Polar Physical Science

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Using airborne remote sensing to investigate glacial geomorphic processes

High resolution remotely sensed data are used increasingly in glaciology to map aspects of the landscape and quantify current environmental change. These data are also used in glacial geomorphology to map landforms, infer processes of erosion and deposition, and characterise past glacial conditions. As more data become available at increasingly high spatial and temporal resolutions, there is a need to automate the process of landform and landscape mapping using objective, consistent and accurate computer-based object and pattern recognition techniques. This project uses a large airborne lidar data set, covering all the large ice caps and outlet glaciers in Iceland, together with their forefields, collected recently as part of a collaborative venture between SPRI, the Icelandic Meteorological Office and the University of Iceland. Algorithms are being developed, and calibrated and evaluated against existing geomorphic maps and field evidence. New fieldwork is planned for further algorithm testing in 2013. A key research output will be a suite of glacial geomorphic maps for Iceland that can be used to identify spatial and temporal patterns of surge and non-surge behaviour as well as important glacial geomorphic processes such as glacier tectonics, styles of sediment deformation, surface hydrology and retreat patterns. The work is being undertaken in collaboration with PhD student Ciaran Robb, and Tomas Johannesson, Icelandic Meteorological Office and Finnur Pálsson, University of Iceland.

Neil Arnold and Ian Willis

Glacier hydrology in the Langtang Khola, Nepal: lake formation and drainage on debris-covered glaciers

As glaciers retreat in response to climate warming, substantial modifications occur to meltwater production, hydrological routing, and water storage and release, resulting in major changes to water flow from glaciated basins. Although high resolution glacierized catchment modelling has been applied successfully in, for example, the European Alps, Scandinavia and North America, far less attention has been given to watersheds in the Himalayas, where basic climate and hydrological data are lacking, where logistical, political and cultural challenges are greater, and yet where some of the largest communities reliant on water from glacierized catchments live. The aims of this project are to: i) collect climate, glacier mass balance and hydrology data in the Langtang region, Nepal; ii) analyse the back catalogue of satellite multispectral data for the region to measure past glaciological and hydrological attributes of the catchments; iii) use the data in (i) and (ii), together with gridded climate reanalysis data for the past, to develop a high spatial (~100 m) and temporal (hourly) resolution glacier mass balance and hydrology model for the region. The model will calculate the filling and draining of surface and ice-marginal lakes, which pose a threat of sudden flooding in the region. Finally, the model will be run into the future to assess the likely changes to glacier mass balance and hydrology into the 21st century in response to projected climate change. We are undertaking this work with PhD student Evan Miles, in collaboration with Francesca Pellicciotti, ETH, Zurich and Dorothea Sturm, ICIMOD, Kathmandu.

Ian Willis and Neil Arnold

Tidewater ice cliffs of Austfonna, Svalbard, the largest ice cap in the Eurasian Arctic

Two new projects on ice-sheet stability in Antarctica

The UK Natural Environmental Research Council has funded several new and ambitious projects within its Ice Sheet Stability (iSTAR) programme. The research programme focuses on the Amundsen Sea and Pine Island Glacier, a key region in West Antarctica where the ice sheet interacts strongly with the adjacent ocean. SPRI is participating in two projects specifically targeting the flow of Pine Island Glacier. The iSTAR-C project, entitled ‘Dynamical control on the response of Pine Island Glacier’, will investigate processes responsible for the dynamic transfer of effects takingplace at the ice-ocean interface and the ice shelf extending in front of the glacier. The iSTAR-D project, entitled ‘The contribution to sea level rise of the Amundsen Sea sector’, is concerned with quantifying the region’s contribution to sea level rise. Forthcoming work within the two projects includes development and application of numerical models, supervision of a PhD student, and fieldwork during scientific traverses of Pine Island Glacier in 2013-14 and 2014-15.

Liz Morris, Poul Christoffersen and Marion Bougamont

Hydrologic forcing of ice streams

Results from numerical ice-sheet modelling at SPRI are shedding new light on the basal environment of fast-flowing ice streams. By implementing realistic, time-dependent and highly nonlinear ‘plastic bed’ properties, fundamental new insights were gained, not only on the causes of fast ice-streaming flow, but also on sedimentary processes occurring beneath the ice streams. The experimental setup produced results in which ice-stream flow was characterized by recurring switching (oscillations) between fast and stagnant modes of flow. The outcomes showed that there was a strong coupling between the amplitude of the ice-stream oscillations and the amount of sediment eroded and transferred by ice streams, due exclusively to the formation and advection of a layer of debris-bearing basal ice. The results also showed that increased incorporation of water from a basal water system amplified the oscillations, thereby promoting erosion and delivery of sediment to the ocean. The results, published in the journal Geology, are consistent with observations made in Antarctica as well as the seemingly erratic behaviour of palaeo-ice streams in the northern hemisphere.

Marion Bougamont and Poul Christoffersen

Spectral and physical characterisation of glacier surfaces

Allen Pope’s investigation of the relationships between the optical properties of a glacier surface and its physical characteristics moved from the data collection to the analysis stage. This is now giving a much clearer and, for the first time, systematic understanding of the importance of spatial and spectral resolution for satellite studies of changing glaciers in the Arctic. Allen also continued to work with the Association of Polar Early Career Scientists, and shared his research with a very wide audience by creating and disseminating a short, very popular, video. He participated in the Juneau Icefield Research Program in Alaska, and was one of the first student members elected to the Council of the American Geophysical Union. He presented his work at numerous venues, including the IPY conference in Montréal, the American Geophysical Union conference in San Francisco and the 12th International Circumpolar Remote Sensing Symposium in Levi, Finland.

Gareth Rees and Allen Pope

Understanding the behaviour of the Arctic treeline

For over a decade, SPRI has been central to the international effort to understand the characteristics and behaviour of the transition region between boreal forest and tundra that lies to its north. Arctic treeline research has been carried out within the project ‘PPS Arctic’ (Present day processes, Past changes, and Spatiotemporal variability of biotic, abiotic and socioenvironmental conditions and resource components along and across the Arctic delimitation zone), an international collaboration of over 100 scientists and students working at about 30 sites around the Arctic. PPS Arctic is coordinated by the Norwegian Institute for Nature Research and by SPRI. A significant finding is that the Arctic treeline is not responding to climate change in the way predicted by coupled climate-vegetation models (DGVMs). These models, based on the assumption that global vegetation, where not locally disturbed, is in equilibrium with climate, predict that boreal forest should be advancing into the tundra at a rate of about 2 km per year. At this rate, models predict that about 40% of Arctic tundra will be lost by the end of the century. In fact, the observed rates of advance seem to be very much less than predicted. If this result, which is already firmly established for northern Fennoscandia, is verified across the entire Arctic, it could have significant implications for understanding the behaviour of the global climate. As part of our effort, Katya Shipigina has developed a methodology for automated land-cover mapping using satellite images spanning a wide spatial and temporal range, capable of monitoring the whole of northern Fennoscandia. Anna-Maria Trofaier is also investigating thaw lakes in permafrost using spaceborne radar, obtaining field data from Vaskini Dachi on the Yamal Peninsula, Russia.

Gareth Rees, Katya Shipigina and Anna-Maria Trofaier

Variable history of Quaternary ice-sheet advance across the Beaufort Sea margin, Arctic Ocean

The seismic stratigraphy and architecture of the Beaufort Sea shelf and slope were investigated using a comprehensive grid of high-resolution 2-dimensional seismic-reflection data. Three cross-shelf troughs, representing locations of former ice streams draining a 1,000 km-long section of the Quaternary North American Ice Sheet were examined; the Mackenzie, Amundsen Gulf and M’Clure Strait systems. Dynamics of these palaeo-ice streams influenced ice-sheet configuration and may have forced abrupt climatic change through delivery of ice and freshwater to the Arctic Ocean. A comprehensive understanding of their geometry and dynamics is crucial for constraining numerical models of the former ice sheet. Evidence for two Quaternary ice advances to the shelf break is interpreted from Mackenzie Trough. By contrast, seismic stratigraphy of Amundsen Gulf Trough, 400 km east of the Mackenzie, records at least nine Quaternary ice advances. Here, the outer-shelf consisted of several stacked till sheets, extending to the shelf break and forming a trough-mouth fan. The contrasting glacial histories of these neighbouring ice streams were explained by their positions within the past ice sheet; Mackenzie Trough ice stream was situated at the extreme north-west ice-sheet margin, whereas Amundsen Gulf ice stream had a more central location and larger drainage basin, supplying significant quantities of ice and sediment to the Arctic Ocean through much of the Quaternary. This work has been published recently in Geology, and was undertaken in collaboration with Dr Jeff Pietras of BP.

Christine Batchelor and Julian Dowdeswell

Coal mining history and modern housing in Longyearbyen, Spitsbergen

An extensive and dynamic ice sheet on the West Greenland shelf during the last glacial cycle

Considerable uncertainty surrounds the extent and timing of the advance and retreat of the Greenland Ice Sheet on the continental shelf bordering Baffin Bay during the last glacial cycle. We used marine geophysical and geological data to show that fast-flowing ice-sheet outlets, including the ancestral Jakobshavn Isbræ, expanded several hundred kilometres to the shelf edge during the last glaciation about 20,000 years ago. Retreat of these outlets was asynchronous. Initial retreat from the shelf edge was under way by about 15,000 years ago in Uummannaq Trough. Radiocarbon dates from the adjacent Disko Trough and adjoining trough-mouth fan imply later deglaciation of Jakobshavn Isbræ, and, significantly, an extensive readvance and rapid retreat of this outlet during the Younger Dryas cold interval. This is the first evidence of a major advance of the Greenland Ice Sheet during the Younger Dryas on the West Greenland shelf, although its short-lived duration suggests that it may have been out of phase with temperatures at this time. The field work was undertaken on the RRS James Clark Ross as part of a major NERC-funded research cruise led by Colm Ó Cofaigh (Durham) and involving a team of colleagues from several universities.

Julian Dowdeswell and Kelly Hogan

CryoSat-2

Liz Morris continued to participate in an international programme to validate ice sheet surface-elevation data collected by a new radar altimeter (SIRAL) carried by the CryoSat-2 satellite. Using a unique set of direct determinations of strain rate in polar snow, a new empirical snow densification law was derived which allows the effect of future climate change on ice-surface elevation to be estimated.

Liz has also provided scientific support for a joint services expedition to the Antarctic Peninsula and is a participant in the new NERC consortium project ‘iSTAR-D: the contribution to sea-level rise from the Amundsen Sea sector of Antarctica’. In December 2012 she gave the prestigious Nye Lecture at the Fall Meeting of the American Geophysical Union.

Liz Morris

The village of Qaanaaq in Northwest Greenland

The church in Longyearbyen, Spitsbergen