How will future ocean acidification impact the ocean carbon
cycle and could it further amplify rising CO2 and
climate change?
A key facet of ocean acidification is the impact that changes in
the chemistry of the ocean may have on marine algae, particularly
those that make shell material out of the mineral calcium carbonate
as this will become less easy to precipitate as ocean acidification
intensifies in the future. If the rate of carbonate production by
algae living at the surface slows, there will be less dense shell
material to help weigh down the fluffier organic matter and the
food supply to organisms on the seafloor may be reduced. Weakening
the transport of organic carbon from the surface to the deep ocean
would also act to increase further atmospheric CO2 concentrations.
Other impacts of ocean acidification may include changes in the
amount and nutritional content of organic matter produced in the
ocean, and loss of nitrate, all of which would affect the nutrient
and carbon cycles in the global ocean.
There are large uncertainties surrounding how the carbon cycle
works and the importance of carbonate shells in the sinking of
organic matter, and hence, uncertainties in the impacts of
acidification on the global ocean. Our first aim is to achieve a
much better understanding of the modern ocean carbon cycle – a
prerequisite to making reliable future predictions. We will do this
by using vast datasets describing what the ocean ‘looks’ like today
and running computer models of ocean carbon cycling and climate
thousands of times. Together, this will allow us to improve our
model and also estimate some of the uncertainty in our predictions.
The second aim of the project will build directly on this to make
predictions of the range of potential changes we might see in ocean
carbon and nutrient cycles in the future, and whether these changes
will affect the degree of future warming by emitting greenhouse
gases back to the atmosphere.
The outputs of this programme will:
- Feed into the cross-government Climate
Change Adaptation programme
- Make a significant contribution to the
Living With Environmental Change programme
- Provide evidence to the IPCC 5th
Assessment Report on Climate Change
- Provide information to marine bioresource
managers, policy makers negotiating CO2 emissions
reduction and other stakeholders
- Inform parties interested in exploring how
the geochemical consequences of ocean acidification varies in time
and space
The results of the project will be 3-fold:
- Better constraints on the magnitude of
carbonate production by calcifying algae in the surface ocean in
the modern ocean as well as the controls on their
distribution.
- Improved understanding of the role of
carbonate shells in controlling the sinking of organic matter in
the ocean.
- Estimates of the uncertainty in future
projections of impacts of ocean acidification on marine carbon and
nutrient cycles, taking into account a range of potential future
fossil fuel CO2 emissions as well as prevailing
uncertainty in the sensitivity of climate to
CO2.
The first two results will be primarily utilised by other
scientists, in particular climate modellers and marine biologists.
The third result of the project will be made available to a range
of scientists, policy makers, and the general public, as
follows:
Firstly, we will set up a dedicated web portal (the ‘Online
Global Ocean Acidification Viewer’), creating a web interface to
allow users to interrogate model simulations and answer specific
questions about the impacts of ocean acidification and changing
carbonate chemistry in the future. Thus we will make the ocean
acidification projections available not only to UK Ocean
Acidification Research Programme members and other scientists, but
also to the general public and policy makers. Our model projections
and portal will also make it possible to identify CO2
emissions or atmospheric concentration thresholds that avoid
certain impacts together with a measure of the uncertainty in where
key ocean acidification ‘thresholds’ might lie.
Secondly, we will hold two ocean acidification
modelling workshops. These will not only be open to UK Ocean
Acidification Research Programme participants, but also to BIOACID,
EPOCA, and MEECE participants, and help foster closer links between
the various EU OA programmes. These workshops will provide training
in using and interpreting model projections of ocean acidification
and instil an essential appreciation of model limitations.
Finally, we will make findings available for use in policy
documents, for example, the Marine Climate Change
Impacts Partnership, to help disseminate future projections and
assessments of potential ocean acidification impacts to policy
makers and a wider audience. Results and findings will also be
disseminated through more popular scientific literature and
publications.