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FRINATEK-Fri prosj.st. mat.,naturv.,tek

Characterizing Oldest Ice in Dome Fuji near the base of the Antarctic Ice Sheet

Alternative title: Den eldste isen i Antarktis – karakteristikk og egenskaper fra geofysiske målinger under Dome Fuji

Awarded: NOK 8.9 mill.

The Antarctic Ice Sheet is roughly a circle of 4,500 km diameter, and its central part is elevated nearly 4 km above the ocean surface. Annual air temperature in the inland Antarctica is around -50°C, so that all snowfall remains frozen. As new snow is added on top, older snow moves downwards and becomes ice. This snow and ice contain atmospheric gases and climate information from the past, and thus paleoclimatologists use ice cores drilled vertically from the surface of inland Antarctica as unique climate archives of glacial and interglacial cycles, over which temperature, sea level, and ice volume have varied considerably. Earlier studies have found that inland domes in Antarctica presumably retain very old climate records of about one million years near its base, but details remain unknown. This project will examine ice-penetrating radar data collected at Dome Fuji in Dronning Maud Land to learn about current and past glaciological conditions, such as topography, ice flow, snowfall, and melting and re-freezing at the bottom of the ice sheet, and eventually delineate and characterize the oldest ice on the Earth using remote sensing and ice-flow-modeling techniques.

This project will examine ice-penetrating radar data collected in the Dome Fuji region, central East Antarctica, to characterize the soon-to-be-drilled ice core site to reach the Oldest Ice on the earth, the continuous atmospheric gas records during the Mid-Pleistocene Transition (MPT), 0.9 - 1.2 million years ago. Marine sediments show that the cyclicity of the global sea level has changed from 40,000 years to 100,000 years during the MPT. Available ice-core records are currently limited back to only 800,000 years, and the Oldest Ice that covers the MPT is predicted to be present near the base of the central East Antarctic Ice Sheet. The European Beyond-EPICA Oldest Ice consortium (in which Norway participates) has identified a promising site near Dome C and will start drilling soon. However, multiple ice cores are necessary to confidently reconstruct the MPT climate. We have collaborated with Japan and USA under the Beyond-EPICA consortium to carry out ground-based radar surveys in the Dome Fuji region. This proposed project will analyze this and relevant airborne radar data collected by Germany to reveal (1) surface mass balance in the past seven centuries, (2) geothermal flux and current basal conditions (frozen or thawed), (3) potential passageways of subglacial meltwater and their possible changes in the past, and (4) possible disturbance and folding of basal ice layers where the Oldest Ice can potentially be present. We will develop a novel radar algorithm to diagnose bed conditions, which improves our understanding of subglacial hydrology and facilitates filling a knowledge gap identified by IPCC to estimate Antarctic contributions to sea level. Synthesis of these results will allow us to give (5) three dimensional knowledge on dynamics and evolution in the vicinity of the Oldest Ice core site, which is crucial to rigorously interpret the future ice core data.

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FRINATEK-Fri prosj.st. mat.,naturv.,tek