Climate Change

Greenland’s “Recent Mass Loss” Underestimated?

Posted by William Colgan on March 09, 2015
Climate Change, Communicating Science, New Research / No Comments

There are a variety of methods used to estimate the present rate of mass loss from the Greenland ice sheet, including satellite altimetry, satellite gravimetry and input-output assessments. All of these methods generally agree that since 2005 the ice sheet has been losing c. 250 Gt/yr of mass (equivalent to 8000 tonnes of ice per second). Partitioning this mass loss into climatic surface balance (i.e. snowfall minus runoff) and ice dynamic (i.e. iceberg calving) contributions is a little more challenging. Partitioning recent mass loss into surface balance or ice dynamic components requires us to look at the changes in each of these terms since a period during which the ice sheet was approximately in equilibrium. Conventionally, the ice sheet is assumed to have been in equilibrium during the 1961-1990 so-called “reference period”.1

Figure_6_mass_balance_monitoring

The three main methods of measuring present-day ice sheet mass balance: (1) snowfall input minus iceberg output, (2) changes in elevation using satellite altimetry, and (3) changes in gravity using satellite gravimetry (from Alison et al., 2014)5.

Our recently published study in the Annals of Glaciology takes a hard look at the mass balance of the high elevation interior of the Greenland ice sheet during the reference period2. We difference the ice flowing out of a high elevation perimeter from the snow falling within it, and conclude that the ice sheet was likely gaining at least 20 Gt/yr of mass during the reference period. This implies that rather than ice sheet mass balance decreasing from c. 0 Gt/yr (or “equilibrium”) during reference period to c. -250 Gt/yr since 2005, it may have actually decreased from c. +20 Gt/yr of subtle mass gain during reference period to c. -250 Gt/yr since 2005. This interpretation would mean the “recent” (pre-1990 to post-2005) mass loss of the ice sheet is actually 7 % greater than might conventionally be assumed (270 vs. 250 Gt/yr). Seven percent more recent mass loss than conventionally assumed might not sound like much, but it becomes important when we try to partition mass loss in surface balance or ice dynamics components.

reference_period

Illustration of how a subtle mass gain during reference period (1961-1990) , when the Greenland ice sheet is conventionally assumed to have been in approximate equilibrium, can influence the magnitude of “recent mass loss” used to partition surface balance and ice dynamics components of mass loss.

We also assessed whether surface balance or ice dynamics were responsible for subtle reference period mass gain. We concluded it was more likely long term ice dynamics, resulting from the downward advection through the ice sheet of the transition between relatively soft Wisconsin ice (deposited > 10.8 KaBP) and relatively hard Holocene ice (deposited < 10.8 KaBP). In 1985, Niels Reeh proposed that subtly increasing effective ice viscosity was resulting in cm-scale ice sheet thickening3. Increased iceberg calving, or enhanced ice dynamics, are conventionally assumed to be responsible for c. 100 Gt/yr of recent mass loss4. Since we conclude ice dynamics were likely responsible for subtle reference period mass gain, we are implying that mass loss due to ice dynamics may actually be c. 20 Gt/yr greater than conventionally assumed, or c. 120 Gt/yr rather than c. 100 Gt/yr since 2005. Without invoking any departures from the conventional view of changes in surface balance since reference period, this infers 20 % more mass loss due to ice dynamics since reference period. This becomes important if diagnostic ice sheet model simulations are calibrated to underestimated recent ice dynamic mass loss, which may subsequently bias prognostic model simulations to similarly underestimate future ice dynamic mass loss.

Wisconsin_Tiff

An ice sheet composed of relatively hard Holocene ice is theoretically c. 15 % thicker than one composed of relative soft Wisconsin ice. Today’s ongoing transition from Wisconsin to Holocene ice within the Greenland ice sheet should theoretically result in cm-scale transient thickening (after Reeh, 1985).

Pondering how a millennial-scale shift in ice dynamics may be responsible for subtle mass gain during the 1961-1990 period, and how that ultimately influences our understanding of present-day mass loss partition, is definitely a rather nuanced topic. I am guessing there are not many non-scientists still reading at this point. Spread over the high elevation ice sheet interior, a 20 Gt/yr mass gain is equivalent to a thickening rate of just 2 cm/yr, which is within the uncertainty of virtually all mass balance observation methods, including in situ point measurements. I suppose the thrust of our study is to be receptive to the idea that millennial scale ice dynamics may be contributing to a subtle ice sheet thickening that underlies both past and present ice sheet mass balance, and to appreciate the non-trivial uncertainty in partitioning recent mass loss into surface balance and ice dynamic components that stems from the particular reference period mass balance assumption that is invoked.

1Van den Broeke, M., J. Bamber, J. Ettema, E. Rignot, E. Schrama, W. van de Berg, E. van Meijgaard, I. Velicogna and B. Wouters. 2009. Partitioning Recent Greenland Mass Loss. Science. 326: 984-986.

2Colgan, W., J. Box, M. Andersen, X. Fettweis, B. Csatho, R. Fausto, D. van As and J. Wahr. 2015. Greenland high-elevation mass balance: inference and implication of reference period (1961-90) imbalance. Annals of Glaciology. 56: doi:10.3189/2015AoG70A967.

3Reeh, N. 1985. Was the Greenland ice sheet thinner in the late Wisconsinan than now?
Nature. 317: 797-799.

4Enderlin, E., I. Howat, S. Jeong, M. Noh, J. van Angelen and M. van den Broeke. 2014. An improved mass budget for the Greenland ice sheet. Geophysical Research Letters. 41: doi:10.1002/2013GL059010.

5Alison, I., W. Colgan, M. King and F. Paul. 2014. Ice Sheets, Glaciers, and Sea Level Rise. Snow and Ice-Related Hazards, Risks and Disasters. W. Haeberli and C. Whiteman. Elsevier. 713-747.

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Glacier Mining: Geotechnical and Social Exceptionalism

Posted by William Colgan on November 07, 2014
Applied Glaciology, Climate Change, Glaciers and Society / 1 Comment

When the glaciology lexicon was in its infancy, Carl Benson described glaciers as “monomineralic metamorphic rocks” in his pioneering work with the US Army Engineers1. Given the lower density and strength of ice than coal, it may seem like glacier ice is an easy overburden to remove for open pit mining. Experience, however, has demonstrated that there are exceptional geotechnical challenges associated with removing glacier ice overburden. These challenges stem from geometry, hydrology and phase, all of which change far more rapidly in glaciers than hard rock2. The apparent surge of a waste rock pile at the Kumtor Mine, in Kyrgyzstan, highlights the exceptional geotechnical challenges confronting Centerra Gold in maintaining the world’s largest open ice pit mine.

With glaciers serving as a highly visible indicator of climate change, glacier mining projects often face exceptional social challenges in comparison to conventional hard rock mining projects. The Pascua Lama Mine, which spans the Chile-Argentina border, highlights how glacier preservation is a global movement that adapts to local issues. Glaciers therefore serve as the basis for a “glocal”, or globalized local, social movement3. Barrick Founder Peter Munk has commented on the social challenges confronting Pascua Lama: “It’s not enough to have money, it’s not enough to have reserves, it’s not enough to have great mining people. Today, the single most critical factor in growing a mining company is a social consensus – a license to mine.”4

The combination of long term increases in resource demand, retreating glaciers due to climate change, and improved mining technology and prospecting techniques, are making the exploitation of pro- and sub-glacial mineral deposits more feasible. This means a more widespread confrontation of the geotechnical and social exceptionalism of glacier mining in the coming decades!

Kumtor_1975_2013

Glacier and waste rock extent between 1975 and 2013 in the vicinity of Kumtor Mine (from Landsat archive).

PascuaLama

Glaciers in the vicinity of the Pascua Lama Mine on the Chile-Argentina border (from WikiCommons).

1Benson, C. 1962. Stratigraphic studies in the snow and firn of the Greenland ice sheet. Snow, Ice and Permafrost Research Esatablishment. US Army. Research Report 70.

2Colgan, W. and L. Arenson. 2013. Open-Pit Glacier Ice Excavation: Brief Review.
Journal of Cold Regions Engineering. 27: doi:10.1061/(ASCE)CR.1943-5495.0000057.

3Urkidi, L. 2010. A glocal environmental movement against gold mining: Pascua–Lama in Chile. Ecological Economics. 70: 219-227.

4Smith, C. 2014. Sustainability Challenges: When Good Intentions Backfire. NSEAD Knowledge

Additional Landsat images of Kumtor here.

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KSM Project gets provincial approval

Posted by William Colgan on November 03, 2014
Applied Glaciology, Climate Change, Glaciers and Society / No Comments

The Kerr-Sulphurets-Mitchell (KSM) gold mine in British Columbia received provincial approval last week. The federal permitting decision is expected in November. The suite of three open pits are in close proximity to glaciers, with the ultimate outline of the Mitchell pit intersecting the present extent of Mitchell Glacier. The proponent report filed by Seabridge Gold Inc states: “The current recession rate of the Mitchell Glacier has been estimated by Seabridge geologists at 100 m per year. As mining progresses, melting of the ice is expected to clear the area for the ultimate pit and create space needed for a series of diversion dams and ponds as well as the required debris catch basins upstream of the diversion inlets.” Seabridge is also seeking to excavate a 22 km long haulage tunnel that will convey 120,000 tonnes per day of ore underneath glaciers north of the open pits. A 38 km long glacier road, which ascends Berendon Glacier, crosses a local topographic divide, and descends an unnamed glacier, will provide winter access to the trio of open pits. The Berendon Glacier access road would be close proximity to the Knipple Glacier access road proposed by Pretium Resources Inc to access the nearby Bruce Jack Mine. Presumably the KSM project will be keeping a close eye regional glacier projections!

Controversial Canadian KSM mine gets key govt. permits

KSM (Kerr-Sulphurets-Mitchell) Project: Canadian Environmental Assessment Agency

KSM_glacier_road

Kerr-Sulphurets-Mitchell Project glacier access road during the winter. The road ascends Berendon Glacier in the east, crosses the local topographic divide, and descends an unnamed glacier in the west.

KSM_site_map

Site map of the Mitchell Pit at the Kerr-Sulphurets-Michell gold mine. Purple line denotes haulage tunnel. Dashed black line denotes ultimate extent of Mitchell Pit. White areas denote glacier extent.

 

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Iceland Names “New” Glaciers

Posted by William Colgan on October 07, 2014
Climate Change / No Comments

This past week the Icelandic Meteorology Office named 130 glaciers on the Tröllaskagi Peninsula in north-central Iceland. Most of the new glacier names refer to local landmarks. Until recently, many of the previously unnamed glaciers had appeared to be white perennial snowfields, rather than blue ice glaciers, in satellite imagery. Retreating snow lines, however, have begun revealing underlying glacier ice since c. 1996. A glacier snowline marks the lowest elevation limit where year-round snow exists. Climate change is causing an upward migration of snowlines at most Arctic glaciers, due to increased surface melt during the summer season. So, although all of Iceland’s monitored glaciers are consistently exhibiting negative surface mass balance, and recent climate change has committed c. 35 ± 11 % of Iceland’s glacier volume (or c. 850,000,000,000 tons of ice!) to disappear, even in the absence of further climate change, some good new for Iceland: It’s glacier population is growing on paper!

Morgunblaðið: Um 130 nafnlausir jöklar

Mernild, S. H., Lipscomb, W. H., Bahr, D. B., Radić, V., and Zemp, M.: Global glacier changes: a revised assessment of committed mass losses and sampling uncertainties, The Cryosphere, 7, 1565-1577, doi:10.5194/tc-7-1565-2013, 2013.

Tröllaskagi_Peninsula_Iceland

The glaciers of the Tröllaskagi Peninsula, Iceland. (from GoogleEarth)

Iceland_glaciers_recent_surface_mass_balance

Recent surface mass balance observations from Iceland’s monitored glaciers. The ice loss of Tungnaarjokull, Langjokull and Hofsjokull SW now exceeds 3000 mm of water equivalent per year. (data from Mernild et al., 2013)

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A Thaw in the Siachen Glacier Conflict?

Posted by William Colgan on October 01, 2014
Climate Change, Glaciers and Society / No Comments

The Siachen Glacier conflict shows signs of thawing. This week Pakistan’s Senate Foreign Affairs Committee Chairman Haji Muhammad Adeel has called for Siachen Glacier to be declared a non-military zone. India and Pakistan have disputed ownership of the 70 km glacier, and 1000+ square kilometers of surrounding territory, since it was occupied by India in 1984. In the subsequent three decades of conflict India and Pakistan are estimated to have each suffered approximately 2000 fatalities, primarily due to extreme environmental conditions (a ceasefire was declared in 2003). The border between Pakistan and India in the Siachen Glacier region was left undeclared in the 1972 Simla Agreement.

Of interest to glacier watchers: Haji Muhammad Adeel cited increased human activities on the glacier that have accelerated surface melt, as well as increased natural hazards in the form of flash floods and changing weather patterns, in his call for both countries to withdraw their troops from the glacier basin. With approximately 3000 soldiers from each country stationed in the valley, the Siachen Glacier is presumably the most densely populated glacier in the world. If withdrawal does happen, the extensive military infrastructure would offer great logistical support for civilian science in a region where glaciers are an exceptionally important water source in a changing climate!

The Nation: Declare Siachen a non-military zone

Wikipedia: Siachen Conflict

Siachen_Glacier_solider_photo_The_Nation

Solider at Siachen Valley. (from The Nation: Declare Siachen a non-military zone)

 

Siachen_line_of_control_UN_map_clipped

An approximately 80 km gap, spanning Siachen Glacier, in the India-Pakistan line of control resulting from the 1972 Simla Agreement. (from Wikimedia Commons)

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New Report: Greenland Gold Rush

Posted by William Colgan on September 26, 2014
Climate Change, New Research / 1 Comment

The Brookings Institute has just released “The Greenland Gold Rush: Promise and Pitfalls of Greenland’s Energy and Mineral Resources”. The report states that Greenland offshore exploration is now easier than in the past, due to a decrease in sea ice concentration and extent resulting from climate change. The acceleration of Greenland’s tidewater glaciers, however, will result in more icebergs that may “complicate” offshore activities. Onshore, the report finds that climate change has already “relaxed” some of the historical constraints of operating in Greenland, via a lengthening of the summer exploration season and the deglaciation of more land. As expected for a country that is approximately 80 % ice-covered, many onshore resource activities will likely occur in pro-glacial settings.

Report summary: “As the Arctic ice continues to melt due to global warming, Greenland’s mineral and energy resources – including iron ore, lead, zinc, diamonds, gold, rare earth elements, uranium and oil – are becoming more accessible. The political establishment in Greenland has made natural resource extraction a central part of its plans to become economically self-sufficient, and ultimately politically independent, from the Kingdom of Denmark. This will be no easy task, and it is made more difficult by Greenland’s rapidly aging population.”

The Brookings Institute report: http://www.brookings.edu/research/reports/2014/09/24-greenland-energy-mineral-resources-boersma-foley

Greenland_permitted_activities

Currently permitted resource exploration and exploitation activities in Greenland, both offshore (yellow) and onshore (blue). (from NunaGIS.gl)

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