Tracking the Propagation and Effects of Crevasses in the Helheim Glacier in Greenland

Abstract:

That calving events in Greenland’s glaciers generally occur in the form of many small pieces collapsing from the ice front, rather than the large, tabular style often observed in Antarctic ice shelves is related to the high level of crevassing observed in these glaciers. However, the actual transition mechanism from intact, crevassed glacier—possessing a large amount of gravitational potential and fracture energy—to what is essentially a rubble pile in the proglacial fjords below remains something of a mystery. What is the relationship between the crevasse patterns, glacier flow, and calving rate? We present results from a study to better understand these questions.

We focused on Helheim Glacier. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and LandSat images downloaded from the USGS Earth Explorer were employed, for years 2001, 2003-2010, and 2012-2015. These images were used to electronically trace crevasse patterns in the ice. Additionally, we track the terminus position over each year, which reached its maximum retreat in 2005. Since then, the position has fluctuated forward and backward barely reaching halfway between the 2001 and 2005 terminus positions. We measure sizes and density of icebergs in the immediate area of the terminus. Iceberg concentration was studied using yearly snapshots and weekly snapshots for 2012 through 2013. We find large crevassed icebergs in 2006, suggestive of a recent calving event. Greenland Automatic Weather Stations (AWS) air temperature data is used to study the environmental variations between each snapshot. Over our observation time period (2001-2014), we compare our traced crevasse patterns to assess variability over time, finding that the density of crevasses increases nearer to the front.. We will report relationships between this spatial-temporal variability to changing atmospheric and flow conditions to better understand factors that control surface modification of Greenland’s glaciers. We will compare the variable crevasse patterns to the density and size of icebergs in the fjord in order to determine a correlation between changing glacier surface setting and the size of calved blocks. Further analysis is planned to understand the energy system influencing Helheim glacier’s surface crevasses.