My Research
My research focuses on using global climate modeling to determine how the climate system as a whole might respond to changes in the Antarctic Ice Sheet (AIS). Antarctica is currently undergoing rapid changes. Observational evidence indicates that the West Antarctic Ice Sheet (WAIS) is losing mass at an accelerating rate.[1][2][3] This is important because the WAIS is estimated to contain an ice volume equivalent to over 3 m (~10 ft) sea level rise.[4] Modeling projections show that the Antarctic ice sheet as a whole has the potential to contribute up to 1 m (~3.3 ft) of sea level rise by the end of this century.[5] Sea level rise is only one aspect of how changes in Antarctica might impact our world. There are many more ways in which changes in the AIS can impact our planet and these are what I am researching.
What is so special about Antarctica?
Antarctica is split into two basic sections- the East Antarctic Ice Sheet and the West Antarctic Ice Sheet, which are separated by the Transantarctic Mountains. Each side has a distinctive layout of bedrock under the ice and the differences between the two sides lead to there being substantially different stabilities between the two.
What is so special about Antarctica?
Antarctica is split into two basic sections- the East Antarctic Ice Sheet and the West Antarctic Ice Sheet, which are separated by the Transantarctic Mountains. Each side has a distinctive layout of bedrock under the ice and the differences between the two sides lead to there being substantially different stabilities between the two.
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On the eastern side the configuration of the bedrock underlaying the ice sheet is similar to that of Greenland where the bedrock slopes down towards the ocean. The western side on the other hand is marine based with floating ice shelves surrounding the grounded portion of the sheet which sits on bedrock that actually slopes down toward the interior of the continent instead of down towards the ocean. This means that a large portion of the grounded ice is actually below sea level underneath all of the ice above. The ice there is held in place by the buttressing effects of the floating ice shelves, which are attached to the bedrock at what is known as the grounding line.
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Credit- NASA
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As the climate is changing due to human induced greenhouse gas emissions, the atmosphere and ocean are both heating up. The warming ocean waters flow underneath the floating ice shelves and melt away the ice at the base of the sheet near the grounding line. This causes the grounding line to move back towards the interior of the continent as the warm ocean water eats away at it from below which can lead to a process known as Marine Ice Sheet Instability (MISI). When the buttressing effects of the ice shelves are removed and the grounding line retreats the grounded ice begins to slide towards the ocean at which point MISI can become a run away process in which the ice sheet over the continental interior of the WAIS can catastrophically collapse.[4][5][7] Observational evidence suggests that MISI has already begun in West Antarctica.[3]
A simplified side view of the grounding line. Credit- AntarcticGlaciers.org
That sounds bad. What are some of the possible impacts of this?
As the freshwater that was formerly locked up in the ice sheet enters the ocean the sea level will rise leading to displacement of people in coastal communities, damage to infrastructure, and impacts to coastal ecosystems. This is likely the most well known effects of AIS melt, however there will likely be other impacts to the climate system. Changes in ocean circulation patterns alter this transport and this has many implications for the global climate which can include changes in temperature at different regions, shifts in precipitation patterns, changes in wind patterns, and more. The world's oceans are vast but interconnected. Water moves around the planet via currents and these are responsible for transporting heat, salt, and nutrients. The way the water moves is driven by variations in the temperature and salt content which together determine the water's density. There are several spots on the planet where variations in water density cause the water to sink to depth. These regions are called deep water formation areas and they are the driving force of the global currents. The deep water formation areas are located in the North Atlantic and at locations off the coast of Antarctica. If freshwater gets added to these regions it alters the density of the surface water which inhibits deep water formation and can disrupt the global current system affecting heat transport and climate. In Antarctica this primarily happens due to warm water melting the ice from below and from iceberg calving.[6] You could say that what happens in Antarctica doesn't stay in Antarctica- it has the potential to impact all of us all over the planet.
As the freshwater that was formerly locked up in the ice sheet enters the ocean the sea level will rise leading to displacement of people in coastal communities, damage to infrastructure, and impacts to coastal ecosystems. This is likely the most well known effects of AIS melt, however there will likely be other impacts to the climate system. Changes in ocean circulation patterns alter this transport and this has many implications for the global climate which can include changes in temperature at different regions, shifts in precipitation patterns, changes in wind patterns, and more. The world's oceans are vast but interconnected. Water moves around the planet via currents and these are responsible for transporting heat, salt, and nutrients. The way the water moves is driven by variations in the temperature and salt content which together determine the water's density. There are several spots on the planet where variations in water density cause the water to sink to depth. These regions are called deep water formation areas and they are the driving force of the global currents. The deep water formation areas are located in the North Atlantic and at locations off the coast of Antarctica. If freshwater gets added to these regions it alters the density of the surface water which inhibits deep water formation and can disrupt the global current system affecting heat transport and climate. In Antarctica this primarily happens due to warm water melting the ice from below and from iceberg calving.[6] You could say that what happens in Antarctica doesn't stay in Antarctica- it has the potential to impact all of us all over the planet.
This panel shows the progression of ice mass loss for the Amundsen Sea sector of the WAIS in the DeConto/Pollard model under RCP 8.5. Credit: DeConto/Pollard 2016.
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This is clearly an important area of study. How are you going to research it?
To project what may happen in the future we need state of the art climate models which are able to simulate physical processes of the ocean, atmosphere, and ice. I am using the Community Earth System Model (CESM), a high resolution fully coupled ocean-atmosphere model which allows for climate simulations that take into account many complicated and interconnected processes of the land, ocean, atmosphere, and cryosphere. |
The emissions in gigatons of CO2 over time under each RCP scenario (left) and the resulting atmospheric CO2 concentrations (right). Credit: IPCC.
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My experiments will take into account two main things. One of which are the Representative Concentration Pathways (RCPs) created by the Intergovernmental Panel on Climate Change (IPCC). The IPCC RCP scenarios were created by a huge international collaboration of scientists and help describe how climate forcing can differ based on anthropogenic (human caused) greenhouse gas emissions. Since these scenarios are standardized internationally they help scientists compare their results. The second is freshwater discharge where the freshwater is the result of another simulation done by Rob DeConto (UMass Amherst) and Dave Pollard (Penn State). They used a regional ice sheet-ice shelf model for Antarctica to look at how the AIS may evolve under greenhouse gas forcing of the RCP scenarios. Their results give us a very high resolution look at how the ice sheet may change and provide data on the amounts of freshwater released as ice calving, sub-ice sheet melting, and more. Since their regional model is state of the art and very high resolution it gives a much more intricate picture of changes in the ice sheet. I can then feed in their results to the global climate model, along with the RCP scenarios, and get a better picture of how greenhouse gas induced radiative forcing changes and ice mass loss in the WAIS could impact changes in ocean circulation, global temperatures, wind patterns, and more. Preliminary results from my experiments will be forthcoming.
References:
[1] Jeong, S., Howart, I., Bassis, J. Accelerated ice shelf rifting and retreat at Pine Island Glacier, West Antarctica. Geophysical Research Letters, November 2016.
[2] Khazendar, A., et. al. Rapid submarine ice melting in the grounding zones of ice shelves in West Antarctica. Nature Communications, October 2016.
[3] Rignot, E. et. al. Widespread, rapid grounding line retreat of Pine Island, Thwaites, Smith, and Kohler glaciers, West Antarctica, from 1992 to 2011. Geophysical Research Letters, May 2014.
[4] Feldman, J. and Levermann, A. Collapse of the West Antarctic Ice Sheet after local destabilization of the Amundsen Basin. PNAS, October 2015.
[5] DeConto, R. and Pollard, D. Contribution of Antarctica to past and future sea-level rise. Nature, Vol. 531, March 2016.
[6] Depoorter, M. et. al. Calving fluxes and basal melt rates of Antarctic ice shelves. Nature, Vol. 502, October 2013.
[7] Joughlin, I., et. al. Ice-sheet Response to Oceanic Forcing. Science, Vol. 338, November 2012.
[1] Jeong, S., Howart, I., Bassis, J. Accelerated ice shelf rifting and retreat at Pine Island Glacier, West Antarctica. Geophysical Research Letters, November 2016.
[2] Khazendar, A., et. al. Rapid submarine ice melting in the grounding zones of ice shelves in West Antarctica. Nature Communications, October 2016.
[3] Rignot, E. et. al. Widespread, rapid grounding line retreat of Pine Island, Thwaites, Smith, and Kohler glaciers, West Antarctica, from 1992 to 2011. Geophysical Research Letters, May 2014.
[4] Feldman, J. and Levermann, A. Collapse of the West Antarctic Ice Sheet after local destabilization of the Amundsen Basin. PNAS, October 2015.
[5] DeConto, R. and Pollard, D. Contribution of Antarctica to past and future sea-level rise. Nature, Vol. 531, March 2016.
[6] Depoorter, M. et. al. Calving fluxes and basal melt rates of Antarctic ice shelves. Nature, Vol. 502, October 2013.
[7] Joughlin, I., et. al. Ice-sheet Response to Oceanic Forcing. Science, Vol. 338, November 2012.