Global warming that causes sea ice in the Arctic to melt is causing the microscopic organism phytoplankton to bloom early. This may have a drastic impact on the marine life food chain and the life cycles of different species of fish and whales.
In a collaborative effort with NASA and researchers from Portugal and Brazil, a team from Scripps Institution of Oceanography analyzed satellite data and discovered that the phytoplankton bloomed almost 50 days early in some places.
This discovery has raised concerns over the effect of the early blooms.
According to biologist Greg Mitchell, earlier blooms might disrupt the life cycle of key fish species or those higher up on the food chain, like whales. The migration pattern of gray whales to the Arctic, for example, is seasonal. If the blooming occurs early, there may be less food available for whales when they arrive, which impacts the health of nursing whales and their calves.
“All this is speculative,” Mitchell said. “But we do know that the life cycles of organisms are timed to take advantage of Arctic blooms. If they are occurring much earlier, this could disrupt these life cycles.”
The earlier the sea ice melts, the more sunlight can penetrate, creating conditions for the phytoplankton to bloom earlier.
“The issue is that huge impacts to the climate can occur with just small changes in mean global temperature,” Mitchell said. “The polar regions in particular will have larger impacts.”
To gather the data that led to this discovery, project scientist Mati Kahru and Mitchell obtained a time series of satellite images over the last 15 years.
Mitchell obtained approval in 1996 to use orbiting satellites to collect ocean color satellite data.
The combined time-series of Ocean Color Satellite Data could only be accurately understood in conjunction with on-ship observations of ocean ecology. The production of chlorophyll, a green pigment produced by plants during respiration, can be used to build a mathematical relationship between ocean ecology and the spectral reflection of the ocean shown in satellite data.
“Using the time-series data from multiple satellites, but especially SeaWiFS, and simple statistical analysis, we have been able to determine the change in timing of oceanic blooms,” Mitchell said.
Kahru and Mitchell, who serves as the lead for all the ship-based observation programs, are also part of ICESCAPE, a NASA Arctic research project. Members of the program are currently carrying out research in order to better understand how to propose the most effective policies to curb the effects of climate change.
“We will continue the satellite time series and using data collected on ships in the Arctic,” Mitchell said. “We will [be able to] improve the satellite algorithms and models to… advance our understanding and move that understanding into policy actions.”
