STAG@EGU2017

St Andrews Glaciology will be out in force at EGU 2017. Doug will be discussing and comparing various calving models, Heidi will be theorising on the potential causes of Svalbard glacier surges, Joe will be showing results from his 3D calving model, and Tom will be discussing how fjord heat transport affects glacier stability. Check out our presentations and posters:

Modelling Tidewater Glacier Calving: from Detailed Process Models to Simple Calving Laws

Doug Benn, Jan Åström, Thomas Zwinger, Joe Todd, and Faezeh Nick

EGU2017-7138 – Oral presentation in Session CR5.1 “Modelling ice sheets and glaciers”
Thursday 27 April, Room G2, 08:45

The simple calving laws currently used in ice sheet models do not adequately reflect the complexity and diversity of calving processes. We have developed a new approach to formulating calving laws, using a) the Helsinki Discrete Element Model (HiDEM) to explicitly model fracture and calving processes, and b) the full-Stokes continuum model Elmer/Ice to identify analyse associated states of stress in the glacier. Our results open the way to developing calving laws that properly reflect the diversity of calving processes, and provide a framework for a unified theory of the calving process continuum.

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Surges of tidewater glaciers initiated at the terminus: observations and mechanisms

Heidi Sevestre, Doug Benn, Adrian Luckman, Chris Nuth, Jack Kohler, Katrin Lindback, Rickard Pettersson

EGU2017-16730 – Oral presentation in Session CR1.1/CL2.18 – “State of the Cryosphere: Observations and Modelling” (co-organized)
Wednesday 26 April, Room G2, 11:15.

There have been numerous reports that surges of tidewater glaciers in Svalbard were initiated at the terminus and propagated up-glacier, in contrast with downglacier-propagating surges of land-terminating glaciers. In this study we present detailed data on the recent surges of Aavatsmarkbreen and Wahlenbergbreen, two tidewater glaciers in western Spitsbergen. High-resolution time-series of glacier velocities and evolution of surface crevasse patterns clearly show that both surges propagated up-glacier in a series of abrupt steps. Prior to the surges, the glaciers underwent strong retreat and significant steepening of their terminal zones, and in the case of Aavatsmarkbreen this can be shown to have caused a doubling of driving stress between 1990 and surge onset in 2013. We conclude that the surges developed in response to two distinct processes. 1) During the late quiescent phase, the terminal zones underwent gradual acceleration due to steepening and increasing driving stress. 2) Acceleration of the glacier termini caused surface crevasses to propagate up-glacier, allowing surface melt- and rain-water to access the bed. The behavior of these glaciers can be understood in terms of the enthalpy cycle model.

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A 3D Full-Stokes Calving Model Applied to a West Greenland Outlet Glacier

Joe Todd, Poul Christoffersen, Thomas Zwinger, Peter Råback, Nolwenn Chauché, Alun Hubbard, Nick Toberg, Adrian Luckman, Doug Benn, Donald Slater, Tom Cowton

EGU2017-14648 – Oral presentation in Session CR5.3/OS2.11 – “Ice shelves and tidewater glaciers – dynamics, interactions, observations, modelling” (co-organized)
Monday 24 April, Room G2, 14:30

The diverse nature of iceberg calving and its complex links to both internal dynamics and external climate make it challenging to incorporate into models of glaciers and ice sheets. Here, we present results from a new 3D calving model applied to Store Glacier, West Greenland. The model, which implements the crevasse depth calving criterion, successfully reproduces the observed seasonal dynamics of the glacier in response to submarine melt undercutting and ice mélange buttressing. The results indicate that submarine melt prevents the glacier from advancing from its current terminus position, but that ice mélange is primarily responsible for observed seasonal evolution.

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Oceanic Forcing and Terminus Retreat at East Greenland’s Tidewater Glaciers

Tom Cowton, Andrew Sole, Peter Nienow, Donald Slater, David Wilton, and Edward Hanna

EGU2017-6318 Poster in session CR5.3/OS2.11 – “Ice shelves and tidewater glaciers – dynamics, interactions, observations, modelling” (co-organized)
Monday 24 April, Board X5.418, Hall X5, 17:30-19:00

Predicting the retreat of Greenland’s tidewater glaciers remains problematic. It has been suggested that warming ocean temperatures may be a key cause of tidewater glacier retreat, but it is not clear how this influence varies between glaciers or over time. To examine this, we model variations in oceanic heat transport to Greenland’s tidewater glaciers, and compare these to the rate of glacier retreat over a 20 year period. Our findings show that on these timescales, a significant portion of tidewater glacier retreat can be explained as a function of oceanic and atmospheric warming, indicating that future retreat of these glaciers may be more predictable than previously thought.