Grounding Line Discharge

Grounding Line Discharge

The majority of mass loss from the Antarctic Ice Sheet is attributable to increases in grounding line discharge – the flux of ice into ice shelves or directly into the Southern Ocean from the grounded Antarctic Ice Sheet. Grounding line discharge is therefore, a key component for quantifying the ‘health’ of the Antarctic Ice Sheet, particularly when combined with surface mass balance (SMB) estimates to determine the overall ice sheet mass. The input-output technique (IOM) uses measurements of ice speed at the grounding line to measure ice mass flowing out of the ice sheet, and regional climate models to estimate the amount of ice mass entering the ice sheet, therefore producing an overall mass balance estimate. IOM is particularly useful as it enables direct partitioning of mass change between SMB and ice discharge, which provides insight into the processes driving ice sheet mass change. Secondly, ice discharge can now be generated through continuous satellite-based monitoring at relatively frequent ~monthly intervals, at the continent scale. These data are available at higher spatial resolution than the other mass change approaches (e.g. altimetry, gravimetry), making the method particularly useful in smaller drainage basins and in regions of more complex, mountainous terrain.

Summary of grounding line discharge datasets planned within 5DAIS:

• Make use of the 5DAIS datasets including IV, SEC and GLL, plus auxiliary data such as bed topography, to produce a grounding line discharge dataset for the Antarctic Ice Sheet using IOM.
• The product will cover the period from 1996 through to the present day, and will use time-varying rates of ice surface elevation change and firn air content.
• The spatial resolution of the product will be tied to the resolution of input datasets. We will produce this dataset over the whole Antarctic continent.