Periodic Reporting for period 4 - RESPONDER (Resolving subglacial properties, hydrological networks and dynamic evolution of ice flow on the Greenland Ice Sheet)
Periodo di rendicontazione: 2021-04-01 al 2022-09-30
The Greenland Ice Sheet is losing mass at a growing rate and is today contributing to global sea level rise at a rate of 1 mm/year. The most severe changes occur in the drainage basins of marine-terminating glaciers, which flow rapidly and drain 88% of the ice sheet. The latest report by the Intergovernmental Panel on Climate Change concluded that the widespread acceleration of these glaciers in recent years was a response to interaction with the ocean; yet, observations have since shown that many of these glaciers respond to the growing volume of surface meltwater, which reaches the bed through fractures and conduits. The mechanism whereby these hydrological connections form is unknown, and there is a lack of observational constraints to assess how the basal drainage system responds when surface water is injected at the bed. This lack of knowledge is a major source of uncertainty in the current generation of ice sheet models used to predict global sea level rise.
The fundamental goal of RESPONDER is to understand how hydrological networks at the base of the Greenland Ice Sheet evolve over seasons and over multiple years, and how this evolution impacts on ice flow in the interior and at the coast. The work in RESPONDER takes place on Sermeq Kujaleq (Store Glacier) and the aims are:
1) to identify glaciological ‘hotspots’ and sites for subglacial access drilling and borehole exploration by tracking hydrological pathways
2) to observe and quantify the hydrological networks linking the glacier bed to the surface of the ice sheet
3) to predict the co-evolution of ice flow and hydrological networks in the Store Glacier drainage basin, and assess the vulnerability of the Greenland Ice Sheet as a whole
The fundamental goal of RESPONDER is to understand how hydrological networks at the base of the Greenland Ice Sheet evolve over seasons and over multiple years, and how this evolution impacts on ice flow in the interior and at the coast. The work in RESPONDER takes place on Sermeq Kujaleq (Store Glacier) and the aims are:
1) to identify glaciological ‘hotspots’ and sites for subglacial access drilling and borehole exploration by tracking hydrological pathways
2) to observe and quantify the hydrological networks linking the glacier bed to the surface of the ice sheet
3) to predict the co-evolution of ice flow and hydrological networks in the Store Glacier drainage basin, and assess the vulnerability of the Greenland Ice Sheet as a whole
Work package 1 in RESPONDER produced technological innovation. By integrating carrier-phase GPS into bespoke, custom-designed UAV systems the project pioneered a new and novel approach, which allows photogrammetric reconstruction of the ice sheet surface with extremely high (10 cm) spatial resolution and equally high accuracy. With multiple surveys conducted when a supraglacial lake drained rapidly in 2018, the team captured the ice sheet’s response as a hydrological connection was between surface and bed was made. This work was published in the Proceedings of the National Academy of Science and reported widely in global news, including National Geographic, Scientific American, CNN, Washington Post and The Times.
This project advanced radio-echo sounding techniques by showing that internal geometry and the base of ice sheets can be captured in 3D. The first record of basal melting from Greenland was a ground-breaking discovery in this project. This finding, also reported in the Proceedings of the National Academy of Science, was reported in >100 global news agencies, including The Times, CNN and Vox. The project also proved the sun can be used as a radio source for basal echo detection and ice thickness measurements.
In work package 2, ten boreholes were drilled at two sites on Sermeq Kujalleq (Store Glacier). Seven boreholes connected with a hydrological system at the glacier base at depths of 953 – 1,043 m below surface. These deep boreholes enabled – for the first time – direct access for instrumentation and observations at the basal interface of a fast-moving outlet glacier in Greenland. Fibre-optic sensing in one of the deep boreholes was a major project success, revealing ice of different types and age as well as the sedimentary nature of the glacier bed. Fibre-optic sensing also produced the most detailed temperature profile to be collected on the Greenland Ice Sheet to date. This discovery was published in Science Advances and reported in global news media.
By bringing together observations and models in work package 3, the RESPONDER project brought new light of the ice flow mechanism. The modelling work introduced a new geostatistical technique, which improved the model resolution and the realisation of ice sheet motion beyond the state of the art. Hence, the project has significantly improved fundamental concepts and the best way in which ice flow can be parameterised theoretically in models.
The team also developed a hydrologically coupled ice flow model. This catchment-scale hydrological model stores water in a distributed cavity system as well as channels, which form and evolve according to the input of meltwater from the surrounding cavities. With feedbacks between i) surface melt, ii) cavity and channel sizes, iii) mechanical friction, iv) ice flow and fracturing, and v) iceberg production, the model offers very realistic simulations and is arguably the most process-rich model to ever be produced.
Over the course of the project, the PI arranged several exhibitions in the Polar Museum in Cambridge, with displays, photographs and scientific instruments. The PI hosted a delegation of 15 Greenlandic youths for the opening of the exhibition: ‘Uummannaq’, which was visited by 25,000 members of the public. A second exhibition (‘Ice from above’) featured drones and aerial imagery acquired in Greenland. Excellent and impactful outreach was made in annual contributions to the Sutton Trust summer school, which is set up to address educational disadvantage and improve social mobility in the UK.
This project advanced radio-echo sounding techniques by showing that internal geometry and the base of ice sheets can be captured in 3D. The first record of basal melting from Greenland was a ground-breaking discovery in this project. This finding, also reported in the Proceedings of the National Academy of Science, was reported in >100 global news agencies, including The Times, CNN and Vox. The project also proved the sun can be used as a radio source for basal echo detection and ice thickness measurements.
In work package 2, ten boreholes were drilled at two sites on Sermeq Kujalleq (Store Glacier). Seven boreholes connected with a hydrological system at the glacier base at depths of 953 – 1,043 m below surface. These deep boreholes enabled – for the first time – direct access for instrumentation and observations at the basal interface of a fast-moving outlet glacier in Greenland. Fibre-optic sensing in one of the deep boreholes was a major project success, revealing ice of different types and age as well as the sedimentary nature of the glacier bed. Fibre-optic sensing also produced the most detailed temperature profile to be collected on the Greenland Ice Sheet to date. This discovery was published in Science Advances and reported in global news media.
By bringing together observations and models in work package 3, the RESPONDER project brought new light of the ice flow mechanism. The modelling work introduced a new geostatistical technique, which improved the model resolution and the realisation of ice sheet motion beyond the state of the art. Hence, the project has significantly improved fundamental concepts and the best way in which ice flow can be parameterised theoretically in models.
The team also developed a hydrologically coupled ice flow model. This catchment-scale hydrological model stores water in a distributed cavity system as well as channels, which form and evolve according to the input of meltwater from the surrounding cavities. With feedbacks between i) surface melt, ii) cavity and channel sizes, iii) mechanical friction, iv) ice flow and fracturing, and v) iceberg production, the model offers very realistic simulations and is arguably the most process-rich model to ever be produced.
Over the course of the project, the PI arranged several exhibitions in the Polar Museum in Cambridge, with displays, photographs and scientific instruments. The PI hosted a delegation of 15 Greenlandic youths for the opening of the exhibition: ‘Uummannaq’, which was visited by 25,000 members of the public. A second exhibition (‘Ice from above’) featured drones and aerial imagery acquired in Greenland. Excellent and impactful outreach was made in annual contributions to the Sutton Trust summer school, which is set up to address educational disadvantage and improve social mobility in the UK.
Over the course of its lifetime, the RESPONDER project delivered:
1. A custom-designed Unmanned Aerial Vehicle (UAV) capable of surveying autonomously along pre-programmed flight paths for up to 1 hour and covering distances of 80-90 km in each flight.
2. A deep hot-water drill, uniquely capable of gaining rapid subglacial access through boreholes drilled in crevassed regions of a fast-moving glacier.
3. Digitalisation of sensors beyond the state of the art allowed more sensors to be installed in each borehole while less power was required to collect the data.
4. A breakthrough scientific advance was achieved using pulsed transmission of light in a fibre-optic cable to measure temperature as well as deformation of ice.
5. Another breakthrough was the ability to image ice sheet's internal geometry and bed in 3D using autonomous radar systems set up on the surface.
6. A ground-breaking discovery was produced using the autonomous radar systems, which also captured day-to-day variations in basal melting with rates that were two orders of magnitude higher than previously reported.
7. The project confirmed that the basal drainage system of ice sheets can be captured remotely with a network of seismometers set up on the surface.
8. A combination of numerical modelling and geostatistical analyses provided a major breakthrough in our understanding of the ice flow mechanism.
9. The grant has implemented iceberg calving and evolving basal drainage systems in a 3D ice flow model written in open-source code. With feedbacks between i) surface melt, ii) channelised network, iii) water sheet, iv) friction, v) subglacial discharge, vi) submarine frontal melt and vii) iceberg calving, the (open-source) model is arguable the most process-rich glacier model to ever be produced
1. A custom-designed Unmanned Aerial Vehicle (UAV) capable of surveying autonomously along pre-programmed flight paths for up to 1 hour and covering distances of 80-90 km in each flight.
2. A deep hot-water drill, uniquely capable of gaining rapid subglacial access through boreholes drilled in crevassed regions of a fast-moving glacier.
3. Digitalisation of sensors beyond the state of the art allowed more sensors to be installed in each borehole while less power was required to collect the data.
4. A breakthrough scientific advance was achieved using pulsed transmission of light in a fibre-optic cable to measure temperature as well as deformation of ice.
5. Another breakthrough was the ability to image ice sheet's internal geometry and bed in 3D using autonomous radar systems set up on the surface.
6. A ground-breaking discovery was produced using the autonomous radar systems, which also captured day-to-day variations in basal melting with rates that were two orders of magnitude higher than previously reported.
7. The project confirmed that the basal drainage system of ice sheets can be captured remotely with a network of seismometers set up on the surface.
8. A combination of numerical modelling and geostatistical analyses provided a major breakthrough in our understanding of the ice flow mechanism.
9. The grant has implemented iceberg calving and evolving basal drainage systems in a 3D ice flow model written in open-source code. With feedbacks between i) surface melt, ii) channelised network, iii) water sheet, iv) friction, v) subglacial discharge, vi) submarine frontal melt and vii) iceberg calving, the (open-source) model is arguable the most process-rich glacier model to ever be produced