Events

What the GISP2 bedrock reveals about Greenland Ice Sheet history: new constraints from triple cosmogenic isotopes (³⁶Cl-²⁶Al-¹⁰Be)

The GISP2 bedrock core provides a unique archive of Greenland Ice Sheet (GrIS) history, preserving direct evidence of past ice-sheet change. Previous ²⁶Al-¹⁰Be measurements suggested that Greenland was at least once nearly ice-free during the Pleistocene. In this talk, I’ll present new ³⁶Cl measurements together with an inversion-based analysis of triple cosmogenic nuclide data from the GISP2 bedrock core. The ³⁶Cl data are consistent with the ²⁶Al-¹⁰Be systematics and require at least one phase of ice-free conditions at the site. Our results further suggest that the central GrIS remained continuously ice-covered during the 100-kyr world (0.7-0.01 Ma), but experienced more frequent deglaciation during the earlier 41-kyr world and the Mid-Pleistocene Transition. Together, these findings point to a fundamental shift in GrIS behaviour, from a more dynamic, low-elevation state to a thicker and more resilient ice sheet, with important implications for past sea-level change.