The Climatic Imprint on Recent Glacier Demise in the Cordillera Darwin, Tierra Del Fuego

• Applicant: Dr. Johannes Fürst
• Subject Area: Physical Geography ; Geophysics
• Term: since 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 431767937

The Cordillera Darwin Icefield (CDI) in Tierra del Fuego is the third largest temperate icefield in the southern hemisphere, storing twice the ice volume of the European Alps. In general, recent glacier evolution of the CDI is dominated by continuous thinning and glacier retreat. Yet, individual glaciers show contrasting behavior with stronger losses in the northern part of the CDI and more stable conditions or even thickening and advance in the central and southern part. Climatic and ice-dynamic controls are the two potential explanations. The former climatic controls are determined by mass and energy fluxes at the glacier surface, whereas the latter ice-dynamic control comprises mass loss over the ice fronts of marine- and lake-terminating glaciers, i.e., frontal ablation. More than half of the CDI glaciers are in direct contact with proglacial lakes or fjords. A convincing attribution to these two controlling factors remains evasive, as the region is poorly surveyed both in climatological and glaciological terms. The key objective is to reliably disentangle the climatic imprint on glacier mass loss in the Cordillera Darwin for the last two decades. This climatic attribution is unprecedented and a unique opportunity to study the effects of climate variability and change in the southern hemisphere’s higher mid latitudes. The envisaged attribution will rely on a mass budgeting approach comparing total mass changes to the climatic mass balance at the glacier surface. Total mass change is readily inferred from geodetic techniques in satellite remote sensing. Yet the surface mass balance, comprising all mass gain and loss terms at the surface, is ultimately tied to robust high-resolution information on the atmospheric conditions. As climatological observations in the Cordillera Darwin are sparse, valuable weather-station data will be collected during a field campaign at the start of the project. In order to extent the available observational records, state-of-the-art statistical downscaling of atmospheric variables will be employed. Special attention will be directed to downscaling of precipitation and the orographic effects over the high relief terrain. Moreover, climate conditions in Southern Patagonia are characterized by year-round westerly winds and strong moisture gradients across the cordillera. Fierce winds imply efficient snow drift, which increases the spatially heterogeneity of snow deposition. This process will be considered in a physically-based model for the surface energy balance and snow pack evolution of the Cordillera Darwin in the last two decades. Climatic and modeling data will be systematically validated with observational data. The results will enable us to analyze variations in SMB across space and time. Mass budgeting will finally enable a first estimate of frontal ablation and thus ice-dynamic controls on glacier changes.

• DFG Programme: Research Grants
• International Connection: Chile
• Co-Investigators: Professor Dr. Matthias Holger Braun; Professor Dr. Tobias Sauter
• Cooperation Partner: Dr. Ricardo Jaña