http://hdl.handle.net/2122/114 Thu, 23 May 2013 01:29:58 GMT 2013-05-23T01:29:58Z http://hdl.handle.net/2122/8168 Title: Process studies on the ecological coupling between sea ice algae and phytoplankton Authors: Tedesco, L.; Marine Research Centre, Finnish Environment Institute; Vichi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Thomas, D.; Marine Research Centre, Finnish Environment Institute Abstract: The seasonal dynamics of pelagic and sea ice communities are closely related in ice-covered waters, however, modelling works that analyse such interactions are scarce. We use the Biogeochemical Flux Model in Sea Ice (BFM-SI) coupled to the pelagic Biogeochemical Flux Model (BFM) in a study area in Greenland to quantitatively investigate: (1) the significance of photoacclimation/photoadaptation strategies of autotrophs, (2) the fate of the sea ice biomass in case of algae seeding, algae aggregation and at different mixed layer depths and (3) the changes in community production under a climate change scenario. The results show that sea ice algae need to be both photoacclimated and photoadapted to the sea ice environment in order to grow, while phytoplankton may adopt different strategies for optimising their growth. The seeding of the phytoplankton bloom shows to be driven, both in timing and magnitude, by the viability of sea ice algae and by the degree of aggregation of algae released from the ice, which also affects the sinking rate to the sea floor. Under a mild climate change scenario (SRES B2, 2071–2090) the sea ice community is projected to be generally more productive, whereas phytoplankton growth will be reduced because the melt of sea ice will occur earlier in the season when light is less favourable to sustain the growth. While it is generally anticipated that the melting of multi-year ice in the Arctic Ocean will cause an increase in marine production, this study shows that seasonal ice-covered seas in the Northern hemisphere may actually be less productive and may shift to more oligotrophic conditions within the next 100 years. Sat, 31 Dec 2011 23:00:00 GMT http://hdl.handle.net/2122/8168 2011-12-31T23:00:00Z http://hdl.handle.net/2122/6870 Title: A dynamic Biologically-Active Layer for numerical studies of the sea ice ecosystem. Authors: Tedesco, L.; CMCC; Vichi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Haapala, J.; FMI; Stipa, T.; FMI Abstract: This work introduces a novel approach for the modelling and coupling of sea ice biology to sea ice physics. The central concept of the coupling is the definition of the Biologically Active Layer, which is the time-varying fraction of sea ice that is connected to the ocean via brine pockets and channels, and acts as a rich habitat for many microorganisms. A simple but comprehensive physical model of the sea ice thermohalodynamics is coupled to a novel sea ice microalgal model of growth in the framework of the Biogeochemical Flux Model. The physical model provides the key physical properties of the Biologically Active Layer and the biological model simulates the physiological and ecological response of the algal community to the physical environment. Numerical simulations of chl-a were compared with observations at two different ice stations, in the Baltic and off the coast of Greenland, showing that this new coupling structure is sufficiently generic to represent well the temporal and spatial distribution of sea ice algae during the whole ice season at both sites. This model implementation and coupling structure is viable as a new component of General Circulation Models, allowing for estimates of the role and importance of sea ice biology in the local and global carbon cycle. Thu, 31 Dec 2009 23:00:00 GMT http://hdl.handle.net/2122/6870 2009-12-31T23:00:00Z