NSFGEO-NERC: Ice-shelf Instability Caused by Active Surface Meltwater Production, Movement, Ponding and Hydrofracture

The floating ice shelves around Antarctica provide a buffer against rapid ice flow from the continent's interior to the ocean. If that buffer is reduced or removed, there will be more rapid ice flow to the ocean contributing to sea level rise. Understanding the controls on ice shelf stability, therefore, is important for the assessment and prediction of possible ice shelf shrinkage or collapse. Evidence shows that one source of ice shelf instability comes from surface melting and the movement of the meltwater. The decade-long development of >2500 surface lakes on the Larsen B Ice Shelf, followed by their abrupt drainage, were the two most conspicuous precursors to the ice shelf's sudden collapse in 2002.

This project will investigate how ice shelves fracture when subjected to strong surface melting using a suite of geophysical observations on the George VI Ice Shelf (GVIIS) of the Antarctic Peninsula. The leading processes to be observed are viscoelastic ice-shelf flexure and fracture in response to surface meltwater movement, loading, and unloading. The team's prior fieldwork provided the first direct measurements of these processes on the McMurdo Ice Shelf (McMIS). However, the results were somewhat limited in their application to other ice shelves due to a heterogeneous debris cover and therefore atypical ablation rates, sparsely-distributed ponds, and ice-flexure measurements made close to an active rift.

Compared to the McMIS, the GVIIS provides a near-perfect opportunity to observe meltwater loading processes, as satellite imagery shows it hosts hundreds of lakes and displays features of viscoelastic rebound in response to lake drainage. Furthermore, GVIIS is thought not to be at risk of imminent breakup due to its compressive stress regime, making the ice shelf a safe working environment. The proposed 4-year project will conduct a 27-month period (November 2019 - January 2022) of measurements on the GVIIS. Seismometers, global positioning system (GPS), water pressure transducers, two automatic weather stations, and thermistor strings will be deployed to record fracture seismicity, ice shelf flexure, water depths, and surface and subsurface melting, respectively, in and around identified meltwater features. These instruments will be deployed in a 20 x 20 km field area immediately adjacent to BAS's Fossil Bluff Station. Field data will be used to validate and extend the team's existing approach to modelling ice-shelf flexure and stress that can lead to hydrofracture, drainage of surface water to the ocean below, and possible Larsen-B style ice-shelf instability.

PI Willis (together with collaborators funded via the NSF component of the grant: Banwell, MacAyeal and Stevens) will engage in a number of specific outreach and community activities designed to enhance the societal value of the science conducted. PI Willis is based at the Scott Polar Research Institute (SPRI), U. Cambridge, which has the largest polar museum in the UK with evolving exhibits showcasing current science and regular outreach programs extending into the local and regional communities, especially those in disadvantaged areas. The museum had over 50,000 visitors in 2017, including around 10,000 young people under 18. Over 17,000 visitors accessed the museum's online educational resources in 2017. Willis will work with the full time museum curator to produce an exhibit for both the museum and online which showcases our proposed ice-shelf research. Willis is also a regular contributor to the annual University Science Festival, where he will also showcase the proposed work in the form of a 'hands on' physical model of ice shelves aimed at young children, and a public lecture aimed at older children and adults.

The three NSF-funded collaborators will also engage in a range of outreach activities. Highlights include:

PI Banwell will continue to develop the Antarctic science/climate change component to a childrens' iPad/tablet app called 'Molly's World' a project led by Richard Weston, former Professor at Cardiff University, UK. The freely available app will be an ideal vehicle for reaching large numbers of children.

PI MacAyeal will continue interaction with an artist consortium called Luftwerk. With MacAyeal's help, this artist consortium developed the 'White Wanderer' display for an outdoor public space in the city of Chicago to draw attention to climate change and the large iceberg that calved from Larsen C, which made the New Yorker Magazine's top 10 sounds for 2017.

PI Stevens will continue to engage with the public through Columbia University, which hosts many outreach events in New York City throughout the year. Stevens will be an active participant in the LDEO Open House, Women in Science Graduate Research Symposium, Girls in Science and Engineering Day at the Intrepid Museum, and will strengthen her community ties in New York City, by working with the Climate Museum to develop programming on surface melt on Antarctic ice shelves.

Broader-impact activities will also involve developing and maintaining a website that will be hosted at U. Colorado Boulder, but mirrored by SPRI, University of Cambridge, designed to give non-scientists a vivid and interesting overview of the project. The website will also have some content intended for the glaciological community, and will enable the exchange of ideas about the project's methods and results, as well as to stimulate similar science by others. A dedicated Twitter account will also be set-up and updated regularly.