Challenges to materials for local glacier conservation
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Risk of glacier collapse in the Southeast Tibetan basin
Glacier collapse is one of the serious cryospheric hazards in the Tibetan Plateau (TP), especially in the southeast of TP. Recent studies on glacier change and glacier collapse events in this region show that the risk of glacier collapse disaster in Southeast Tibet is vague and not specific. Here, we assess the risk of glacier collapse by combining machine learning method, dangerous glacier identification and vulnerability analysis in the basin. This study considers that the glacier collapse events in this area in recent years are mainly driven by temperature, precipitation and seismic activity under the background of steep terrain. A total of 946 km2 of glaciers in southeastern Tibet are potentially at hazard of collapse, with the largest area of about 320 km2 in the southeastern region; The proportion of the southern region is the highest, about 55.6%. Eight basins are at extremely high risk, including 85 residential areas, 131 roads and 52 rivers. This study directly responds to the needs of the disaster prevention and mitigation strategy to determine the key areas, and emphasizes the necessity of coping with the threat of glacier collapse in the extremely high-risk basins in Southeast Tibet.
Active ice sheet conservation cannot stop the retreat of Sermeq Kujalleq glacier, Greenland
Active conservation of an ice sheet seeks to reduce ice sheet mass loss and sea level rise. Here we explore the response of Sermeq Kujalleq in Greenland to limiting warm water inflow to the fjord it terminates by raising the sill by an artificial barrier at its mouth. We asynchronously couple an ice sheet model with a fjord model, and simulate glacier evolution with varying climate scenarios from the year 2020 to 2100. The tallest barrier cools the fjord water and reduces melt at the ice front. But this has minor impacts on glacier retreat under SSP5-8.5 and SSP2-4.5. Cooling the atmospheric forcing to 1990s levels reduces glacier retreat, but even reducing water temperatures with a barrier cannot stabilize the glacier. The glacier seems to be in an unstoppable phase of marine ice sheet instability on a rapidly deepening retrograde sloping bed and in water much deeper than in 2000s.
Progressively smaller glacier lake outburst floods despite worldwide growth in lake area
Glacier lake outburst floods (GLOFs) may originate from larger lakes as these continue to grow with ongoing glacier retreat; however, this perception remains poorly supported in available GLOF databases. Here we mapped the areas of 1,686 glacier lakes, just before they drained, across 13 glaciated mountain regions outside polar regions and examined the trends in pre-GLOF lake areas between 1990 and 2023. We found that pre-GLOF lake areas barely changed, or even decreased, regionally through time, even as the total lake area, and thus hazard potential, grew overall. This counterintuitive finding reflects limits to growing GLOF magnitudes, such as the decoupling of lakes and parent glaciers, the development of wide, low-gradient outlets or human management. Across all regions, pre-GLOF lake areas depend on a few ice-dammed lakes, which have produced ten times more reported outbursts and ten times larger outbursts than moraine- and bedrock-dammed lakes. The latter two dam types will continue to impound growing amounts of meltwater, thereby accounting for most of the overall GLOF hazard potential, while ice-dammed lakes will shrink with deglaciation. As these lake types will evolve differently in the twenty-first century, we call for customized simulations of GLOF outflows and impacts, given the growing exposure of critical infrastructure.
Arctic bacterial diversity and connectivity in the coastal margin of the Last Ice Area
Arctic climate change is leading to sea-ice attrition in the Last Ice Area along the northern coast of Canada and Greenland, but less attention has been given to the associated land-based ecosystems. Here we evaluated bacterial community structure in a hydrologically coupled cryo-ecosystem in the region: Thores Glacier, proglacial Thores Lake, and its outlet to the sea. Deep amplicon sequencing revealed that Polaromonas was ubiquitous, but differed genetically among diverse niches. Surface glacier-ice was dominated by Cyanobacteria, while the perennially ice-capped, well-mixed water column of Thores Lake had a unique assemblage of Chloroflexi, Actinobacteriota, and Planctomycetota. Species richness increased downstream, but glacier microbes were little detected in the lake, suggesting strong taxonomic sorting. Ongoing climate change and the retreat of Thores Glacier would lead to complete drainage and loss of the lake microbial ecosystem, indicating the extreme vulnerability of diverse cryohabitats and unique microbiomes in the Last Ice coastal margin.
Winter subglacial meltwater detected in a Greenland fjord
The interaction between glacier fronts and ocean waters is one of the key uncertainties for projecting future ice mass loss. Direct observations at glacier fronts are sparse, but studies indicate that the magnitude and timing of freshwater fluxes are crucial in determining fjord circulation, ice frontal melt and ecosystem habitability. In particular, wintertime dynamics are severely understudied due to inaccessible conditions, leading to a bias towards summer observations. Here we present in situ observations of temperature and salinity acquired in late winter in Greenland at the front of a marine-terminating glacier and in surrounding fjords. Our observations indicate the existence of an anomalously fresh pool of water by the glacier front, suggesting that meltwater generated at the bed of the glacier discharges during winter. The results suggest that warm Atlantic water and nutrients are entrained at the glacier front, leading to enhanced frontal melt and increased nutrient levels. Our findings have implications for understanding the heat exchange between glacier fronts and ocean waters, glacier frontal melt rates, ocean mixing and currents, and biological productivity.
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