
Dr Joseph Stewart
PhD (Soton.), MESc (Oxon.)
Current positions
Research Fellow
School of Earth Sciences
Contact
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Research interests
I am an isotope geochemist studying the chemistry of marine biogenic carbonates to better understand the chemistry of the seawater in which these organisms lived.
My previous research has involved the taxonomic classification and geochemical measurement of ancient calcified plankton (foraminifera) recovered from deep ocean sediment cores to reconstruct ancient seawater temperatures (e.g. Mg/Ca) and changing patterns of continental weathering (e.g. Nd isotopes)
More recently research efforts have been focused on the refinement and application of boron isotope proxy for seawater pH measured in corals and calcified algae. The aims of this research are (i) to identify suitable coral substrates for use as pH biosensors, (ii) document changes in past ocean pH and (iii) to further our understanding of coral bio-mineralization and the impact of ocean acidification on marine califiers.
Projects and supervisions
Thesis supervisions
Stylasterid coral geochemistry
Supervisors
Deep-sea coral records of the intermediate Atlantic Ocean during the last glacial cycle
Supervisors
Subpolar North Atlantic paleoceanography over the last millennium and Holocene using cold-water coral geochemistry
Supervisors
Exploring recent ocean ventilation and biogeochemical variations using deepsea corals
Supervisors
Publications
Selected publications
01/10/2020NIST RM 8301 Boron Isotopes in Marine Carbonate (Simulated Coral and Foraminifera Solutions)
Geostandards and Geoanalytical Research
Refining trace metal temperature proxies in cold-water scleractinian and stylasterid corals
Earth and Planetary Science Letters
CO2 storage and release in the deep Southern Ocean on millennial to centennial timescales
Nature
Recent publications
15/01/2025Delayed onset of ocean acidification in the Gulf of Maine
Scientific Reports
Radiocarbon evidence of a North Atlantic intermediate water reconfiguration between the 1960s and 1980s
Earth and Planetary Science Letters
Contrasting responses of commercially important Northwest Atlantic bivalve species to ocean acidification and temperature conditions
PLOS Climate
Arctic and Antarctic forcing of ocean interior warming during the last deglaciation
Scientific Reports
Ba/Ca of stylasterid coral skeletons records dissolved seawater barium concentrations
Chemical Geology