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Glaciers around the globe are experiencing a notable retreat and thinning, triggered by atmospheric warming. Tidewater glaciers in particular have received much attention, because they have been recognized to contribute substantially to global sea level rise. How-ever, lake calving glaciers in Alaska show increasingly high thinning and retreat rates and are therefore contributors to sea level rise. The number of such lake calving systems is increasing worldwide as land-terminating glaciers retreat into overdeepened basins and form proglacial lakes. Yakutat Glacier in Southeast Alaska is a low elevation lake calving glacier with an accumulation to total area ratio of 0.03. It experienced rapid thinning of 4.43 ± 0.06 m w.e. yr−1 between 2000-2010 and terminus retreat of over 15 km since the beginning of the 20th century. Simultaneously, adjacent Yakutat Icefield land-terminating glaciers thinned at lower but still substantial rates (3.54 ± 0.06 m w.e. yr−1 for the same time period), indicating lake calving dynamics help drive increased mass loss. Yakutat Glacier sustained a ~3 km long floating tongue for over a decade, which started to disintegrate into large tabular icebergs in 2010. Such floating tongues are rarely seen on temperate tidewater glaciers. The floating ice was weakened by surface ablation, which then allowed rifts to form and intersect. Ice velocity from GPS measurements showed that the ice on the floating tongue was moving substantially faster than grounded ice, which was attributed to rift opening between the floating and grounded ice. Temporal variations of rift opening were determined from time-lapse imagery, and correlated well with variations in ice speeds. Larger rift opening rates occurred during and after precipitation or increased melt episodes. Both of these events increased subglacial discharge and could potentially increase the subaqueous currents towards the open lake and thus increase drag on the ice underside. Simultaneously, increased water input may cause lake level in rifts to rise resulting in faster rift propagation and spreading. Similar formation and disintegration of floating tongues are expected to occur in the glacier's future, as the ice divide lies below the current lake level. In addition to calving retreat, Yakutat Glacier is rapidly thinning, which lowers its surface and therefore exposes the ice to warmer air temperatures causing increased thinning. Even under a constant climate, this positive feedback mechanism would force Yakutat Glacier to quickly retreat and mostly disappear. Simulations of future mass loss were run for two scenarios, keeping the current climate and forcing it with a projected warming climate. Results showed that over 95% of the glacier ice will have disappeared by 2120 or 2070 under a constant vs projected climate, respectively. For the first few decades, the glacier will be able to maintain its current thinning rate by retreating and thus losing areas of lowest elevation. However, once higher elevations have thinned substantially, the glacier cannot compensate any more to maintain a constant thinning rate and transfers into an unstable run-away situation. To stop this collapse and transform Yakutat Glacier into equilibrium in its current geometry, air temperatures would have to drop by 1.5 K or precipitation would have to increase by more than 50%. An increase in precipitation alone is unlikely to lead to a stable configuration, due to the very small current accumulation area.
"Mendenhall Glacier is a lake-calving glacier in southeastern Alaska that is experiencing substantial thinning and increasingly rapid recession. Long-term mass wastage linked to climatic trends is responsible for thinning of the lower glacier and leaving the terminus vulnerable to buoyancy-driven calving and accelerated retreat. Bedrock topography may playa role in stabilizing the terminus between periods of rapid calving and retreat. Lake-terminating glaciers form a population distinct from both tidewater glaciers and polar ice tongues, with some similarities to both groups. Lacustrine termini experience fewer perturbations (e.g. tidal flexure, high subaqueous melt rates) and are therefore inherently more stable than tidewater termini. At Mendenhall, rapid thinning and simultaneous retreat into a deeper basin led to floatation conditions along approximately 50% of the calving front. This unstable terminus geometry lasted for ~ 2 years and culminated in large-scale calving and terminus collapse during summer 2004. We used a 1-dimensional viscoelastic model to investigate the transient response of a floating glacier tongue to buoyant forcing. Results suggest that creep may be capable of accommodating buoyant torque if it is applied gradually. As unresolved bending stresses approach the tensile strength of ice, small rapidly applied perturbations may cause buoyancy-driven calving"--Leaf iii.
This edited volume, showcasing cutting-edge research, addresses two primary questions - what are the main drivers of change in high-mountains and what are the risks implied by these changes? From a physical perspective, it examines the complex interplay between climate and the high-mountain cryosphere, with further chapters covering tectonics, volcano-ice interactions, hydrology, slope stability, erosion, ecosystems, and glacier- and snow-related hazards. Societal dimensions, both global and local, of high-mountain cryospheric change are also explored. The book offers unique perspectives on high-mountain cultures, livelihoods, governance and natural resources management, focusing on how global change influences societies and how people respond to climate-induced cryospheric changes. An invaluable reference for researchers and professionals in cryospheric science, geomorphology, climatology, environmental studies and human geography, this volume will also be of interest to practitioners working in global change and risk, including NGOs and policy advisors.
Climate Change: Observed Impacts on Planet Earth, Third Edition, brings together top global researchers across many disciplines to provide a comprehensive review on the complex issue of climate change and weather patterns. The third edition continues its tradition of focusing on the science and evidence on this highly politicized topic. Every chapter is updated, with this new edition featuring new chapters on topics such as glacier melt, the impacts of rising temperatures, extreme weather, modeling techniques, biodiversity, and more. This book is essential for researchers, environmental managers, engineers, and those whose work is impacted by, or tied to, climate change and global warming. Provides a comprehensive resource on climate change and weather patterns, ranging from causes and indicators to modeling and adaptation Covers the Jet Stream, catastrophic modeling, extreme weather, the carbon cycle, socioeconomic impacts, biological diversity, deforestation and global temperature Contains 25 updated chapters and 10 new chapters, all written by global experts who provide a current overview of the state of knowledge on climate change across a wide array of disciplines
The new Second Edition of Glacial Geology provides a modern, comprehensive summary of glacial geology and geomorphology. It is has been thoroughly revised and updated from the original First Edition. This book will appeal to all students interested in the landforms and sediments that make up glacial landscapes. The aim of the book is to outline glacial landforms and sediments and to provide the reader with the tools required to interpret glacial landscapes. It describes how glaciers work and how the processes of glacial erosion and deposition which operate within them are recorded in the glacial landscape. The Second Edition is presented in the same clear and concise format as the First Edition, providing detailed explanations that are not cluttered with unnecessary detail. Additions include a new chapter on Glaciations around the Globe, demonstrating the range of glacial environments present on Earth today and a new chapter on Palaeoglaciology, explaining how glacial landforms and sediments are used in ice-sheet reconstructions. Like the original book, text boxes are used throughout to explain key concepts and to introduce students to case study material from the glacial literature. Newly updated sections on Further Reading are also included at the end of each chapter to point the reader towards key references. The book is illustrated throughout with colour photographs and illustrations.
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