History of the Larsen C Ice Shelf reconstructed from sub–ice shelf and offshore sediments

Because ice shelves respond to climatic forcing over a range of time scales, from years to millennia, an understanding of their long-term history is critically needed for predicting their future evolution. We present the first detailed reconstruction of the Larsen C Ice Shelf (LCIS), eastern Antarctic Peninsula (AP), based on data from sediment cores recovered from below and in front of the ice shelf. Sedimentologic and chronologic information reveals that the grounding line (GL) of an expanded AP ice sheet had started its retreat from the midshelf prior to 17.7 ± 0.53 calibrated (cal.) kyr B.P., with the calving line following ~6 k.y. later. The GL had reached the inner shelf as early as 9.83 ± 0.85 cal. kyr B.P. Since ca. 7.3 ka, the ice shelf has undergone two phases of retreat but without collapse, indicating that the climatic limit of LCIS stability was not breached during the Holocene. Future collapse of the LCIS would therefore confirm that the magnitudes of both ice loss along the eastern AP and underlying climatic forcing are unprecedented during the past 11.5 k.y.