Royal Netherlands Institute for Sea Research
Royal Netherlands
Institute for Sea Research
Phone number
+31 (0)222 36 9351
Location
Texel
Department
Ocean Systems (OCS)
Function
Tenure track Scientist
Expertise
  • Carbon cycle
  • Marine biogeochemistry
  • Anthropogenic carbon dioxide and ocean acidification
  • Seawater carbonate chemistry
  • Alkalinity and chemical buffering
Read the Academic Story of Matthew Humphreys

Dr. Matthew Humphreys

Tenure track Scientist

How do the oceans function as a sponge for CO2?

Oceanographer Dr Matthew Humphreys investigates the chemistry of the marine carbon cycle and CO2 exchange between the atmosphere and ocean. ‘The ocean absorbs about a quarter of the CO2 we emit each year, reducing the rate of human-driven climate change. But there is a drawback: absorbing extra CO2 changes the chemistry of seawater, for example lowering its pH, which is known as ocean acidification. My research focuses on understanding the balance of the equilibrium chemical reactions involved. How do these equilibria in the ocean 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?’

North Sea lends a helping hand

‘Relative to the global ocean, the North Sea is rather small. But from a biological perspective, the North Sea is highly productive, so its role in the marine carbon cycle is greater than expected from it size. The chemical buffering capacity of seawater is also high here, thanks to inputs of alkalinity from rivers and sediments, which allows its waters to absorb more CO2 and resist the resulting chemical changes. In one project with Rijkswaterstaat, and also through a second project with a consortium led by Fugro, I therefore study how the North Sea punches above its weight in absorbing CO2 from the atmosphere.’

Solving the marine carbonate system

‘Solving the marine carbonate system is an important computational step in marine carbon cycle research. This means computing the overall balance of all the different chemical reactions in seawater based on a limited set of routinely measurable parameters. I design and develop scientific software (Python packages) to help run these calculations, using both stoichiometric (PyCO2SYS) and thermodynamic (Pytzer) approaches, and my research that aims to improve the parameterisations in these models and understand their inherent uncertainties.’

Chemical buffering and the CaCO3 cycle

‘Calcium carbonate (CaCO3) minerals, used by many marine organisms such as coral, oysters and various plankton to create their shells and skeletons, play an important role in the marine carbon cycle. For example, dissolving CaCO3 raises seawater alkalinity, buffering against the effects of our CO2 addition. In a joint project with Dr Mariëtte Wolthers at Utrecht University (BEYΩND), I am investigating how seawater chemistry controls the rate and mechanisms of CaCO3 dissolution in the ocean.’

Academic history

  • 2007–2011: MA, MSci in Natural Sciences (Geology), University of Cambridge (Churchill College), UK
  • 2011–2015: PhD in Ocean and Earth Science, University of Southampton / National Oceanography Centre Southampton, UK
  • 2015–2017: Senior Research Assistant in Marine Biogeochemistry, University of Southampton / National Oceanography Centre Southampton, UK
  • 2017–2019: Senior Research Associate in Marine Physical Chemistry, University of East Anglia, UK
  • 2019–present: Tenure-Track Scientist, NIOZ Royal Netherlands Insitute for Sea Research, Texel

Linked news

Friday 29 July 2022
How coastal seas help the ocean in absorbing carbon dioxide from the atmosphere
The biologically productive North Sea impacts the global climate through exchange of carbon and nutrients with the Atlantic Ocean. A Dutch consortium of scientists will investigate how big this role of the North Sea really is. Under the leadership of…
Tuesday 09 February 2021
Autonomous measurements of the marine carbon cycle in the North Sea
A consortium of Fugro, NIOZ and two partner companies has been granted EUR 3.3 million by the Netherlands Enterprise Agency (RVO) for the RoboDock project.

Linked blogs

Wednesday 04 December 2019
NIOZ@SEA | Sinkhole expedition to the Sababank
From 5 to 18 December, NIOZ and Wageningen Marine Research (WMR) are organizing an expedition to the Saba Bank, near the Dutch island of Saba in the Caribbean. Experts on board the research vessel Pelagia hope to gain more knowledge about the…

NIOZ publications

  • 2022
    Clegg, S.L.; Humphreys, M.P.; Waters, J.F.; Turner, D.R.; Dickson, A.G. (2022). Chemical speciation models based upon the Pitzer activity coefficient equations, including the propagation of uncertainties. II. Tris buffers in artificial seawater at 25 °C, and an assessment of the seawater ‘Total’ pH scale. Mar. Chem. 244: 104096. https://dx.doi.org/10.1016/j.marchem.2022.104096
    Humphreys, M.P.; Lewis, E.R.; Sharp, J.D.; Pierrot, D. (2022). PyCO2SYS v1.8: marine carbonate system calculations in Python. Geosci. Model Dev. 15(1): 15-43. https://dx.doi.org/10.5194/gmd-15-15-2022
    Humphreys, M.P.; Meesters, E.H.; de Haas, H.; Karancz, S.; Delaigue, L.; Bakker, K.; Duineveld, G.; de Goeyse, S.; Haas, A.F.; Mienis, F.; Ossebaar, S.; van Duyl, F.C. (2022). Dissolution of a submarine carbonate platform by a submerged lake of acidic seawater. Biogeosciences 19(2): 347-358. https://dx.doi.org/10.5194/bg-19-347-2022
    Humphreys, M.P.; Waters, J.F.; Turner, D.R.; Dickson, A.G.; Clegg, S.L. (2022). Chemical speciation models based upon the Pitzer activity coefficient equations, including the propagation of uncertainties: Artificial seawater from 0 to 45 °C. Mar. Chem. 244: 104095. https://dx.doi.org/10.1016/j.marchem.2022.104095
    Read more
    Jiang, L.-Q.; Pierrot, D.; Wanninkhof, R.; Feely, R.A.; Tilbrook, B.; Alin, S.; Barbero, L.; Byrne, R.H.; Carter, B.R.; Dickson, A.G.; Gattuso, J.-P.; Greeley, D.; Hoppema, M.; Humphreys, M.P.; Karstensen, J.; Lange, N.; Lauvset, S.K.; Lewis, E.R.; Olsen, A.; Pérez, F.F.; Sabine, C.; Sharp, J.D.; Tanhua, T.; Trull, T.W.; Velo, A.; Allegra, A.J.; Barker, P.; Burger, E.; Cai, W.-J.; Chen, C.-T.A.; Cross, J.; Garcia, H.; Hernandez-Ayon, J.M.; Hu, X.; Kozyr, A.; Langdon, C.; Lee, K.; Salisbury, J.; Wang, Z.A.; Xue, L. (2022). Best practice data standards for discrete chemical oceanographic observations. Front. Mar. Sci. 8: 705638. https://dx.doi.org/10.3389/fmars.2021.705638
    Sulpis, O.; Humphreys, M.P.; Wilhelmus, M.M.; Carroll, D.; Berelson, W.M.; Menemenlis, D.; Middelburg, J.J.; Adkins, J.F. (2022). RADIv1: a non-steady-state early diagenetic model for ocean sediments in Julia and MATLAB/GNU Octave. Geosci. Model Dev. 15(5): 2105-2131. https://dx.doi.org/10.5194/gmd-15-2105-2022
    Živkovic, I.; Humphreys, M.P.; Achterberg, E.P.; Dumousseaud, C.; Woodward, E.M.S.; Bojanic, N.; Solic, M.; Bratkic, A.; Kotnik, J.; Vahcic, M.; Obu Vazner, K.; Begu, E.; Fajon, V.; Shlyapnikov, Y.; Horvat, M. (2022). Enhanced mercury reduction in the South Atlantic Ocean during carbon remineralization. Mar. Pollut. Bull. 178: 113644. https://dx.doi.org/10.1016/j.marpolbul.2022.113644
  • 2021
    Possenti, L.; Humphreys, M.P.; Bakker, D.C.E.; Cobas-García, M.; Fernand, L.; Lee, G.A.; Pallottino, F.; Loucaides, S.; Mowlem, M.C.; Kaiser, J. (2021). Air-Sea Gas fluxes and remineralization from a novel combination of pH and O2 sensors on a glider. Front. Mar. Sci. 8: 696772. https://dx.doi.org/10.3389/fmars.2021.696772
    Possenti, L.; Skjelvan, I.; Atamanchuk, D.; Tengberg, A.; Humphreys, M.P.; Loucaides, S.; Fernand, L.; Kaiser, J. (2021). Norwegian Sea net community production estimated from O2 and prototype CO2 optode measurements on a Seaglider. Ocean Sci. 17(2): 593-614. https://doi.org/10.5194/os-17-593-2021
    Rahlff, J.; Khodami, S.; Voskuhl, L.; Humphreys, M.; Stolle, C.; Martínez-Arbizu, P.; Wurl, O.; Ribas-Ribas, M. (2021). Short-term responses to ocean acidification: effects on relative abundance of eukaryotic plankton from the tropical Timor Sea. Mar. Ecol. Prog. Ser. 658: 59-74. https://doi.org/10.3354/meps13561
    Zhu, K.; Birchill, A.J.; Milne, A.; Ussher, S.; Humphreys, M.P.; Carr, N.; Mahaffey, C.; Lohan, M.C.; Achterberg, E.P.; Gledhill, M. (2021). Equilibrium calculations of iron speciation and apparent iron solubility in the Celtic Sea at ambient seawater pH using the NICA-Donnan model. Mar. Chem. 237: 104038. https://dx.doi.org/10.1016/j.marchem.2021.104038
  • 2020
    Donald, H.K.; Foster, G.L.; Fröhberg, N.; Swann, G.E.A.; Poulton, A.J.; Moore, C.M.; Humphreys, M.P. (2020). The pH dependency of the boron isotopic composition of diatom opal (Thalassiosira weissflogii). Biogeosciences 17(10): 2825-2837. https://dx.doi.org/10.5194/bg-17-2825-2020