In our studies, we use different models of the Earth system as well as statistical methods to analyse instrumental and proxy data. Analysing paleoclimate records and model results in tandem allows for an improved understanding of climate transitions and the identification of forcing and feedback mechanisms in the climate system.

Paleoclimate simulations with complex Earth System Models

For our simulations we use different earth system models in coupled an uncoupled modes.
To include all major climate components such as land vegetation, the cryosphere, and the marine biosphere in our simulations we use the earth system model MPI-ESM, and the precursor version ESM-COSMOS. Such models provide a laboratory for the numerical simulation of various past climates as well as for future climate changes. As a new feature, we implemented an interactive cryosphere into the model and adapt the model system for long-term climate simulations.

The Finite Element Sea-Ice Ocean Model (FESOM) which was developed at the Alfred Wegener Institute, uses an unstructured triangular surface mesh which allows to locally increase the resolution in an otherwise coarser global setup without grid nesting techniques. This enables a regional downscaling for particular areas of interest in a global setup. The earth system model AWI-CM (coupling of FESOM with the atmosphere model ECHAM6) is also a novel model development from our institute. In climate scenarios, long-term changes can be evaluated on focussed areas such as coasts or polar latitudes.

Examples from our research:

Mid-Holocene Atlantic circulation

West Antarctic ice sheet dynamics

Shift of western boundary currents

Isotope Modelling

Water and carbon isotopes are widely used as climate proxies in paleoclimate research. They can be seen as a “common currency” among many different types of climate archives, e.g. ice cores, marine and lake sediments, speleothems, corals, tree rings, and others. The isotope variations stored in these archives allow reconstructing past changes of regional temperatures, precipitation amounts and the Earth’s water cycle, as well as the carbon cycle properties.

Some of our tools have been equipped with explicit isotope diagnostics, especially water isotopes. Such isotope-enabled general circulation models provide a mechanistic understanding of the physical and environmental processes influencing the isotopic composition of different branches of the climate system. Climate simulations with isotope-enabled models are therefore very useful for an improved interpretation of present and past climate variability.

Stable water isotopes in ECHAM5/MPI-OM  

Stable water isotopes during the Last Interglacial

Glacial Carbon-13

Dynamical system theory and conceptual models

In addition to our work using complex climate models, we heavily apply statistical data analysis, and develop low-order as well as conceptual models.
This complementary approach has been successfully applied to a number of questions regarding feedback mechanisms and the basic dynamical behaviour of the climate system.  For the data analyses, we detect climate modes using several statistical tools and environmental data, where we collaborate with various other groups at AWI and beyond.
Furthermore, we develop and apply models of the recorder system. This helps to understand how the climate variations are documented in proxy data.

Examples from our research:

Atmospheric bridge on orbital time scales

Greenland ice cores and European climate

Atmospheric blocking and sea ice export