Greenhouse climates, ocean circulation and monsoon strength

Prof Paul Wilson, Dr Chuang Xuan, Dr Anya Crocker
Rationale: 

Global warming has already reached 1°C above the pre-industrial level because of ongoing greenhouse gas emissions. The polar regions are losing ice mass, the ocean is warming, rainfall patterns are changing and reduced ventilation of deep waters is limiting oxygen supply to marine ecosystems. These interconnecting changes are relevant globally and it is most acute and urgent to study where regional factors predispose the system towards anoxia.

 

In this project, we will develop palaeoclimate records to learn lessons from past intervals of global warmth and ice sheet retreat such as the peak of the last interglacial (~125 thousand years ago and the Pliocene (~3 to 5 million years ago).

 

We will study the Mediterranean Sea and nearby Atlantic Ocean. Bottom waters in the Mediterranean were regularly stripped of oxygen when past warming strengthened the African monsoon, spawning a green Sahara with northward-flowing rivers that placed a buoyant freshwater cap over surface sea waters, preventing overturning circulation and resulting in oxygen-depleted subsurface waters hostile to life. We will investigate the relationships between changes in past global warmth, polar ice volume, monsoon strength and oxygenation (ventilation) in this natural laboratory including abrupt superimposed transient events linked to changes in Atlantic Meridional Overturning Circulation (AMOC). 

 

Methodology: 

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 from the Mediterranean and nearby Atlantic Ocean obtained by scientific drilling. This approach is ideally suited to climate reconstruction 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 marine microfossils in these cores will be used to reconstruct changes in 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. Sediment composition, including elemental and radiogenic isotope geochemistry and sediment magnetic properties will be used to distinguish the source and transport mechanisms of terrestrial sediments to the ocean (wind-blown dust vs. riverine material) to reconstruct changes in monsoonal strength over land.   

 

Location: 
University of Southampton
Training: 

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 the US. Travel to international scientific meetings to present project results is encouraged and supported. Project-specific training includes:

  • Stratigraphy and chronology of deep-sea drill-cores
  • 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
  • Continuous u-channel sampling procedures for high-resolution studies of drill-cores
  • Palaeomagnetism, and rock and environmental magnetism studies of u-channel samples
  • Correlation, integration, and interpretation of multi-proxy datasets from deep-sea cores

 

Eligibility & Funding Details: 
Please see https://inspire-dtp.ac.uk/how-apply for details.
 
Background Reading: 

Blanchet et al., (2021) Drivers of river reactivation in North Africa during the last glacial cycle. Nature Geoscience, 14, 97-103.

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

Westerhold et al., (2020) An astronomically dated record of Earth’s climate and its predictability over the last 66 million years. Science, 369, 1383-1387.

 

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