Seasonal and Interannual Variability of Columbia Glacier, Alaska (2011–2016): Ice Velocity, Mass Flux, Surface Elevation and Front Position

Abstract

Alaskan glaciers are among the largest contributors to sea-level rise outside the polar ice sheets. The contributions include dynamic discharge from marine-terminating glaciers which depends on the seasonally variable ice velocity. Columbia Glacier is a large marine-terminating glacier located in Southcentral Alaska that has been exhibiting pronounced retreat since the early 1980s. Since 2010, the glacier has split into two branches, the main branch and the west branch. We derived a 5-year record of surface velocity, mass flux (ice discharge), surface elevation and changes in front position using a dense time series of TanDEM-X synthetic aperture radar data (2011)(2012)(2013)(2014)(2015)(2016). We observed distinct seasonal velocity patterns at both branches. At the main branch, the surface velocity peaked during late winter to midsummer but reached a minimum between late summer and fall. Its near-front velocity reached up to 14 m day −1 in May 2015 and was at its lowest speed of~1 m day −1 in October 2012. Mass flux via the main branch was strongly controlled by the seasonal and interannual fluctuations of its velocity. The west branch also exhibited seasonal velocity variations with comparably lower magnitudes. The role of subglacial hydrology on the ice velocities of Columbia Glacier is already known from the published field measurements during summers of 1987. Our observed variability in its ice velocities on a seasonal basis also suggest that they are primarily controlled by the seasonal transition of the subglacial drainage system from an inefficient to an efficient and channelized drainage networks. However, abrupt velocity increase events for short periods (2014-2015 and 2015-2016 at the main branch, and 2013-2014 at the west branch) appear to be associated with strong near-front thinning and frontal retreat. This needs further investigation on the role of other potential controlling mechanisms. On the technological side, this study demonstrates the potential of high-resolution X-band SAR missions with a short revisit interval to examine glaciological variables and controlling processes.

Resolving Seasonal Ice Velocity of 45 Greenlandic Glaciers With Very High Temporal Details

“…(36) during 2009 to 2013. A link between ice front changes and ice velocities is documented in a number of previous studies (Bevan et al, 2012, Howat et al, 2008, Moon et al, 2014, Vijay & Braun, 2017, and our work further supports this connection. A link between ice front changes and ice velocities is documented in a number of previous studies (Bevan et al, 2012, Howat et al, 2008, Moon et al, 2014, Vijay & Braun, 2017, and our work further supports this connection.…”

Evolving Environmental and Geometric Controls on Columbia Glacier's Continued Retreat

“…Previous observations of Alaskan tidewater glacier speeds suggest that seasonal changes in surface meltwater production alter the subglacial drainage network and thus basal drag (Durkin et al, ; McNabb et al, ; Ritchie et al, ; Stearns et al, ). Using a similar TSX‐derived record of surface speeds from 2011 to 2016, Vijay and Braun () recently postulated that speed seasonality at Columbia and Post is driven primarily by the evolution of the subglacial drainage network. As in our analysis, they observed that flow speeds reach their seasonal maxima in spring, then rapidly decrease throughout the summer months, reaching their seasonal minima in late fall—typically November (Figure b).…”

“…To extend the 1952–2012 record of Columbia Glacier terminus positions by McNabb and Hock (), which is derived from historical topographic maps and Landsat images, we manually digitized terminus positions from 2013 to 2016 in cloud‐free Landsat 7 and 8 panchromatic images. Terminus positions could also be delineated from the available TerraSAR‐X and TanDEM‐X SAR imagery, as in Vijay and Braun (). A comparison of 2012 and 2013 terminus position time series constructed from Landsat imagery and from TerraSAR‐X/TanDEM‐X SAR imagery indicates that the seasonal to interannual patterns of terminus position change of interest here are captured equally well by the two satellite platforms.…”

“…To extend the 1952-2012 record of Columbia Glacier terminus positions by McNabb and Hock (2014), which is derived from historical topographic maps and Landsat images, we manually digitized terminus positions from 2013 to 2016 in cloud-free Landsat 7 and 8 panchromatic images. Terminus positions could also be delineated from the available TerraSAR-X and TanDEM-X SAR imagery, as in Vijay and Braun (2017). August 2016.…”

Spatiotemporal Distributions of Icebergs in a Temperate Fjord: Columbia Fjord, Alaska

“…Between 2010 and 2013 the average ice flux into the fjord was measured at 2.23 km 3 yr -1 (Pfeffer, 2013b), most of which came from the main branch of the glacier. Between 2011 and 2014 the average mass flux from the main branch of Columbia Glacier was measured to be 1.18 ± 0.30 Gt yr -1 (~1.29 km 3 yr -1 ) (Vijay and Braun, 2017). 5…”