Massive phytoplankton bloom solves missing carbon mystery
There's good news for folks worried that atmospheric CO2 levels in the Arctic have passed 400ppm for the first time: a vast CO2-sucking phytoplankton bloom has been discovered beneath Arctic ice – and it may thank global warming for its presence.
"This wasn't just any phytoplankton bloom," Stanford University marine scientist Kevin Arrigo told The Christian Science Monitor. "It was literally the most intense phytoplankton bloom I've ever seen in my 25 years of doing this type of research."
Arrigo's research, conducted in the Chukchi Sea last year as part of NASA's ICESCAPE Arctic-research expedition, is discussed in the online issue of the journal Science in a report entitled "Life Blooms Under Arctic Ice".
The massive under-ice bloom discovered during ICESCAPE was thoroughly unexpected. The meager amount of phytoplankton in that area's open waters had led scientists to believe that under-ice phytoplankton would be even more rare. Not so. Due to the recent thinning of the Arctic ice sheets, enough light is now able to penetrate below the ice, enabling phytoplankton to thrive.
According to Don Perovich of the US Army Corps of Engineers' Cold Regions Research and Engineering Laboratory, ponds of meltwater form on the surface of the ice sheet, acting as "skylights" that let light reach the phytoplankton below. These skylights don't have to let the light travel far: since satellite observations began in 1979, summer ice has declined by about 45 per cent due to global warming, wind patterns, and pollution.
Perovich told the Monitor that much of the melt-season sea ice is now no more than around six feet thick, and has little or no snow cover. No snow cover, more melting; more melt ponds, more skylights; more sunlight, more phytoplankton.
The amount of phytoplankton blooming beneath the ice, the theory goes, is so great that it contributes to the lack of blooms in open water – the under-ice blooms simply eat up all the available nutrients before they have a chance to make it out to the open ocean.
The huge amount of CO2 photosynthesized by the phytoplankton, in fact, may help explain why the ocean is absorbing more of that greenhouse gas than calculations would otherwise indicate: even though the amount of dissolved CO2 in Arctic waters is below predicted levels, that carbon is finding another home in the photosynthetic systems of the phytoplankton.
Although the extent of Arctic ice surveyed by ICESCAPE was small, there's little reason to suspect why other ice-covered areas over continental shelves – given the right amount of nutrients and light – wouldn't also be harboring mammoth blooms.
As with most environmental switcheroos, however, there's a possible downside to this one, as well – namely, that since the blooms change the timing of the nutrient chain, their effect on the rest of the food web is currently unknown.
"It's entirely possible that it would be a disaster," biological oceanographer Walker Smith told Science, "and entirely possible [marine fauna] could adapt to this change fairly easily – most likely it's in between."
In any case, it appears that some biological systems – phytoplankton, in this case – when handed global-warming lemons are making lemonade, albeit in this example it's a rather green, algae-filled liquid refreshment.
ICESCAPE, by the way, is another of those increasingly common "backronyms" – acronyms created through convoluted phraseology. ICESCAPE stands for "Impacts of Climate on the Eco-Systems and Chemistry of the Arctic Pacific Environment." Might we please stop this silliness, people?
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