Surprise discovery in the Arctic
By Michael Richardson
For the Straits Times
Two years ago, a Canadian research team alarmed climate scientists when it published the results of a survey of the oceans, the health of which will be a major focus of the United Nations Conference on Sustainable Development summit in Rio de Janeiro this week.
The researchers reported that the world’s phytoplankton – tiny, plant-like organisms that grow in sea water – seemed to have been disappearing at a rate of about 1 per cent a year for the last century.
Using measurements of ocean clarity, they found that phytoplankton biomass had shrunk by about 40 per cent on average since 1950, and that the decline was observed in eight of 10 oceans and seas that circle the globe.
Water murkiness increases or decreases depending on the amount of phytoplankton drifting on or near the surface. In bloom, masses of microscopic marine algae show up in images taken from satellites as spectacular swathes of bright green or blue in the oceans. The fewer the phytoplankton, the clearer the water, with the exception of zones of near-coast pollution.
The lead author of the study, Mr Daniel Boyce, a marine scientist at Canada’s Dalhousie University, says that a global phytoplankton decline of this magnitude was” shocking”.
Why? Because phytoplankton act in the same way as living trees and plants on land. They consume carbon dioxide (C02) and release oxygen as they grow.
Scientists say phytoplankton provide more than half of the oxygen needed for life on earth.
The tiny marine plants also remove up to 40 per cent of the C02 released into the atmosphere each year, mainly from burning fossil fuels and clearing forests.
C02 is the long-lasting global warming gas from human activity that most concerns climate scientists. Even small changes in the growth and density of phytoplankton could affect atmospheric C02 concentrations, which have been rising steadily.
Phytoplankton are also the basis of the marine food chain and sustain the health of fisheries. They are eaten by small ocean animals that are, in turn, eaten by larger fish and ocean creatures.
In the Arctic, the region of the world that is warming fastest, researchers have long assumed that the algae blooms start only in summer in open waters after the sea ice melts, allowing sunlight to reach the marine plants and fostering growth.
But an on-the-spot scientific survey in 2010 and last year using an icebreaker has come up with a result that astonished the scientists involved. The survey was sponsored by the United States space agency, Nasa, to validate images from its earth observation satellites.
The scientists found huge and highly productive phytoplankton blooms that satellite sensors could not detect because they were hidden under Arctic Ocean ice, a phenomenon one said was akin to finding a rainforest in a desert. Their findings were published on June 7. One of the blooms extended from the sea-ice edge about 100km into the ice pack. It was up to 70m deep in places.
The phytoplankton under the sea ice were extremely productive, doubling in number more than once a day. Blooms in open water grow at a much slower rate, doubling in two to three days.
The researchers estimated that phytoplankton production under the ice in parts of the Arctic Ocean could be up to 10 times higher than in the nearby open ocean. They believe that thinning Arctic sea ice is allowing sunlight to reach waters underneath and that about a quarter of the Arctic Ocean now has conditions conducive to such blooms.
Does this mean that the global ecosystem has a self-righting mechanism and that as humans pump ever more C02 into the atmosphere, warming the atmosphere and sea and melting ice, phytoplankton production will increase and absorb the surplus greenhouse gas? The jury is still out. But Dr Paula Bontempi, Nasa’s ocean biology and biogeochemistry programme manager in Washington, says the discovery “most certainly changes what we thought was happening in the Arctic” , where earlier research showed that phytoplankton was diminishing.
If Arctic sea ice melts earlier in the summer because of climate change, the under-ice blooms could grow in extent or happen earlier in the year. This could affect marine life species that time their eating and breeding cycles to match peak phytoplankton growth.
Mr Kevin Arrigo, a Stanford, University climate scientist and lead author of the new study, says it is still unknown if the rich phytoplankton blooms have been occurring under the Arctic Ocean ice for a long time without being observed, or if they will become more widespread even as Arctic sea-ice cover continues to thin as a result of global warming.
The question has major political ramifications, since many countries are reluctant to curb their C02 emissions because of the cost to economic growth. It will be answered only with more extensive research.
The writer is a visiting senior research fellow at the Institute of Southeast Asian Studies.