PISM-LakeCC: Implementing an adaptive proglacial lake boundary into an ice sheet model

Abstract

Abstract. Geological records show that vast proglacial lakes existed along the land terminating margins of palaeo ice sheets in Europe and North America. Proglacial lakes impact ice sheet dynamics by imposing marine-like boundary conditions at the ice margin. These lacustrine boundary conditions include changes in the ice sheet’s geometry, stress balance and frontal ablation and therefore affect the entire ice sheet’s mass balance. This interaction, however, has not been rigorously implemented in ice sheet models. In this study, the implementation of an adaptive lake boundary into the Parallel Ice Sheet Model (PISM) is described and applied to the glacial retreat of the Laurentide Ice Sheet (LIS). The results show that the presence of proglacial lakes locally enhances the ice flow. Along the continental ice margin, ice streams and ice lobes can be observed. Lacustrine terminating ice streams cause immense thinning of the ice sheet’s interior and thus play a significant role in the demise of the LIS. Due to the presence of lakes, a process similar to the marine ice sheet instability causes the collapse of the ice saddle over Hudson Bay, which blocked drainage via the Hudson Strait. In control experiments without a lake model, Hudson Bay is still glaciated at the end of the simulation. Future studies should target the development of parametrizations that better describe the glacial-lacustrine interactions.

Glacial Isostatic Adjustment Shapes Proglacial Lakes Over Glacial Cycles

“…GIA most strongly influences proglacial lake geometry in low‐relief landscapes with reverse bed slopes, and the presence of these GIA‐enlarged lakes at 14.2–11.5 ka correlates with faster ice‐margin retreat. Our results support the idea that coupled lake growth and ice‐margin retreat through PLISI likely contributed to rapid collapse of the Laurentide ice sheet (Hinck et al., 2022; Quiquet et al., 2021) and the asymmetric shape of ice age sea level variability (Fowler et al., 2013; Pollard, 1982).…”

“…Hinck et al. (2022) achieved similar results when implementing an adaptive proglacial lake boundary in the Parallel Ice Sheet Model. Since retreating ice sheets leave larger topographic depressions than advancing ones, it has been postulated that proglacial lakes form more frequently during deglaciations than glaciations, thereby contributing to the asymmetric shape—slow advances, rapid retreats—of Quaternary sea‐level change (Fowler et al., 2013; Pollard, 1982).…”

“…Third, since observed ice‐sheet margin locations are typically used to constrain but not produce physics‐based ice‐sheet models, the resulting ice‐sheet model may not necessarily precisely match them. Lastly, lake‐filling algorithms include some approximations—for example, requiring a certain fill rate to maintain numerical stability (Hinck et al., 2022) or filling lakes up to sea level rather than the spillway (Quiquet et al., 2021). In this study we address many of these limitations at the expense of not modeling ice‐sheet physics.…”

“…They can also impact regional to global climate—for example, abrupt drainage of proglacial lake Agassiz–Ojibway at 8.2 ka likely cooled the Northern Hemisphere by slowing Atlantic Ocean circulation (Barber et al., 1999; Wiersma & Renssen, 2006). Including proglacial lakes explicitly or as boundary conditions in ice‐sheet models enhances ice loss through localized mechanical instabilities (Hinck et al., 2022; Quiquet et al., 2021; Sutherland et al., 2020), which Quiquet et al. (2021) termed “proglacial lake ice sheet instability” (PLISI).…”

PISM-LakeCC: Implementing an adaptive proglacial lake boundary in an ice sheet model

“…The climate forcing data from Zhang et al (2013) and Hossain et al (2018), used in our study, are not publicly available, but can be provided upon request. Model output for the experiments LAKE, CTRL and DEF is available at https://doi.org/10.5281/zenodo.6346394 (Hinck et al, 2022).…”