Antarctic Peninsula ice shelves | Ice shelf collapse on the Antarctic Peninsula | Rifting on Larsen C | Impact of calving the large iceberg | Sea level rise following ice-shelf collapse | References | Comments |
Antarctic Peninsula ice shelves
The Antarctic Peninsula is fringed by floating ice shelves. They are floating extensions of the glaciers on land, and receive mass by snowfall and marine freeze-on. They lose mass by melting at their base and by calving icebergs. Larsen C Ice Shelf, the largest ice shelf on the Antarctic Peninsula, is currently being closely watched. Following a series of high-profile ice-shelf collapse events on the Antarctic Peninsula over the last few decades, all eyes are watching Larsen C and wondering when, and if, it will collapse.
A growing rift on Larsen C Ice Shelf
Those concerns are growing more acute as a large rift on Larsen C Ice Shelf is growing rapidly, threatening to soon calve a huge iceberg, equivalent to losing 10% of the area of the ice shelf. This could destabilise the ice shelf, making it more susceptible to a total collapse.
Larsen C rift animation uses #Sentinel1 InSAR to illustrate recent jumps in rift progression. From Prof. Adrian Luckman.
The Antarctic Peninsula is warming very rapidly, about six times the global average[1-3]. There has been a 95% increase in positive degree day sums since 1948. Glaciers in the region are accelerating, in response to frontal thinning and recession. In addition, ice shelves are collapsing, glacier fronts are retreating. The causes for much of these changes has often been attributed to ocean forcing, with warm ocean waters melting these glaciers from below[8-11]. However, while ocean forcing may dominate further south, such as at Pine Island Glacier, a few recent papers have highlighted the importance of surface processes and surface melt induced by warmer surface air temperatures and longer melt seasons, specifically on the Antarctic Peninsula. Continue reading
A major new review of the last glaciation of the entire Antarctic Ice Sheet has just been published by Quaternary Science Reviews. The special issue of the journal includes a suite of review papers involving an international team of experts regarding the last glaciation of the entire Antarctic Ice Sheet. This review, which comprises six review papers and an overview paper in a special issue of Quaternary Science Reviews, is now complete and all papers have been accepted for publication. As this is the most important, up to date and inclusive review ever to be attempted for the glaciation and recession of the Antarctic Ice Sheet, it represents a major step forward in our understanding of palaeo ice-sheet dynamics, provides a benchmark against which future research needs can be identified and highlighted, and provides a compilation of data unlike anything seen before, which can be used to test and calibrate numerical ice-sheet models.
Marine ice sheet instability
The West Antarctic Ice Sheet (WAIS) is the world’s most vulnerable ice sheet. This is because it is grounded below sea level, and marine ice sheets such as these are susceptible to rapid melting at their base. Fast-flowing ice streams draining the WAIS (Pine Island Glacier and Thwaites Glacier in particular) into the Amundsen Sea have a grounding line on a reverse bed slope, becoming deeper inland. Recession of the grounding line means that the ice stream is grounded in deeper water, with a greater ice thickness. Stable grounding lines cannot be established on these reverse bed slopes1, because ice thickness is a key factor in controlling ice flux across the grounding line. Thicker ice in deeper water drives increased calving, increased ice discharge, and further grounding-line recession in a positive feedback loop2, 3. This process is called Marine Ice Sheet Instability4.
Davies, B.J., and Glasser, N.F., 2014. Analysis of www.AntarcticGlaciers.org as a tool for online science communication. Journal of Glaciology 60(220), 399-406.
Download the preprint: Davies_et_al_2014_preprint.
The following is a shorter, simpler version of the published paper.
Science communication for the time-limited academic
Academic research into climate change is driven by pressing human concerns. Because climate change has the potential to seriously affect our society, the effective communication of this research is increasingly important1. As such, increasing numbers of academics and researchers are taking part in public engagement2-4. But a key question is,
How can time-limited academics, who work in full-time positions, implement effective outreach strategies with limited budgets?
As the 2013 year draws to a close, I thought it would be great to highlight some of our most important science discoveries in Antarctic Glaciology. Enjoy! Continue reading
A new paper by Levermann et al. in PNAS uses the record of past rates of sea level rise from palaeo archives and numerical computer models to understand how much sea level rise we can expect per degree of warming in the future. These data suggest that we can expect a global sea level rise of 2.3 m per 1°C of warming within the next 2000 years: well within societal timeframes. A 2°C of warming would result in a global sea level rise of 4.8 m within 2000 years. This would inundate many coastal cities in Europe alone, and cause untold economic and societal damage.
J.Boex, C. Fogwill, S. Harrison, N.F. Glasser, A. Hein, C. Schnabel and S. Xu. Rapid thinning of the Late Pleistocene Patagonian Ice Sheet followed migration of the Southern Westerlies. Scientific Reports 3: 2118, p. 1-6
Download the PDF
The Patagonian Ice Sheet
Patagonian mountains east of the North Patagonian Icefield. Credit: Stephan Harrison
This recent open-access paper in the new journal Science Communications, which is part of the Nature group, has demonstrated that the during the deglacial period (~19,000 years ago), the Patagonian Ice Sheet in South America responded rapidly in response to changing precipitation patterns and warming during the last deglaciation. The fact that the Patagonian Ice Sheet responded so quickly to changes in precipitation and temperature has vivid implications for the current, and future, behaviour of the current North Patagonian Icefield and South Patagonian Icefield. We already know that the shrinkage of the North and South Patagonian ice fields was faster over the last decade or so than at any point in the last couple of centuries. Understanding on a broader scale how these sensitive, high-latitude ice masses are dependent on small changes in atmospheric circulation means that we will better be able to predict the future behaviour of these ice sheets. Reconstructing rates of ice-sheet decay since the Last Glacial Maximum means that we can better assess the mechanisms of climate change (including changing wind patterns) during a major climate transition. Continue reading
Holt, T.O., Glasser, N.F., Quincey, D. and Siegfried, M.R., 2013. Speedup and fracturing of George VI Ice Shelf, Antarctic Peninsula. The Cryosphere, 7: 797-816.
George VI Ice Shelf
George VI Ice Shelf, Alexander Island, showing ice flowing onto the ice shelf from both the Antarctic Peninsula and Alexander Island
Alexander Island and George VI Ice Shelf is an area I’m particularly interested in (see our project details), and the ice shelf is worth investigating for several reasons. For a start, it’s unusual, being trapped between the mainland and Alexander Island, and secondly, because it’s right on the -9°C mean annual air temperature isotherm (like a contour, but of mean annual air temperatures). Some people have argued that this mean annual air temperature is the critical threshold above which ice shelves may dramatically collapse, which has implications for accelerated flow of glaciers and ice-sheet thinning. Ice shelves are also susceptible to warming from below by warm currents penetrating onto the continental shelf. So, research into this important part of the peninsula is always welcome. Holt and colleagues have just completed a study (open access) that investigates the response of George VI Ice Shelf to environmental change (i.e., oceanic and atmospheric temperature variations), and offer an assessment as to its future stability (Holt et al., 2013). Continue reading
Sea ice and ice shelves
What is sea ice? Sea ice is frozen sea water; it perennially expands and contracts during each year’s winter and summer. Amongst the sea ice are icebergs calved from tidewater glaciers and ice shelves. Melting sea ice does not contribute directly to sea level rise (ice floats and displaces the same volume of water), but sea ice is important because it enhances climate warming. It changes the reflectivity of the sea water, reflecting lots of sunlight back (it has a high albedo), and is therefore an important component of the climate and cryospheric (icey) system.