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Iceberg calving is a major component of glacier mass ablation that is not well understood due to a lack of detailed temporal and spatial observations. Here, we measure glacier speed and surface elevation at 3 min intervals using a portable radar interferometer at Kangilernata Sermia, West Greenland, for a period of 2 weeks in July 2016. We detect a 20% diurnal variation in glacier speed in phase with tidal height propagating kilometers inland. We find no speedup from ice shedding off the calving face or the detachment of floating ice blocks but a 30% speedup within a few hundred meters of the ice front that persists for days when calving removes full‐thickness grounded ice blocks. Within one ice thickness from the calving front, we detect maximum strain rates 2 to 3 times larger than observable from satellite data, which has implications for studying iceberg calving as a fracturing process. Plain Language Summary: The calving of icebergs from glaciers is a major process of mass loss along the margins of the Greenland Ice Sheet that is poorly understood because it is not well observed with existing systems. We present detailed field observations of glacier speed and elevation acquired every 3 min over 2 weeks along the calving front of a major glacier in Greenland to learn about these processes. We find that the glacier responds to changes in oceanic tide, namely, the glacier speeds up in phase with the tidal height of the ocean waters, and that only calving events that remove full‐thickness ice blocks that were resting on the ground, instead of being afloat, affect the glacier speed. Following the calving of grounded ice, the glacier speed is affected for several days but only within a few hundred meters of the ice front. Furthermore, we find that the glacier deformation regime near the ice front is more pronounced than observable from existing spaceborne radars, which has implications for the study of ice fracture, iceberg calving mechanisms, and modeling glacier dynamics. Key Points: Iceberg calving triggers glacier speedup in the proximity of the ice front when a full‐thickness grounded part of the glacier is removedOceanic tides modulate Kangilernata glacier speed daily by 20% at least several km inlandMaximum strain rates along the calving front are 2–3 times larger than previously thought [ABSTRACT FROM AUTHOR]

Ice shelves play a critical role in the long-term stability of ice sheets through their buttressing effect. The underlying bathymetry and cavity thickness are key inputs for modelling future ice sheet evolution. However, direct observation of sub-ice-shelf bathymetry is time-consuming, logistically risky, and in some areas simply not possible. Here we use new compilations of airborne and marine gravity, radar depth sounding, and swath bathymetry to provide new estimates of sub-ice-shelf bathymetry outboard of the rapidly changing West Antarctic Thwaites Glacier and beneath the adjacent Dotson and Crosson ice shelves. This region is of special interest, as the low-lying inland reverse slope of the Thwaites Glacier system makes it vulnerable to marine ice sheet instability, with rapid grounding line retreat observed since 1993 suggesting this process may be underway. Our results confirm a major marine channel >800 m deep extends tens of kilometres to the front of Thwaites Glacier, while the adjacent ice shelves are underlain by more complex bathymetry. Comparison of our new bathymetry with ice shelf draft reveals that ice shelves formed since 1993 comprise a distinct population where the draft conforms closely to the underlying bathymetry, unlike the older ice shelves, which show a more uniform depth of the ice base. This indicates that despite rapid basal melting in some areas, these recently floated parts of the ice shelf are not yet in dynamic equilibrium with their retreated grounding line positions and the underlying ocean system, a factor which must be included in future models of this region's evolution. [ABSTRACT FROM AUTHOR]

Getz Ice Shelf, the largest producer of ice shelf meltwater in Antarctica, buttresses glaciers that hold enough ice to raise sea level by 22 cm. We present a new bathymetry of its sub‐ice shelf cavity using a three‐dimensional inversion of airborne gravity data constrained by multibeam bathymetry at sea and a reconstruction of the bedrock from mass conservation on land. The new bathymetry is deeper than previously estimated with differences exceeding 500 m in a number of regions. When incorporated into an ocean model, it yields a better description of the spatial distribution of ice shelf melt, specifically along glacier grounding lines. While the melt intensity is overestimated because of a positive bias in ocean thermal forcing, the study reveals the main pathways along which warm oceanic water enters the cavity and corroborates the observed rapid retreat of Berry Glacier along a deep channel with a retrograde bed slope. Plain Language Summary: The Getz Ice Shelf is a major ice shelf in West Antarctica that is rapidly melting. Its exposure to warm oceanic water has made it the largest producer of ice shelf meltwater in Antarctica. To understand its evolution and the impact on sea level rise of the glaciers that flow into it, it is essential to obtain a better description of the bathymetry beneath its hundreds of meters of floating ice. We use a combination of airborne gravity and other data to infer the depth of the cavity. We find the seabed to be in several regions more than 500 m deeper than previously reported, hence revealing one of the deepest ice shelf cavities in West Antarctica. When used in combination with an ocean model, the bathymetry helps to better explain the spatial variability in melt observed from remote sensing data, the pathways for warm waters to reach the ice shelf, and the recent evolution of selected glaciers. Key Points: Sub‐ice shelf bathymetry reconstructed with a 3D inversion of gravity data reveals one of the deepest ice shelf cavities in West AntarcticaAn ocean model coupled with the new bathymetry indicates pathways where warm ocean water enters the cavityThe new bathymetry helps elucidate the recent evolution of Getz glaciers and explain why Getz is a large producer of meltwater [ABSTRACT FROM AUTHOR]

The article presents research report on how ocean forcing drives glacier retreat in Greenland. Topics include enhanced intrusion of warm Atlantic Waters (AW) into fjords, but this assertion has not been quantitatively tested on a Greenland- wide basis or included in models; and ocean-induced melt from numerical models and in situ data indicate an average melt intensity for the submerged part of the glaciers comparable.