Project Aims to Better Understand “Doomsday” Glacier

On April 30, 2018, the largest joint United States-United Kingdom Antarctic project since the 1940s was announced at the British Antarctic Survey in Cambridge. The International Thwaites Glacier Collaboration (ITGC) will focus on the Thwaites glacier of West Antarctica, one of the world’s largest and fastest melting glaciers.

The Thwaites has already contributed to 4 percent of observed global sea-level rise, but the rapid melting of the Thwaites is not scientists’ only concern. The glacier acts as a sort of plug, protecting the rest of the West Antarctic ice sheet from melting. But if the Thwaites were to collapse, most of the West Antarctic ice sheet would be destabilized, likely leading to its impending collapse. This so called “‘Doomsday”’ scenario would cause sea levels to rise 10 feet on average across the Earth.

Photo of the Thwaites Glacier from above
Aerial view of the Thwaites Glacier (Source: Earth Insitute/Twitter).

The ITGC, a $25 million, five-year collaboration between the U.S. National Science Foundation and UK Natural Environment Research Council, will include six scientific field studies with over 100 scientists using a number of different technologies and techniques to analyze the changes to the Thwaites and surrounding ocean.

Getting to the white expanses of the Thwaites is no easy task due to its remote location in Antarctica. In fact, only a handful of people have actually stood on the glacier. For this reason, most scientific research takes place at the more accessible national research stations, according to Jessica O’Reilly, an anthropologist at Indiana University who studies the Antarctic. “Deep field” projects like the ITGC are much rarer because of logistical challenges like coordinating multiple flights to remote areas in erratic weather and the sheer cost of such endeavors, she added.    

This threshold system is further unique to West Antarctica, according to O’Reilly, because it is a marine ice sheet, meaning its grounding line (where ice meets the underlying bed) is under water instead of on land. “Therefore, not only does air surface temperature interact with the ice sheet, but the warming ocean underneath it can also destabilize it,” she said. This distinction makes the Thwaites and rest of the West Antarctic extremely vulnerable to melting, a reality that has inspired a geoengineering proposal to build underwater walls at the grounding line of glaciers like the Thwaites to slow down melting and possibly prevent collapse.

NERC figure depicting the project's different missions
NERC figure depicting the project’s different missions (Source: NERC).

The U.S.-UK research endeavor and its six-field missions will assess just how at risk the Thwaites is to a catastrophic collapse. One of these missions will be led by Penn State Glaciologist Sridhar Anandakrishnan, who spoke to GlacierHub about the project. In Antarctica, Anandakrishnan and his team will be conducting geophysical surveys to characterize the base of the glacier. The surface where ice meets bedrock affects the way the Thwaites flows and is important for projecting how the glacier will retreat. Presently, according to Anandakrishnan, there is a need for improved information on this surface at the Thwaites. “Is it soft or hard? Is it smooth or rough? And so on,” he said.

To obtain this information, Anandakrishnan’s team will use both seismic and radar techniques. From a seismic approach, small explosives will be set off right below the glacier’s surface. The team will then listen for the explosion’s echo from the bottom of the glacier. Based on the time it takes for the echo to return and its strength, the team will be able to better understand the surface where glacial ice meets bedrock.

The radar approach involves a similar process where the team will emit a radar pulse, detect the reflected pulse, and interpret the time and amplitude of the returned pulse for information such as ice thickness, according to Anandakrishnan.

Thwaites Glacier from above
The seemingly endless expanses of the Thwaites Glacier (Source: Hannah Hickey/Twitter).

In addition to this field mission, the five others will examine the Thwaites from different focuses. These include measuring the glacier’s melting at its grounding line; measuring ocean circulation and glacial thinning underneath the floating portion of the glacier using autonomous submersibles; sampling bedrock beneath the glacier to better understand its past retreats and recoveries; analyzing the glacier’s margins to study what controls its width and speed; and examining sediments deposited in the ocean near the glacier to reconstruct past environmental changes and the Thwaites’s response to these changes.

Two other non-field missions will utilize computer models and simulations to assess processes that could cause the rapid retreat and collapse of the glacier and to improve projections on its future behavior and contribution to sea level rise.  

Photo of Boaty McBoatface
The autonomous submersible Boaty McBoatface which will participate in the project (Gizmodo/Twitter).

According to Anandakrishnan, these missions fall in line with one of the main goals of the ITGC: to better understand the Thwaites by improving modeling and projections of the future state of the glacier. Even without a collapse, the Thwaites could contribute up to one meter of sea-level rise over the next century, a change that would have devastating effects on the world’s coastal communities.

If the goals of the project can be accomplished, “we can better estimate what this glacier would do under various future climate scenarios,” Anandakrishnan said. Overall, the U.S.-UK Antarctic project will be a big step forward for humanity’s understanding of a glacier that could have a profound impact on society if it were to collapse.   

 

Life on the Edge: The Science of Glaciers that Meet Oceans

Tidewater glacier on Antarctic coast (source: Jason Auch/Flickr)
Tidewater glacier on Antarctic coast (source: Jason Auch/Flickr)

In an October 2015 article in Earth & Space Science News, David Holland and Denise Holland suggest steps to increase the understanding of glacier melt to improve projections of sea level rise.

IPCC (Intergovernmental Panel on Climate Change) reports have concluded that anthropogenic causes are to blame for glacier retreat in the last century. They predict that increased melt in the present century will rise global sea levels. The authors report that the contribution of the West Antarctic Ice Sheet, alone will change low-lying coastal and communities worldwide and threaten marine ecosystems.

They note that the rate of sea level rise will be influenced by a number of factors, including the local shifts in the gravitational pull of land masses, along with changes in water currents, wind patterns, and water temperature and salinity. The rebound of land masses, once the weight of glaciers and ice sheets is removed, will also influence sea levels.

Map_of_the_McMurdo-South_Pole_highway
Map of Antarctica (source: Maximilian Dörrbecker [Chumwa])
The complex nature of the interface between ice sheets and the ocean also creates uncertainty about the future of many of the West Antarctic glaciers, as it is difficult to make predictions of how the ice will react in the future. In one possible scenario, the circulation of warm ocean waters that is currently held off by continued cold meltwater runoff from Antarctica could grow larger, and the cold water barrier would no longer block it from teaching the continent. The warm water would thus be able to make direct contact with the underside of the glacier and warm it from below, greatly increasing the glacier melt.

Holland and Holland note that many problems with predicting the effects of West Antarctic glacier melt stem from a deficit of data. Though satellites are able to measure glacier volume, they are unable to observe the water resting underneath glaciers or the land mass upon which some glaciers rest. Another area of difficulty in predicting the melting of the West Antarctic glacier involves a shortfall in scientific understanding of calving—the process in which the section of a glacier front breaks and falls into the ocean. Scientists compare the difficulties of constructing models of calving to the challenges of predicting earthquakes. They remain unable to make long-term predictions about when they will occur.

https://upload.wikimedia.org/wikipedia/commons/b/b2/Antarctic_shelf_ice_hg.png
Sketch of the Antarctic coast showing interactions of ice sheet, glaciers and oceans. (Source: Hannes Grobe, Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany )

Holland and Holland state that in order to create accurate predictions for the contributions of the West Antarctic Ice Sheet to sea level rise, scientists need to couple glacier and ocean models. Currently there is little cooperation between glaciologists and oceanographers, even though both work on sea level rise since each uses separate models specific to their disciplines. To address this problem Holland and Holland report, the World Climate Research Programme (WCRP) has established a project, Climate and Cryosphere (CliC). This project held a meeting in October 2014, in which the Marine Ice Sheet–Ocean Model Intercomparison Project (MISOMIP) was established. The project seeks to draw on the efforts glaciological and oceanographic modelers. The participants in the project work together to create coupled and interactive glacier-ocean models. The goal is to follow this suite of glacier-ocean models with regional simulations of specific outlet glaciers such as those found in West Antarctica.

Holland and Holland say that scientists, by coupling glacier and ocean models, can greatly improve the accuracy of future sea level rise projections attributed to the West Antarctic Ice Sheet and its outlet glaciers. Because of the increasing threat of sea level rise to communities around the world, the accuracy of such projections is of great value. It is to be hoped that this importance will support efforts to produce these projections, which require increased cooperative effort between nations and between disciplines.