Modelling the Filling and Draining of Connected Glacial Lakes
Abstract
Storage and release of water from glacial lakes has been observed at a range of scales: from mountain glaciers to large ice sheets. The filling and draining of these lakes influences water pressure in the subglacial drainage system. Basal sliding laws often rely on variations in water pressure to determine the slip rate. However, observations of lake drainage influencing the basal slip rate are inconclusive. In some studies, enhanced sliding has been suggested based on lake volume changes, but the coupling in many studies is unclear. The interaction between neighboring lakes further complicates this since draining of an upstream lake can cause subsequent filling and draining of a downstream lake. Here, we examine drainage of a coupled system of lakes. We model the evolution of two ice-dammed lakes that are connected by a subglacial channel. We modify Nye's (1976) drainage equations and force them with effective pressure boundary conditions that are determined by lake depths. While the upstream lake is provided a constant meltwater source, the downstream lake additionally receives input from a channel draining the upstream lake. This channel input source causes a wide range of behaviors in the downstream lake. Many complex filling-and-draining oscillations are observed. In order to draw comparisons with field studies, we examine the effect of relative size and spacing on the evolution of both lakes' filling-and-draining cycles. We find that distant lakes tend to fill and drain out of phase, with the downstream lake having small-amplitude oscillations. Closely-spaced lakes oscillate in-phase if the downstream lake is of similar or smaller size. A commonly observed feature in this scenario is the presence of two peaks per cycle in the downstream lake depth. These peaks decompose into a series of smaller peaks as the size of the second lake is reduced. Anti-phase oscillations are also possible if the downstream lake is sufficiently larger than the upstream lake. The theory developed here also explains many observed behaviors such as synchronous and multiple-peaked filling-and-draining events. How these events influence sliding likely depends on relative lake size, spacing, and number of lakes in sequence. If time permits, the stability of various natural configurations will be discussed.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.C51E1104S
- Keywords:
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- 0720 Glaciers;
- CRYOSPHEREDE: 0726 Ice sheets;
- CRYOSPHEREDE: 0774 Dynamics;
- CRYOSPHEREDE: 0776 Glaciology;
- CRYOSPHERE