Controls on the growth of a supraglacial drainage network on the Amery Ice Shelf, East Antarctica
Abstract
Changes in surface hydrological networks on Antarctic ice shelves potentially have long-term and globally significant impacts. Models predict a continent-wide increase in surface melting this century and that this could accelerate the collapse of ice-shelves. Understanding how drainage networks may expand and deliver water to vulnerable parts of ice shelves, in response to increase melting, can improve predictions of global sea-level rise. We focus on the Amery Ice Shelf (AIS), East Antarctica.
Hundreds of meltwater ponds and channels (up to and exceeding 100 km in length) have been observed on AIS since the 1940's. We use multispectral data from MODIS Terra/Aqua and Landsat 4,5,7 and 8,and Synthetic Aperture Radar (SAR) from Sentinel-1 to track changes in surface area, lake shape, and channel networks from 1974-2017. We focus on the largest lake, which fills from upstream into a trough near Clemence Massif (S72.2°, E68.7°), and extends into a snow-covered region . The lake is present in approximately half the years for which observations are available and reached its maximum observed length of over 130 km in 1992. Using repeat SAR imagery from 2016-2017, we interpret a progressive transition from high to low backscatter as the lake freezing through. This interpretation is supported by agreement between the predictions of a simple freezing model and Landsat-derived lake depths. We hypothesize that refrozen water from previous lake-filling events alters lake-bed geometry and porosity, allowing lake length to grow during consecutive years of melting. We test this hypothesis by comparing the results of a climate-forced meltwater-percolation and lake-formation model (Buzzard et al., 2018) to the Landsat and Sentinel records. Our findings have implications for understanding how surface meltwater lakes form and respond to changes in climate, with consecutive warm years being the key trigger of drainage-system expansion, rather than isolated extreme melt events. Future work will extend these ideas to other lakes that terminate in snow-covered regions, which are common around the continent.- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.C51G1140S
- Keywords:
-
- 0720 Glaciers;
- CRYOSPHEREDE: 0726 Ice sheets;
- CRYOSPHEREDE: 1827 Glaciology;
- HYDROLOGYDE: 1863 Snow and ice;
- HYDROLOGY