UKRI Future Leaders Fellow 'Fate of ocean oxygenation in a warming world'

My research interests are in reconstructing past climates to develop a better understanding of how our planet functions under different boundary conditions. By creating a better understanding of earth past climates, we can contribute to understanding current and future climate change. I study the interaction between large-scale ocean circulation, the cycling of carbon, and climate change in the past.

My Future Leaders Fellowship focusses on the development and application of proxy methods to reconstruct oxygen concentrations of seawater during warm periods in the geological past.

Since the 1960s the oceans have lost ~2% of their oxygen, a trend expected to accelerate in relation with global warming. Future deoxygenation, along with overfishing, threatens the sustainability of economically important fisheries and marine ecosystems and will impact global biogeochemical cycles (carbon, nitrogen). However, predictions of the future are hampered by a poor understanding of the longer-term natural oxygen cycle. By reconstructing oxygen concentrations in the past, using novel methods, we are extending our knowledge of the longer term oxygen cycle, and help improve predictions of future oxygen level changes.

The material we use to develop proxy methods and past time-series involves deep sea sediments. Not only do we use the bulk sediments, we also study some fossils that are preserved within them: the shells of microorganisms called foraminifera. Some foraminifera species float near the ocean surface, called planktonic foraminifera, and can be used to assess the presence of subsurface oxygen minimum zones, seawater temperatures, etc. Species that live on or in sediments at the bottom of the ocean are termed benthic foraminifera and can be used to reconstruct bottom water oxygen concentrations and ventilation.

My group are working with sediments from the International Ocean Discovery Program to determine if there have been changes in the natural extent and intensity of the Atlantic Ocean, the shallow Pacific Ocean OMZ oxygen minimum (or 'dead') zones (e.g. areas where oxygen levels are too low to support aerobic life). Some of our work has focussed on the last glacial-interglacial cycle (e.g. last ca. 130,000 years). Over the last 4 years we have been looking at the effect of the closure of the Panama Isthmus on ocean oxygenation, through both deep time sediment reconstructions, and climate modelling. Currently we are looking at more recent warm periods in the geological past, of the Pliocene and Pleistocene.

My group is also looking at utilizing organic carbon in foraminifera to understand past ocean productivity, carbon cycling and climate change.