Morainal bank evolution and fjord infilling during a tidewater glacier stillstand, on seasonal to decadal timescales
Abstract
Sedimentary processes are known help to facilitate tidewater glacier advance, but their role in modifying rates of tidewater glacier retreat are uncertain and poorly quantified. Moreover, knowledge of dynamic sedimentary processes at the grounding line is often derived from static pictures of abandoned end moraines in de-glaciated fjords. In this study we use bathymetric profiles near the terminus of LeConte Glacier, Alaska, to evaluate the morphodynamics of an active morainal bank, over seasonal to decadal time scales (2000-2018). Following rapid retreat in the mid-1990s, the glacier stabilized at a constriction and during the next 17 years constructed a morainal bank with rates of sediment delivery of 3.3x105-3.8x105 m3 a-1. After six years of growth, the terminus shape began to change as the glacier interacted with the moraine. In 2016-2018, repeated bathymetric surveys revealed a dynamic feature characterized by push ridges, slopes of ~18-20°, evidence of active gravity flows, and active bulldozing by the glacier at rates of up to several meters per day. Material shed from the front of the moraine by slope failures and delivered from suspension settling has accumulated in the adjacent basin at rates of up to 4 m a-1 seaward of the moraine. From a sedimentological perspective, the morphodynamics observed over two seasons offer a rare view of the dynamic processes of sediment distribution in a fjord. From a glaciological perspective, this rapid moraine construction has decreased the area of the terminus exposed to warm ocean water by up to 22% in just 17 years, and also altered the terminus stress balance, likely with important consequences for glacier stability.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.C32A..08E
- Keywords:
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- 0758 Remote sensing;
- CRYOSPHERE;
- 0774 Dynamics;
- CRYOSPHERE;
- 0798 Modeling;
- CRYOSPHERE