Influence of Climate Variability in King George Island Glacier Retreat – Antarctic Peninsula

<p>This research aims to explain the influence of climatic variables (temperature and precipitation) in King George Island (KGI) glacier shrinkage on the Antarctic Peninsula. It employed Landsat satellite images from 1989 to 2020, climatic data and ONI index from 1980 to 2019.</p><p>King George Island glaciers have lost 10% of their coverage in the last 31 years. Greater glacier shrinkage was shown until the first mid-period assessed, while the retreat rate slowed down for the second half of the studied period. Furthermore, of 73 KGI glaciers, 37% were marine- and land-terminating, 42% were land-terminating and 21% were sea-terminating. Nonetheless, the decreases in the ice-coverage of marine-contact glaciers (35% of glacier coverage reduced) were higher than land-terminating glaciers (17% of glacier coverage reduced).</p><p>There was a perceivable fluctuation in annual average air temperature for the 1980-2006 period. Nevertheless, from around 2007 to 2015/2016 there was a slight continuous cooling period and precipitation was somewhat above the average. Therefore, these patterns could explain the recent KGI glacier-retreat deceleration.</p><p>Unlike the 1982/1983 and 1997/1998 El Niño events, the 2015/2016 El Niño was colder with precipitation reduction from the sustained annual amount (since roughly 2007 to 2015/2016) to values below the average. Moreover, during the 2015/2016 El Niño, KGI glacier coverage reduction was the lowest for the 31 year-long evaluated. However, it was revealed that the glacier's height could increase by accumulation in El Niño years, but glacier mass balance could be more negative due to basal melting. Additionally, land-terminating glaciers have lost more glacier coverage than sea-terminating glaciers throughout this ENSO event.</p><p>Hence, climate variability might play a significant role in KGI glacier shrinkage, but calving process, glacier features and so on, further a combination of them should be assessed to reach a better understanding of KGI glacier retreat.</p>

Emerging water scarcity risks in tropical Andean glacier-fed river basins

<p>In the tropical Andes and adjacent lowlands, human and natural systems often rely on high-mountain water resources. Glaciated headwaters play an essential role in safeguarding water security for downstream water use. However, there is mounting concern particularly about long-term water supply as the timing and magnitude of glacier meltwater contribution to river streamflow become less reliable with rapid glacier shrinkage. This concern matches an increase in water demand from growing irrigation, population and hydropower capacity in combination with high social-ecological vulnerabilities threatening sustained water security. Despite important progress in assessing the impacts of glacier shrinkage and consequences for meltwater availability, little is known about the associated hydrological risks and how they propagate downstream. Therefore, integrated approaches are needed that combine a detailed picture of the meltwater propagation through the terrestrial water cycle with human vulnerabilities and exposure to water scarcity. However, the complex topographic and sociocultural setting including scarce data, limited local capacities and frequent water conflicts hamper a more thorough process understanding and water security assessment at a basin scale.</p><p>Under high complexity and uncertainty, we propose a coupled risk framework combining water scarcity hazards, exposed people and multiple human vulnerabilities to address these limitations. An important aspect of the framework is the recognition of knowledge from indigenous and rural communities that can potentially be integrated into current scientific baselines and innovative adaptation debates. Our framework interlinks a broad set of hydroclimatic, socioeconomic and water management variables at unprecedented detail. We put particular emphasis on the quantification and understanding of multidimensional vulnerabilities as a key element for evaluating the enabling effects of these impacts in social-environmental systems. However, the assessment of corresponding vulnerabilities might not be relevant if the degree of the systems’ exposure is not sufficiently addressed. Therefore, we further analyse the interplay of the diverse variables and critical system thresholds that determine the dimensions and spatiotemporal patterns which enable meaningful assessments of cascading processes and interconnected risks to water scarcity.</p><p>Our risk framework provides a thorough baseline to support assessments of future water availability for guiding climate change adaptation, water management, and governance in rapidly changing mountain basins. Nonetheless, remaining uncertainties and limited understanding relate to the availability of local data and highlight the need for additional data collection. Lastly, we identify specific opportunities to explore the use of nature-based solutions, such as source water and wetland protection, in combination with a strong engagement of local communities and policy makers as an efficient pathway to cope with emerging risks to water scarcity in glacier-fed river basins.</p>

Glacier shrinkage in the Alps continues unabated as revealed by a new glacier inventory from Sentinel-2

The ongoing glacier shrinkage in the Alps requires frequent updates of glacier outlines to provide an accurate database for monitoring, modelling purposes (e.g. determination of run-off, mass balance, or future glacier extent), and other applications. With the launch of the first Sentinel-2 (S2) satellite in 2015, it became possible to create a consistent, Alpine-wide glacier inventory with an unprecedented spatial resolution of 10 m. The first S2 images from August 2015 already provided excellent mapping conditions for most glacierized regions in the Alps and were used as a base for the compilation of a new Alpine-wide glacier inventory in a collaborative team effort. In all countries, glacier outlines from the latest national inventories have been used as a guide to compile an update consistent with the respective previous interpretation. The automated mapping of clean glacier ice was straightforward using the band ratio method, but the numerous debris-covered glaciers required intense manual editing. Cloud cover over many glaciers in Italy required also including S2 scenes from 2016. The outline uncertainty was determined with digitizing of 14 glaciers several times by all participants. Topographic information for all glaciers was obtained from the ALOS AW3D30 digital elevation model (DEM). Overall, we derived a total glacier area of 1806±60 km2 when considering 4395 glaciers >0.01 km2. This is 14 % (−1.2 % a−1) less than the 2100 km2 derived from Landsat in 2003 and indicates an unabated continuation of glacier shrinkage in the Alps since the mid-1980s. It is a lower-bound estimate, as due to the higher spatial resolution of S2 many small glaciers were additionally mapped or increased in size compared to 2003. Median elevations peak around 3000 m a.s.l., with a high variability that depends on location and aspect. The uncertainty assessment revealed locally strong differences in interpretation of debris-covered glaciers, resulting in limitations for change assessment when using glacier extents digitized by different analysts. The inventory is available at https://doi.org/10.1594/PANGAEA.909133 (Paul et al., 2019).

Economic losses from changing hydrology under future climate change, glacier shrinkage and growing water demand in the Tropical Andes

<p>In the Tropical Andes, glaciers play a fundamental role for sustaining human livelihoods and ecosystems in headwater areas and further downstream. However, current rates of glacier shrinkage driven by climate change as well as increasing water demand levels bear a threat to long-term water supply. While a growing number of research has covered impacts of climate change and glacier shrinkage on the terrestrial water cycle and potential disaster risks, the associated potential economic losses have barely been assessed.</p><p>Here we present an integrated surface-groundwater assessment model for multiple water sectors under current conditions (1981-2016) and future scenarios (2050) of glacier shrinkage and growing water demand. As a case, the lumped model has been applied to the Santa river basin (including the Cordillera Blanca, Andes of Peru) within three subcatchments and considers effects from evapotranspiration, environmental flows and backflows of water use. Therefore, coupled greenhouse gas concentration (RCP2.6 and RCP8.5) and socioeconomic scenarios are used, which provide a broad range of the magnitude of glacier and water volume changes and associated economic impacts. Finally, net water volume released on the long term due to deglaciation effects is quantified and by multiple metrics converted into potential economic costs and losses for the agriculture, household and hydropower sectors. Additionally, the potential damages from outburst floods from current and future lakes have been included. Results for the entire Santa river basin show that water availability would diminish by about 11-16% (57-78 10<sup>6</sup> m³) in the dry season (June-August) and by some 7-10% (103-155 10<sup>6</sup> m³) during the wet season (December-February) under selected glacier shrinkage scenarios until 2050. This is a consequence of diminishing glacier contribution to streamflow which until 2050 would reduce from about 45% to 33% for June-August and from 6% to 4% for December-February. A first rough estimate suggests associated economic losses for main water demand sectors (agriculture, hydropower, drinking water) on the order of about 300 10<sup>6</sup> USD/year by 2050. Additionally, with ongoing glacier shrinkage and the formation of new lakes, about 45,000 inhabitants and 30,000 buildings are expected to be exposed to the risk of outburst floods in the 21<sup>st</sup> century.</p><p>The pressure on water resources and interconnected socio-eonvironmental systems in the basin is already challenging and expected to further exacerbate within the next decades. Currently, water demand levels are considerably increasing driven by growing irrigated (export) agriculture, population and energy demand which is in a large part sustained by hydropower. A coupling of potential water scarcity driven by climate change with a lack of water governance and high human vulnerabilities, bears strong conflict potentials with negative feedbacks for socio-economic development in the Santa basin and beyond. In this context, our coupled hydro-glacial economic impact model provides important support for future decision-making and long-term water management planning. However, uncertainties are relatively high (uncertainty range to be estimated) due to a lack of (good) hydro-climatic and socio-economic information at appropriate spatiotemporal scales. The presented model framework is potentially transferable to other high mountain catchments in the Tropical Andean region and beyond.</p>

Terminal motions of Longbasaba Glacier and their mass contributions to proglacial lake volume during 1988–2018

The interaction between a glacier and its glacial lake plays an increasingly important role in glacier shrinkage and proglacial lake expansion, and it increases the risk of glacial lake outburst floods (GLOFs). Longbasaba Glacier is directly contacted by a moraine-dammed lake with a high outburst risk in the central Himalayas, and has drawn a great deal of attention from scientists and local governments. Based on Landsat images and in-situ measurements, the evolution records of the shrinkage of Longbasaba Glacier and the corresponding expansion of its proglacial lake were determined for 1988–2018, and the mass contributions of glacier shrinkage to the increase in lake water volume were assessed. During the past three decades, Longbasaba Glacier has experienced a continuous and accelerating recession in glacier area and length but accompanied by the decelerating surface lowing and ice flow. Consequently, Longbasaba Lake has expanded significantly at an accelerating rate. The glacier surface lowering played a predominant role in the mass contribution of glacier shrinkage to the increase in lake water volume, while ice avalanches were the main potential trigger for failure of moraine dams and subsequent GLOF events. Due to the areal expansion, decreasing mass contributions from parent glacier shrinkage, and some mitigation measures by local governments to improve the drainage systems, the potential risk of outburst for Longbasaba Lake has continuously decreased during the last decade.

Glacier shrinkage in the Alps continues unabated as revealed by a new glacier inventory from Sentinel-2

The on-going glacier shrinkage in the Alps requires frequent updates of glacier outlines to provide an accurate database for monitoring or modeling purposes (e.g. determination of run-off, mass balance, or future glacier extent) and other applications. With the launch of the first Sentinel-2 (S2) satellite in 2015, it became possible to create a consistent, Alpine-wide glacier inventory with an unprecedented spatial resolution of 10 m. Fortunately, already the first S2 images acquired in August 2015 provided excellent mapping conditions for most of the glacierised regions in the Alps. We have used this opportunity to compile a new Alpine-wide glacier inventory in a collaborative team effort. In all countries, glacier outlines from the latest national inventories have been used as a guide to compile a consistent update. However, cloud cover over many glaciers in Italy required including also S2 scenes from 2016. Whereas the automated mapping of clean glacier ice was straightforward using the band ratio method, the numerous debris-covered glaciers required in-tense manual editing. The uncertainty in the outlines was determined with a multiple digitising experiment of 14 glaciers by all participants. Topographic information for all glaciers was derived from the ALOS AW3D30 DEM. Overall, we derived a total glacier area of 1806 ± 60 km2 when considering 4394 glaciers > 0.01 km2. This is 14 % (−1.2 %/a) less than the 2100 km2 derived from Landsat scenes acquired in 2003 and indicating an unabated continuation of glacier shrinkage in the Alps since the mid-1980s. Due to the higher spatial resolution of S2 many small glaciers were additionally mapped in the new inventory or increased in size compared to 2003. An artificial reduction to the former extents would thus result in an even higher overall area loss. Still, the uncertainty assessment revealed locally considerable differences in interpretation of debris-covered glaciers, resulting in limitations for change assessment when using glacier extents digitised by different analysts. The inventory is available at: https://doi.pangaea.de/10.1594/PANGAEA.909133 (Paul et al., 2019).