Slow change since the Little Ice Age at a far northern glacier with the potential for system reorganization: Thores Glacier, northern Ellesmere Island, Canada

Relatively little is known about the glaciers of northern Ellesmere Island, Canada. Here we describe the first field and remote sensing observations of Thores Glacier, located 50 km inland from the Arctic Ocean. The glacier is slow-moving, with maximum velocities of 26 m a −1 and a maximum observed thickness of 360 ± 4.3 m. There has been little change in terminus position since at least 1959, with a maximum advance of 170 m at the northwest terminus ending on land and retreat up to 130 m at the southeast terminus ending in Thores Lake. There is little evidence for change since the Little Ice Age as bedrock weathering patterns suggest retreat of no more than 20–30 m around most of the glacier margin. The supraglacial drainage network is generally poorly developed, without moulins and with few crevasses, and therefore no evidence of water reaching the glacier bed. This is supported by one-dimensional modelling, which suggests current basal temperatures of −7.0 °C to −12.0 °C along the centerline. Thores Glacier currently dams Thores Lake, which causes drainage to flow to the southeast. However, if the glacier thins or retreats sufficiently, regional drainage will reverse and flow to the north, and Thores Lake would no longer exist

Draining and filling of ice-dammed lakes at the terminus of surge-type Dań Zhùr (Donjek) Glacier, Yukon, Canada

Recent surges of Dań Zhùr (Donjek) Glacier have formed lakes at the glacier terminus that have drained catastrophically, resulting in hazards to people and infrastructure downstream. Here we use air photos and satellite imagery to describe lake formation, and the timing of filling and draining, since the 1930s. Between the 1930s and late 1980s, lakes were typically small (1 km2) and drain rapidly through or under the glacier by breaking a terminal ice dam. For the past two surges, since 2001, the lakes formed during or immediately after a surge in an increasingly larger basin between the Neoglacial maximum moraine and an increasingly smaller maximum terminus extent. Most recently, the 2012–2014 surge created a lake that drained in summer 2017, refilled, and drained again in both summer 2018 and summer 2019. The 2019 lake was 2.2 km2, the largest on record, and drained entirely within 2 days. While a lake is unlikely to form again before the next expected surge in the mid-2020s, future surges of Dań Zhùr Glacier are still likely to create terminal lakes, necessitating continued monitoring for surge activity and lake formation.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Patterns and mechanisms of repeat drainages of glacier-dammed Dań Zhùr (Donjek) Lake, Yukon

Dań Zhùr (Donjek) Glacier is a surge-type glacier that undergoes cyclical periods of rapid advance over ∼1–2 years, followed by retreat for ∼10 years. Since the 1990s, the advances have caused the formation of ice-dammed Dań Zhùr Lake, which has filled and drained in summers following a surge event. Here, we report how these drainages initially occur through a subglacial channel under the glacier terminus, which then typically closes the following winter, enabling another lake to form and drain the next summer. However, our remote sensing and field observations indicate that after several drainage events, a subaerial ice canyon is formed through the glacier terminus, which prevents another lake from forming until after the glacier surges again. We predict that the next surge of Dań Zhùr Glacier will occur around the mid-2020s, causing the formation of a larger Dań Zhùr Lake during the following quiescent phase because, despite periodic advances, a long-term trend of glacier recession is exposing a larger basin for the lake to form in. However, each subsequent surge is causing less terminus advance than the previous one, until ultimately the surges will be insufficient to dam Dań Zhùr Chù’ (Donjek River), and lakes will cease to form

Modelling Permafrost Distribution using the Temperature at Top of Permafrost Model in the Boreal Forest Environment of Whatì, NT.

Current permafrost models in Canadian boreal forests are generally low spatial resolution as they cover regional or continental scales. This study aims to understand the viability of creating a temperature at top of permafrost (TTOP) model on a local scale in the boreal wetland environment of Whatì, Northwest Territories from short-term field-collected temperature data. The model utilizes independent variables of vegetation, topographic positioning index and elevation, with the dependent variables being ground surface temperature collected from 60 ground temperature nodes (GTN) and 1.5 m air temperature collected from 10 temperature stations. In doing this the study investigates the relationship vegetation and disturbance have on ground temperature and permafrost distribution. The model predicts that 31 % of the ground is underlain by permafrost, based on a mean annual temperature at TTOP of < 0 °C. This model shows an accuracy of 62.5 % when compared to Cryotic Assessment Sites (CAS). Most inaccuracies, showing the limitation of the TTOP model, came from peat plateaus that had undergone burn in the most recent forest fire in 2014. These resulted in out of equilibrium permafrost and climatic conditions which TTOP cannot handle well. Commonly permafrost mapping places Whatì in the extensive discontinuous zone estimating that between 50 % to 90 % of the ground is underlain by permafrost. The study shows that a climatically driven TTOP model calibrated with CAS can be used to illustrate ground temperature heterogeneity from short-term data in boreal forest wetland environments. However, this approach likely underestimates permafrost extent and is perhaps not the best-suited modelling choice for near-surface permafrost, which is currently out of equilibrium with the current climat

Modelling air, ground surface and permafrost temperature variability across four dissimilar valleys, Yukon, Canada

Spatial maps of the air and ground thermal regime were generated for four Yukon valleys. The aim was to model air, ground surface and ground temperature (at fine spatial resolution) using locally measured inverted surface lapse rates (SLR), to better predict temperature along an elevation gradient. These local models were then compared to a regional permafrost probability model, which utilized differing inversion assumptions, as well as circumpolar and national models generated without considering inversions. Overall, permafrost probability in the regional model matched well with the local models where assumptions of treeline and inverted SLRs held true. When normal SLRs were assumed, permafrost presence was overestimated in each valley. This discrepancy was greatest at high elevations where permafrost was predicted to be coldest and most widespread. However, the difference between valleys was dependent on surface and subsurface characteristics such as higher snow cover, mature forest or thick organic layers showed a greater disassociation from the air temperature overall. Appropriate characterization of the SLR is essential for accurate predictions of the ground thermal regime’s spatial distribution and permafrost presence. These models also provide a starting point for better predictions of warming in these valleys and other areas subject to inversions of similar magnitudes

RADARSAT-2 Derived Glacier Velocities and Dynamic Discharge Estimates for the Canadian High Arctic: 2015–2020

RADARSAT-2 imagery collected each winter from 2015/2016 to 2019/2020 is used to quantify and characterize the variability in the motion of, and the discharge from, the major marine-terminating ice masses of the Queen Elizabeth Islands (QEI: Devon, Ellesmere and Axel Heiberg Islands) in the Canadian High Arctic. The majority of the glaciers did not experience significant variations in flow speeds over the observation period, and for most that did the variations are attributed to pulse and surge processes. However, there are exceptions where the velocity record indicates continued acceleration of the glaciers by processes that appear distinct from surging or pulsing, such as dynamic thinning. These include Trinity and Wykeham glaciers (Prince of Wales Icefield) and Belcher Glacier (Devon Ice Cap). The combination of surface velocities with ice thicknesses indicates that average ice discharge to the ocean for the QEI over the observation period was 2.78 ± 0.52 Gt a−1 (ranging between ∼2.37 ± 0.48 Gt a−1 and ∼3.20 ± 0.55 Gt a−1), ∼50% of which was channeled through the Trinity-Wykeham glacier basin alone. The results presented here, combined with those of previous studies, provide a comprehensive record of ice motion and discharge from the QEI between 2008 and 2020

Repeated subglacial jökulhlaups in northeastern Greenland revealed by CryoSat

Surface height changes above three previously undetected subglacial lakes in northeastern Greenland are documented using CryoSat, DEMs and ICESat-2. Between 7 February and 6 March 2012, the central ice region (22.6 km2) above the largest lake dropped by ~37 m followed by a further drop of 12 m in the following 29 days. This implies a subglacial water outflow, or jökulhlaup, of at least 1 km3 at rates of hundreds of cubic meters per second. A comparable outflow occurred again between 23 July and 15 September 2019, with smaller outflows in the fall of 2014 and 2016. In contrast, a second smaller subglacial lake at a higher elevation had two subglacial outbursts of ~0.3 km3 in 2012 and 2019 but the lake filling was gradual and not strongly seasonal or episodic. Water remained in both lakes after the outflows but this may not be the case for the third smallest and lowest subglacial lake. While there appears to be some hydrological link between the three lakes, the flux of water moving under the ice in this area appears to be larger than would be expected from local summer melt. However, the source of the excess water remains uncertain