous studies of phytoplankton distribution and VOCs in ice covered and ice free regions of the Arctic. During the Polarstern cruise ARK_25_2 in July 2010 we studied together the occurrence of phytoplankton (marker pigments and flow cytometer) and the various trace gases (carbon monoxide, saturated and unsaturated light hydrocarbons) in the Fram Strait with major emphasis in the region of the deep sea observatory Hausgarten and along the 78,59°N Transect. Samples were taken form a surface line (8m) and from vertical CTD profiles covering the upper 100m. On a few stations additional samples for halocarbons depth profiles were taken.Preliminary results indicate that some of the hydrocarbons (e.g. isoprene) and halocarbons (e.g. bromoform, dibromomethane) are closely related to a biological production indicated by their highest concentrations occurring in the chlorophyll maximum. In contrast, CO and alkenes show most of the time decreasing concentrations with depth. These profiles, following the light availability, reflect the importance of their photolytic production by dissolved organic matter. However other profiles clearly demonstrate an additional biological production indicated by high subsurface values closely related to the chlorophyll maximum. Highest CO surface concentrations were both observed in the ice covered regions and in areas of elevated phytoplankton biomass. Together with the environmental data and a detailed study of the phytoplankton groups we aim to find characteristic CO and VOCs productions regimes for ice covered and ice free regions of the Fram Strait.
Helmholtz Research Programs > PACES I (2009-2013) > TOPIC 1: The Changing Arctic and Antarctic > WP 1.3: A Bi-Polar Perspective of Sea Ice - Atmosphere - Ocean - Ecosystem Interactions