Roundup: A New Glacier Surge Study, Three Decades of Caucasus Glacier-Debris Change, and Mining Expansion in Greenland

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.

Storstrømmen and L. Bistrup Bræ in east Greenland probably are the largest surge‐type glaciers in the world (Source: WikiCommons).

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.

Supra-glacial debris cover increase on the Elbrus Massif from 1986 to 2014. SPOT-7 image from 20 August 2016 is used as the background. Blue shows retreat of clean-ice parts. Clean ice in 1986 consists of the clean ice in 2014 (light blue, transparent) plus clean-ice area that retreated between 1986 and 2014 (dark blue) (Source: Tielidze et al)

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:

  1. 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;
  2. An updated Digital Elevation Model that will show the magnitude and spatial distribution of recent changes in glacier thickness; and
  3. 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?

Read More on GlacierHub:

Photo Friday: Engabreen Glacier and Subglacial Laboratory

Black History Month: Honoring an Arctic Explorer

Video of the Week: A Daring Swim Across a Glacial Lake to Protest Climate Change

Roundup: Plant Succession, Glacier Surges and Organic Pollutants

Phosphorus, Not Nitrogen, Limits Primary Succession

From Science Advances: “Current models of ecosystem development hold that low nitrogen availability limits the earliest stages of primary succession, but these models were developed from studies conducted in areas with temperate or wet climates. We combine field and microcosm studies of both plant and microbial primary producers and show that phosphorus, not nitrogen, is the nutrient most limiting to the earliest stages of primary succession along glacial chronosequences in the Central Andes and central Alaska. We also show that phosphorus addition greatly accelerates the rate of succession for plants and for microbial phototrophs, even at the most extreme deglaciating site at over 5000 meters above sea level in the Andes of arid southern Peru.”

Read more about the factors affecting plant succession in cold-arid regions here.

Plant succession occurring after the retreat of the Exit Glacier, Alaska (Source: National Park Service).

 

Tidewater Glacier Surges Initiated at the Terminus

From Journal of Geophysical Research: “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. We present detailed data on the recent surges of two tidewater glaciers, Aavatsmarkbreen and Wahlenbergbreen, in Svalbard. High‐resolution time series of glacier velocities and evolution of crevasse patterns show that both surges propagated up‐glacier in abrupt steps. Geometric changes near the terminus of these glaciers appear to have led to greater strain heating, water production, and storage at the glacier bed. Water routing via crevasses also likely plays an important role in the evolution of surges.“

Find out more about this proposed mechanism of glacier surges here.

Profile of a glacier during normal conditions (left) and during a surge event (right) (Source: Jean-Louis Etienne).

 

Hexachlorobenzene Accumulation in Svalbard Fjords

From Springer: “In the present study, we investigated the spatial and historical trends of hexachlorobenzene (HCB) contamination in dated sediments of three Svalbard fjords (Kongsfjorden, Hornsund, Adventfjorden) differing in environmental conditions and human impact. HCB concentrations ranging from below limit of quantification (6.86 pg/g d.w.) to 143.99 pg/g d.w. were measured… In case of several sediment cores, the HCB enrichment in surface (recent) sediments was noticed. This can indicate importance of secondary sources of HCB, e.g., the influx of HCB accumulated over decades on the surface of glaciers. Detected levels of HCB were generally low and did not exceed background concentration levels; thus, a negative effect on benthic organisms is not expected.”

Discover more about organic pollutions in Norway here.

The Arctic fox and other living organisms in Svalbard could be affected by hexachlorobenzene contamination (Source: Natalie Tapson/Flickr).