Impact of climate change and seasonal trends on the fate of Arctic oil spills.

We investigated the effects of a warmer climate, and seasonal trends, on the fate of oil spilled in the Arctic. Three well blowout scenarios, two shipping accidents and a pipeline rupture were considered. We used ensembles of numerical simulations, using the OSCAR oil spill model, with environmental data for the periods 2009-2012 and 2050-2053 (representing a warmer future) as inputs to the model. Future atmospheric forcing was based on the IPCC's A1B scenario, with the ocean data generated by the hydrodynamic model SINMOD. We found differences in "typical" outcome of a spill in a warmer future compared to the present, mainly due to a longer season of open water. We have demonstrated that ice cover is extremely important for predicting the fate of an Arctic oil spill, and find that oil spills in a warming climate will in some cases result in greater areal coverage and shoreline exposure.

Modelling produced water dispersion and its direct toxic effects on the production and biomass of the marine copepod Calanus finmarchicus.

Zooplankton is a key group in North Atlantic and Arctic food chains, and assessment and minimization of adverse effects from petroleum activities to this resource are important. The potential direct effects of produced water discharges on the biomass of Calanus finmarchicus were evaluated using a fully coupled, high resolution 3D hydrodynamic-ecological model system (SINMOD). Several scenarios with varying effects of produced water concentrations were considered. In order to reduce numerical dilution of the produced water effluents, a "sub grid" model component of higher resolution (80 m horizontal resolution vs 800 m for the main model grid) was developed and implemented. The results show that dilution and dispersion of produced water varies between locations. In general, realistically simulated concentrations of produced water were too low to have significant effects on the C. finmarchicus biomass and reproduction according to the toxicity-dilution profiles used, even when the toxicity of the produced water was increased 10-fold. The decrease in C. finmarchicus biomass was partially compensated by a slight increase in production.

New production regulates export stoichiometry in the ocean.

The proportion in which carbon and growth-limiting nutrients are exported from the oceans' productive surface layer to the deep sea is a crucial parameter in models of the biological carbon pump. Based on >400 vertical flux observations of particulate organic carbon (POC) and nitrogen (PON) from the European Arctic Ocean we show the common assumption of constant C:N stoichiometry not to be met. Exported POC:PON ratios exceeded the classical Redfield atomic ratio of 6.625 in the entire region, with the largest deviation in the deep Central Arctic Ocean. In this part the mean exported POC:PON ratio of 9.7 (a:a) implies c. 40% higher carbon export compared to Redfield-based estimates. When spatially integrated, the potential POC export in the European Arctic was 10-30% higher than suggested by calculations based on constant POC:PON ratios. We further demonstrate that the exported POC:PON ratio varies regionally in relation to nitrate-based new production over geographical scales that range from the Arctic to the subtropics, being highest in the least productive oligotrophic Central Arctic Ocean and subtropical gyres. Accounting for variations in export stoichiometry among systems of different productivity will improve the ability of models to resolve regional patterns in carbon export and, hence, the oceans' contribution to the global carbon cycle will be predicted more accurately.