How much variability is there in oceanic CO2 uptake
and what are the trends for the future?
“Acidification” of ocean waters is a consequence of the rising
concentration of carbon dioxide (CO2) in the atmosphere.
It is calculated that surface ocean pH has decreased on average by
about 0.1 units since pre-industrial times due to the ocean’s
uptake of CO2. By 2100 this decrease may reach 0.3
units, with potentially serious consequences for some marine
ecosystems.
However, acidification is not occurring
uniformly everywhere; evidence from the scattered measurements
available suggests that surface pH varies substantially. Variations
are from place to place, season to season, year to year and decade
to decade. These natural variations form a scale against
which human-caused changes may be measured. Acidification that
moves the natural system beyond the natural variations is likely to
be more damaging than changes that remain within natural bounds. It
is important therefore to establish this natural variability, by
increasing systematic measurements.
The aims of this project are:
- To quantify the rate of change of ocean pH
in the north Atlantic and European shelf (UK coastal waters in
particular) and also parts of the Southern Ocean.
- To gather pH observations from commercial
“ships of opportunity”, small research vessels, and the regular
surveys undertaken by the Centre for Environment, Fisheries and
Aquaculture Science (CEFAS).
- To collaborate with marine scientists
worldwide, who are researching ocean acidification, to obtain a
much wider and more complete picture of the issue. We will
therefore take a lead in the “Surface Ocean CO2 atlas”,
which has recently begun to synthesise global data on changing
carbonate chemistry that controls ocean pH. By this means we will
synthesise the best available estimates of how pH has changed in
the past, as well as how it is currently changing and predict
likely changes in the future, for the ocean regions of
interest.
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
Results from this project will leave a lasting legacy,
including:
- Existing observation systems, which
measure the uptake of CO2 by the oceans, will be
maintained and upgraded, to ensure that data can be used to
accurately calculate pH.
- New observations round much of the coastal
waters of the UK using surveys undertaken by CEFAS.
- Collaboration and co-ordination with
international partners in Europe and the US to instrument several
other shipping routes covering the North Atlantic.
- A leading role will be taken in the
international marine science community, to make a database
available under the “Surface Ocean CO2 atlas (SOCAT)”
project, documenting observations relevant to the pH of the surface
oceans, and use these to synthesise the best available picture of
how pH has varied in the past over the global ocean, but
particularly in our regions of interest. SOCAT is aimed primarily
at calculating the changing CO2 content of the surface
ocean, but from this and with additional information, pH can be
calculated.
- An update of the presently rather
schematic notion of how acidification will proceed, under given
increases in CO2 later this century. We should be able
to answer what pH change and variability the regions in our study
have seen in the recent past and what they will see in the near
future, enabling more accurate predictions about the more distant
future.
- Data will be made as widely available as
possible via the British Oceanographic Data Centre (BODC) and the
Carbon Dioxide Information Analysis Center (CDIAC).