Modeling oscillations in connected glacial lakes

Aaron G Stubblefield,Jonathan Kingslake,Timothy T Creyts,Marc Spiegelman

doi:10.1017/jog.2019.46

Aaron G Stubblefield, Jonathan Kingslake + Show 2 more

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https://doi.org/10.1017/jog.2019.46

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Abstract

AbstractMountain glaciers and ice sheets often host marginal and subglacial lakes that are hydraulically connected through subglacial drainage systems. These lakes exhibit complex dynamics that have been the subject of models for decades. Here we introduce and analyze a model for the evolution of glacial lakes connected by subglacial channels. Subglacial channel equations are supplied with effective pressure boundary conditions that are determined by a simple lake model. While the model can describe an arbitrary number of lakes, we solve it numerically with a finite element method for the case of two connected lakes. We examine the effect of relative lake size and spacing on the oscillations. Complex oscillations in the downstream lake are driven by discharge out of the upstream lake. These include multi-peaked and anti-phase filling–draining events. Similar filling–draining cycles have been observed on the Kennicott Glacier in Alaska and at the confluence of the Whillans and Mercer ice streams in West Antarctica. We further construct a simplified ordinary differential equation model that displays the same qualitative behavior as the full, spatially-dependent model. We analyze this model using dynamical systems theory to explain the appearance of filling–draining cycles as the meltwater supply varies.

Highlights

Ice-dammed and subglacial lakes have been observed to periodically fill and drain
We introduced a generalized model for hydraulically connected ice-dammed lakes that extends previous work on singlelake systems (Fowler, 1999; Ng and Björnsson, 2003; Fowler, 2009; Kingslake and Ng, 2013a; Kingslake, 2015)
We explored how lake size and spacing influence the coupled depth-discharge oscillations in double-lake systems

Summary

Introduction

Ice-dammed and subglacial lakes have been observed to periodically fill and drain. The classical example of this behavior is the cyclic jökulhlaups from the Grímsvötn caldera lake on the Vatnajökull Ice Cap, Iceland (Nye, 1976; Fowler, 1999; Björnsson, 2003; Fowler, 2009). The Grímsvötn jökulhlaup cycle is characterized by a slow filling phase that lasts several years followed by a sudden draining of water beneath the glacier that results in intense flooding of proglacial rivers and outwash plains (Björnsson, 2003). Hidden Creek Lake sits upstream of the much smaller Donoho Falls Lake. Hidden Creek drains on a yearly cycle, causing Donoho Falls to fill and drain in response to subglacial water pressure variations. Donoho Falls acts as a pressure gauge that records the passing of the flood (Anderson and others, 2005)

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