Long-term climate modelling

Fig. 1: Sketch of the climate-ice-sheet model setup used for long-term climate simulations. In this setup the MPI Earth System Model is coupled to ice sheet model mPISM and solid earth model VILMA. Additional modules allow to account for changes in river directions, the land-sea mask and bathymetry as well as the explicit modeling of icebergs.

For our long-term climate studies, we put the emphasis on investigating the mechanisms behind paleoclimate changes. The long-term goal is to perform transient simulations of the full last glacial cycle (135,000 years before present to today) with our coupled climate-ice sheet model framework. To achieve this goal we currently focus on transient simulations of the glacial inception (125,000-95,000 years before present) and the last deglaciation (21,000 years before present to today). With these simulations, we aim at investigating the drivers and timing of sudden climate swings during these periods.

Our main tool to explore key processes is a coupled climate-ice sheet model framework. This model system consists of the coarse resolution version of the Max Planck Institute Earth System Model (MPI-ESM), the ice-sheet model mPISM, and the solid-earth model VILMA (Fig. 1). Spatial model resolution is a compromise between computational demands of long-term climate simulations and accuracy. The use of state-of-the-art models for the atmosphere, ocean, land, ice sheets and solid earth within our model framework allows us to model each component of the climate system in its full complexity. Hence, we can explicitly investigate feedback mechanisms between these components. It further allows us to test and validate our models for different parameter ranges and compare our transient simulations to observations from natural climate archives.

In addition to our fully coupled transient simulations, we also perform time slice simulations and simulations with sub model systems to explore the sensitivity of the climate system. One particular focus is the effect of icebergs on the climate. By developing and integrating an iceberg module into the model framework we investigate how iceberg discharge from ice sheets affects the Atlantic Meridional Overturning Circulation (AMOC) and the ocean heat transport. Another focus has been the response of the AMOC to perturbations of greenhouse gas concentrations and ice-sheet forcing to identify potential tipping points and threshold behavior. Further, to explore the effect of rotation on the climate we performed a simulation where Earth’s rotation was reserved and analyzed it in an collaborative effort across all departments of our Institute.

Focal points of our research:

  • Fully coupled climate-ice sheet simulations of the last deglaciation (more)
  • Simulation of the last glacial maximum and last deglaciation with model sub systems
  • Simulation of Heinrich event-like ice sheet surges (more)
  • AMOC sensitivity to CO2 and ice sheets and self-sustained AMOC oscillations (more)
  • AMOC sensitivity to iceberg forcings (more)
  • The climate of a retrograde Earth (more)

 

Contacts: Olga Erokhina, Marie Kapsch, Uwe Mikolajewicz, Clemens Schannwell, Florian Ziemen*

Regional climate modelling

Fig. 2: Sketch of the regionally coupled climate model setup (consisting of the global ocean model MPIOM and the regional atmospheric model REMO) used for downscaling global climate model simulations. Not all grid-lines are shown. Shifting one ocean’s pole onto Europe increases the model resolution over the North West European Shelf and the North Sea, our region of interest.

The region of focus of our regional modelling studies is the Northwest European Shelf (NWES). We investigate key aspects of the climate system, including the physical and biogeochemical exchange processes between shelf seas and the open ocean, air-sea interactions, and extreme events such as storm floods. In modelling these processes we seek to understand both the natural variability in the climate system for past and present-day, as well as their future characteristics in projections with anthropogenic climate change.

As the spatial resolution of global general circulation models is insufficient to resolve small scale processes and complex topography of the NWES, we set up a global coupled model system with a higher horizontal resolution in our region of interest (see Fig. 2). This model system consists of the global ocean-sea ice model MPIOM including the biogeochemistry model HAMOCC, both with a zoom on the NWES, the regional atmosphere model REMO and the hydrological discharge model HD. Using this model setup, we downscale global climate model simulations performed by MPIOM-ECHAM to investigate the regional impact on the NWES in past, present and future. By downscaling of ensemble simulations, we have a useful tool to better quantify the natural variability and to isolate climate change signals.

Focal points of our research:

  • Impacts of the downscaling strategy on projected climate change signals in the NWES (more)
  • Evolution of the Atlantic nutrient supply to the NWES under future climate conditions (more)
  • Characteristics and large-scale drivers of the long-term variability of extreme storm floods in the southern North Sea and future changes in their statistics (more)
  • Higher storm surges in the German Bight due to global warming (more)

 

Contacts: Andreas Lang*, Uwe Mikolajewicz, Katharina Six

 

* former group member