Grounding Line Retreat of Denman Glacier, East Antarctica, Measured With COSMO‐SkyMed Radar Interferometry Data

Abstract

Denman Glacier, East Antarctica, holds an ice volume equivalent to a 1.5 m rise in global sea level. Using satellite radar interferometry from the COSMO-SkyMed constellation, we detect a 5.4 ± 0.3 km grounding line retreat between 1996 and 2017-2018. A novel reconstruction of the glacier bed topography indicates that the retreat proceeds on the western flank along a previously unknown 5 km wide, 1,800 m deep trough, deepening to 3,400 m below sea level. On the eastern flank, the grounding line is stabilized by a 10 km wide ridge. At tidal frequencies, the grounding line extends over a several kilometer-wide grounding zone, enabling warm ocean water to melt ice at critical locations for glacier stability. If warm, modified Circumpolar Deep Water reaches the sub-ice-shelf cavity and continues to melt ice at a rate exceeding balance conditions, the potential exists for Denman Glacier to retreat irreversibly into the deepest, marine-based basin in Antarctica. Plain Language SummaryUsing satellite radar data from the Italian COSMO-SkyMed constellation, we document the grounding line retreat of Denman Glacier, a major glacier in East Antarctica that holds an ice volume equivalent to a 1.5 m global sea level rise. The grounding line is retreating asymmetrically. On the eastern flank, the glacier is protected by a subglacial ridge. On the western flank, we find a deep and steep trough with a bed slope that makes the glacier conducive to rapid retreat. If warm water continues to induce high rates of ice melt near the glacier grounding zone, the potential exists for Denman Glacier to undergo a rapid and irreversible retreat, with major consequences for sea level rise.

Reply to Lanari, R., et al. Comment on “Pre-Collapse Space Geodetic Observations of Critical Infrastructure: The Morandi Bridge, Genoa, Italy” by Milillo et al. (2019)

“…InSAR time series techniques were originally developed 20 years ago. They reached their maturity for the detection of surface displacements in geophysical processes, such as earthquakes [3,4], landslides [5,6], volcanoes [7][8][9][10][11] and glacier motion [12][13][14][15][16][17][18]. In the last decade, the latest generation of radar satellites has provided high spatial resolution, short revisit time and millimeter precision.…”

Recent acceleration of Denman Glacier (1972–2017), East Antarctica, driven by grounding line retreat and changes in ice tongue configuration

“…Geological evidence suggests that there may have been substantial retreat of the ice margin in the ASB during the warm interglacials of the Pliocene (Williams et al, 2010;Young et al, 2011;Aitken et al, 2016;Scherer et al, 2016), which potentially resulted in global mean sea level contributions of up to 2 m from the ASB (Aitken et al, 2016). This is important because these warm periods of the Pliocene may represent our best analogue for climate by the middle of this century under unmitigated emission trajectories (Burke et al, 2018). Indeed, numerical models now predict future sea level contributions from the outlet glaciers which drain the ASB over the coming decades to centuries (Golledge et al, 2015;Ritz et al, 2015;DeConto and Pollard, 2016), but large uncertain-B.…”

Evaluation of ICEYE Microsatellites Sensor for Surface Motion Detection—Jakobshavn Glacier Case Study

“…It allows for almost real-time mapping of entire regions, such as Greenland [40] or Antarctica [41]. Moreover, usage of radar data improved investigation of such problems like ice classifications [42] or assessment of the grounding line position [43][44][45]. Thanks to that it is possible to show the impact of e.g., increase of average air temperature on glacier's terminus retreat [46].…”