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Long believed to be insignificant, melt activity on the Northeast Greenland Ice Stream (NEGIS) has increased in recent years. Summertime Arctic clouds have the potential to strongly affect surface melt processes by regulating the amount of radiation received at the surface. However, the cloud effect over Greenland is spatially and temporally variable and high‐resolution information on the northeast is absent. This study aims at exploring the potential of a high‐resolution configuration of the polar‐optimized Weather Research & Forecasting Model (PWRF) in simulating cloud properties in the area of the Nioghalvfjerdsfjorden Glacier (79 N Glacier). Subsequently, the model simulations are employed to investigate the impact of Arctic clouds on the surface energy budget and on surface melting during the extensive melt event at the end of July 2019. Compared to automatic weather station (AWS) measurements and remote‐sensing data (Sentinel‐2A and the Moderate Resolution Imaging Spectroradiometer, MODIS), PWRF simulates cloud properties with sufficient accuracy. It appears that peak melt was caused by an increase in solar radiation and sensible heat flux (SHF) in response to a blocking anticyclone and foehn winds in the absence of clouds. Cloud warming over high‐albedo surfaces helped to precondition the surface and prolonged the melting as the anticyclone abated. The results are sensitive to the surface albedo and suggest spatiotemporal differences in the cloud effect as snow and ice properties change over the course of the melting season. This demonstrates the importance of including high‐resolution information on clouds in analyses of ice sheet dynamics., German Federal Ministry for Education and Research http://dx.doi.org/10.13039/501100002347, https://doi.org/10.5065/EM0T-1D34, https://cds.climate.copernicus.eu/cdsapp/#!/search?type=dataset, https://ladsweb.modaps.eosdis.nasa.gov/search/

Most glaciers in South America and on the Antarctic Peninsula are retreating and thinning. They are considered strong contributors to global sea level rise. However, there is a lack of glacier mass balance studies in other areas of the Southern Hemisphere, such as the surrounding Antarctic Islands. Here, we present a detailed quantification of the 21st century glacier elevation and mass changes for the entire South Georgia Island using bi-static synthetic aperture radar interferometry between 2000 and 2013. The results suggest a significant mass loss since the beginning of the present century. We calculate an average glacier mass balance of -1.04 0.09 m w.e.a(-1) and a mass loss rate of 2.28 0.19 Gt a(-1) (2000-2013), contributing 0.006 0.001 mm a(-1) to sea-level rise. Additionally, we calculate a subaqueous mass loss of 0.77 0.04 Gt a(-1) (2003-2016), with an area change at the marine and lake-terminating glacier fronts of -6.58 0.33 km(2) a(-1), corresponding to similar to 4% of the total glacier area. Overall, we observe negative mass balance rates in South Georgia, with the highest thinning and retreat rates at the large outlet glaciers located at the north-east coast. Although the spaceborne remote sensing dataset analysed in this research is a key contribution to better understanding of the glacier changes in South Georgia, more detailed field measurements, glacier dynamics studies or further long-term analysis with high-resolution regional climate models are required to precisely identify the forcing factors.

The northeast region of Greenland is of growing interest due to changes taking place on the large marine-terminating glaciers which drain the north east Greenland ice stream. Nioghalvfjerdsfjordern, or 79° N glacier, is one of these glaciers that is currently experiencing accelerated thinning, retreat and enhanced surface melt. Understanding both the influence of atmospheric processes on the glacier and the interactions between the atmosphere and the changing surface is crucial for our understanding of present stability and future change. However, relatively few studies have focused on the atmospheric processes in this region, and even fewer have used high-resolution modelling as a tool for these research questions. Here we present a high-resolution (1 km) atmospheric modelling dataset, NEGIS_WRF, for the 79° N and northeast Greenland region from 2014–2018, and an evaluation of the model’s success at representing daily near-surface meteorology compared with two automatic weather station records. The dataset, (Turton et al, 2019b: https://doi.org/10.17605/OSF.IO/53E6Z), is now available for a wide variety of applications ranging from atmospheric dynamics, to input for hydrological and oceanic modelling studies.

North‐westerly airflow and associated atmospheric rivers (ARs) have been found to profoundly influence New Zealand’s west coasts, by causing flooding, landslides and extreme ablation and accumulation on glaciers in the Southern Alps. However, the response of local glacier mass balance to synoptic‐scale circulation, including events with ARs, has typically not been investigated by considering mesoscale processes explicitly. In this study, high‐resolution atmospheric simulations from the Weather Research and Forecasting model are used to investigate the mesoscale drivers of an extreme ablation event on Brewster Glacier (Southern Alps), which occurred on February 6, 2011 during the landfall of an AR on the South Island. The following processes were found to be crucial for transferring the high temperature and water vapor contained in the AR into energy available for melt on Brewster Glacier: First, the moist‐neutral character of the air mass enabled the flow to pass over the ridge, leading to the development of orographic clouds and precipitation on the windward side of the orography, and foehn winds on the leeside. These processes fueled melt through longwave radiation and strong turbulent and rain heat fluxes within the high‐condensation environment of the orographic cloud. Second, orographic enhancement occurred due to both cellular convection within the cloud and the combined effect of multiple precipitating systems by the seeder‐feeder‐mechanism. These results indicate the potential importance of AR dynamics for New Zealand’s glaciers. They also illustrate the benefit of mesoscale atmospheric modeling for advancing process understanding of the glacier‐climate relationship in New Zealand., Plain Language Summary: Atmospheric rivers, which are elongated, narrow structures in the atmosphere that convey large amounts of moisture through the midlatitudes, have been found to impact coastal regions worldwide, including New Zealand. Besides causing flooding and landslides, they can affect glaciers in coastal mountains such as the Southern Alps. The processes causing the high temperature and moisture in atmospheric rivers to trigger melt (or snowfall) at the glacier surface have, however, not been investigated explicitly because they operate at the size of mountain valleys and ridges which are difficult to represent in global data‐sets. We address this by using an atmospheric model with high spatial detail to simulate a case study, where an atmospheric river coincided with extreme melt on Brewster Glacier in the Southern Alps. We find that the stability characteristics of the impinging warm and moist air masses lent the air the potential to ascend the mountain instead of being directed around. This resulted in cloud and precipitation development on the windward slopes whereby rain amounts were further enhanced by internal processes within the clouds. Melt was promoted through heat released from condensation and rainfall. Conversely, on the lee slopes, downslope winds caused warm and dry conditions., Key Points: The mass balance of Brewster Glacier is affected by an atmospheric river causing extreme melt through rain and turbulent energy transfer. Orographic enhancement and weak stability in the atmospheric river cause precipitation on windward slopes while leesides are foehn‐affected. Regional atmospheric modeling can advance the process understanding of the glacier‐climate relationship in New Zealand’s mountains., Alexander von Humboldt‐Stiftung (Humboldt‐Stiftung) German Research Foundation (DFG): MO 2869/4‐1 http://dx.doi.org/10.13039/100005156