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1. A tale of Two Events: Arctic Rain-on-Snow Meteorological Drivers

   Voveris, J and (March 2023, Annals of glaciology)

   Arctic warming may lead to altered occurrences and strengthening of extreme weather events. Arctic rain-on-snow (ROS) events are of a particular interest in this regard. ROS conditions generate hazards for the transportation sector, ranging from flooding and icing to airport closures, and can severely damage infrastructure through wet-snow avalanches. ROS events, and the resulting ice growth, interfere with foraging by reindeer, caribou, and musk oxen, heavily relied upon species among Indigenous peoples. There have been documented mass starvations of these animals due to ROS. This study addresses the meteorological setups of Arctic ROS events. We focus on cases for Iqaluit, Nunavut, in Canada and Nuuk, Greenland, using ERA5 atmospheric reanalysis, surface weather station data, and atmospheric soundings. At the synoptic scale, we find that blocking patterns play leading roles in ROS initiation, with atmospheric rivers contributing to both direct and indirect effects. Cyclone-induced low-level jets and resultant “warm noses” of higher air temperatures and elevated moisture transport are other key features in ROS generation. We conclude by postulating how climate change may alter the severity and frequency of Arctic ROS events, drawing on this improved knowledge of weather patterns leading to ROS conditions. 

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2. Anomalous Arctic warming linked with severe winter weather in Northern Hemisphere continents

   https://doi.org/10.1038/s43247-024-01720-0  

   Cohen, Judah; Francis, Jennifer A; Pfeiffer, Karl (December 2024, Communications Earth & Environment)

   We have extended a recently developed metric that ingests United States station data—the accumulated winter season severity index—to a global indicator based on temperature and snowfall from reanalysis output. The expanded index is analyzed to reveal relationships between Arctic air temperatures/pressures and the probability of severe winter weather across the Northern Hemisphere midlatitudes. Here we find a direct and quasilinear relationship between anomalously high Arctic temperatures/pressures and increased severe winter weather, especially in northeastern continental regions downstream of maximum regional Arctic warming. Positive temperature trends in the Arctic are associated with positive trends in severe winter weather across the continents in mid- to latewinter, coinciding with an increase in stratospheric polar vortex disruptions. During the era of rapid Arctic warming, variability has decreased over the Arctic Ocean and Europe, but has increased in Canada, the Northern US and northeast Asia, indicating more pronounced shifts in weather conditions. 

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3. Greenland Ice Sheet wide supraglacial lake evolution and dynamics: insights from the 2018 and 2019 melt seasons

   https://doi.org/10.31223/X5871P  

   Dunmire, Devon; Subramanian, Aneesh; Hossain, Emam; Gani, Md; Banwell, Alison; Younas, Hammad; Myers, Brendan (July 2024, Eartharxiv)

   Supraglacial lakes on the Greenland Ice Sheet (GrIS) can impact both the ice sheet surface mass balance and ice dynamics. Thus, understanding the evolution and dynamics of supraglacial lakes is important to provide improved parameterizations for ice sheet models to enable better projections of future GrIS changes. In this study, we utilize the growing inventory of optical and microwave satellite imagery to automatically determine the fate of Greenland-wide supraglacial lakes during 2018 and 2019; cool and warm melt seasons respectively. We develop a novel time series classification method to categorize lakes into four classes: 1) refreezing, 2) rapidly draining, 3) slowly draining, and 4) buried. Our findings reveal significant interannual variability between the two melt seasons, with a notable increase in the proportion of draining lakes in 2019. We also find that as mean lake depth increases, so does the percentage of lakes that drain, indicating that lake depth may influence hydrofracture potential. However, we also observe that non-draining lakes are deeper during the cooler 2018 melt season, suggesting that additional factors may predispose lakes to drain earlier in a warmer year. Our automatic classification approach and the resulting two-year ice-sheet-wide dataset provide unprecedented insights into GrIS supraglacial lake dynamics and evolution, offering a valuable resource for future research. 

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4. Diagnosing the Influence of a Receding Snow Boundary on Simulated Midlatitude Cyclones Using Piecewise Potential Vorticity Inversion

   https://doi.org/10.1175/MWR-D-20-0056.1  

   Breeden, Melissa L.; Clare, Ryan; Martin, Jonathan E.; Desai, Ankur R. (November 2020, Monthly Weather Review)

   null (Ed.)

   Abstract Previous research has found a relationship between the equatorward extent of snow cover and low-level baroclinicity, suggesting a link between the development and trajectory of midlatitude cyclones and the extent of preexisting snow cover. Midlatitude cyclones are more frequent 50–350 km south of the snow boundary, coincident with weak maxima in the environmental Eady growth rate. The snow line is projected to recede poleward with increasing greenhouse gas emissions, possibly affecting the development and track of midlatitude cyclones during Northern Hemisphere winter. Detailed examination of the physical implications of a modified snow boundary on the life cycle of individual storms has, to date, not been undertaken. This study investigates the impact of a receding snow boundary on two cyclogenesis events using Weather Research and Forecasting Model simulations initialized with observed and projected future changes to snow extent as a surface boundary condition. Potential vorticity diagnosis of the modified cyclone simulations isolates how changes in surface temperature, static stability, and relative vorticity arising from the altered boundary affect the developing cyclone. We find that the surface warm anomaly associated with snow removal lowered heights near the center of the two cyclones investigated, strengthening their cyclonic circulation. However, the direct effect of snow removal is mitigated by the stability response and an indirect relative vorticity response to snow removal. Because of these opposing effects, it is suggested that the immediate effect of receding snow cover on midlatitude cyclones is likely minimal and depends on the stage of the cyclone life cycle. 

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5. Seasonal detections of bearded seal (Erignathus barbatus) vocalizations in Baffin Bay and Davis Strait in relation to sea ice concentration

   https://doi.org/10.1007/s00300-020-02723-1  

   Boye, Tenna K.; Simon, Malene J.; Laidre, Kristin L.; Rigét, Frank; Stafford, Kathleen M. (August 2020, Polar Biology)

   There is limited information about the biology and seasonal distribution of bearded seals (Erignathus barbatus) in Greenland. The species is highly ice-associated and depends on sea ice for hauling out and giving birth, making it vulnerable to climate change. We investigated the seasonality and distribution of bearded seal vocalizations at seven different locations across southern Baffin Bay and Davis Strait, West Greenland. Aural M2 and HARUphone recorders were deployed on the sea bottom during 2006–2007 and 2011–2013. Recordings were analyzed for presence/absence of bearded seal calls relative to location (including distance to shore and depth), mean sea ice concentration and diel patterns. Calling occurred between November and late June with most intense calling during the mating season at all sites. There was a clear effect of depth and distance to shore on the number of detections, and the Greenland shelf (< 300 m) appeared to be the preferred habitat for bearded seals during the mating season. These results suggest that bearded seals may retreat with the receding sea ice to Canada during summer or possibly spend the summer along the West Greenland coast. It is also possible that, due to seasonal changes in bearded seal vocal behavior, animals may have been present in our study area in summer, but silent. The number of detections was affected by the timing of sea ice formation but not sea ice concentration. Diel patterns were consistent with patterns found in other parts of the Arctic, with a peak during early morning (0400 local) and a minimum during late afternoon (1600 local). While vocalization studies have been conducted on bearded seals in Norwegian, Canadian, northwest Greenland, and Alaskan territories, this study fills the gap between these areas. 

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