Current Research

Carbon dioxide in the atmosphere and ocean.

Carbon emissions from fossil fuels and land-use changes are causing levels of atmospheric carbon dioxide to increase. The increase in atmospheric carbon dioxide leads to climate change through the greenhouse effect. This climate change is likely to alter the natural carbon cycle further, leading to a carbon-climate feedback that either enhances or dampens the rise in atmospheric carbon dioxide. My research investigates how carbon-climate feedbacks affect atmospheric carbon dioxide levels, both in the future in response to fossil fuel emissions, and as part of natural climate cycles in the past.

Past natural climate cycles: Bubbles in polar ice reveal the atmospheric carbon dioxide level when the air-bubbles were trapped. From these records it is known that past changes in atmospheric carbon dioxide contributed to the climate swings between cold glacial ice ages and warm interglacial periods. When the climate was warm carbon dioxide levels were high, and when climate was cold carbon dioxide levels were low. By a process of elimination, it is likely that when atmospheric carbon dioxide levels were low, the extra carbon was stored in the ocean. However, it is not understood what ocean processes caused this increase in ocean carbon storage, removing carbon dioxide from the atmosphere.

Future response to emissions: Some of the carbon emitted today enters the ocean, a process called ‘ocean invasion', causing the ocean to become more acidic. After many centuries ocean invasion will stop, and around 30% of the emitted carbon will still remain in the atmosphere. Over many tens of thousands of years the ocean acidification will cause dissolution of CaCO3 sediments, which chemically removes more fossil fuel carbon from the atmosphere. Considering only ocean chemistry, even after one hundred thousand years approximately 10% of today's fossil fuel emission will remain in the atmosphere. Carbon-climate feedbacks are highly uncertain, and will likely alter how atmospheric carbon dioxide levels respond to emissions during ocean invasion (over the next thousand years) and then during dissolution of CaCO3 sediments (over the next hundred thousand years). Carbon climate feedbacks will thus have a significant impact on the magnitude of human forcing of climate over the next one hundred thousand years.

Current research topics include:

1. Combining numerical models and observational data to constrain past ocean carbon cycling to better understand the role of the ocean in glacial-interglacial cycles in atmospheric CO2.
2. Using numerical models and theory to evaluate future carbon-climate feedbacks on timescales ranging from one year to one hundred thousand years.


 


Last updated on 04-May-12 14:26