Global scales
Research themes on a Global Scale:
The only way to validate the applied models on a parameter range substantially different from present climate is the application to past climate changes. This also provides the opportunity to identify feedbacks that were not considered so far.
- long-term changes in the earth system
- interactions between ice-sheets and climate
- paleoclimate (like e.g. Last Glacial Maximum, or early Holocene)
- future climate changes on long time scales (centuries and longer)
Interactions between ice sheets and climate system
The ice sheets in Greenland and Antarctica belong to the slowest components of the climate system. Still, current observations and paleoclimatic reconstructions show that the ice sheets are subject to short-term fluctuations. In recent years, velocities of Greenland's ice streams have doubled and in Antarctica large ice shelves have broken off. During the last glacial period, ice sheets experienced giant collapses; these are called Heinrich Events.
To explore the feedbacks between ice sheets on one hand and the ocean and atmosphere on the other hand, we interactively couple ice sheet models with our earth system model. In doing so the determination of the ice sheet’s surface mass balance is critical to perform realistic simulations. We employ two coupling schemes. Either we utilize the empirical positive degree day (PDD) method or explicitly compute the surface mass balance from energy fluxes in the climate model.
With our experiments, we investigate the fundamental interactions between ice sheets and the other components of the climate system. From the results, we quantify the strengths of the feedbacks that result from the interaction between ice sheets and the other components of the climate system. We furthermore investigate the uncertainties that arise from neglecting the ice sheet dynamics in climate models without ice sheet components.
Mineral dust variability in the Southern Ocean
The past provides many opportunities to evaluate dust-cycle models under very different conditions from today, and global Quaternary records of dust suggest that different climatic periods are accompanied by a large variation in dust flux. Ice core records from Antarctica and Greenland show that aeolian deposition rates at high latitudes were 20 times greater during glacial then interglacial periods.
The main goals of the study are to analyze and understand the effect of different modeled climate conditions on the dust emission, transport and deposition in the Southern Hemisphere, with particular focus on the Antarctic region and the effect of the dust on the climate changes.