PhD Candidate: Amber Boot

Defence date: 03-04-2024
Time: 16:15
Institute: Utrecht University
Location: Academiegebouw, Domplein 29, Utrecht
Online:  Livestream

PhD supervisors:
prof. dr. ir. H.A. Dijkstra
dr. A.S. Von der Heydt

Title thesis: Cycle Feedbacks and Climate Tipping Behavior

Abstract:

The climate of the past millions of years is strongly coupled to the carbon cycle and has shown a lot of variability. This variability might be caused by tipping points, relatively quick and large changes in an element in the climate system compared to their forcing. The coupling between temperature and the carbon cycle suggests an important role for the carbon cycle by either showing tipping behavior or by providing positive feedbacks to the climate while interacting with a tipping element. A better understanding of these relations is important since they might play a role under future climate change. In this thesis, we study whether there are tipping points in the marine carbon cycle and how the marine carbon cycle interacts with large changes in the circulation of the Atlantic Ocean, a potential tipping element.
By using simple models we have looked for tipping points in the marine carbon cycle, but we did not find these, making it unlikely they are present. With the same models we have looked at the relation between atmospheric pCO2 and the strength of the
circulation in the Atlantic Ocean on long (thousands of years) timescales. We studied the same relation with complex climate models under future climate change up to 2100. Both model types show a weak relation between atmospheric pCO2 and the strength of the ocean circulation. In the complex models this is because of regionally compensating effects causing a weak global response. Locally a weakening of the ocean circulation can have severe implications for ecosystems and society.