Interconnections of past greenhouse climates

Wilson PA, Stockey RG, Crocker AJ, University of Southampton

Global warming has already reached 1°C above pre-industrial levels because of greenhouse gas emissions. The polar regions are losing ice mass, the ocean is heating up and rainfall patterns are shifting, reducing seawater mixing and oxygenation (ventilation) and limiting oxygen supply to marine ecosystems.


To help frame predictions of Earth’s future we need datasets much longer than those possible by direct observation. You will study past intervals of CO2-induced global warmth from the Plio-Pleistocene and Miocene.


We will focus on regions such as the Mediterranean and Arabian seas because geological records show that they are early warning sites for ocean hypoxia.


In the past, bottom waters in these semi-enclosed basins were regularly stripped of oxygen when astronomically driven warming strengthened the African and South Asian monsoons, spawning green, vegetated landscapes, reactivating ancient dry riverbeds and cutting off dust supply to the oceans. These changes drove seawater anoxia by capping the Mediterranean with buoyant freshwaters, preventing overturning and by supercharging wind-driven upwelling and the biological pump in the Arabian Sea.


However, the response of these climate interconnections to CO2-driven global warmth is poorly understood.  You will tackle this problem by studying past warm intervals in these natural laboratories.



Geological data provide a way to reach beyond historical records of climate change to past intervals known to be important to future-relevant conditions of known warmth and high CO2.


For this project, you will produce data from marine drill-cores obtained by scientific drilling from the Arabian and Mediterranean seas. This approach is ideally suited for climate reconstructions because marine sediments: (1) are typically less disturbed by erosion than terrestrial ones, (2) can be dated more accurately because of their continuity and fossil content, and (3) record environmental change both on land and in the oceans.


The geochemistry of organic matter and marine microfossils in these cores will be used to reconstruct changes in sea water hypoxia, ocean temperature, salinity and polar ice volume (stable isotopes and trace element composition of foraminifera). These records will be compared to published global sea-surface temperature and CO2 reconstructions. Monsoonal strength will be reconstructed by tracing changes in the flux and provenance of terrigenous material to core sites using X-ray fluorescence (XRF) core scanning and radiogenic isotopes. The project also offers an opportunity to work with state-of-the-art 3D models of ancient ocean biogeochemistry and to participate in scientific cruises.


Waterfront Campus, University of Southampton

The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted in the School of Ocean and Earth Science.


Travel: There are opportunities to participate in a scientific cruise and work in mainland Europe, the US and Japan.


Travel to international scientific meetings to present project results is encouraged and supported. Project-specific training will include:

  • Stratigraphy and chronology of deep-sea drillcores
  • Stable oxygen, carbon and nitrogen isotope and radiogenic (Sr, Nd) isotope analysis of terrestrial and marine samples
  • X-ray Fluorescence core scanning and elemental composition of microfossils
  • Earth system modelling (cGENIE) – dynamic responses of marine oxygen and seawater temperature to climate; geochemical data assimilation.
  • Correlation, integration, and interpretation of multi-proxy datasets from deep-sea cores for palaeoclimatic and palaeoceanographic reconstructions


Eligibility & Funding Details: 

Please see for details.


Background Reading: 

Crocker et al., (2022) Astronomically controlled aridity in the Sahara since at least 11 million years ago Nature Geoscience 15, 671–676.


Oschlies et al., (2018) Drivers and mechanisms of ocean deoxygenation. Nature Geoscience, 11, 467–473.


Stockey et al., (2021) Decreasing Phanerozoic extinction intensity as a consequence of Earth surface oxygenation and metazoan ecophysiology Proceedings of the National Academy of Sciences 18 (41) e2101900118.


Further relevant literature available on request from: