Fine resolution topographic data derived from methods such as Structure from Motion (SfM) and Multi-View Stereo (MVS) have the potential to provide detailed observations of geomorphological change, but have thus far been limited by the logistical constraints of conducting repeat surveys in the field. Here, we present the results from an automated time-lapse camera array, deployed around an ice-marginal lake on the western margin of the Greenland ice sheet. Fifteen cameras acquired imagery three-times per day over a 426 day period, yielding a dataset of ~19 000 images. From these data we derived 18 point clouds of the ice-margin across a range of seasons and successfully identified calving events (ranging from 234 to 1475 m²in area and 815–8725 m³in volume) induced by ice cliff undercutting at the waterline and the collapse of spalling flakes. Low ambient light levels, locally reflective surfaces and the large survey range hindered analysis of smaller scale ice-margin dynamics. Nevertheless, this study demonstrates that an integrated SfM-MVS and time-lapse approach can be employed to generate long-term 3-D topographic datasets and thus quantify ice-margin dynamics at a fine spatio-temporal scale. This approach provides a template for future studies of geomorphological change.

Ice thickness distribution and volume are both key parameters for glaciological and hydrological applications. This study presents VOLTA (Volume and Topography Automation), which is a Python script tool for ArcGISTM that requires just a digital elevation model (DEM) and glacier outline(s) to model distributed ice thickness, volume and bed topography. Ice thickness is initially estimated at points along an automatically generated centreline network based on the perfect-plasticity rheology assumption, taking into account a valley side drag component of the force balance equation. Distributed ice thickness is subsequently interpolated using a glaciologically correct algorithm. For five glaciers with independent field-measured bed topography, VOLTA modelled volumes were between 26.5% (underestimate) and 16.6% (overestimate) of that derived from field observations. Greatest differences were where an asymmetric valley cross section shape was present or where significant valley infill had occurred. Compared with other methods of modelling ice thickness and volume, key advantages of VOLTA are: a fully automated approach and a user friendly graphical user interface (GUI), GIS consistent geometry, fully automated centreline generation, inclusion of a side drag component in the force balance equation, estimation of glacier basal shear stress for each individual glacier, fully distributed ice thickness output and the ability to process multiple glaciers rapidly. VOLTA is capable of regional scale ice volume assessment, which is a key parameter for exploring glacier response to climate change. VOLTA also permits subtraction of modelled ice thickness from the input surface elevation to produce an ice-free DEM, which is a key input for reconstruction of former glaciers. VOLTA could assist with prediction of future glacier geometry changes and hence in projection of future meltwater fluxes. The VOLTA model is presented to estimate ice thickness distribution and volume.The model requires just glaciers outlines and a DEM as inputs.VOLTA can rapidly estimate volume and bed topography for multiple glaciers.The model was tested against glaciers with independent field based observations.Modelled volumes were between 26.5% (underestimate) and 16.6% (overestimate).

Glaciers and ice caps (GICs) are important contributors of meltwater runoff and to global sea level rise. However, knowledge of GIC mass changes is largely restricted to the last few decades. Here we show the extent of 5327 Greenland GICs during Little Ice Age (LIA) termination (1900) and reveal that they have fragmented into 5467 glaciers in 2001, losing at least 587 km³ from their ablation areas, equating to 499 Gt at a rate of 4.34 Gt yr⁻¹. We estimate that the long‐term mean mass balance in glacier ablation areas has been at least −0.18 to −0.22 m w.e. yr⁻¹ and note the rate between 2000 and 2019 has been three times that. Glaciers with ice‐marginal lakes formed since the LIA termination have had the fastest changing mass balance. Considerable spatial variability in glacier changes suggest compounding regional and local factors present challenges for understanding glacier evolution.