Recent velocity observations of Hubbard Glacier: A comparison of RADARSAT Constellation Mission with Sentinel-1, TerraSAR-X and RADARSAT-2 derived velocity maps to determine seasonal flow patterns

Abstract

Hubbard Glacier is an advancing tidewater glacier in Alaska, with large seasonal variations in flow speeds of 1500 to 5200 m a-1. The large size and fast speeds of Hubbard Glacier caused it to have possibly the largest rates of steady-state discharge of all glaciers outside of Greenland and Antarctica. Previous studies found the fastest flow on Hubbard Glacier to occur between May and June and the slowest flow between September to November. However, we observed a different seasonal pattern when looking at velocities at a higher temporal resolution than used before (image pairs of SAR and optical imagery with a separation in the range of ~4-30 days). In some years, the seasonal flow pattern of Hubbard Glacier changes to having higher velocities in the winter than what is seen in the spring/summer maximums. Here, we show that with the utilization of RADARSAT Constellation Mission (RCM) data, which has a higher temporal resolution than has previously been used to quantify glacier motion on Hubbard Glacier (4-day repeat pass), seasonality can be explored in much greater detail than formally possible. The results of velocities derived from RCM data will be compared to products derived from other SAR sensors (Sentinel-1, TerraSAR-X, and RADARSAT-2) to assess its feasibility in determining velocity patterns of Hubbard Glacier. This comparison provides an example of the improved ability to resolve glacier dynamics using RCM data and provides insight into how this SAR dataset can be used to characterize seasonality on other glaciers within the St. Elias region.