Anna Jean Crawford

The University of Stirling

We present the first simulations of Jakobshavn Isbrae (Sermeq Kujalleq), west Greenland, using a 3D Stokes calving model that permits unrestricted advance and retreat. Using the position-based crevasse-depth calving law, the model is applied to simulate the calving dynamics of 2016–2017 season when Jakobshavn Isbrae is assumed to be stable because...

The western region of the wide Thwaites Glacier terminus is characterized by a near‐vertical calving front. The grounding line at this western calving front (WCF) rests on a relatively high ridge, behind which exists a reverse‐sloping bed; retreat of the grounding line into this over‐deepening basin could therefore expose deep calving faces that ma...

The collapse of ice shelves could expose tall ice cliffs at ice sheet margins. The marine ice cliff instability (MICI) is a hypothesis that predicts that, if these cliffs are tall enough, ice may fail structurally leading to self-sustained retreat. To date, projections that include MICI have been performed with a single model based on a simple para...

A new calving algorithm is developed in the glacier model Elmer/Ice that allows unrestricted calving and terminus advance in 3D. The algorithm uses the meshing software Mmg to implement anisotropic remeshing and allow mesh adaptation at each time step. The development of the algorithm, along with the implementation of the crevasse depth law, produc...

A new calving algorithm was developed in the glacier model Elmer/Ice that allows unrestricted calving and terminus advance in 3D. The algorithm used the meshing software Mmg to implement anisotropic remeshing and allow mesh adaptation at each timestep. The development of the algorithm along with the implementation of the crevasse depth law produced...

The largest uncertainty in future sea-level rise is loss of ice from the Greenland and Antarctic Ice Sheets. Ice shelves, freely floating platforms of ice that fringe the ice sheets, play a crucial role in restraining discharge of grounded ice into the ocean through buttressing. However, since the 1990s, several ice shelves have thinned, retreated,...

To increase inclusivity, diversity, equity and accessibility in Antarctic science, we must build more positive and inclusive Antarctic field work environments. The International Thwaites Glacier Collaboration (ITGC) has engaged in efforts to contribute to that goal through a variety of activities since 2018, including creating an open-access ‘Field...

Large, tabular icebergs known as "ice islands" frequently transit the eastern Canadian Arctic and sub-Arctic after breaking away from ice tongues in northern Greenland. Here, we mine the Canadian Ice Island Drift, Deterioration and Detection (CI2D3) Database to contribute a descriptive assessment of the drift and grounding locations of Petermann ic...

Ice shelves play a key role in the dynamics of marine ice sheets by buttressing grounded ice and limiting rates of ice flux to the oceans. In response to recent climatic and oceanic change, ice shelves fringing the West Antarctic Ice Sheet (WAIS) have begun to fragment and retreat, with major implications for ice-sheet stability. Here, we focus on...

Ice shelves play a key role in the dynamics of marine ice sheets, by buttressing grounded ice and limiting rates of ice flux to the oceans. In response to recent climatic and oceanic change, ice shelves fringing the West Antarctic Ice Sheet (WAIS) have begun to fragment and retreat, with major implications for ice sheet stability. Here, we focus on...

Between 2014 and 2017, ocean melt eroded a large cavity beneath and along the western margin of the fast-flowing core of Thwaites Glacier. Here we show that from 2017 to the end of 2020 the cavity persisted but did not expand. This behaviour, of melt concentrated at the grounding line within confined sub-shelf cavities, fits with prior observations...

Cliff collapse Tall ice cliffs at the edges of ice sheets can collapse under their own weight in spectacular fashion, a process that can considerably hasten ice sheet mass loss. Bassis et al. used a dynamic ice model to demonstrate that this kind of collapse can be slowed either by upstream thinning of the ice sheet or by the resistive forces from...

Marine ice-cliff instability could accelerate ice loss from Antarctica, and according to some model predictions could potentially contribute >1 m of global mean sea level rise by 2100 at current emission rates. Regions with over-deepening basins >1 km in depth (e.g., the West Antarctic Ice Sheet) are particularly susceptible to this instability, as...

Between 2014 and 2017, ocean melt eroded a large cavity beneath and along the western margin of the fast-flowing core of Thwaites Glacier. Here we show that from 2017 to the end of 2020 the cavity persisted but did not expand. This behaviour, of melt concentrated at the grounding line within confined sub-shelf cavities, fits with prior observations...

A 130 km2 tabular iceberg calved from Petermann Glacier in northwestern Greenland on 5 August 2012. Subsequent fracturing generated many individual large “ice islands”, including Petermann ice island (PII)-A-1-f, which drifted between Nares Strait and the North Atlantic. Thinning caused by basal and surface ablation increases the likelihood that th...

Stationary ice-penetrating radar (sIPR) systems can be used to monitor temporal changes in electromagnetically sensitive properties of glaciers and ice sheets. We describe a system intended for autonomous operation in remote glacial environments, and document its performance during deployments in cold and temperate settings. The design is patterned...

A 130 km² tabular iceberg calved from Petermann Glacier in northwest Greenland on 5 August 2012. Subsequent fracturing generated many individual large “ice islands”, including “Petermann Ice Island (PII)-A-1-f”, that drifted between Nares Strait and the North Atlantic. Thinning caused by basal and surface ablation increases the likelihood that thes...

A data collection program was carried out between October 2015 and September 2017 to monitor the thinning and overall deterioration of "Petermann Ice Island (PII)-A-1-f". This large, tabular iceberg was a fragment of the 2012 Petermann Glacier calving event. Four field teams visited the ice island, and a stationary ice penetrating radar (sIPR) was...

Three large calving events occurred at Petermann Glacier in northwest Greenland between 2008 and 2012 that generated ice islands (large tabular icebergs) that ranged from ~30 to 300 km² in areal extent. Ice islands are known to deteriorate, via fracture and melt, during their drift through regional water bodies where they pose a potential risk to o...

Ice islands are large, tabular icebergs that calve from ice shelves and floating ice tongues. Their drift and deterioration is of concern to offshore industry and influences the dispersal of freshwater from Earth’s major ice sheets. However, the analysis and modelling of ice island deterioration is constrained by a lack of systematic studies using...

The Canadian Ice Island Drift, Deterioration and Detection (CI2D3) Database - ANNA CRAWFORD, GREGORY CROCKER, DEREK MUELLER, LUC DESJARDINS, RON SAPER, TOM CARRIERES

Icebergs and ice islands (large, tabular icebergs) are challenging targets to survey due to their size, mobility, remote locations, and potentially difficult environmental conditions. Here, we assess the precision and utility of aerial photography surveying with structure-from-motion multi-view stereo photogrammetry processing (SfM) and vessel-base...

In August 2010, a 253 km^2 ice island calved from the floating glacial tongue of Petermann Glacier in Northwest Greenland. Petermann Ice Island (PII)-B, a large fragment of this original ice island, is the most intensively observed ice island in recent decades. We chronicle PII-B’s deterioration over four years while it drifted more than 2,400 km s...

Ice islands are massive, tabular icebergs which calve from ice shelves and floating glacier tongues. The ability to identify, monitor and predict the drift and deterioration of these immense ice hazards is crucial for mitigating the associated risks to marine navigation and offshore infrastructure in their vicinity. A joint initiative between the W...

Accurate characterization and volume determination of iceberg sails is important for calculating wind drag effects on iceberg drift and estimating total iceberg mass, respectively. This information is of direct relevance to the shipping and offshore hydrocarbon industries operating on Canada’s east coast. A field campaign was completed in April 201...

Temperature and salinity data collected around grounded tabular icebergs in Baffin Bay in 2011, 2012 and 2013 indicate wind-induced upwelling at certain locations around the icebergs. These data suggest that along one side of the iceberg, wind forcing leads to Ekman transport away from the iceberg, which causes upwelling of the cool saline water fr...

A 4-week micro-meteorological dataset was collected by an automatic weather station on a small ice island (0.13 km2) adrift off Bylot Island (Lancaster Sound, Nunavut, Canada) during the 2011 melt season. This dataset provided an opportunity to identify the environmental variables and energy fluxes that contribute most to surface ablation during th...

Triplicate aerial-photo and LiDAR surveys of two iceberg sails were conducted to evaluate the capability of each technique to detect iceberg or ice island deterioration. This evaluation lays out how the spatial pattern and rate of iceberg deterioration could be measured with repeat surveys. 3D representations of the iceberg sails were generated fro...

We study a mechanism of iceberg breakup that may act together with the recognized melt and wave-induced decay processes. Our proposal is based on observations from a recent field experiment on a large ice island in Baffin Bay, East Canada. We observed that successive collapses of the overburden from above an unsupported wavecut at the iceberg water...

Knowledge regarding the deterioration processes of large tabular icebergs, known as ice islands, is limited within the Canadian Arctic. This study analyzed ice island deterioration through two aspects: 1) horizontal (areal) and 2) vertical (surface melt or ‘ablation’). Satellite images were digitized to monitor areal dimensions, classify deteriorat...

Understanding subsurface shape, topography and roughness of icebergs and ice islands (large tabular icebergs) in the Canadian High Arctic is limited by a paucity of underwater ice terrain data. This information is critical for calibrating operational iceberg drift and deterioration models that aim to mitigate hazards to shipping and the offshore pe...

Canada’s system of national parks and historic sites is the most influential method for biodiversity conservation within the country. The size of these areas is crucial. By using the species-area relationship, predictions can be made to the amount of species (mammals, birds, amphibians and reptiles) that will be represented from the respective regi...