Ocean-ice Interactions at Breiðamerkurjökull Glacier, Southeast Iceland
Ocean-ice Interactions at Breiðamerkurjökull Glacier, Southeast Iceland

Author: Phaedra C. Tinder

Publisher:

Published: 2012

Total Pages:

ISBN-13:

DOWNLOAD EBOOK

Abstract: While iceberg calving makes up a substantial portion of mass loss for marine-terminating glaciers, these dynamics remain poorly represented in predictions of sea-level rise and large-scale climate models, requiring more robust observational datasets. Breiðamerkurjökull glacier functions as a uniquely controlled field setting for obtaining a wide variety of environmental and geodetic measurements in conjunction with monitoring calving flux, making it possible to more carefully constrain the sometimes-contradictory relationships between calving and environmental conditions observed in previous studies. A time-lapse camera and water level logger were placed roughly 1 km from the glacier ice front to monitor ice loss and iceberg-generated tsunamis from April to September 2011. This record was used to estimate the volume of ice lost by calving during this period and obtain calving rates on hourly, daily, and weekly timescales. Weather, tide, and contemporaneous records of the temperature-salinity structure of the lagoon were used to examine relationships between these factors and calving. Calving was shown to be more common during the falling tide in both spring and fall.

Flow Dynamics of a Soft-bedded Glacier in Southeast Iceland During Basal Sliding Events
Flow Dynamics of a Soft-bedded Glacier in Southeast Iceland During Basal Sliding Events

Author: Julie T. Markus

Publisher:

Published: 2011

Total Pages:

ISBN-13:

DOWNLOAD EBOOK

Abstract: The purpose of this study is to determine how glacier motion and stresses vary spatially and temporally in order to clarify weaknesses in current understanding of soft-bedded glacier motion using data collected from Breiðamerkurjökull, Iceland. The dynamics of ice motion are the most substantial source of uncertainty in current models of future ice sheet mass-loss and resulting sea level rise. Currently, there is a general lack of quantitative understanding of how glacial basal conditions, such as the hydrology and till rheology at the bed, control ice motion. This study focuses on the examination of high spatial and temporal resolution surface velocities retrieved from a 12-station GPS grid in the melt seasons of 2009 and 2010 to evaluate the variation of glacial motion and strain rates over time on Breiðamerkurjökull. The first specific objective is to identify any short-term velocity variations. The second is to use the surface motion data to calculate strain rates and other components of the force budget. The third objective is to explain the variations in velocity and force budget components while taking into account glaciomorphic features of the bed. Results reveal five distinct periods of increased surface motion, termed sliding events, corresponding to periods of rainfall and/or increased temperatures during the 2009 and 2010 melt seasons. Along-flow strain rates show extension upglacier and compression downglacier during sliding events. The force budget solution indicates that upglacier, basal drag decreases substantially during speed-up events and cannot resist the local driving stress, most likely indicating pressurization of a distributed subglacial drainage system. The excess driving stress is then transferred downglacier, through gradients in longitudinal stress, to a more efficiently draining terminus where water pressures are lower and basal drag is sufficient to support the excess stress. The results demonstrate that the till at the terminus accommodates the excess stress, possibly through extensive grain bridging and dilatant hardening or by a relocation of stress to bedrock bumps during sliding events. This buttressing role of the till-bedded margin in resisting increased upglacier sliding, likely over bedrock, is novel and counter to the prevailing view of soft beds, with implications for simulating the evolution of past and current ice masses.

Late Quaternary Ice-ocean Interactions in Central West Greenland
Late Quaternary Ice-ocean Interactions in Central West Greenland

Author: David John McCarthy

Publisher:

Published: 2011

Total Pages:

ISBN-13:

DOWNLOAD EBOOK

A greater knowledge of the interactions between the Greenland Ice Sheet and climate is critical to understanding the possible impacts of future global warming, including ice sheet contribution to global sea-level rise and perturbations to ocean circulation. Recent acceleration, thinning and retreat of major tidewater glaciers in Greenland and Antarctica during the past two decades demonstrate the potential for ice sheets to respond to climate change much faster than previously assumed. One approach to understanding the role of atmospheric and oceanic warming to ice sheet dynamics is to investigate how ice sheets responded to past periods of climate change. This thesis uses benthic foraminifera as a proxy to reconstruct past changes in the temperature of the relatively warm West Greenland Current, to investigate the possible influence of ocean warming on ice sheet dynamics during the initial marine-based deglaciation phase, and throughout the Holocene, when the ice was positioned close to the present margin. This thesis finds that the marine-based ice sheet in central West Greenland collapsed rapidly due to a combination of high relative sea-level and ice sheet thinning due to climatic warming. Foraminiferal evidence does not support a major influence of ocean forcing on initial deglaciation. However, Holocene changes in the relative temperature of the West Greenland Current may have had a more significant influence on ice stream dynamics following the marine-based ice retreat, when outlet glaciers were positioned within coastal fjords. Changes in the relative temperature of the West Greenland Current are determined?upstream? by wider scale changes in the North Atlantic region.

Ocean Dynamics of Greenland’s Glacial Fjords at Subannual to Seasonal Timescales
Ocean Dynamics of Greenland’s Glacial Fjords at Subannual to Seasonal Timescales

Author: Robert M. Sanchez

Publisher:

Published: 2023

Total Pages: 0

ISBN-13:

DOWNLOAD EBOOK

Mass loss of the Greenland Ice Sheet is expected to accelerate in the 21st century in response to both a warming atmosphere and ocean, with consequences for sea level rise, polar ecosystems and potentially the global overturning circulation. Glacial fjords connect Greenland's marine-terminating glaciers with the continental shelf, and fjord circulation plays a critical role in modulating the import of heat from the ocean and the export of freshwater from the ice sheet. Understanding fjord dynamics is crucial to predicting the cryosphere and ocean response to a changing climate. However, representing glacial fjord dynamics in climate models is an ongoing challenge because fjord circulation is complex and sensitive to glacial forcing that is poorly understood. Additionally, there are limited observations available for constraining models and theory. This dissertation aims to improve our understanding of fjord dynamics, focusing on key aspects (heat variability, freshwater residence time, and fjord exchange) which need to be included in glacial fjord parameterizations. We use three approaches combining novel observations, idealized, modeling and numerical simulations to investigate the dynamics of fjord circulation at different spatial scales. First, we investigate the heat content variability in the fjord using acoustic travel time (Chapter 2). We demonstrate that acoustic travel time can be used to model fjord stratification during winter months and monitor heat content variability at synoptic and seasonal timescales. Secondly, we use a combination of in situ observations and an idealized box model to evaluate freshwater residence time in a west Greenland Fjord (Chapter 3). We find that meltwater from the ice sheet is mixed downward across multiple layers near the glacier terminus resulting in freshwater storage and a delay in freshwater export from the fjord. Finally we analyze a multi-year realistically forced numerical simulation of Sermilik Fjord in southeast Greenland and identify the impact of shelf and glacial forcing on fjord exchange (Chapter 4). We show that the glacial-driven circulation is more efficient at renewing the fjord and that the sign of the exchange flow is related to the along-shelf wind stress. This dissertation strengthens our understanding of the fundamental connections between oceans and glaciers, and will lead to improved representation of ice-ocean interactions in climate models.

GLACIAL LANDSYSTEMS
GLACIAL LANDSYSTEMS

Author: David J.A. Evans

Publisher: Routledge

Published: 2014-02-04

Total Pages: 544

ISBN-13: 1444119168

DOWNLOAD EBOOK

This book is a comprehensive overview of the ever-captivating field of glaciation from the perspective of glacial landsystems. This approach models the many processes, forms and interactions that can be found in glaciated landscapes throughout the world. Landsystems models allow the glacial geologist and geomorphologist to evaluate these landscapes in relation to the dynamics of glaciation and to climate and geology. Glacial Landsystems brings together the expertise of an international range of specialists to provide an up-to-date summary of landsystems relevant to both modern and ancient glacier systems and also in the reconstruction and interpretation of former glacial environments. The models are applicable at all scales from ice sheets to small valley glaciers. This book is an essential reference for anyone embarking upon research or engineering surveys in glaciated basins and provides a wide-ranging handbook of glacial landsystem types for students of glaciation.

Glacier Science and Environmental Change
Glacier Science and Environmental Change

Author: Peter G. Knight

Publisher: John Wiley & Sons

Published: 2008-04-15

Total Pages: 544

ISBN-13: 0470750235

DOWNLOAD EBOOK

Glacier Science and Environmental Change is an authoritative and comprehensive reference work on contemporary issues in glaciology. It explores the interface between glacier science and environmental change, in the past, present, and future. Written by the world’s foremost authorities in the subject and researchers at the scientific frontier where conventional wisdom of approach comes face to face with unsolved problems, this book provides: state-of-the-art reviews of the key topics in glaciology and related disciplines in environmental change cutting-edge case studies of the latest research an interdisciplinary synthesis of the issues that draw together the research efforts of glaciologists and scientists from other areas such as geologists, hydrologists, and climatologists color-plate section (with selected extra figures provided in color at www.blackwellpublishing.com/knight). The topics in this book have been carefully chosen to reflect current priorities in research, the interdisciplinary nature of the subject, and the developing relationship between glaciology and studies of environmental change. Glacier Science and Environmental Change is essential reading for advanced undergraduates, postgraduate research students, and professional researchers in glaciology, geology, geography, geophysics, climatology, and related disciplines.

Structure from Motion in the Geosciences
Structure from Motion in the Geosciences

Author: Jonathan L. Carrivick

Publisher: John Wiley & Sons

Published: 2016-07-15

Total Pages: 208

ISBN-13: 1118895827

DOWNLOAD EBOOK

Structure from Motion with Multi View Stereo provides hyperscale landform models using images acquired from standard compact cameras and a network of ground control points. The technique is not limited in temporal frequency and can provide point cloud data comparable in density and accuracy to those generated by terrestrial and airborne laser scanning at a fraction of the cost. It therefore offers exciting opportunities to characterise surface topography in unprecedented detail and, with multi-temporal data, to detect elevation, position and volumetric changes that are symptomatic of earth surface processes. This book firstly places Structure from Motion in the context of other digital surveying methods and details the Structure from Motion workflow including available software packages and assessments of uncertainty and accuracy. It then critically reviews current usage of Structure from Motion in the geosciences, provides a synthesis of recent validation studies and looks to the future by highlighting opportunities arising from developments in allied disciplines. This book will appeal to academics, students and industry professionals because it balances technical knowledge of the Structure from Motion workflow with practical guidelines for image acquisition, image processing and data quality assessment and includes case studies that have been contributed by experts from around the world.