We present the first systematic inventory of surge-type glaciers for the whole of Greenland compiled from published datasets and multitemporal satellite images and digital elevation models. The inventory allows us to define the spatial and climatic distribution of surge-type glaciers and to analyse the timing of surges from 1985 to 2019. We identified 274 surge-type glaciers, an increase of 37% compared to previous work. Mapping surge-type glacier distribution by temperature and precipitation variables derived from ERA5-Land reanalysis data shows that the west and east clusters occur in well-defined climatic envelopes. Analysis of the timing of surge active phases during the periods ~1985 to 2000 (T1) and ~2000 to 2019 (T2) suggests that overall surge activity is similar in T1 and T2, but there appears to be a reduction in surging in the west cluster in T2. Our climate analysis shows a coincident increase in mean annual and mean winter air temperature between T1 and T2. We suggest that as glaciers thin under current warming, some surge-type glaciers in the west cluster may be being prevented from surging due to (1) their inability to build-up sufficient mass and (2) a switch from a polythermal to a largely cold-based thermal regime.

We assess the evolution of glaciological structures during the 2003–05 surge in the Paulabreen glacier system, Svalbard. Glaciological structures on the glacier surface were mapped using aerial photographs captured in the early stages of the surge (2003) and 5 years after surge termination (2011). Three-dimensional measurements of glaciological structures were collected at the tidewater front in 2013. These datasets document the physical changes during (1) the late quiescent phase; (2) the early phase of the surge as the surge front propagated down Skobreen and advanced into Paulabreen and (3) the final stages of the surge following the surge front reaching the glacier terminus. Crevasse patterns and clusters of arcuate shear planes record zones of compressive and extensional flow associated with the downglacier progression of the surge front. The transfer of surging ice from Skobreen into Paulabreen caused lateral displacement of the medial moraines to the northeast. At the ice front, this movement tilted glaciological structures in the same direction. Structures at the southwest margin record strike–slip faulting and the elevation of debris into the ice in a zone of compression and transpression. We summarise these observations in a schematic reconstruction of structural evolution during the surge.

We present the first general theory of glacier surging that includes both temperate and polythermal glacier surges, based on coupled mass and enthalpy budgets. Enthalpy (in the form of thermal energy and water) is gained at the glacier bed from geothermal heating plus frictional heating (expenditure of potential energy) as a consequence of ice flow. Enthalpy losses occur by conduction and loss of meltwater from the system. Because enthalpy directly impacts flow speeds, mass and enthalpy budgets must simultaneously balance if a glacier is to maintain a steady flow. If not, glaciers undergo out-of-phase mass and enthalpy cycles, manifest as quiescent and surge phases. We illustrate the theory using a lumped element model, which parameterizes key thermodynamic and hydrological processes, including surface-to-bed drainage and distributed and channelized drainage systems. Model output exhibits many of the observed characteristics of polythermal and temperate glacier surges, including the association of surging behaviour with particular combinations of climate (precipitation, temperature), geometry (length, slope) and bed properties (hydraulic conductivity). Enthalpy balance theory explains a broad spectrum of observed surging behaviour in a single framework, and offers an answer to the wider question of why the majority of glaciers do not surge.

We investigate an internal surge of Karayaylak Glacier, which was reported by the media in May 2015. To differentiate the May 2015 glacier surge from other glacier advances, we surveyed changes in velocity, crevasses and glacier area using Landsat 8 OLI L1T, ZY-1-02C and Gaofen-1 images from October 2014 to July 2015. The velocity, measured by automatic feature extraction and tracking during the active phase, was 10–100 times the velocity during the quiescent phase, with a maximum of (20.2 ± 0.9) m d−1 (mean ± standard error) from 8 to 15 May 2015 in the west branch of the glacier. The surge initiation and termination took place from 13 April to 16 June 2015. Ice in the west branch (length, 7 km; area, 6.8 km2) of Karayaylak Glacier accelerated down to the east branch, leading to the development of crevasses and ice covering an additional 0.1 km2 of summer pasture on the northwestern side. However, we detected no advance of the glacier's terminus.