Glacier response to Holocene warmth inferred from in situ ¹⁰Be and ¹⁴C bedrock analyses in Steingletscher's forefield (central Swiss Alps)

Mid-latitude mountain glaciers are sensitive to local summer temperature changes. Chronologies of past glacier fluctuations based on the investigation of glacial landforms therefore allow for a better understanding of natural climate variability at local scale, which is relevant for the assessment of the ongoing anthropogenic climate warming. In this study, we focus on the Holocene, the current interglacial of the last 11 700 years, which remains a matter of dispute regarding its temperature evolution and underlying driving mechanisms. In particular, the nature and significance of the transition from the early to mid-Holocene and of the Holocene Thermal Maximum (HTM) are still debated. Here, we apply an emerging approach by combining in situ cosmogenic 10Be moraine and 10Be–14C bedrock dating from the same site, the forefield of Steingletscher (European Alps), and reconstruct the glacier's millennial recession and advance periods. The results suggest that, subsequent to the final deglaciation at ∼10 ka, the glacier was similar to or smaller than its 2000 CE extent for ∼7 kyr. At ∼3 ka, Steingletscher advanced to an extent slightly outside the maximum Little Ice Age (LIA) position and until the 19th century experienced sizes that were mainly confined between the LIA and 2000 CE extents. These findings agree with existing Holocene glacier chronologies and proxy records of summer temperatures in the Alps, suggesting that glaciers throughout the region were similar to or even smaller than their 2000 CE extent for most of the early and mid-Holocene. Although glaciers in the Alps are currently far from equilibrium with the accelerating anthropogenic warming, thus hindering a simple comparison of summer temperatures associated with modern and paleo-glacier sizes, our findings imply that the summer temperatures during most of the Holocene, including the HTM, were similar to those at the end of the 20th century. Further investigations are necessary to refine the magnitude of warming and the potential HTM seasonality.

Differences in the transient responses of individual glaciers: a case study of the Cascade Mountains of Washington State, USA

Mountain glaciers have response times that govern retreat due to anthropogenic climate change. We use geometric attributes to estimate individual response times for 383 glaciers in the Cascade mountain range of Washington State, USA. Approximately 90% of estimated response times are between 10 and 60 years, with many large glaciers on the short end of this distribution. A simple model of glacier dynamics shows that this range of response times entails consequential differences in recent and ongoing glacier changes: glaciers with decadal response times have nearly kept pace with anthropogenic warming, but those with multi-decadal response times are far from equilibrium, and their additional committed retreat stands well beyond natural variability. These differences have implications for changes in glacier runoff. A simple calculation highlights that transient peaks in area-integrated melt, either at the onset of forcing or due to variations in forcing, depend on the glacier's response time and degree of disequilibrium. We conclude that differences in individual response times should be considered when assessing the state of a population of glaciers and modeling their future response. These differences in response can arise simply from a range of different glacier geometries, and the same basic principles can be expected in other regions as well.

The geoPebble System: Design and Implementation of a Wireless Sensor Network of GPS-Enabled Seismic Sensors for the Study of Glaciers and Ice Sheets

The geoPebble system is a network of wirelessly interconnected seismic and GPS sensor nodes with geophysical sensing capabilities for the study of ice sheets in Antarctica and Greenland, as well as mountain glaciers. We describe our design methodology, which has enabled us to develop these state-of-the art units using commercial-off-the-shelf hardware combined with custom-designed hardware and software. Each geoPebble node is a self-contained, wirelessly connected sensor for collecting seismic activity and position information. Each node is built around a three-component seismic recorder, which includes an amplifier, filter, and 24-bit analog-to-digital converter that can sample incoming seismic signals up to 10 kHz. The timing for each node is available from GPS measurements and a local precision oscillator that is conditioned by the GPS timing pulses. In addition, we record the carrier-phase measurement of the L1 GPS signal in order to determine location at sub-decimeter accuracy (relative to other geoPebble nodes within a radius of a few kilometers). Each geoPebble includes 32 GB of solid-state storage, wireless communications capability to a central supervisory unit, and auxiliary measurements capability (including tilt from accelerometers, absolute orientation from magnetometers, and temperature). The geoPebble system has been successfully validated in the field in Antarctica and Greenland.

Climatically Driven Landscape Evolution in the High-Mountainous Russian Altai and Its Human Occupation Over the Past 20 Thousand Years

Multidisciplinary studies of various natural archives indicate contrasting changes in the human habitat in the high-mountainous southeastern part of the Russian Altai during the last 20,000 years. This period includes the final stage of the last glaciation and its degradation, the formation of the last giant ice-dammed lakes in the intermountain basins and their cataclysmic draining, considerable transformation of glacial landscapes to modern diverse and mosaic structure. Warmer and more humid climate in the first half of the Holocene was followed by cooling and repeated advances of mountain glaciers. The general trend to cooling and aridization in the second half of the Holocene is the most pronounced during the last two millennia. Deglaciation and final drying of intermountain basins boosted a renovation of the local ecosystems and established an environmental baseline of human occupation in the region. The arid climate, widespread permafrost and low population density determined a good preservation of archaeological heritage in the region, which is located at the crossroad between East and West, North and South. This paper presents the analysis of previously published and new data including newly obtained 14C and OSL dates, which allow to correlate climatically driven landscape transformations with habitat of ancient communities and cultures shifting in the region during the last 20, 000 years, as well as to assess the anthropogenic impact on the environment.

Deep learning speeds up ice flow modelling by several orders of magnitude

This paper introduces the Instructed Glacier Model (IGM) – a model that simulates ice dynamics, mass balance and its coupling to predict the evolution of glaciers, icefields or ice sheets. The novelty of IGM is that it models the ice flow by a Convolutional Neural Network, which is trained from data generated with hybrid SIA + SSA or Stokes ice flow models. By doing so, the most computationally demanding model component is substituted by a cheap emulator. Once trained with representative data, we demonstrate that IGM permits to model mountain glaciers up to 1000 × faster than Stokes ones on Central Processing Units (CPU) with fidelity levels above 90% in terms of ice flow solutions leading to nearly identical transient thickness evolution. Switching to the GPU often permits additional significant speed-ups, especially when emulating Stokes dynamics or/and modelling at high spatial resolution. IGM is an open-source Python code which deals with two-dimensional (2-D) gridded input and output data. Together with a companion library of trained ice flow emulators, IGM permits user-friendly, highly efficient and mechanically state-of-the-art glacier and icefields simulations.

The Challenge of Non-Stationary Feedbacks in Modeling the Response of Debris-Covered Glaciers to Climate Forcing

Ongoing changes in mountain glaciers affect local water resources, hazard potential and global sea level. An increasing proportion of remaining mountain glaciers are affected by the presence of a surface cover of rock debris, and the response of these debris-covered glaciers to climate forcing is different to that of glaciers without a debris cover. Here we take a back-to-basics look at the fundamental terms that control the processes of debris evolution at the glacier surface, to illustrate how the trajectory of debris cover development is partially decoupled from prevailing climate conditions, and that the development of a debris cover over time should prevent the glacier from achieving steady state. We discuss the approaches and limitations of how this has been treated in existing modeling efforts and propose that “surrogate world” numerical representations of debris-covered glaciers would facilitate the development of well-validated parameterizations of surface debris cover that can be used in regional and global glacier models. Finally, we highlight some key research targets that would need to be addressed in order to enable a full representation of debris-covered glacier system response to climate forcing.

Modelling Glacier Evolution in Bhutanese Himalaya during the Little Ice Age

Mountain glaciers provide us a window into past climate change and landscape evolution, but the pattern of glacier evolution at centennial or suborbital timescale remains elusive, especially in monsoonal Himalayas. We simulated the glacier evolution in Bhutanese Himalaya, a typical monsoon influenced region, during the Little Ice Age (LIA), using the Open Global Glacier Model and six paleo-climate datasets. Compared with the mapped glacial landforms, the model can well capture the glacier length changes, especially for the experiment driving by the GISS climate dataset, but overestimates the changes in glacier area. Simulation results reveal four glacial substages at 1270s–1400s, 1470s–1520s, 1700s–1710s, and 1820s–1900s in the study area. From further analysis, a negative correlation between the number of the substages and glacier length was found, which suggests that the number and occurrence of glacial substages are regulated by the heterogeneous responses of glaciers to climate change. In addition, the changes in summer temperature dominated the glacier evolution in this region during the LIA.

Do You Drink Glacier Water? Probably

This chapter discusses the relationship between glacier melt, sea level, and water supply and the relationship between the water we drink at home and use for agriculture to mountain glaciers. It describes the Earth’s freshwater supply and its various compositions and locations. It gives concrete examples of different sized glaciers and their relative freshwater contribution to nearby populations. It reviews the freshwater basin storage and regulation role that glaciers play in ecosystems and the importance of glaciers as sources of freshwater for human consumption and agriculture during warm and dry months as well as during prolonged drought periods.

Run! The Mountain Is Coming!

This chapter explains the dynamics of Glacier Lake Outburst Floods (GLOFs) or glacier tsunamis. It describes how climate change and resulting global warming is destabilizing high mountain glaciers perched above deep glacier lakes formed by receding glaciers and subsequent melting. The chapter goes on to explain how the collapse of large pieces of ice result in mountain top born tsunami waves that destroy downstream ecosystems, people, and infrastructure and how climate change is raising the likelihood that these glacier tsunamis will occur throughout the world. It recounts historical GLOF events throughout the world, detailing the impacts and risks of these tragic events.