Sea ice fastened to coasts, icebergs and ice shelves is of crucial importance for climateand ecosystems. At the same time, it is not represented in climate models and many processes affecting its energy- and mass balance are currently only poorly understood. Near Antarctic ice shelves, which fringe about 44 % of the coastline, this landfast sea ice exhibits unique characteristics that distinguish it from most other sea ice: 1. Ice platelets form and grow in supercooled water masses, which originate from cavities below the ice shelves. These crystals rise to the surface, where they accumulate beneath the solid sea-ice cover. Through freezing of interstitial water they are incorporated into the sea-ice fabric as platelet ice. 2. A thick and highly stratified snow cover accumulates on the fast ice, altering the response of the surface to remote sensing and affecting sea-ice energy- and mass balance. Combining a variety of methods from different disciplines, we aim to improve our understanding of Antarctic sea-ice, its interaction with ice shelves and its role in the climate system. Here we present our major research questions, introduce our methods and present some exemplary results.