The influence of proglacial lakes on climate and surface mass balance of retreating ice sheets: A study of the North American and Scandinavian ice sheets at 13 ka BP

This study investigates the effect of proglacial lakes in direct contact with large ice sheets on regional climate and surface mass balance (SMB). A novel subroutine was implemented for this purpose, enabling the atmospheric general circulation model ECHAM6 to incorporate proglacial lakes and their specific characteristics. Other lakes can still freely evolve according to a mixed layer scheme. As a first application the impact of proglacial lakes during the Allerød interstadial 13 ka BP (ka is thousand years before present) was studied for the Laurentide (LIS) and Fennoscandian (FIS) ice sheets. This was achieved using three atmosphere stand-alone experiments: 1. with 13 ka BP land surface boundary conditions (GLAC-1D, Ivanovic et al., 2016) and a modern lake configuration 2. same as (1) but with additional lakes around LIS and FIS 3. same as (2) but additional lakes are treated with to new proglacial lake approach. All three simulations were evaluated with respect to the regional climate response, while ice sheet specific parameters like SMB were analysed using the diurnal Energy Balance Model (dEBM, Krebs-Kanzow et al., 2021). Even though the desired equilibrium state of the climate was not achieved during this study, the results still look promising and are indicating a considerable positive effect of proglacial lakes. Lake area seems to be primary factor in these changes, followed then by colder lake surface temperatures