Abstract
Abstract. Climate change has reduced global ice mass over the last 2 decades as enhanced warming has accelerated surface melt and runoff rates. Glaciers have undergone dynamic processes in response to a warming climate that impacts the surface geometry and mass distribution of glacial ice. Until recently no single technique could consistently measure the evolution of surface flow for an entire glaciated region in three dimensions with high temporal and spatial resolution. We have improved upon earlier methods by developing a technique for mapping, in unprecedented detail, the temporal evolution of glaciers. Our software computes north, east, and vertical flow velocity and/or displacement time series from the synthetic aperture radar (SAR) ascending and descending range and azimuth speckle offsets. The software can handle large volumes of satellite data and is designed to work on high-performance computers (HPCs) as well as workstations by utilizing multiple parallelization methods. We then compute flow velocity–displacement time series for glaciers in southeastern Alaska during 2016–2021 and observe seasonal and interannual variations in flow velocities at Seward and Malaspina glaciers as well as culminating phases of surging at Klutlan, Walsh, and Kluane glaciers. On a broader scale, this technique can be used for reconstructing the response of worldwide glaciers to the warming climate using archived SAR data and for near-real-time monitoring of these glaciers using rapid revisit SAR data from satellites, such as Sentinel-1 (6 or 12 d revisit period) and the forthcoming NISAR mission (12 d revisit period).
Highlights
The magnitude and direction of glacier flow adjust in response to the warming climate, leading to changes in seasonal flooding and droughts, landscapes and habitats, and sea level variations
We present a technique that can be used for measuring the temporal evolution of surface flow for an entire glaciated region in three dimensions (3D) with high temporal and spatial resolution
We focus on studying the dynamic changes along six landterminating glaciers in southeastern Alaska during 20 October 2016–21 January 2021: Agassiz, Seward, Malaspina, Klutlan, Kluane, and Walsh glaciers (Fig. 4)
Summary
The magnitude and direction of glacier flow adjust in response to the warming climate, leading to changes in seasonal flooding and droughts, landscapes and habitats, and sea level variations. We present a technique that can be used for measuring the temporal evolution of surface flow for an entire glaciated region in three dimensions (3D) with high temporal and spatial resolution. Modern techniques and platforms used for monitoring glacier flow include synthetic aperture radar (SAR) (Goldstein et al, 1993; Mohr et al, 1998; Rignot, 2002; Joughin, 2002), the Global Navigation Satellite System (GNSS) (van de Wal et al, 2008; Bartholomew et al, 2010), optical imagery (Berthier et al, 2005; Herman et al, 2011; Dehecq et al, 2015; Fahnestock et al, 2016), and uncrewed aerial vehicles (Immerzeel et al, 2014). SAR is the only active side-looking sensor with global coverage at high temporal and spatial resolution that can operate in any weather conditions, day or night. SAR techniques comprise displacement measurements with sub-meter to meter-scale precision using speckle offset tracking (SPO) (Strozzi et al, 2002), split-beam interferometry (or multi-aperture interferometry, MAI) (Bechor and Zebker, 2006; Gourmelen et al, 2011), and centimeter-scale differential interferometry
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