The Impact of a Shrinking Arctic Ice Cover on Marine Primary Production
Kevin
Robert
Arrigo, Stanford University, arrigo@stanford.edu
(Presenting)
Gert
L.
van Dijken, Stanford University, dept. of environ. earth system science
Sudeshna
Pabi, Stanford University, dept. of environ. earth system science
Loss of Arctic sea ice has accelerated in recent years, culminating in a summer minimum ice extent in 2007 that was 23% below the previous low. These ice losses likely will have wide-ranging impacts on the climate system and human activities in the Arctic and produce large ecological changes, including a shift in the relative sizes of the sea ice and open water habitats throughout the Arctic Ocean. Here we couple satellite-derived observations of sea ice extent, sea surface temperature, and phytoplankton abundance to a primary production algorithm developed for Arctic waters to quantify the impact of this unprecedented loss of sea ice on marine primary production. We find that annual primary production in the Arctic has increased yearly by an average of 27.5 Tg C/yr over the last five years and by 35 Tg C/yr between 2006 and 2007. Approximately 30% of the 2007 increase is attributable to the large decrease in the summer minimum sea ice extent, while 70% is explained by a longer phytoplankton growing season that characterized much of the Arctic. Should these trends in increasing productivity continue, possibly enhanced by increased shelf break upwelling of nutrients, then a complete loss of sea ice in the Arctic during spring could boost Arctic productivity by >1300 Tg C/yr, a value >3-fold higher than the 1998-2002 mean (416 Tg C/yr). Increased production should enhance the coupling between the pelagic and benthic environments, resulting in greater resource availability to benthic organisms and their predators. Higher Arctic production also could represent a negative feedback on increasing atmospheric CO2 concentrations as well as enhance benthic denitrification on the vast continental shelves, resulting in larger losses of fixed nitrogen that may impact rates of nitrogen fixation in the north Atlantic.
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