Magnitude of the present-day horizontal ice flow velocity (Graphic: Thomas Kleiner, Alfred-Wegener-Institut)

The large ice sheets of Greenland and Antarctica are of major importance for the global climate system, as there are complex interactions with ocean and atmosphere. It has now been verified that ice sheets and glaciers are losing mass worldwide. This trend towards loss of mass is clear and shows that the ice masses were responsible for more than half of the annual rise in sea level in the period from 2005 to 2010. It is also a fact that glaciers in the marginal regions of Greenland and the Antarctic have significantly increased their flow speed. For this reason glaciers like it transport more ice to the bordering ocean and thus increasingly contribute to the rise in sea level.

Projections of potential contribution to sea level of the ice sheets depend on the level of understanding of the dynamics of the ice masses and the underlying processes. However, in many places we currently lack key parameters to be able to understand the dynamics of the present-day system and assess future changes. Among the major unknowns in glaciology is lubrication of ice sheets and ice streams by subglacial water, grounding line dynamics of marine ice sheets, stability of ice shelves, and calving.

Modelling of flow of ice sheets, glaciers, ice streams and ice shelves aims to establish prognoses of future  evolution of ice sheets. To this end, we simulate the dynamics of ice masses, thus ice flow velocities, temperature and geometry evolution, numerically. In contrast to observation of ice dynamics in Greenland and Antarctica, which capture the response of the system to numerous factors, models allows testing the impact of individual factors on the dynamics of ice masses and thus drive the understanding of the interaction within the complex system of ice sheets, ice streams and ice shelves. This also allows separating the internal variability of a system and the climate driven changes.

The modeling team of the Section Glaciology performs system studies for the entire ice sheets of Greenland and Antarctica, for individual ice stream-ice shelf systems, e.g. Recovery Glacier – Filchner Ice Shelf, Pine Island Glacier, Jakobshavn Isbræ, 79°N Glacier, and process studies. The system studies follow a hybrid-physics multi-scale approach, which balances uncertainties and computational resources efficiently.  Process studies include the modeling of subglacial water, temperate ice, grounding line migration, sliding and calving.

Within the Section Glaciology the ice modeling team benefits from various other fields: from field glaciology, which perform observations of quantities required for modeling, from the process understanding derived from ice microstructure studies and the remote sensing team that obtains the data required for validation of models.