Modelling the age-depth and temperature profiles of deep ice cores from the Antarctic Peninsula and the Weddell Sea region

Three deep ice cores, obtained from Fletcher Promontory, Berkner Island, and James Ross Island across the Antarctic Peninsula (AP) and Weddell Sea region, preserve a climate record that can yield important information on the region. However, before this information can be interpreted, an accurate age-depth profile is required. This study seeks to develop optimal age-depth profiles for the three deep ice cores. The first branch of work is a modelling synthesis of the different physical relationships that reconstruct past surface temperature, accumulation, and the subsequent compaction of accumulation to annual layer thickness (thinning) at an ice-core site. From these relationships, one can estimate an age-depth profile for an ice core. The second half of the study includes the results of chemical analysis on the three deep ice cores. The results of these analyses yield observational data that has been used to assess the accuracy and reliability of the modelling results presented in this part of the study. The OptAcc age-depth model has been developed through this study; it uses an inverse approach to anchor reconstructed profiles of accumulation, thinning, and annual layer thickness profiles to observational data preserved in the ice core. This has been done for the deep ice cores from the AP and Weddell Sea region. Interpretation of the results from this study provides information on the climate history of the region. In particular, the OptAcc model suggests that the coastal proximity of each ice core site leads to high inter-annual variability in accumulation that cannot be reconstructed using standard mathematical relationships. Additionally, an accurate surface temperature, accumulation and age-depth reconstruction for each ice-core site over the Holocene period suggests that an increase in the mean annual surface temperature of 1-3 K is sufficient to lead to significant deglaciation of the AP and Weddell Sea region.