Sea ice

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The Canadian Beaufort Shelf of the Arctic Ocean is of prime social, economic and cultural importance for coastal communities. It also serves as "feeding areas for large aggregations of resident and migrant marine birds and mammals.” Tremblay et al. (2011) set out to determine what would happen to the productivity of this important coastal region if temperatures were to rise, comparing time series of ice cover, wind forcing and satellite-based assessments of photosynthetic carbon production for the years 2002-2008 with corresponding in situ measurements of salinity, nutrients, new production, biological stocks and biogenic fluxes obtained during overwintering surveys in 2003-2004 and 2007-2008.

The researchers reported, first of all, that in 2007-2008 -- in areas where ice was no longer present, due to enhanced seasonal warming -- there was significant wind-induced upwelling of growth-promoting nitrates, which were brought up from deep waters into the euphotic zone, where photosynthesis occurs. As a result of this fertilization effect, the herbivorous copepod Calanus glacialis, sedimentary chlorophyll, and benthic carbon demand were all higher than observed in the past. It appears that "repeated instances of ice ablation and upwelling during fall 2007 and summer 2008 multiplied the production of ice algae, phytoplankton, zooplankton and benthos by 2 to 6 fold." These phenomena are “likely to prevail with the increasingly deep and frequent seaward retreat of the central ice pack and the greater incidence of upwelling-favorable winds.” These developments should be good news for the resident and migrant marine birds and mammals that frequent these important coastal marine communities, as well as for local marine food industries.

References

Tremblay, J.-E., Belanger, S., Barber, D.G., Asplin, M., Martin, J., Darnis, G.;, Fortier, L., Gratton, Y., Link, H., Archambault, P., Sallon, A., Michel, C., Williams, W.J., Philippe, B., and Gosselin, M. 2011. Climate forcing multiplies biological productivity in the coastal Arctic Ocean. Geophysical Research Letters 38: 10.1029/2011GL048825.

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