Oceanographer Dr Matthew Humphreys investigates the exchange of CO2 between the atmosphere and the oceans. ‘The oceans currently take up about one-quarter of all our CO2 emissions. In that sense, the oceans definitely keep us out of trouble. However, there is a drawback to that. This uptake of additional CO2 is acidifying the oceans. My research focuses on understanding those balances. How do chemical equilibria in the top few hundred metres of the oceans control the exchange of CO2? And what is the role of biological processes, such as the cycle of plankton growing in the sunlit surface ocean and sinking after they die, which can transport carbon down into the deep sea?’
‘Compared to the total quantity of water in the seas and oceans, the North Sea is rather small. At the same time, from a biological perspective, the North Sea is highly productive compared to much of the open ocean. In one of my projects, I, therefore, study how that North Sea can punch above its weight in contributing to the uptake of carbon from the atmosphere.’
'Oddly enough, the role of the immense Indian Ocean in the circulation of carbon – and certainly smaller quantities of minerals too – is still relatively poorly monitored. Therefore, the second aspect of my research focuses on describing the processes in the water between Africa, Australia and Antarctica. I do that within the international project GEOTRACES.’
‘A third project focuses on the contribution of river water. The weathering of some types of rock on the land causes river water to become alkaline, and on entering the sea, that water partly neutralises the acidification of the oceans. But how will that change in the future if rivers are dammed more often, and the drainage of rainwater occurs in more extreme peaks and troughs?'
‘Technological solutions to reduce the quantity of CO2 in the oceans as a way of tackling the climate problem are spoken about increasingly often. I believe we should first acquire a thorough understanding of the natural exchange, acidification and weathering processes before we can even start to think about such geoengineering approaches.'Read more +
The main theme of my research is to understand how the ocean responds to ongoing anthropogenic emission of carbon dioxide (CO2). I study the processes that drive anthropogenic CO2 to dissolve into seawater, scrutinise the consequent progress of ocean acidification, and unravel the interactions between the changing carbon cycle and other marine biogeochemical systems.
I tackle these topics with a broad approach including collecting new observations at sea, experimental work in the lab, investigations of the theory behind the equilibrium chemistry of seawater, scientific software development, analysis of regional and global datasets compiled from many sources, and comparisons between observations and computational models.
Total alkalinity measured off the west coast of southern Africa during a GEOTRACES cruise in the Benguela upwelling region. Total alkalinity controls the chemical capacity for seawater to take up CO2 from the atmosphere and is critical for marine mitigation of anthropogenic climate change.
My work is highly collaborative, and I actively seek to engage with scientists in other fields where the chemistry of CO2 in seawater is pertinent. This includes palaeo-proxy development, physical transports of carbon in the interior ocean, links with other biogeochemical cycles, and experimental work investigating the response of marine species and ecosystems to ocean acidification.
You can find out more about my ongoing projects on my website: mvdh.xyz
I'm also active on Twitter: @matthew_vdh