Greenhouse climates, ocean circulation and monsoon strength

Global warming has already reached 1 Celsius 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).