Here's how climate change helps melting glaciers feed ocean
Friday, August 14, 2015, 7:51 PM - While melting Antarctic glaciers have been widely attributed to global warming and worrisome long-term trends, a new study suggests the nutrient-rich water is actually nourishing the ocean food chain.
The research published in the Journal of Geophysical Research: Oceans, finds Antarctica's ice carries concentrations of iron that is being shuttled by melting water to open areas of the ocean called polynyas, whereby it stimulates the growth of phytoplankton, creating feeding "hot spots." Essentially, phytoplankton forms the base of the marine food chain. Fish thrive on phytoplankton and in turn, these smaller animals support penguins, seals and whales.
“These coastal polynyas are sensitive to inputs from adjacent glaciers, and these glaciers are probably going to accelerate their melting in the future, which is certainly going to have implications for these polynyas,” said Kevin Arrigo lead author of the study in a news release. “Coastal Antarctica is likely to become a more productive place in the future,” Arrigo said.
Polynyas are created when winds ramp up off the Antarctic Ice Sheet in the summer, pushing floating sea ice away from shore, according to the American Geophysical Union (AGU) news release. These large areas of open water range from the size of San Diego to an area equal to the Great Lakes combined and are rich in phytoplankton.
"When you look at satellite images of ocean colour, these areas just light up (green) compared to the (blue) waters around them," said Arrigo in the release.
While sunlight and temperature were previously thought to be the largest drivers behind the boost of phytoplankton, the study shows it is indeed the amount of water leaving melting Antarctic glaciers.
Researchers used satellite images from 1997 to 2014 to calculate the amount of phytoplankton growing in 46 polynas along the coast of Antarctica. The imagery helps scientists to further understand how the Antarctic marine food web works and how it could be affected by climate change.
While an increase of iron in the polynyas is good for the food chain, any positive effects can be offset by other climate change-driven environmental shifts, the press release notes. This includes global increases in ocean temperatures and acidification.
In addition, the new research could help scientists investigate how carbon is stored in the ocean. The study notes how phytoplankton in the polynyas could be drawing in large amounts of carbon dioxide from the atmosphere by means of photosynthesis.
"These polynyas appear to be disproportionately important, for their size, as sinks of carbon," Arrigo noted in the press release. "And the reality is that they really are not included in anyone's carbon budget."