Background
The authors introduce the report of their new study by writing that "between the late 1970s and the early part of the 21st century, the extent of Arctic Ocean sea ice cover has declined during all months of the year, with the largest declines reported in the boreal summer months, particularly in September (8.6 ± 2.9% per decade)," citing the work of Serreze et al. (2007).

What was done
To "quantify the change in marine primary productivity in Arctic waters resulting from recent losses of sea ice cover," Arrigo et al. "implemented a primary productivity algorithm that accounts for variability in sea ice extent, sea surface temperature, sea level winds, downwelling spectral irradiance, and surface chlorophyll a concentrations," and that "was parameterized and validated specifically for use in the Arctic (Pabi et al., 2008) and utilizes forcing variables derived either from satellite data or NCEP reanalysis fields."

What was learned
By means of the protocol they pursued, the three researchers determined that "annual primary production in the Arctic has increased yearly by an average of 27.5 Tg C per year since 2003 and by 35 Tg C per year between 2006 and 2007," 30% of which total increase was attributable to decreased minimum summer ice extent and 70% of which was due to a longer phytoplankton growing season.

What it means
Arrigo et al. conclude that if the trends they discovered continue, "additional loss of ice during Arctic spring could boost productivity >3-fold above 1998-2002 levels." Hence, they additionally state that if the 26% increase in annual net CO2 fixation in the Arctic Ocean between 2003 and 2007 is maintained, "this would represent a weak negative [our italics] feedback on climate change."

References
Pabi, S., van Dijken, G.S. and Arrigo, K.R. 2008. Primary production in the Arctic Ocean, 1998-2006. Journal of Geophysical Research 113: 10.1029/2007JC004578.

Serreze, M.C., Holland, M.M. and Stroeve, J. 2007. Perspectives on the Arctic's shrinking sea-ice cover. Science 315: 1533-1536.