New Quaternary sedimentary records from near the Larsen C and former Larsen B ice shelves; evidence for Holocene stability
Glacial and post-glacial shelf sedimentation near the Larsen C and former Larsen B ice shelves is compared to records from ice shelves farther north, which underwent mid-Holocene retreat. A core from Larsen C comprises a lower unit of deformation till, overlain by thick mud interpreted as water lain from suspension under the ice shelf. Iceberg-rafted debris occurs only in the top 50 cm, suggesting that prior to that layer's deposition, the ice shelf had not receded past the site since the last deglaciation. Subsequently the site appears to have been seasonally ice free, and the ice shelf has retreated further and is now 15 km landward of the site. A core from Larsen B also consists of a lower unit, interpreted as sub-glacial lodgement till. The overlying mud is thinner, more poorly sorted, with evidence of powerful winnowing of sediments suggesting strong currents. The absence of iceberg-rafted debris implies that this site was covered by an ice shelf continuously from the last deglaciation until its collapse in 2002. Strong currents could have facilitated basal erosion, contributing to its collapse. The Larsen C shelf is also thinning and historical records show retreat in the last hundred years. With continued rising temperatures, Larsen C may eventually retreat to a point at which it collapses.