Temperatures in the Arctic are rising faster
than the rest of the world. Now, new research suggests microscopic
algae could speed up warming even further.
These miniscule floating plants, which do
everything from storing carbon to supporting the ocean food web,
could drive faster sea ice melt as the Earth heats up, the lead
author tells Carbon Brief.
Microalgae are already showing signs of adapting
to warmer oceans, says a second study. But this is no guarantee
they'll be able to cope with future temperature increases, the
Foundation for life
Microalgae, or phytoplankton
, are tiny plants that float in the upper part of the ocean.
Just like plants on land, they photosynthesise - using sunlight and
carbon dioxide to generate energy for growth. In this way they take
carbon dioxide out of atmosphere and help to buffer the impact of
emissions from human activities.
The by-product of photosynthesis is oxygen, and
microalgae are responsible for producing around half of
the oxygen in the atmosphere. Microalgae are also
the foundation of the food web, meaning they're ultimately the
reason there's any life in the oceans at all.
As algae serve such an important purpose,
scientists are trying to work out how their abundance and
distribution could change in the future as the Earth
Temperatures in the Arctic are increasing
twice as fast as the global average. The intense
warming, known as
Arctic amplification, is largely caused by
diminishing sea ice. Energy from the sun that would have been
reflected away by sea ice is instead absorbed by the
Previous research has shown that shrinking
sea ice has given a boost to algae abundance. But there's a
downside to this accelerated growth. A new study, published
Proceedings of the National Academy of
Sciences, suggests the increase in algae could
intensify Arctic warming, and sea ice melt, in the
So how could algal blooms intensify sea ice
decline? As the Arctic warms up and the sea ice melts, more
sunlight can penetrate into the ocean surface, triggering more
growth in the algae.
With more microalgae floating around in the
surface waters of the ocean, they absorb an increasing amount of
the sun's energy, which causes the water to warm up. A warmer ocean
means more sea ice melts, boosting algal growth even further, and
creating a positive feedback loop.
The researchers looked at how this feedback loop
could play out in a changing climate. They linked their marine
ecosystem model to a climate model and ran simulations where carbon
dioxide levels increase by 1% per year until the total amount in
the atmosphere is twice what it was in 1990.
You can see the results in the maps below. These
show the difference in Arctic temperature and sea ice between model
runs with and without the added impacts of microalgae.
Projections of Arctic changes under a doubling of
atmospheric carbon dioxide: A) annual average temperature, B) sea
ice concentration, C) number of ice-free days, and D) concentration
of chlorophyll. Source: Park et al. (2015).