Baseline data for monitoring geomorphological effects of glacier lake outburst flood: a very-high-resolution image and GIS datasets of the distal part of the Zackenberg River, northeast Greenland

The polar regions experience widespread transformations, such that efficient methods are needed to monitor and understand Arctic landscape changes in response to climate warming and low-frequency, high-magnitude hydrological and geomorphological events. One example of such events, capable of causing serious landscape changes, is glacier lake outburst floods. On 6 August 2017, a flood event related to glacial lake outburst affected the Zackenberg River (NE Greenland). Here, we provided a very-high-resolution dataset representing unique time series of data captured immediately before (5 August 2017), during (6 August 2017), and after (8 August 2017) the flood. Our dataset covers a 2.1 km long distal section of the Zackenberg River. The available files comprise (1) unprocessed images captured using an unmanned aerial vehicle (UAV; https://doi.org/10.5281/zenodo.4495282, Tomczyk and Ewertowski, 2021a) and (2) results of structure-from-motion (SfM) processing (orthomosaics, digital elevation models, and hillshade models in a raster format), uncertainty assessments (precision maps), and effects of geomorphological mapping in vector formats (https://doi.org/10.5281/zenodo.4498296, Tomczyk and Ewertowski, 2021b). Potential applications of the presented dataset include (1) assessment and quantification of landscape changes as an immediate result of a glacier lake outburst flood; (2) long-term monitoring of high-Arctic river valley development (in conjunction with other datasets); (3) establishing a baseline for quantification of geomorphological impacts of future glacier lake outburst floods; (4) assessment of geohazards related to bank erosion and debris flow development (hazards for research station infrastructure – station buildings and bridge); (5) monitoring of permafrost degradation; and (6) modelling flood impacts on river ecosystem, transport capacity, and channel stability.

Was there a glacial outburst flood in the Torngat Mountains during Marine Isotope Stage 3?

We report previously unpublished evidence for a Marine Isotope Stage 3 (MIS 3; 60–26 ka) glacial outburst flood in the Torngat Mountains (northern Quebec/Labrador, Canada). We present 10Be cosmogenic exposure ages from legacy fieldwork for a glacial lake shoreline with evidence for outburst flooding in the Torngat Mountains, with a minimum age of 36 ± 3 ka (we consider the most likely age, corrected for burial, to be ~56 ± 3 ka). This shoreline position and age can potentially constrain the Laurentide Ice Sheet margin in the Torngat Mountains. This region, considered a site of glacial inception, has no published dated geologic constraints for high-elevation MIS 3 ice margins. We estimate the freshwater flux associated with the inferred glacial outburst flood using high-resolution digital elevation maps corrected for glacial isostatic adjustment. Using assumptions about the ice-dammed locations we find that a freshwater flood volume of 1.14 × 1012 m3 could have entered the Hudson Strait. This glacial outburst flood volume could have contributed to surface ocean freshening to cause a measurable meltwater signal in δ18O records, but would not necessarily have been associated with substantial ice rafted debris. Future work is required to refine estimates of the size and timing of such a glacial outburst flood. Nevertheless, we outline testable hypotheses about the Laurentide Ice Sheet and glacial outburst floods, including possible implications for Heinrich events and glacial inception in North America, that can be assessed with additional fieldwork and cosmogenic measurements.

Experimental Investigation of the Outburst Discharge of Landslide Dam Overtopping Failure

Research on the factors and mechanisms that influence outburst floods are essential for estimating outflow hydrographs and the resulting inundation. In this study, large flume tests are conducted to investigate the effects of the upstream inflow and the presence of loose erodible deposits on the breaching flow and the subsequent outburst floods. Experimental results reveal that hydrographs of the breaching flow and outburst flood can be divided into three stages where each stage is separated by inflection points and peak discharges. It is found that the larger the inflow discharge, the larger the peak discharge of the outburst flood and the shorter the time needed to reach the peak and inflection discharges of the outburst flood. The breaching flow decreases along the longitudinal direction at rates that increase with the inflow discharge. The ratio between the length of the upstream dam shoulder and the dam width is inversely related to the ratio of the outburst discharge to inflow discharge. We also show that the presence of loose deposits at the dam toe can amplify the peak discharge of outburst flood by increasing the solids content of the water flow.

Hazard Assessment for a Glacier Lake Outburst Flood in the Mo Chu River Basin, Bhutan

The frequency of glacier lake outbursts floods (GLOFs) is likely to increase with the ongoing glacier retreat, which produces new glacial lakes and enlarges existing ones. Here, we simulate the outburst of a potentially dangerous glacial lake in Bhutan by applying hydrodynamic modelling. Although the lake volume is known, several parameters connected to the dam breach and the routing of the flood are rough estimates or assumptions, which introduce uncertainties in the results. For this reason, we create an ensemble of nine outburst scenarios. The simulation of magnitude and timing of possible inundation depths is an important asset to prepare emergency action plans. For our case study in the Mo Chu River Basin, the results show that, even under the worst case scenario, little damage to residential buildings can be expected. However, such an outburst flood would probably destroy infrastructure and farmland and might even affect the operation of a hydroelectric powerplant more than 120 km downstream the lake. Our simulation efforts revealed that, by using a 30-m elevation model instead of a 5-m raster, flood magnitude and inundation areas are overestimated significantly, which highly suggests the use of high-resolution terrain data. These results may be a valuable input for risk mitigation efforts.

Formation factors of surface inflow to antarctic lakes of the Larsemann Hills oasis

The study aims to identify formation factors of water inflow to the Antarctic lakes of the Larsemann Hills oasis (East Antarctica). The objects of study are 11 lakes of the oasis. The analysis was performed based on the expeditionary data of the Russian Antarctic Expedition (RAE): 63rd season (23 December 2017 – 3 February 2018), 64th season (12 January 2019 – 27 February 2019), 65th season (2 November 2019 – 24 March 2020). Data of lakes water level observations, aerial photography of the unmanned aerial vehicle (UAV) and route surveys are given, the results of identifying the boundaries of the lakes catchments are presented. The factors that determine the formation of water inflow to the lakes in this region were identified based on the analysis of the materials. The most significant are the meteorological conditions, the presence of perennial snowfields and glacial areas in the catchments, and the presence of lakes that can cause outburst flood. The seasonally thawed layer also has an impact on the formation of the inflow to the lakes. The vegetation cover is not so important for inflow formation in this region due to the physical and geographical conditions. As for anthropogenic activity, it mainly affects the environmental situation of the catchments and water quality, while the anthropogenic influence on the formation of water inflow to the lakes in the oasis is limited to the territories of polar stations. The factors identified should be taken into account in the further study of hydrological processes, the creation of models that describe them, and the organization of field observations.