Response of Glacier Melt and Discharge to Future Climate Change, Susitna Basin, Alaska

A large dam for hydropower with a 67 km long reservoir is proposed in the Susitna basin, leading to multiple studies of the basin. This study focuses on the response of climate change of the Susitna basin glaciers and the effects on basin discharge

Re-evaluating the Relevance of Vegetation Trimlines in the Canadian Arctic as an Indicator of Little Ice Age Paleoenvironments

The origin of trimlines associated with the so-called “lichen-free” areas in the Canadian Arctic has been attributed both to perennial snowfield expansion during the Little Ice Age (LIA) and to seasonally persistent snow cover in more recent times. Because of the disparate hypotheses (ecological versus paleoclimatic) regarding the formation of these trimlines, their use as a paleoclimatic indicator has been abandoned for more than two decades. We re-examine this debate and the validity of the opposing hypotheses in the light of new regional mapping of trimlines across the Queen Elizabeth Islands (QEI). The ecological hypothesis—insufficient duration of the growing season resulting from seasonally persistent snow cover—fails to account for the poikilohydric nature of lichens and their ability to endure short growing seasons. It cannot adequately explain the existence of sharp trimlines or account for the occurrence of those trimlines on sparsely vegetated carbonate terrain. Furthermore, trimlines outlining the former extent of thin plateau ice caps are accordant with trimlines associated with former perennial snowfields, indicating that these trimlines record snow and ice expansion during the LIA rather than the seasonal persistence of more recent snow cover. We suggest that these features represent an important LIA climate indicator and should therefore be used for paleoclimatic reconstruction.L’origine des épaulements propres aux zones dites sans lichen de l’Arctique canadien a été attribuée tant à l’expansion des champs de neige pérenne pendant le petit âge glaciaire qu’à la couverture de neige longévive d’époques plus récentes. Puisqu’il existe des hypothèses disparates (écologiques par opposition à paléoclimatiques) quant à la formation de ces épaulements, on a arrêté de s’en servir à titre d’indicateur paléoclimatique depuis plus d’une vingtaine d’années. Ici, ce débat fait l’objet d’un nouvel examen où l’on se penche sur la validité des hypothèses divergentes à la lumière du nouveau mappage régional des épaulements des îles de la Reine-Élisabeth. L’hypothèse d’ordre écologique —durée insuffisante de la saison de croissance découlant de la couverture de neige longévive en saison —omet de tenir compte de la nature poecilitique du lichen et de son aptitude à endurer de courtes saisons de croissance. Cette hypothèse ne permet pas d’expliquer adéquatement l’existence d’épaulements précis ou de tenir compte de la présence de ces épaulements en terrain carbonaté à végétation éparse. Par ailleurs, les épaulements qui délimitent l’ancienne étendue des minces calottes glaciaires des plateaux correspondent aux épaulements associés aux anciens champs de neige pérenne, ce qui indique que ces épaulements dénotent les expansions de neige et de glace du petit âge glaciaire et non pas de la couverture de neige longévive saisonnière plus récente. On suggère que ces caractéristiques représentent un important indicateur climatique du petit âge glaciaire et par conséquent, qu’on devrait s’en servir à des fins de reconstruction paléoclimatique

Estimating Future Flood Frequency and Magnitude in Basins Affected by Glacier Wastage

INE/AUTC 15.0

Snow avalanches are a primary climate-linked driver of mountain ungulate populations

Snow is a major, climate-sensitive feature of the Earth’s surface and catalyst of fundamentally important ecosystem processes. Understanding how snow influences sentinel species in rapidly changing mountain ecosystems is particularly critical. Whereas effects of snow on food availability, energy expenditure, and predation are well documented, we report how avalanches exert major impacts on an ecologically significant mountain ungulate - the coastal Alaskan mountain goat (Oreamnos americanus). Using long-term GPS data and field observations across four populations (421 individuals over 17 years), we show that avalanches caused 23−65% of all mortality, depending on area. Deaths varied seasonally and were directly linked to spatial movement patterns and avalanche terrain use. Population-level avalanche mortality, 61% of which comprised reproductively important prime-aged individuals, averaged 8% annually and exceeded 22% when avalanche conditions were severe. Our findings reveal a widespread but previously undescribed pathway by which snow can elicit major population-level impacts and shape demographic characteristics of slow-growing populations of mountain-adapted animals.Alaska Climate Adaptation Science Center. Alaska Department of Fish and Game. Federal Aid in Wildlife Restoration Program. Alaska Department of Transportation and Public Facilities. Alaska Division of Geological and Geophysical Surveys. Bureau of Land Management. City of Sitka. Coeur Alaska. Federal Highway Administration. Wild Sheep Foundation.Abstract -- Introduction -- Results -- Discussion -- Methods -- Data availability -- Code availability -- References -- Acknowledgements -- Author information -- Ethics declarations -- Peer review -- Additional information -- Supplementary information -- Rights and permissions -- About this article -- CommentsYe

Big avalanches in a changing climate: Using tree-ring Derived avalanche chronologies to examine avalanche frequency across multiple climate types

Large-magnitude snow avalanches pose a hazard to humans and infrastructure worldwide. Analyzing the spatiotemporal behavior of avalanches and the contributory climate factors is important for understanding historical variability in climate-avalanche relationships as well as improving avalanche forecasting. This study uses established dendrochronological methods to develop long-term regional avalanche chronologies for three different climate types: high-latitude maritime climate of southeast Alaska, intermountain climate of the northern Rocky Mountains, and continental climate of Colorado. In the maritime study area, we collected 434 cross sections throughout six avalanche paths near Juneau, Alaska. This resulted in 2706 identified avalanche growth disturbances between year 1720 and 2018 Common Era (CE), which allowed us to reconstruct 82 years with large magnitude avalanche activity across three sub-regions. By combining this tree-ring derived avalanche dataset with a suite of climate and atmospheric variables and applying a generalized linear model to fit a binomial regression, we found February and March precipitation and the Oceanic Niño Index (ONI) were significant predictors of large magnitude avalanche activity in the southeast Alaska study area. In the intermountain climate study area, tree-rings from 647 trees exhibited 2134 avalanche-related growth disturbances in the northern Rocky Mountains of northwest Montana from 1867 to 2019. The data show that the amount of snowpack across the northern Rocky Mountain region is directly related to avalanche probability. Coincident with warming and regional snowpack reductions, a decline of ~ 14% (~ 2% per decade) in overall large magnitude avalanche probability is apparent through the period 1950–2017 CE. In the continental climate of Colorado, we sampled 24 avalanche paths throughout the state and collected 1188 total samples with 4135 identified growth disturbances from 1698 to 2019. Preliminary results suggest years with large magnitude avalanche activity across the sub-regions of this study area are generally characterized by stormy winters with above average snowpack development but that early and late winter temperature and precipitation also play an important role in large avalanche activity. Characterizing historical climate-avalanche relationships across different climate types provides a broad baseline for understanding potential future changes in avalanche activity. Overall, this work helps forecasters and planners better understand the influence of climate on large magnitude avalanche frequency, and how potential changes in avalanche character and occurrence will affect their operations in the context of a warming climate.Abstract -- Keywords -- 1. Introduction -- 2. Methods -- 3. Results -- 4. Discussion -- 5. Conclusion -- Disclaimer -- Acknowledgements -- References

Deglacierization of a marginal basin and implications for outburst floods

This article was submitted to Cryospheric Sciences, a section of the journal Frontiers in Earth ScienceSuicide Basin is a partly glacierized marginal basin of Mendenhall Glacier, Alaska, that has released glacier lake outburst floods (GLOFs) annually since 2011. The floods cause inundation and erosion in the Mendenhall Valley, impacting homes and other infrastructure. Here, we utilize in-situ and remote sensing data to assess the recent evolution and current state of Suicide Basin. We focus on the 2018 and 2019 melt seasons, during which we collected most of our data, partly using unmanned aerial vehicles (UAVs). To provide longer-term context, we analyze DEMs collected since 2006 and model glacier surface mass balance over the 2006–2019 period. During the 2018 and 2019 outburst flood events, Suicide Basin released ∼ 30 Å~ 106 m3 of water within approximately 4–5 days. Since lake drainage was partial in both years, these ∼ 30 Å~ 106 m3 represent only a fraction (∼ 60%) of the basin’s total storage capacity. In contrast to previous years, subglacial drainage was preceded by supraglacial outflow over the ice dam, which lasted ∼ 1 day in 2018 and 6 days in 2019. Two large calving events occurred in 2018 and 2019, with submerged ice breaking off the main glacier during lake filling, thereby increasing the basin’s storage capacity. In 2018, the floating ice in the basin was 36 m thick on average. In 2019, ice thickness was 29 m, suggesting rapid decay of the ice tongue despite increasing ice inflow from Mendenhall Glacier. The ice dam at the basin entrance thinned by more than 5 m a–1 from 2018 to 2019, which is approximately double the rate of the reference period 2006–2018. While ice-dam thinning reduces water storage capacity in the basin, that capacity is increased by declining ice volume in the basin and longitudinal lake expansion, with the latter process challenging to predict. The potential for premature drainage onset (i.e., drainage before the lake’s storage capacity is reached), intermittent drainage decelerations, and early drainage termination further complicates prediction of future GLOF events.This work was funded by the Alaska Climate Adaptation Science Center (AK CASC). UAVs and other surveying equipment were partly funded through the U.S. National Science Foundation (NSF) award EAR-1921598. EH and SH were partially supported by the NSF award OIA-1753748 and the State of Alaska. Streamflow monitoring of the Mendenhall River and real-time imagery of Suicide Basin were funded by the U.S. Geological Survey Groundwater and Streamflow Information Program. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Ye

The state of the Martian climate

60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes

PHOTOGRAMMETRICALLY DERIVED ESTIMATES OF SNOW DEPTH VARIABILITY IN COMPLEX TERRAIN

ABSTRACT: Seasonal snow is a key cryospheric variable because of its influence on energy and water budgets, regional economies, and public safety. Quantitative information on the spatial distribution of snow depth and snow water equivalence (SWE) is central to numerous applications in cryospheric research. However, in complex terrain, strong orographic gradients and wind redistribution produce complicated accumulation patterns that are difficult to capture using traditional in situ and satellite-based approaches, and are challenging to model with acceptable levels of uncertainty. Here we present results from a pilot study where we apply a repeat airborne photogrammetric approach and employ a Structure from Motion (SfM) processing method to generate digital surface models (DSMs) of terrain during snowfree (fall 2014) and snow-covered (spring 2015) periods. Surface elevation differencing of these datasets produces continuous and accurate maps of end-of-winter snow depth variability over complex terrain in the maritime-continental transition zone of the eastern Chugach Mountains, Alaska, and provides valuable data for assessing avalanche susceptibility and modeling avalanche runout

End-of-winter snow depth variability on glaciers in Alaska

A quantitative understanding of snow thickness and snow water equivalent (SWE) on glaciers is essential to a wide range of scientific and resource management topics. However, robust SWE estimates are observationally challenging, in part because SWE can vary abruptly over short distances in complex terrain due to interactions between topography and meteorological processes. In spring 2013, we measured snow accumulation on several glaciers around the Gulf of Alaska using both ground- and helicopter-based ground-penetrating radar surveys, complemented by extensive ground truth observations. We found that SWE can be highly variable (40% difference) over short spatial scales (tens to hundreds of meters), especially in the ablation zone where the underlying ice surfaces are typically rough. Elevation provides the dominant basin-scale influence on SWE, with gradients ranging from 115 to 400 mm/100 m. Regionally, total accumulation and the accumulation gradient are strongly controlled by a glacier’s distance from the coastal moisture source. Multiple linear regressions, used to calculate distributed SWE fields, show that robust results require adequate sampling of the true distribution of multiple terrain parameters. Final SWE estimates (comparable to winter balances) show reasonable agreement with both the Parameter-elevation Relationships on Independent Slopes Model climate data set (9–36% difference) and the U.S. Geological Survey Alaska Benchmark Glaciers (6–36% difference). All the glaciers in our study exhibit substantial sensitivity to changing snow-rain fractions, regardless of their location in a coastal or continental climate. While process-based SWE projections remain elusive, the collection of ground-penetrating radar (GPR)-derived data sets provides a greatly enhanced perspective on the spatial distribution of SWE and will pave the way for future work that may eventually allow such projections