Gerrit Lohmann, head of the AWI Section ‘Paleoclimate Dynamics‘

Without models, we can’t grasp the interrelations in the system or explain the phenomena we observe.

I work with Earth system models. My priority in doing so is to better grasp the broad range of solutions and uncertainties in the climate system, as well as its variability over timespans ranging from days to several million years. The latter aspect includes alternating glacial and interglacial periods, the cli­mate’s sensitivity to external forcing, and the ­climatic trends of the past few millennia.

In addition, we develop prognoses for as yet unseen factors and make estimates for future climate conditions. Our goal is to use Earth system models for all time scales – and from the past to the future. Depending on the specific question at hand, we include new Earth system components. For instance, we’ve recently begun using ice sheet models that provide insights into sea level variations. What fascinates me most are the feedback loops in the Earth system. Models allow us
to develop new ideas and hypotheses and
to test them. To do so, we not only have to understand the model but also consider suitable boundary conditions and climate simulations.

Dörthe Handorf, Researcher in the Section ‘Physics of the Atmosphere‘

We also need simplified climate models, which allow us to isolate some of these additional influences.

One of my research focuses is on the question of how the dramatic climate changes in the Arctic are connected to the weather and climate in central Europe. The difficult thing about these interactions is the fact that, in addition to the Arctic factors, other aspects – like changes in the tropics and the climate system’s internal variability – also make a difference. If our goal is to estimate the scope of these aspects, it’s not enough to analyse our observational data, or to calculate it using highly complex climate models.

In this regard we use a simplified atmospheric model of the Northern Hemisphere that, despite its simplicity, does an excellent job of simulating the variability of the large-scale atmospheric circulation. In the latest experiments we were able to show that, in response to rising temperatures in the Arctic, the model simulates changes in that circulation – and that these changes are in fact related to the increased frequency of harsher winters in central Europe. This tells us that atmospheric dynamics are important with regard to interactions between the Arctic and the middle latitudes.

Claudia Wekerle, Researcher in the Section ‘Physical Oceanography‘

If we can realistically simulate the past and present processes at work in the Fram Strait, we can then calculate projections for the future.

I work with FESOM, the Finite Element Sea ice-Ocean Model, which is used on diverse time scales, from paleoclimate simulations to future projections. The model was developed in the AWI’s Climate Dynamics section, where it is constantly being refined. Unlike traditional ocean models, which are based on structured grids, FESOM uses triangle-based unstructured grids to simulate ocean currents, hydrography and sea ice. I’m currently using FESOM to simulate the circulation in the Fram Strait, which is located between Greenland and Svalbard and represents one of the most important connections between the Arctic Ocean and the North Atlantic. In the past few years, we’ve seen a major decline in Arctic sea ice in the region. In addition, more warm and salty water is being transported from the Atlantic to the Arctic. Modelling helps us to better understand the underlying processes and the exchange of water masses that takes place in this important waterway.

Personally, I find FESOM fascinating, because its unstructured grid function is extremely flexible; it helps us simulate vital regions like narrow straits in high resolution, while also putt­ing our computer resources to optimal use.

Annette Rinke, Sektion „Physik der Atmosphäre“

For instance, I’m taking a loser look at a potential connection between extreme storms and changes in sea ice.

Right now, I’m working with a regional climate model for the Arctic. The model consists of several components: the atmosphere, sea ice,
ocean and land. Simulations with this model help us interpret the Arctic climate, its variability and trends (e.g. polar amplification) in the past 40 years and gain new insights into various feedback processes.

I also use the model to create future climate scenarios for the Arctic. Given the dramatic warming and the growing industrialisation of the Arctic, the region’s climate is of interest to decision-makers from the political and business communities and to society at large. I’m especially enthusiastic about the virtually limitless options the model offers for sensitivity studies, which can help us to understand complex climate processes better, bit by bit.