The Role of the Ocean Carbon Cycle in Climate Change

The ocean carbon cycle plays a twofold role in the context of climate change: (1) through carbon dioxide gas exchange with the atmosphere and carbon cycle climate feedbacks, the ocean regulates the carbon dioxide concentration in the atmosphere and hence has a strong influence on the heat budget of the Earth; (2) the paleo-climatic marine sediment core record is largely based on biogenic matter fluxes from the ocean surface to the sea floor, which are part of the marine carbon cycle. The ocean is important for global carbon cycling, primarily due to three factors: (1) the ocean is a huge carbon reservoir with a relatively short turnover time; (2) carbon dioxide in sea water is effectively dissociated inorganically into other substances; (3) marine plankton is keeping the surface ocean carbon dioxide concentration at a lower level than would a lifeless ocean. On intermediate to long time scales, the ocean provides the most important sink for anthropogenic carbon dioxide. The marine uptake kinetics for carbon dioxide work on a longer time scale than current and projected emissions by humans.

Download Full-text

A fishy tale: A missing part of the inorganic ocean carbon cycle

The Biochemist ◽

10.1042/bio03303030 ◽

2011 ◽

Vol 33 (3) ◽

pp. 30-34

Author(s):

Rod W. Wilson ◽

Erin E. Reardon ◽

Christopher T. Perry

Keyword(s):

Carbon Cycle ◽

Ocean Acidification ◽

Fossil Fuels ◽

Sea Water ◽

Atmospheric Co2 ◽

Co2 Production ◽

Ph Change ◽

Ocean Carbon Cycle ◽

Sea Levels ◽

Ocean Carbon

Human activities, such as burning fossil fuels, are playing an important role in the rising levels of carbon dioxide (CO2) in the Earth's atmosphere1. The oceans may store a large portion of CO2 that we are releasing into the atmosphere, with up to 40% already taken up by the oceans. Although this absorption helps to offset some of the greenhouse effect of atmospheric CO2, it also contributes to ocean acidification, or a fall in the pH of sea water. The historical global mean pH of oceanic sea water is about 8.2, and this has already declined by 0.1 pH units (a 30% increase in H+ concentration) and is predicted to reach pH ~7.7 by the end of the century if current rates of fossil fuel use continue, leading to an atmospheric CO2 level of 800 p.p.m.1,2. Even this extreme potential fall in pH would still leave seawater above the neutral point (pH 7.0), so technically it is more accurate to say that the ocean is becoming less alkaline, rather than truly acidic (i.e. below pH 7.0). However, the magnitude is perhaps less important than the speed of pH change which is occurring faster than at any time during the previous 20 million years. Over this time, the average ocean pH has probably never fallen below pH 8.02,3. It is only during the last decade that the importance of ocean acidification has come to the forefront of concerns for scientists1,2. Consequences of these changes in global CO2 production are predicted to include elevated global temperatures, rising sea levels, more unpredictable and extreme weather patterns, and shifts in ecosystems1. In order to more fully understand the implications of ocean acidification, teams of researchers, including fisheries scientists, physiologists, geologists, oceanographers, chemists and climate modellers, are working to refine current understanding of the ocean carbon cycle.

Download Full-text

Ocean Carbon Cycle in a Changing Climate: Climate Change Detection

The Ocean Carbon Cycle and Climate ◽

10.1007/978-1-4020-2087-2_9 ◽

2004 ◽

pp. 297-315 ◽

Cited By ~ 3

Author(s):

Richard J. Matear

Keyword(s):

Climate Change ◽

Carbon Cycle ◽

Change Detection ◽

Ocean Carbon Cycle ◽

Changing Climate ◽

Ocean Carbon ◽

Climate Change Detection

Download Full-text

Climate–Carbon Cycle Feedback Analysis: Results from the C4MIP Model Intercomparison

Journal of Climate ◽

10.1175/jcli3800.1 ◽

2006 ◽

Vol 19 (14) ◽

pp. 3337-3353 ◽

Cited By ~ 2085

Author(s):

P. Friedlingstein ◽

P. Cox ◽

R. Betts ◽

L. Bopp ◽

W. von Bloh ◽

...

Keyword(s):

Climate Change ◽

Carbon Cycle ◽

Net Primary Productivity ◽

Future Climate ◽

Climate Feedback ◽

Future Climate Change ◽

Ocean Carbon Cycle ◽

Intergovernmental Panel ◽

Ocean Carbon ◽

The Impact

Abstract Eleven coupled climate–carbon cycle models used a common protocol to study the coupling between climate change and the carbon cycle. The models were forced by historical emissions and the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) A2 anthropogenic emissions of CO2 for the 1850–2100 time period. For each model, two simulations were performed in order to isolate the impact of climate change on the land and ocean carbon cycle, and therefore the climate feedback on the atmospheric CO2 concentration growth rate. There was unanimous agreement among the models that future climate change will reduce the efficiency of the earth system to absorb the anthropogenic carbon perturbation. A larger fraction of anthropogenic CO2 will stay airborne if climate change is accounted for. By the end of the twenty-first century, this additional CO2 varied between 20 and 200 ppm for the two extreme models, the majority of the models lying between 50 and 100 ppm. The higher CO2 levels led to an additional climate warming ranging between 0.1° and 1.5°C. All models simulated a negative sensitivity for both the land and the ocean carbon cycle to future climate. However, there was still a large uncertainty on the magnitude of these sensitivities. Eight models attributed most of the changes to the land, while three attributed it to the ocean. Also, a majority of the models located the reduction of land carbon uptake in the Tropics. However, the attribution of the land sensitivity to changes in net primary productivity versus changes in respiration is still subject to debate; no consensus emerged among the models.

Download Full-text