Periodic Reporting for period 3 - PALGLAC (Palaeoglaciological advances to understand Earth’s ice sheets by landform analysis)
Período documentado: 2021-10-01 hasta 2023-03-31
Ice sheets regulate Earth’s climate by reflecting sunlight away, enabling suitable temperatures for human habitation. Warming is reducing these ice masses and raising sea level. Glaciologists predict ice loss using computational ice sheet models which interact with climate and oceans, but with caveats highlighting that some processes are inadequately encapsulated. Weather forecasting made a leap in skill by comparing modelled forecasts with actual outcomes to improve physical realism of their models. This project sets out to adopt this data-modelling approach in ice sheet modelling. Given their longer timescales (100-1000s years) we will use geological and geomorphological records of former ice sheets to provide the evidence; the rapidly growing field of palaeoglaciology.
Focussing on the most numerous and spatially-extensive records of palaeo ice sheet activity - glacial landforms - the project aims to revolutionise understanding of past, present and future ice sheets. Our mapping campaign (Work-Package 1), complemented by machine learning techniques (WP2), and will vastly increase the evidence-base. Resolution of how subglacial landforms are generated and how hydrological networks develop (WP3) would be major breakthroughs leading with key implications for ice flow models and hydrological effects on ice dynamics. By pioneering techniques and coding for combining ice sheet models with landform data (WP4) we will improve knowledge of the role of palaeo-ice sheets in Earth system change. Trialling of numerical models in these data-rich environments will highlight deficiencies in process-formulations, leading to better models.
Example figure: From landform mapping and analysis we built a model and scaling metrics of how subglacial water pressurisation can overwhelm the host drainage conduit, with water expanding laterally across the bed, important for controlling ice flow speeds (from Lewington et al 2020).
Focussing on the most numerous and spatially-extensive records of palaeo ice sheet activity - glacial landforms - the project aims to revolutionise understanding of past, present and future ice sheets. Our mapping campaign (Work-Package 1), complemented by machine learning techniques (WP2), and will vastly increase the evidence-base. Resolution of how subglacial landforms are generated and how hydrological networks develop (WP3) would be major breakthroughs leading with key implications for ice flow models and hydrological effects on ice dynamics. By pioneering techniques and coding for combining ice sheet models with landform data (WP4) we will improve knowledge of the role of palaeo-ice sheets in Earth system change. Trialling of numerical models in these data-rich environments will highlight deficiencies in process-formulations, leading to better models.
Example figure: From landform mapping and analysis we built a model and scaling metrics of how subglacial water pressurisation can overwhelm the host drainage conduit, with water expanding laterally across the bed, important for controlling ice flow speeds (from Lewington et al 2020).
Many tens of terabytes of metre-resolution digital elevation data have been downloaded and processed for Fennoscandia and Greenland, and parts of northern Europe and Canada. These data have been used to map over 339,000 landforms covering those recording ice flow direction, subglacial water flow and successive ice margin positions. Much analysis remains to be conducted on these valuable data. Thus far, we have published a model and scaling metrics of subglacial conduits becoming over-pressurised with water that spreads out across the bed; have found amazingly high temporal resolution records (quasi-annual) of ice margin retreat in Canada and Greenland, have published on the former and the latter is still in progress. We have been usefully distracted by some new discoveries on esker enlargements and strange crack systems in sediments adjacent to tunnel valleys, for which we have devised novel explanations that might be correct, and take us in some new directions. We have developed coding routines that plot streamlines of ice sheet flow and which are used to transfer bed roughness to surface roughness. These estimates have been used to forecast supraglacial lake extents for the Greenland Ice Sheet to the year 2300 (paper in review) and are being used on a palaeo ice sheet to assess the extent to which such lake drainage to the bed might influence retreat rates.
Prior to the pandemic we conducted fieldwork in a remote part of NE Greenland and now have samples for dating ice sheet retreat, but our other field activities across northern Europe have been delayed. We have advanced modelling of the creation and development of glacial landforms notably: 1) sedimentation in subglacial water pipes (regarding eskers); 2) spatial and temporal transitions between drumlins and subglacial ribs; and 3) tunnel valleys, subglacial ribs and ice marginal fans. Two papers report on these results and a further two are in final preparation.
On the PalGlac focus on data-modelling integration, two approaches have been devised, coded, published and used in action, namely, 1) scoring ice sheet model performance against observational evidence; 2) using observational evidence to directly nudge or correct model simulations, and another approach just started, 3) using evidence and model simulations to build a statistical emulator of ice sheet models that can advance approaches for modelling experiments. Data-constrained numerical modelling of the British-Irish and Scandinavian ice sheets have been used in glacio-isostatic modelling (i.e. ice mass loading of the lithosphere) to simulate relative sea level variation of the last deglaciation. These results have been used in six publications including one on forecasting 21st century sea levels around Britain and NW Europe.
Prior to the pandemic we conducted fieldwork in a remote part of NE Greenland and now have samples for dating ice sheet retreat, but our other field activities across northern Europe have been delayed. We have advanced modelling of the creation and development of glacial landforms notably: 1) sedimentation in subglacial water pipes (regarding eskers); 2) spatial and temporal transitions between drumlins and subglacial ribs; and 3) tunnel valleys, subglacial ribs and ice marginal fans. Two papers report on these results and a further two are in final preparation.
On the PalGlac focus on data-modelling integration, two approaches have been devised, coded, published and used in action, namely, 1) scoring ice sheet model performance against observational evidence; 2) using observational evidence to directly nudge or correct model simulations, and another approach just started, 3) using evidence and model simulations to build a statistical emulator of ice sheet models that can advance approaches for modelling experiments. Data-constrained numerical modelling of the British-Irish and Scandinavian ice sheets have been used in glacio-isostatic modelling (i.e. ice mass loading of the lithosphere) to simulate relative sea level variation of the last deglaciation. These results have been used in six publications including one on forecasting 21st century sea levels around Britain and NW Europe.
We have now established methods, data processing and coding that permit large volumes of landform data to be acquired, interpreted and used for scoring, or guiding/constraining, numerical ice sheet model simulations. This takes us beyond the state of the art, both in terms of data volume and spatial extent of the useable information, and by integrating previously disparate observational and modelling approaches. We have published on these methodological advances and PalGlac is now leading by example, hopefully we can further direct the field down this route with large gains to be made in both simulations of Earth history and climate and for improvements in robustness of numerical modelling. We have made some glacial geomorphological discoveries, finding new expressions of landforms that require explanation, and of records of ice marginal retreat at an unprecedented, quasi-annual, level of detail.