Progress Made Toward Understanding Glacier Surge Motion
Previous studies of glacial surges neglected to account for till mechanics––the unsorted glacial sediments underlying glacier beds. A new study submitted to Proceedings of the Royal Society A in January 2020 accounts for the hydromechanical properties of those sediments.
From the abstract: “Glacier surges are quasi-periodic episodes of rapid ice flow that arise from increases in slip-rate at the ice-bed interface. The mechanisms that trigger and sustain surges are not well-understood. Here, we develop a new model of incipient surge motion for glaciers underlain by sediments to explore how surges may arise from slip instabilities within this thin layer of saturated, deforming subglacial till. Our model represents the evolution of internal friction, porosity, and pore water pressure within the sediments as functions of the rate and history of shearing. Changes in pore water pressure govern incipient surge motion, with less-permeable till facilitating surging because dilation-driven reductions in pore-water pressure slow the rate at which till tends toward a new steady state, thereby allowing time for the glacier to thin dynamically. The reduction of overburden pressure at the bed caused by dynamic thinning of the glacier sustains surge acceleration in our model. The need for changes in both the hydromechanical properties of the till and thickness of the glacier creates restrictive conditions for surge motion that are consistent with the rarity of surge-type glaciers and their geographic clustering.”
Read the full study here.
Supra-glacial Debris Cover Changes in the Greater Caucasus from 1986 to 2014
New research on debris atop glaciers in the Caucasus––an important and understudied region––spans nearly three decades of change for nearly 700 of the area’s glaciers. While some debris accelerates melt; a lot can protect against it. A new study exploring the pattern was published on February 14 in The Cryosphere.
From the abstract: “Knowledge of supra-glacial debris cover and its changes remain incomplete in the Greater Caucasus, in spite of recent glacier studies. Here we present data of supra-glacial debris cover for 659 glaciers across the Greater Caucasus based on Landsat and SPOT images from the years 1986, 2000 and 2014. We combined semi-automated methods for mapping the clean ice with manual digitization of debris-covered glacier parts and calculated supra-glacial debris-covered area as the residual between these two maps.”
Read the full study here.
Glacier Retreat Could Allow Expansion of Mining in Greenland
As Greenland’s glaciers retreat, mining companies are prospecting the exposed mineral riches. One Canadian company is going after molybdenum, an important metal for electronics and communication. According to Live Science, small amounts of molybdenum can be found in a wide variety of products: missiles, engine parts, drills, saw blades, electric heater filaments, lubricant additives, ink for circuit boards and protective coatings in boilers. It is also used as a catalyst in the petroleum industry.
Greenland Resources Inc is a Canadian reporting issuer regulated by the Ontario Securities Commission, focused on the acquisition, exploration and development of mineral properties in Greenland. Yahoo Finance reports that the The Greenland Mineral Authority has provided comments on environmental and social impact assessments and is working with the Geological Survey of Denmark and Greenland on three deliverables:
- A high-resolution satellite study to forecast glacial ablation at Malmbjerg during the years 2028-2048 to better understand how the Malmbjerg molybdenum surface mineable mineral resource estimate may increase with the current accelerated glacial ablation that could positively impact project economics;
- An updated Digital Elevation Model that will show the magnitude and spatial distribution of recent changes in glacier thickness; and
- A time-series of annual surface mass balance on Malmbjerg, to understand the site-specific increase in ice melt over the past four decades.
Will other rapidly de-glaciating regions of the world, like Antarctica, be next?