Why do I research Greenland and Antarctica's ice shelves?

While the polar ice sheets are amongst the most remote locations in the world, they both respond to, and influence, the behaviour of human societies. By developing economies based on the extraction of fossil fuels, humans have warmed - and are warming - the climate. This causes increased melting and loss of ice from the Antarctic and Greenland ice sheets. These processes at the poles, in turn, cause global sea-level rise which will profoundly affect the lives of millions of people living in low-lying coastal areas.

Fundamentally, my research is motivated by a desire to better under processes that will affect the stability of the Antarctic and Greenland ice sheets in a warming climate. By improving our understanding of processes that affect the stability of ice shelves (and therefore the ice sheet), we can make better predictions about sea-level rise and help policymakers make better-informed decisions about climate change mitigation. 

The Antarctic ice sheets store over 50 m of potential sea-level rise, and the Greenland Ice Sheet another 7 m. These ice sheets are not disappearing anytime soon, but there is a real potential for them to make substantial losses and contribute a significant amount to sea-level over the course of this century and (especially) beyond.  It is argued that much of this rise is already ‘locked-in‘ but there remains much uncertainty about the processes that govern the ice sheet’s stability and also about the degree to which the atmosphere will warm.  The melting and collapse of ice shelves does not in itself contribute to sea-level rise, because they already float and displace water (like an ice cube in a drink).  However, they provide an important ‘buttressing force’ that holds back the glaciers that feed them.  When an ice shelf collapses, the loss of this force can lead to the acceleration of the glaciers that feed it (which does cause sea-level rise).  This is exactly what happened when the Larsen B Ice Shelf collapsed in 2002.  Furthermore, it can cause retreat of the glacier’s ‘grounding line’, the point where the ice transitions between resting on bedrock and floating on the ocean.  As much of West Antarctica is below sea-level, grounding line retreat could lead to the incursion of warm ocean waters deep into the Antarctic Ice Sheet.

 Projected sea-level rise under a ‘business as usual’ carbon emissions scenario (red) and ’emissions peak within this decade’ scenario (blue), according to the IPCC 5th Assessment Report. Read more at  http://www.realclimate.org/index.php/archives/2013/11/sea-level-rise-what-the-experts-expect/

Projected sea-level rise under a ‘business as usual’ carbon emissions scenario (red) and ’emissions peak within this decade’ scenario (blue), according to the IPCC 5th Assessment Report. Read more at http://www.realclimate.org/index.php/archives/2013/11/sea-level-rise-what-the-experts-expect/

  Why care about sea-level rise?  Sea-level rise is not only a problem for areas that could actually fall below sea-level (such as parts of Bangladesh, The Netherlands and various micronation islands). Higher sea-levels increase the risk from storms and floods, making events like Hurricane Sandy a much more common occurrence. The above figure shows the ‘flood frequency multiplier’ for 0.5m of sea-level rise. For example, a multiplier of 100, means that a flood currently deemed a ‘once in a thousand year flood’ would be expected to occur every ~ten years. (Source IPCC via Michael Oppenheimer)

Why care about sea-level rise? Sea-level rise is not only a problem for areas that could actually fall below sea-level (such as parts of Bangladesh, The Netherlands and various micronation islands). Higher sea-levels increase the risk from storms and floods, making events like Hurricane Sandy a much more common occurrence. The above figure shows the ‘flood frequency multiplier’ for 0.5m of sea-level rise. For example, a multiplier of 100, means that a flood currently deemed a ‘once in a thousand year flood’ would be expected to occur every ~ten years. (Source IPCC via Michael Oppenheimer)

The Larsen B Ice Shelf, part of the Antarctic Peninsula, a large tabular ice shelf roughly the size of the state of Rhode Island collapsed in just weeks in January-March 2002 (see below).  The sudden disintegration of this massive ice shelf into thousands of icebergs provides an example of what could happen to many of Antarctica’s remaining ice shelves (see above), with massive implications for the continental ice that feeds them.

 A series of images from January 31st to March 7th 2002, show the Larsen B Ice Shelf covered in meltwater ponds, and the subsequent drainage of those lakes and the catastrophic collapse of the ice shelf (NSIDC)

A series of images from January 31st to March 7th 2002, show the Larsen B Ice Shelf covered in meltwater ponds, and the subsequent drainage of those lakes and the catastrophic collapse of the ice shelf (NSIDC)

Especially striking, is that in the days prior to the collapse, thousands of surface lakes drained through the ice shelf, suggesting a causal link.  One paper, by my advisor Alison Banwell and others, suggests that as the lakes lie on the ice-shelf they exert a force due to their gravitational load that ‘flexes’ the ice-shelf.  They suggest that the removal of this load when the lake drains through a fracture in the ice causes the ice to partially rebound, which again flexes the ice causing fractures to develop in the ice.  Cracks in ice-shelves can propagate through the full thickness of the ice, esepecially when they are filled with water, causing the icebergs to break off. As temperatures increase in Antarctica, the proportion of ice shelves covered in surface lakes will increase, making it especially important that we learn to improve our knowledge of them.  Our mission is to gather data on, and model, the flexural impact of these lakes so that we can better understand what their impact is on ice shelves.