Over-winter persistence of supraglacial lakes on the Greenland Ice Sheet: results and insights from a new model

Robert Law,Alison Banwell,Neil Arnold,Ian Willis,Marco Tedesco,Corinne Benedek

doi:10.1017/jog.2020.7

Abstract

AbstractWe present a newly developed 1-D numerical energy-balance and phase transition supraglacial lake model: GlacierLake. GlacierLake incorporates snowfall, in situ snow and ice melt, incoming water from the surrounding catchment, ice lid formation, basal freeze-up and thermal stratification. Snow cover and temperature are varied to test lake development through winter and the maximum lid thickness is recorded. Average wintertime temperatures of −2 to$-30^{\circ }{\rm C}$and total snowfall of 0 to 3.45 m lead to a range of the maximum lid thickness from 1.2 to 2.8 m after${\sim }250$days, with snow cover exerting the dominant control. An initial ice temperature of$-15^{\circ }{\rm C}$with simulated advection of cold ice from upstream results in 0.6 m of basal freeze-up. This suggests that lakes with water depths above 1.3 to 3.4 m (dependent on winter snowfall and temperature) upon lid formation will persist through winter. These buried lakes can provide a sizeable water store at the start of the melt season, expedite future lake formation and warm underlying ice even in winter.

Highlights

Mass loss from the Greenland Ice Sheet (GrIS) has significantly accelerated during the last several decades to become a major cryospheric contributor to global sea-level rise (Rignot and others, 2011; Jacob and others, 2012; The IMBIE Team, 2019)
This study has presented the first model for the full multi-year evolution of supraglacial lakes in the ablation zone of the GrIS
GlacierLake shows that the sum of the ice-lid thickness and basal freeze-up is unlikely to exceed 3.9 m with no snow cover, or 2.8 m with 1 m of snow cover at the end of the melt season

Summary

Introduction

Mass loss from the Greenland Ice Sheet (GrIS) has significantly accelerated during the last several decades to become a major cryospheric contributor to global sea-level rise (Rignot and others, 2011; Jacob and others, 2012; The IMBIE Team, 2019). The thermal signature of lakes is important in cryohydrologic warming (Phillips and others, 2010, 2013) as another way to warm the near-surface ice sheet, and for temperature analysis where surface features are found to exert a strong influence on temperature profiles (Catania and Neumann, 2010; Lüthi and others, 2015; Hills and others, 2017) These studies emphasise the need for a physically based and rigorous analysis of multi-year supraglacial lake evolution to provide better information for GrIS hydrology studies on the fate, and thermal effects, of lakes following the end of the summer melt season.

Cwater ice melt

Findings

Discussion

Conclusion