Seasonal glacier surface velocity fluctuation and contribution of the Eastern and Western Tributary Glaciers in Amery Ice Shelf, East Antarctica

Glaciers play a crucial role in the study of the climate change pattern of the Earth. Remote sensing with access to large archives of data has the ability to monitor glaciers frequently throughout the year. Therefore, remote sensing is the most beneficial tool for the study of glacier dynamics. Fed by many tributaries from different sides, the Amery Ice Shelf (AIS) is one of the largest ice shelves that drains ice from the Antarctic ice sheet into the Southern Ocean. This study focuses on the eastern and the western tributaries of the AIS. The primary objective of the study was to derive the velocity of the tributary glaciers and the secondary objective was to compare variations in their velocities between the summer and winter season. This study was carried on using the European Space Agency’s (ESA) Sentinel-1 satellite’s Synthetic Aperture Radar (SAR) data acquired from the Sentinel data portal. Offset tracking method was applied to the Ground Range Detected (GRD) product of the Sentinel-1 interferometric wide (IW) swath acquisition mode. The maximum velocity in summer was observed to be around 610 m/yr in the eastern tributary glacier meeting the ice shelf near the Pickering Nunatak, and around 345 m/yr in the Charybdis Glacier Basin from the western side. The maximum velocity in the winter was observed to be 553 m/yr in the eastern side near the Pickering Nunatak whereas 323 m/yr from the western side in the Charybdis Glacier Basin. The accuracy of the derived glacier velocities was computed using bias and root mean square (RMS) error. For the analysis, the publicly available velocity datasets were used. The accuracy based on RMS error was observed to be 85-90% for both seasons with bias values up to 25 m/yr and root mean square error values up to 30 m/yr

An Inter-Comparison of Techniques for Determining Velocities of Maritime Arctic Glaciers, Svalbard, Using Radarsat-2 Wide Fine Mode Data

Glacier dynamics play an important role in the mass balance of many glaciers, ice caps and ice sheets. In this study we exploit Radarsat-2 (RS-2) Wide Fine (WF) data to determine the surface speed of Svalbard glaciers in the winters of 2012/2013 and 2013/2014 using Synthetic Aperture RADAR (SAR) offset and speckle tracking. The RS-2 WF mode combines the advantages of the large spatial coverage of the Wide mode (150 × 150 km) and the high pixel resolution (9 m) of the Fine mode and thus has a major potential for glacier velocity monitoring from space through offset and speckle tracking. Faster flowing glaciers (1.95 m · d − 1 –2.55 m · d − 1 ) that are studied in detail are Nathorstbreen, Kronebreen, Kongsbreen and Monacobreen. Using our Radarsat-2 WF dataset, we compare the performance of two SAR tracking algorithms, namely the GAMMA Remote Sensing Software and a custom written MATLAB script (GRAY method) that has primarily been used in the Canadian Arctic. Both algorithms provide comparable results, especially for the faster flowing glaciers and the termini of slower tidewater glaciers. A comparison of the WF data to RS-2 Ultrafine and Wide mode data reveals the superiority of RS-2 WF data over the Wide mode data

Seasonal and Multi-year Variability of Ice Dynamics of South Croker Bay Glacier, Devon Ice Cap, Canadian Arctic from 2015 to 2021

The effects of climate change have already been observed across the globe, impacting weather, ecosystems, and society. These effects have been most pronounced in polar regions, which experience warming at a faster rate than other latitudes due to positive feedbacks resulting from reduced ice and snow cover. Compared to the 1.1oC of warming around the globe since the 1980s, the Arctic has warmed by 3oC. Glaciers and ice caps are of particular concern as they have profound impacts on water resources, shipping and travel routes, and global sea level rise. As such, glacier dynamics play a key role in understanding effects on the global system. The Canadian High Arctic in particular has doubled in rates of mass loss since the 1990s, which is of great concern as it is the third largest contributor to global sea level rise after Antarctica and Greenland. While glacier flow within the region has been studied, some glaciers have been observed to not align with current understandings of dynamics. The subject of this study, South Croker Bay Glacier, located on Devon Ice Cap in Nunavut, Canada has exhibited velocity variability on oscillating temporal scales which do not align with surging, pulsing, or consistent acceleration explanations. The primary objective of this thesis was to create a dense record of velocities derived from TerraSAR-X imagery every 11 days from 2015 to 2021 to gain insight into seasonal and multi-annual velocity variability. As a result, a near-continuous velocity record of South Croker Bay Glacier has been created, highlighting a shift in velocities which occurred during the winter of 2018/19. The second objective was to explore the potential drivers of the observed velocity variability, which were hydrology, sea ice buttressing, and bed topography. Looking at the spatial propagation of acceleration and terminus position as well, it is concluded that the variability is not driven by surge- or pulse-type mechanisms. Instead, it is suggested that the driver of the observed variability on the glacier is the result of the evolving configuration of the hydrological network. This is supported by surface air temperature and surface lake area records during the study period. Finally, the third objective was to assess the feasibility of utilizing remote sensing for seasonal variability detection. Based on the analysis, the method was successful in the proposed objectives, creating a record of velocities that was not previously available for South Croker Bay Glacier

Investigation of intra-annual glacier velocity and seasonality of White and Thompson Glaciers, Axel Heiberg Island, Nunavut

The Canadian Arctic Archipelago (CAA) is undergoing rapid atmospheric warming at rates that are twice that of the global average and are greater than any other time in the past four millennia. Consequently, changes in glacier behavior are being experienced due to this increase in air temperature, including longer and more intense melt seasons, modifications in glacier motion, and persistent glacier mass loss. To further understand the impacts of this warming trend on glacier flow, this study investigates seasonality and long-term changes in ice motion with a focus on two glaciers: Thompson and White Glaciers on Axel Heiberg Island, with White Glacier containing the longest in situ mass balance record in the Canadian Arctic. This study builds on previous research by creating a dense time series of glacier motion over a ~10-year period (winter 2008/2009 to winter 2021/2022), thus improving upon spatial and temporal resolution of earlier work. The main objectives of this study are to (1) utilize a large catalogue of previously unused SAR (R2 and TSX) data to produce velocity maps of White and Thompson Glaciers, (2) perform a comparison of different SAR datasets and (3) investigate seasonality and long-term changes in velocity structure

Intra-annual and Long-term Dynamic Behaviour of Hubbard and Valerie Glaciers, Alaska

Western North American mountain regions are warming at a faster rate than the global average, which is influencing the retreat and melting of glaciers, with a 75% disappearance of glacier volume in Western North America possible by 2100. The impacts of this are wide reaching, including increasing contributions to sea level rise, decreased freshwater availability, loss of stability of mountain slopes and changing aquatic ecosystems. Hubbard and Valerie glaciers are in the St. Elias Mountains of Alaska/Yukon, which is an important area of study as Alaskan glaciers are likely to respond to climate change differently than glaciers in other regions of the world. The studies on seasonal velocity flow of both glaciers have been limited, with few recent reports of dynamics and mass balance. The goals of this study were to 1) determine the seasonality of Hubbard and Valerie glaciers by creating the densest record of flow to date from July 2013-April 2022; 2) analyze the long-term velocity trend from 1985-2022 to confirm if both glaciers are decelerating; and 3) use surface elevation change and temperature data to analyze potential drivers of the determined velocity patterns. The velocity record of Hubbard and Valerie glaciers was created using ITS_LIVE, RADARSAT-2, RADARSAT Constellation Mission, and TerraSAR-X/TanDEM-X derived measurements. Valerie glacier had an expected seasonal pattern of peak velocities in May and minimum velocities between August-November. Hubbard Glacier had a seasonal pattern that had never been identified in previous studies, with peak velocities between December-February, velocities dropping slightly between January-April, a second velocity peak in May, and minimum velocities in August/September. The May peak and late summer minimum of both glaciers was determined to be from surface melt reaching the bed, increasing flow speeds with an inefficient drainage system before changing to a channelized subglacial hydrological system that causes a velocity drop. It is likely Hubbard Glacier’s winter velocity peak and slowdown before its May peak is internally driven, however the exact driver was not identified. The long-term velocity trend revealed Hubbard Glacier is decelerating, with a minimal deceleration near its terminus that was similar to the minimal deceleration on Valerie Glacier, while there was increased deceleration further up-glacier. For both glaciers, the deceleration did not match the expected patterns of thinning/thickening. Previous instances of pulsing were not resolved in this data. Overall, this study helps improve the knowledge of tidewater glacier dynamics through the identification of a unique intra-annual velocity pattern and can assist in improving sea level rise, ice dynamics, and mass loss models