A large ice island has broken off the Petermann Glacier in northern Greenland.

NASA satellite image (MODIS).

This iceberg is about twice the size of Manhattan but approximately half the size of the previous recent break-off in 2010 (blog post here).  Unlike the 2010 event the current ice has broke off further up glacier and marks a retreat of the calving front of the glacier.  The crack and rift that led to this break off has been known and observed for some time and so this event was expected in this regards.  However, the question is still being asked as to how unusual these large calving events are and whether they were caused by climate change.  Certainly we can say that these changes have not been seen for at least a 150 years (see previous post and this discussion article).  However, we can’t say for certain that these two massive calving event are a direct result of climate change.  An interesting discussion on these questions is provided in this BBC article.

The Guardian has a little interactive page where you can watch the iceberg break off in context (click here).

Glaciologist Tim Creyts provides an insightful radio interview here.

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Frozen Planet, BBCs new landmark natural history seven part TV series on the frozen wildernesses of the Arctic and Antarctic, has just finished showing in the UK.  The last episode includes some spectacular location footage of the research project I’m involved in.  This includes watching my boss, Alun Hubbard, abseil down a moulin into the depths of the Greenland Ice Sheet (see here).

The footage covers the drainage of a meltwater lake as it gushes down glacier incising channels into the ice before descending down a moulin (vertical shaft) through a kilometer of ice to the bed.  My own involvement in the research project is to model the effects this water has on the flow of the overlying ice.  Check out our new website to learn more:

http://www.aber.ac.uk/greenland/index.html

My contribution can be found in the Modelling section of this link: http://www.aber.ac.uk/greenland/Russell.html

This is a photo of the Petermann Ice Island taken by a NASA International Space Station crew.   This amazing image reveals the ice island complete with melt ponds and supraglacial meltwater channels clearly visible.

A series of close-up photos of this huge ice chunk taken in August 2011 can be viewed here.  Currently the ice island is located off the coast of Newfoundland, as seen in July from this satellite image, and reported in this CBC new article.

Updates on the progress of the ice island can be tracked from the Environment Canada webpage.

The drifting ice island originated from the Petermann Glacier in Northwest Greenland breaking off as a giant iceberg of unprecedented size (five times the size of Manhattan Island) on August 5, 2010 (see satellite images here).  The Petermann Glacier drains about 6% of the Greenland ice sheet.  Previously this ice-front had a relatively stable position, but recent environmental changes raise questions about the possible further retreat of the ice-tongue and the knock-on contributions to sea-level rise.  See this article for more context and scientific insight.

K. K. Falkner, H. Melling, A. M. Munchow, J. E. Box, T. Wohlleben, H. L. Johnson, P. Gudmandsen, R. Samelson, L. Copland, K. Steffen, E. Rignot, and A. K. Higgins.  Context for the Recent Massive Petermann Glacier Calving Event, EOS, 92, 117-124, 2011.

Another major iceberg is poised to break off again from Petermann Glacier, probably next year now, according to Glaciologist Jason Box (see media reports here and here).

Here is a short video interview with Glaciologist Dorthe Dahl-Jensen by APECS (Association of Polar Early Career Scientists).  Professor Dahl-Jensen heads up the Greenland ice-core drilling project at Summit camp this is the highest point on the Greenland Ice Sheet (~3200 metres above sea level).  She describes how she got into Glaciology and Climate research and why we collect ice-cores in Greenland.

Here is my submitted abstract for the American Geophysical Union (AGU) Fall Meeting, San Francisco, 5-9 December, 2011.

Modeling seasonal velocity variability and assessing the influence of glacial hydrology and sea-ice buttressing at the Belcher Glacier, Arctic Canada

“Seasonal ice dynamics on marine outlet glaciers can be influenced by the effects of both glacial hydrology and sea-ice buttressing.  In summer surface meltwater finds its way through crevasses and moulins into the subglacial drainage system thereby modulating the extent of glacier sliding.  Whereas in winter sea-ice build-up in front of the glacier terminus provides a buttressing effect exerting a back stress on the glacier ice.  In this study we seek to distinguish between contributions from these two processes at a large fast-flowing tidewater-terminating Arctic glacier.  The Belcher Glacier is the largest outlet glacier of the Devon Island Ice Cap in the Canadian high-Arctic.  We employ the use of a hydrologically coupled higher-order ice-flow model together with field data collected in 2008 and 2009.  Model output is compared against surface GPS observations as well as remotely sensed velocities derived using speckle tracking methods on Radarsat-2 imagery.  Five major drainage sub-catchments have been identified on the Belcher and a melt model is used to generate daily surface runoff for each sub-catchment.  The observed timing of lake drainage and moulin openings in each sub-catchment allow a seasonal timeseries of meltwater inputs to the subglacial drainage system to be constructed.  Model simulations for 2008 and 2009 forced with this meltwater input timeseries are presented.  Model responses to tidal forcing and changes in sea-ice back stress at the terminus are examined and compared alongside hydrologically driven accelerations.”

by Pimentel*, Flowers, Boon, Clavano, Copland, Danielson, Duncan, Kavanaugh, Sharp, and Van Wychen.

Update: The above abstract has been cancelled as I will no longer be able to attend the meeting.

I’m also an author on another abstract:

Subglacial hydrological modelling of a rapid lake drainage event on the Russell Glacier catchment, SW Greenland

“We use local-scale subglacial hydrological models to assess the development of the basal drainage system in response to a rapid lake tapping event on the Russell Glacier catchment, SW Greenland. Water inputs to the model are constrained by in-situ records of the lake drainage rate. Subglacial conditions are estimated from active seismic line analysis including basal topography and substrate characteristics.

A borehole slug test model is used to determine the radial flux of water from the drainage input point. Water flowing in the downstream direction is used to drive a 1-D flowband model, which allows development of interacting channelised and distributed drainage systems. The simulated basal water pressures are applied to an elastic beam model to assess vertical uplift at the lake drainage site. Modelled uplift outputs are compared with results from GPS stations located next to the lake.  Initial modelling results suggest that channels are necessary for evacuation of water from rapid lake drainage events, even with the presence of a sediment-based bed, the latter of which is usually associated with distributed drainage.”

by Dow*, Pimentel, Doyle, Booth, Fitzpatrick, Jones, Kulessa and Hubbard.

Recent increases in ice discharge from marine outlet glaciers in Greenland (e.g., [1], [2]) have been associated with ice-ocean interactions (e.g., [3], [4], [5]). Warming of subsurface waters in contact with the submarine bases of these glaciers result in additional melting of the ice and changes to the stress balance of the ice flow.

Here’s a short video from WHOI physical oceanographer Fiamma Straneo explaining the connection between ocean conditions and climate-driven changes to Greenland glaciers (she also describes some of the challenges in conducting scientific research in the far north).

Currently, numerical ice-dynamic models are not suitably equipped to capture these interactions and therefore this hampers our ability to predict Greenland’s contribution to sea level rise.  Part of my research aim is to work towards improving ice-flow models so that they better represent these processes.

References:

[1] Joughin, I., Abdalati, W., Fahenstock, M., 2004. Large fluctuations in speed on Greenland’s Jakobshavn Isbrae Glacier. Nature 432, 608-610.

[2] Rignot, E., Kanagaratnam, P., 2006. Changes in the velocity structure of the Greenland Ice Sheet. Science 311, 986–990.

[3] Holland, D. M., Thomas, R. H., Young, B. D., Ribergaard, M. H., 2008. Acceleration of Jakobshavn Isbrae triggered by warm subsurface ocean waters. Nat. Geosci. 1, 659–664.

[4] Straneo, F., Hamilton, G. S., Sutherland, D. S., Stearns, L. A., Davidson, F., Hammill, M. O., Stenson, G. B., Rosing-Asvid, A., 2010. Rapid circulation of warm subtropical waters in a major glacial fjord in East Greenland. Nat. Geosci. 3, 182-186.

[5] Rignot, E., Koppes, M., Velicogna, I., 2010. Rapid submarine melting of the calving faces of West Greenland glaciers. Nat. Geosci. 3, 187-191.

So I mentioned in an earlier post that I attended (and spoke at) a workshop organized by a nuclear waste consortium consisting of NWMO (Canada), SKB (Sweden), and Posiva (Finland). They’ve initiated a research study called the Greenland Analogue Project (GAP). I should just add here that although I am doing research related to this project (GAP) I am not funded by GAP (I receive no money from a nuclear waste company – not that I would necessarily have anything against that!).

I will now attempt to explain why nuclear waste companies are interested in Glaciology and more particularly modelling subglacial hydrology (which is what I do). So here goes …

High-level radioactive waste from spent nuclear fuel (as a result of nuclear power generation) has to be disposed of – safely of course! This is a difficult problem because every precaution has to be made to contain and isolate radioactive material and prevent any interaction with the biosphere for at least 100,000 years.  The radioactive waste will be buried deep (>0.5 km) in an underground repository in ancient bedrock and measures taken to ensure against every possible scenario.

Within its lifespan, this final repository site, will undergo glaciation (an ice age) – how will these conditions affect the stringent safety standards?  What are the conditions and processes that impact the recharge of glacial meltwater into the geosphere, in particular to repository depth in a fractured crystalline rock?  In order to help answer these questions investigations are focused on Greenland – the closest current analogue to these conditions (hence the title name GAP).

The overall aim of the Greenland Analogue Project is to improve the current understanding of how an ice sheet affects the groundwater flow and the water chemistry around a deep geological repository in crystalline bedrock during glacial periods.

My own research in modelling subglacial hydrology has principally been driven by a need to understand how hydrology influences ice dynamics, because water at the base of an ice sheet governs glacier sliding.  However, the interest related to the above project is how subglacial and ice dynamic interactions influence the geosphere, i.e. what is the interaction with the groundwater circulation around a deep geological repository.

Quantities of interest include knowledge of subglacial water volumes and pressures.  They will want to know how much meltwater seeps into the underlying bedrock, and whether seasonal subglacial network evolution and discrete flooding events are important in constraining leakage into the groundwater system on geological timescales.

This is my own personal understanding of the situation and does not represent any official take on the matter or the views of any nuclear waste management organization.