Research Interests

I am interested in the role of the ocean in climate and climatic change. Together with my research students, post-docs, and collaborators I try to tackle the fundamentals of how the ocean works in the Earth system. My approach to research has been characterised by two recurrent themes: I have to the extent possible used both models and observations, and I have employed the whole spectrum of ocean and climate models, from the fully complex to the highly idealised. 


The phenomenon that has dominated my research more than anything else has been the Meridional Overturning Circulation (MOC) in the Atlantic, sometimes also known under the less accurate name of Thermohaline Circulation (THC, driven by surface heat and freshwater fluxes). My unwavering fascination for the Atlantic MOC arises both from its climatic importance the MOC-induced heat transport is responsible for Europe's unusually mild climate, given its geographical location and from the MOC's complex variability and potential for abrupt change.


Prior to moving to Hamburg, I led the UK effort to establish the national programme RAPID, which as its cornerstone installed the first monitoring system for the Atlantic MOC, at 26.5° N; (see Opens external link in current windowRAPID-MOC). Through students and post-docs, I still participate in the RAPID fieldwork and data analysis, although I find it increasingly difficult to find the time to go to sea myself.


The possibilities at MPI-M, in particular its staff and its history of state-of-the-art climate modelling, have enabled me to expand my interests significantly beyond pure large-scale physical oceanography. Some of my students here have worked on extreme climates of the past the Snowball Earth or the Palaeocene-Eocene Thermal Maximum or have investigated potential extreme climates of the future or on other planets the Runaway Greenhouse. These research areas draw a particular benefit from the combination of simple and complex models.


The combination of modelling and observations, on the other hand, provides a fertile ground for a research direction that fills an ever-expanding part of my personal agenda and that of my department: multi-year to decadal climate prediction. I proposed to the German Ministry for Education in Research in 2007 to establish a national programme on decadal climate prediction, a programme (called Opens external link in current windowMiKlip) that I now co-ordinate and that started on 1 September 2011. 


A small but extremely exciting portion of my research activity is filled by a collaboration with Opens external link in current windowProf. Manfred Milinski from the Opens external link in current windowMPI for Evolutionary Biology, a collaboration that arose from a chance encounter at an annual meeting of the Max Planck Society. We perform laboratory experiments in which our human subjects play for real money giving us insight into the conditions under which people are willing to invest into climate protection.