New study suggests oceans are losing the ability to absorb carbon dioxide
New research published online this week suggests that man-made
climate change is diminishing the ocean's ability to 'take up' CO2
from the atmosphere.
Plants, trees and the soil all absorb carbon from the
atmosphere, but the ocean is the world's largest 'carbon sink' and
since the industrial revolution, the ocean has probably soaked up
a third and half of all man-made CO2 emissions.
The removal of manmade CO2 from the atmosphere by seawater is
clearly an important process. However, researchers now suggest
that the ocean's ability to absorb atmospheric CO2 might be
declining. It's a combination of atmospheric CO2 levels and
seawater chemistry that determines how much CO2 seawater can hold,
and warmer water cannot hold as much dissolved CO2 as cold
Researchers analysed existing CO2 and temperature data for the
North Atlantic Ocean over the last three decades. Their results
showed that for a large section of the North Atlantic, less CO2 has
been able to dissolve as the surface temperature of seawater has
risen. This is in line with previous research conducted in other
oceans, such as the
Southern Ocean and
Sea of Japan, which have also been found to be taking up less
CO2 as a result of man-made climate change.
When considering the same question, previous
studies in the North Atlantic have come to conflicting
conclusions. The authors of this new study suggest that this is
down to a high degree of natural variability which can mask
Professor McKinley, the study's author, says:
"Because the ocean is so variable, we
need at least 25 years' worth of data to really see the effect of
carbon accumulation in the atmosphere. This is a big issue in many
branches of climate science - what is natural variability, and what
is climate change?"
This new study considers nearly thirty years worth of data,
which the team think is enough to determine a real trend. Their
findings have big implications for how much CO2 will be absorbed by
oceans in the future, given the projected temperature rise
associated with man-made greenhouse gas emissions. McKinley
"...This is some of the first evidence
for climate damping the ocean's ability to take up carbon from the
McKinley stresses the need for this type of analysis in other
oceans so that ocean CO2 uptake trends can continue to be refined.
But the results of the study demonstrate that on a warming planet,
natural carbon sinks can't be taken for granted.