12 GREENLAND BASAL WATER CONDITIONS SUBGLACIAL HYDROLOGY EXERTS PRIMARY CONTROL ON ICE FLUX, THE REDISTRIBUTION OF MELT WATER, AND SEDIMENT MOVEMENT FOR THE GREENLAND ICE SHEET. THEREFORE, UNDERSTANDING THE BASE WINTER STATE OF THE HYDROLOGIC ENVIRONMENT ALONG THE BED OF GREENLAND IS OF CRITICAL IMPORTANCE AS THE BASE STATE IS KEY TO UNDERSTANDING FUTURE CHANGES. SPECIFICALLY, THE BASE STATE INFORMS HOW THE SUBGLACIAL DRAINAGE CAN CHANGE AND, ULTIMATELY, HOW THE GREENLAND ICE SHEET REORGANIZES IN RESPONSE TO EXTERNAL FORCING, INCLUDING SEASONAL VARIATIONS AND LONG-TERM CLIMATE CHANGES. RECENT ADVANCES IN AIRBORNE RADAR SOUNDING TECHNOLOGY AND ANALYSIS APPROACHES COUPLED WITH INCREASED SURVEY COVERAGE AND DENSITY ACROSS GREENLAND PROVIDE A UNIQUE OPPORTUNITY FOR CHARACTERIZING THE BASAL WATER SYSTEM. HOWEVER, MUCH OF THE DATA REMAINS UNDERUTILIZED AND CAN BE EXPLOITED FURTHER TO OBTAIN ROBUST ESTIMATES OF HYDROLOGIC CONDITIONS. HERE, WE PROPOSE TO OBSERVATIONALLY CONSTRAIN THESE WATER SYSTEMS FOR THREE CATCHMENTS WITH RELATIVELY DENSE COVERAGE AS A PART OF NASAS OPERATION ICE BRIDGE MISSION: JAKOBSHAVN ISBRAE, PETERMANN GLACIER, AND THE NORTHEAST GREENLAND ICE STREAM (ZACHARAIE/79 NORTH GLACIERS). OUR RESEARCH PLAN INCLUDES (1) CHARACTERIZING THE DISTRIBUTION OF SUBGLACIAL WATER, INCLUDING WHERE THE BED IS FROZEN AND THAWED, (2) ESTIMATING THE ROUGHNESS AND CATCHMENT TOPOGRAPHY AT SCALES RELEVANT TO THE HYDROLOGIC SYSTEM AND (3) USING THESE TO UNDERSTAND THE SPATIAL VARIATION IN PROCESSES OCCURRING ALONG THE BED, WITH THE GOAL OF UNDERSTAND THE DIRECTIONALITY OF FLOW AND THE VARIATION RESULTING FROM THE DIFFERENCE BETWEEN THE ICE AND WATER PRESSURES. SIMILAR STUDIES HAVE PROVED SUCCESSFUL FOR THE THWAITES GLACIER CATCHMENT IN WEST ANTARCTICA, BUT THE RADAR SYSTEMS USED TO COLLECT DATA OPERATION ICE BRIDGE OVER GREENLAND ARE SIGNIFICANTLY DIFFERENT AND REQUIRE BOTH THE ADAPTATION OF TECHNIQUES AND DEVELOPMENT OF NEW CONCEPTS TO CHARACTERIZE THE GREENLAND SUBGLACIAL SYSTEMS. THESE NEW CONCEPTS INCLUDE EXPANDING EXISTING BED CHARACTERIZATION TECHNIQUES TO TAKE ADVANTAGE OF CROSS-TRACK INFORMATION AVAILABLE IN THE CRESIS MCORDS MULTI-CHANNEL RADAR SOUNDER. THIS EXPANSION WILL PROVIDE IMPROVED BED ROUGHNESS AND SMALL-SCALE TOPOGRAPHY ESTIMATES. WE WILL USE THE STATISTICS OF THE SAMPLED AREAS TO POPULATE NEARBY AREAS BETWEEN SURVEY LINES TO PROVIDE HIGHER RESOLUTION AND MORE GEOSTATISTICALLY CONSISTENT BED TOPOGRAPHIES FOR WATER ROUTING THAN OTHER INTERPOLATION APPROACHES. WE AIM TO USE THESE IN ENSEMBLE FASHION TO QUANTIFY THE OVERALL STRUCTURE OF THE SUBGLACIAL WATER SYSTEM. WHILE COMMONLY USED SUBGLACIAL ROUTING ALGORITHMS GIVE A FLAVOR FOR WHERE WATER CAN FLOW, THEY ARE ALSO SIMPLISTIC BECAUSE THEY DO NOT INCLUDE OR PREDICT DIRECTIONALITY INFORMATION. SUCH INFORMATION IS FUNDAMENTAL TO WATER FLOW AND APPEARS IN THE HYDRAULIC CONDUCTIVITY. WE PLAN TO ESTIMATE THE DIRECTIONAL INFORMATION OF THE WATER PATHWAYS FROM BED ROUGHNESS, THERMAL REGIME, EFFECTIVE PRESSURE AND WATER DEPTH. THEREFORE, WE AIM TO USE THE RADAR JOINTLY WITH IMPROVED MODELS TO PROVIDE AN ENHANCED THE UNDERSTANDING OF HYDROLOGIC CONDITIONS AT THE BED OF THE GREENLAND ICE SHEET. TOGETHER, OUR OBJECTIVES WILL PROVIDE THE FIRST COMMON TEMPLATE FOR UNDERSTANDING THE HYDROLOGY OF THREE DIFFERENT CATCHMENTS. WORK PROPOSED HERE ALSO INCLUDES MEMBERS OF THE RADAR ENGINEERING, RADIOGLACIOLOGY, AND SUBGLACIAL HYDROLOGY COMMUNITIES IN ORDER TO FACILITATE A COMMON UNDERSTANDING OF RADAR INSTRUMENT CAPABILITIES AND SIGNAL INFORMATION IN CONSTRAINING GLACIOLOGICAL OBSERVABLES. WE EXPECT THIS PLAN TO LEAD TO FURTHER DEVELOPMENTS FOR UNDERSTANDING SUBGLACIAL DRAINAGE, BOTH FROM THE PERSPECTIVE OF OPTIMIZING RADAR DATA COLLECTION AND PROCESSING AS WELL AS UNDERSTANDING THE ICE FLOW AND DISCHARGE ALONG THE BED AT LOCAL AND REGIONAL SCALES FOR THE ICE SHEET. Funding Only Action ($4) 10/25/22 Not listed GREENLAND BASAL WATER CONDITIONS SUBGLACIAL HYDROLOGY EXERTS PRIMARY CONTROL ON ICE FLUX THE REDISTRIBUTION OF MELT WATER AND SEDIMENT MOVEMENT FOR THE GREENLAND ICE SHEET. THEREFORE UNDERSTANDING THE BASE WINTER STATE OF THE HYDROLOGIC ENVIRONMENT ALONG THE BED OF GREENLAND IS OF CRITICAL IMPORTANCE AS THE BASE STATE IS KEY TO UNDERSTANDING FUTURE CHANGES. SPECIFICALLY THE BASE STATE INFORMS HOW THE SUBGLACIAL DRAINAGE CAN CHANGE AND ULTIMATELY HOW THE GREENLAND ICE SHEET REORGANIZES IN RESPONSE TO EXTERNAL FORCING INCLUDING SEASONAL VARIATIONS AND LONG-TERM CLIMATE CHANGES. RECENT ADVANCES IN AIRBORNE RADAR SOUNDING TECHNOLOGY AND ANALYSIS APPROACHES COUPLED WITH INCREASED SURVEY COVERAGE AND DENSITY ACROSS GREENLAND PROVIDE A UNIQUE OPPORTUNITY FOR CHARACTERIZING THE BASAL WATER SYSTEM. HOWEVER MUCH OF THE DATA REMAINS UNDERUTILIZED AND CAN BE EXPLOITED FURTHER TO OBTAIN ROBUST ESTIMATES OF HYDROLOGIC CONDITIONS. HERE WE PROPOSE TO OBSERVATIONALLY CONSTRAIN THESE WATER SYSTEMS FOR THREE CATCHMENTS WITH RELATIVELY DENSE COVERAGE AS A PART OF NASAS OPERATION ICE BRIDGE MISSION: JAKOBSHAVN ISBRAE PETERMANN GLACIER AND THE NORTHEAST GREENLAND ICE STREAM (ZACHARAIE/79 NORTH GLACIERS). OUR RESEARCH PLAN INCLUDES (1) CHARACTERIZING THE DISTRIBUTION OF SUBGLACIAL WATER INCLUDING WHERE THE BED IS FROZEN AND THAWED (2) ESTIMATING THE ROUGHNESS AND CATCHMENT TOPOGRAPHY AT SCALES RELEVANT TO THE HYDROLOGIC SYSTEM AND (3) USING THESE TO UNDERSTAND THE SPATIAL VARIATION IN PROCESSES OCCURRING ALONG THE BED WITH THE GOAL OF UNDERSTAND THE DIRECTIONALITY OF FLOW AND THE VARIATION RESULTING FROM THE DIFFERENCE BETWEEN THE ICE AND WATER PRESSURES. SIMILAR STUDIES HAVE PROVED SUCCESSFUL FOR THE THWAITES GLACIER CATCHMENT IN WEST ANTARCTICA BUT THE RADAR SYSTEMS USED TO COLLECT DATA OPERATION ICE BRIDGE OVER GREENLAND ARE SIGNIFICANTLY DIFFERENT AND REQUIRE BOTH THE ADAPTATION OF TECHNIQUES AND DEVELOPMENT OF NEW CONCEPTS TO CHARACTERIZE THE GREENLAND SUBGLACIAL SYSTEMS. THESE NEW CONCEPTS INCLUDE EXPANDING EXISTING BED CHARACTERIZATION TECHNIQUES TO TAKE ADVANTAGE OF CROSS-TRACK INFORMATION AVAILABLE IN THE CRESIS MCORDS MULTI-CHANNEL RADAR SOUNDER. THIS EXPANSION WILL PROVIDE IMPROVED BED ROUGHNESS AND SMALL-SCALE TOPOGRAPHY ESTIMATES. WE WILL USE THE STATISTICS OF THE SAMPLED AREAS TO POPULATE NEARBY AREAS BETWEEN SURVEY LINES TO PROVIDE HIGHER RESOLUTION AND MORE GEOSTATISTICALLY CONSISTENT BED TOPOGRAPHIES FOR WATER ROUTING THAN OTHER INTERPOLATION APPROACHES. WE AIM TO USE THESE IN ENSEMBLE FASHION TO QUANTIFY THE OVERALL STRUCTURE OF THE SUBGLACIAL WATER SYSTEM. WHILE COMMONLY USED SUBGLACIAL ROUTING ALGORITHMS GIVE A FLAVOR FOR WHERE WATER CAN FLOW THEY ARE ALSO SIMPLISTIC BECAUSE THEY DO NOT INCLUDE OR PREDICT DIRECTIONALITY INFORMATION. SUCH INFORMATION IS FUNDAMENTAL TO WATER FLOW AND APPEARS IN THE HYDRAULIC CONDUCTIVITY. WE PLAN TO ESTIMATE THE DIRECTIONAL INFORMATION OF THE WATER PATHWAYS FROM BED ROUGHNESS THERMAL REGIME EFFECTIVE PRESSURE AND WATER DEPTH. THEREFORE WE AIM TO USE THE RADAR JOINTLY WITH IMPROVED MODELS TO PROVIDE AN ENHANCED THE UNDERSTANDING OF HYDROLOGIC CONDITIONS AT THE BED OF THE GREENLAND ICE SHEET. TOGETHER OUR OBJECTIVES WILL PROVIDE THE FIRST COMMON TEMPLATE FOR UNDERSTANDING THE HYDROLOGY OF THREE DIFFERENT CATCHMENTS. WORK PROPOSED HERE ALSO INCLUDES MEMBERS OF THE RADAR ENGINEERING RADIOGLACIOLOGY AND SUBGLACIAL HYDROLOGY COMMUNITIES IN ORDER TO FACILITATE A COMMON UNDERSTANDING OF RADAR INSTRUMENT CAPABILITIES AND SIGNAL INFORMATION IN CONSTRAINING GLACIOLOGICAL OBSERVABLES. WE EXPECT THIS PLAN TO LEAD TO FURTHER DEVELOPMENTS FOR UNDERSTANDING SUBGLACIAL DRAINAGE BOTH FROM THE PERSPECTIVE OF OPTIMIZING RADAR DATA COLLECTION AND PROCESSING AS WELL AS UNDERSTANDING THE ICE FLOW AND DISCHARGE ALONG THE BED AT LOCAL AND REGIONAL SCALES FOR THE ICE SHEET. ($4) 10/25/22 Not listed GREENLAND BASAL WATER CONDITIONS SUBGLACIAL HYDROLOGY EXERTS PRIMARY CONTROL ON ICE FLUX THE REDISTRIBUTION OF MELT WATER AND SEDIMENT MOVEMENT FOR THE GREENLAND ICE SHEET. THEREFORE UNDERSTANDING THE BASE WINTER STATE OF THE HYDROLOGIC ENVIRONMENT ALONG THE BED OF GREENLAND IS OF CRITICAL IMPORTANCE AS THE BASE STATE IS KEY TO UNDERSTANDING FUTURE CHANGES. SPECIFICALLY THE BASE STATE INFORMS HOW THE SUBGLACIAL DRAINAGE CAN CHANGE AND ULTIMATELY HOW THE GREENLAND ICE SHEET REORGANIZES IN RESPONSE TO EXTERNAL FORCING INCLUDING SEASONAL VARIATIONS AND LONG-TERM CLIMATE CHANGES. RECENT ADVANCES IN AIRBORNE RADAR SOUNDING TECHNOLOGY AND ANALYSIS APPROACHES COUPLED WITH INCREASED SURVEY COVERAGE AND DENSITY ACROSS GREENLAND PROVIDE A UNIQUE OPPORTUNITY FOR CHARACTERIZING THE BASAL WATER SYSTEM. HOWEVER MUCH OF THE DATA REMAINS UNDERUTILIZED AND CAN BE EXPLOITED FURTHER TO OBTAIN ROBUST ESTIMATES OF HYDROLOGIC CONDITIONS. HERE WE PROPOSE TO OBSERVATIONALLY CONSTRAIN THESE WATER SYSTEMS FOR THREE CATCHMENTS WITH RELATIVELY DENSE COVERAGE AS A PART OF NASAS OPERATION ICE BRIDGE MISSION: JAKOBSHAVN ISBRAE PETERMANN GLACIER AND THE NORTHEAST GREENLAND ICE STREAM (ZACHARAIE/79 NORTH GLACIERS). OUR RESEARCH PLAN INCLUDES (1) CHARACTERIZING THE DISTRIBUTION OF SUBGLACIAL WATER INCLUDING WHERE THE BED IS FROZEN AND THAWED (2) ESTIMATING THE ROUGHNESS AND CATCHMENT TOPOGRAPHY AT SCALES RELEVANT TO THE HYDROLOGIC SYSTEM AND (3) USING THESE TO UNDERSTAND THE SPATIAL VARIATION IN PROCESSES OCCURRING ALONG THE BED WITH THE GOAL OF UNDERSTAND THE DIRECTIONALITY OF FLOW AND THE VARIATION RESULTING FROM THE DIFFERENCE BETWEEN THE ICE AND WATER PRESSURES. SIMILAR STUDIES HAVE PROVED SUCCESSFUL FOR THE THWAITES GLACIER CATCHMENT IN WEST ANTARCTICA BUT THE RADAR SYSTEMS USED TO COLLECT DATA OPERATION ICE BRIDGE OVER GREENLAND ARE SIGNIFICANTLY DIFFERENT AND REQUIRE BOTH THE ADAPTATION OF TECHNIQUES AND DEVELOPMENT OF NEW CONCEPTS TO CHARACTERIZE THE GREENLAND SUBGLACIAL SYSTEMS. THESE NEW CONCEPTS INCLUDE EXPANDING EXISTING BED CHARACTERIZATION TECHNIQUES TO TAKE ADVANTAGE OF CROSS-TRACK INFORMATION AVAILABLE IN THE CRESIS MCORDS MULTI-CHANNEL RADAR SOUNDER. THIS EXPANSION WILL PROVIDE IMPROVED BED ROUGHNESS AND SMALL-SCALE TOPOGRAPHY ESTIMATES. WE WILL USE THE STATISTICS OF THE SAMPLED AREAS TO POPULATE NEARBY AREAS BETWEEN SURVEY LINES TO PROVIDE HIGHER RESOLUTION AND MORE GEOSTATISTICALLY CONSISTENT BED TOPOGRAPHIES FOR WATER ROUTING THAN OTHER INTERPOLATION APPROACHES. WE AIM TO USE THESE IN ENSEMBLE FASHION TO QUANTIFY THE OVERALL STRUCTURE OF THE SUBGLACIAL WATER SYSTEM. WHILE COMMONLY USED SUBGLACIAL ROUTING ALGORITHMS GIVE A FLAVOR FOR WHERE WATER CAN FLOW THEY ARE ALSO SIMPLISTIC BECAUSE THEY DO NOT INCLUDE OR PREDICT DIRECTIONALITY INFORMATION. SUCH INFORMATION IS FUNDAMENTAL TO WATER FLOW AND APPEARS IN THE HYDRAULIC CONDUCTIVITY. WE PLAN TO ESTIMATE THE DIRECTIONAL INFORMATION OF THE WATER PATHWAYS FROM BED ROUGHNESS THERMAL REGIME EFFECTIVE PRESSURE AND WATER DEPTH. THEREFORE WE AIM TO USE THE RADAR JOINTLY WITH IMPROVED MODELS TO PROVIDE AN ENHANCED THE UNDERSTANDING OF HYDROLOGIC CONDITIONS AT THE BED OF THE GREENLAND ICE SHEET. TOGETHER OUR OBJECTIVES WILL PROVIDE THE FIRST COMMON TEMPLATE FOR UNDERSTANDING THE HYDROLOGY OF THREE DIFFERENT CATCHMENTS. WORK PROPOSED HERE ALSO INCLUDES MEMBERS OF THE RADAR ENGINEERING RADIOGLACIOLOGY AND SUBGLACIAL HYDROLOGY COMMUNITIES IN ORDER TO FACILITATE A COMMON UNDERSTANDING OF RADAR INSTRUMENT CAPABILITIES AND SIGNAL INFORMATION IN CONSTRAINING GLACIOLOGICAL OBSERVABLES. WE EXPECT THIS PLAN TO LEAD TO FURTHER DEVELOPMENTS FOR UNDERSTANDING SUBGLACIAL DRAINAGE BOTH FROM THE PERSPECTIVE OF OPTIMIZING RADAR DATA COLLECTION AND PROCESSING AS WELL AS UNDERSTANDING THE ICE FLOW AND DISCHARGE ALONG THE BED AT LOCAL AND REGIONAL SCALES FOR THE ICE SHEET. $0 8/25/21 11 GREENLAND BASAL WATER CONDITIONS SUBGLACIAL HYDROLOGY EXERTS PRIMARY CONTROL ON ICE FLUX, THE REDISTRIBUTION OF MELT WATER, AND SEDIMENT MOVEMENT FOR THE GREENLAND ICE SHEET. THEREFORE, UNDERSTANDING THE BASE WINTER STATE OF THE HYDROLOGIC ENVIRONMENT ALONG THE BED OF GREENLAND IS OF CRITICAL IMPORTANCE AS THE BASE STATE IS KEY TO UNDERSTANDING FUTURE CHANGES. SPECIFICALLY, THE BASE STATE INFORMS HOW THE SUBGLACIAL DRAINAGE CAN CHANGE AND, ULTIMATELY, HOW THE GREENLAND ICE SHEET REORGANIZES IN RESPONSE TO EXTERNAL FORCING, INCLUDING SEASONAL VARIATIONS AND LONG-TERM CLIMATE CHANGES. RECENT ADVANCES IN AIRBORNE RADAR SOUNDING TECHNOLOGY AND ANALYSIS APPROACHES COUPLED WITH INCREASED SURVEY COVERAGE AND DENSITY ACROSS GREENLAND PROVIDE A UNIQUE OPPORTUNITY FOR CHARACTERIZING THE BASAL WATER SYSTEM. HOWEVER, MUCH OF THE DATA REMAINS UNDERUTILIZED AND CAN BE EXPLOITED FURTHER TO OBTAIN ROBUST ESTIMATES OF HYDROLOGIC CONDITIONS. HERE, WE PROPOSE TO OBSERVATIONALLY CONSTRAIN THESE WATER SYSTEMS FOR THREE CATCHMENTS WITH RELATIVELY DENSE COVERAGE AS A PART OF NASAS OPERATION ICE BRIDGE MISSION: JAKOBSHAVN ISBRAE, PETERMANN GLACIER, AND THE NORTHEAST GREENLAND ICE STREAM (ZACHARAIE/79 NORTH GLACIERS). OUR RESEARCH PLAN INCLUDES (1) CHARACTERIZING THE DISTRIBUTION OF SUBGLACIAL WATER, INCLUDING WHERE THE BED IS FROZEN AND THAWED, (2) ESTIMATING THE ROUGHNESS AND CATCHMENT TOPOGRAPHY AT SCALES RELEVANT TO THE HYDROLOGIC SYSTEM AND (3) USING THESE TO UNDERSTAND THE SPATIAL VARIATION IN PROCESSES OCCURRING ALONG THE BED, WITH THE GOAL OF UNDERSTAND THE DIRECTIONALITY OF FLOW AND THE VARIATION RESULTING FROM THE DIFFERENCE BETWEEN THE ICE AND WATER PRESSURES. SIMILAR STUDIES HAVE PROVED SUCCESSFUL FOR THE THWAITES GLACIER CATCHMENT IN WEST ANTARCTICA, BUT THE RADAR SYSTEMS USED TO COLLECT DATA OPERATION ICE BRIDGE OVER GREENLAND ARE SIGNIFICANTLY DIFFERENT AND REQUIRE BOTH THE ADAPTATION OF TECHNIQUES AND DEVELOPMENT OF NEW CONCEPTS TO CHARACTERIZE THE GREENLAND SUBGLACIAL SYSTEMS. THESE NEW CONCEPTS INCLUDE EXPANDING EXISTING BED CHARACTERIZATION TECHNIQUES TO TAKE ADVANTAGE OF CROSS-TRACK INFORMATION AVAILABLE IN THE CRESIS MCORDS MULTI-CHANNEL RADAR SOUNDER. THIS EXPANSION WILL PROVIDE IMPROVED BED ROUGHNESS AND SMALL-SCALE TOPOGRAPHY ESTIMATES. WE WILL USE THE STATISTICS OF THE SAMPLED AREAS TO POPULATE NEARBY AREAS BETWEEN SURVEY LINES TO PROVIDE HIGHER RESOLUTION AND MORE GEOSTATISTICALLY CONSISTENT BED TOPOGRAPHIES FOR WATER ROUTING THAN OTHER INTERPOLATION APPROACHES. WE AIM TO USE THESE IN ENSEMBLE FASHION TO QUANTIFY THE OVERALL STRUCTURE OF THE SUBGLACIAL WATER SYSTEM. WHILE COMMONLY USED SUBGLACIAL ROUTING ALGORITHMS GIVE A FLAVOR FOR WHERE WATER CAN FLOW, THEY ARE ALSO SIMPLISTIC BECAUSE THEY DO NOT INCLUDE OR PREDICT DIRECTIONALITY INFORMATION. SUCH INFORMATION IS FUNDAMENTAL TO WATER FLOW AND APPEARS IN THE HYDRAULIC CONDUCTIVITY. WE PLAN TO ESTIMATE THE DIRECTIONAL INFORMATION OF THE WATER PATHWAYS FROM BED ROUGHNESS, THERMAL REGIME, EFFECTIVE PRESSURE AND WATER DEPTH. THEREFORE, WE AIM TO USE THE RADAR JOINTLY WITH IMPROVED MODELS TO PROVIDE AN ENHANCED THE UNDERSTANDING OF HYDROLOGIC CONDITIONS AT THE BED OF THE GREENLAND ICE SHEET. TOGETHER, OUR OBJECTIVES WILL PROVIDE THE FIRST COMMON TEMPLATE FOR UNDERSTANDING THE HYDROLOGY OF THREE DIFFERENT CATCHMENTS. WORK PROPOSED HERE ALSO INCLUDES MEMBERS OF THE RADAR ENGINEERING, RADIOGLACIOLOGY, AND SUBGLACIAL HYDROLOGY COMMUNITIES IN ORDER TO FACILITATE A COMMON UNDERSTANDING OF RADAR INSTRUMENT CAPABILITIES AND SIGNAL INFORMATION IN CONSTRAINING GLACIOLOGICAL OBSERVABLES. WE EXPECT THIS PLAN TO LEAD TO FURTHER DEVELOPMENTS FOR UNDERSTANDING SUBGLACIAL DRAINAGE, BOTH FROM THE PERSPECTIVE OF OPTIMIZING RADAR DATA COLLECTION AND PROCESSING AS WELL AS UNDERSTANDING THE ICE FLOW AND DISCHARGE ALONG THE BED AT LOCAL AND REGIONAL SCALES FOR THE ICE SHEET. Other Administrative Action $0 8/25/21 10 GREENLAND BASAL WATER CONDITIONS SUBGLACIAL HYDROLOGY EXERTS PRIMARY CONTROL ON ICE FLUX, THE REDISTRIBUTION OF MELT WATER, AND SEDIMENT MOVEMENT FOR THE GREENLAND ICE SHEET. THEREFORE, UNDERSTANDING THE BASE WINTER STATE OF THE HYDROLOGIC ENVIRONMENT ALONG THE BED OF GREENLAND IS OF CRITICAL IMPORTANCE AS THE BASE STATE IS KEY TO UNDERSTANDING FUTURE CHANGES. SPECIFICALLY, THE BASE STATE INFORMS HOW THE SUBGLACIAL DRAINAGE CAN CHANGE AND, ULTIMATELY, HOW THE GREENLAND ICE SHEET REORGANIZES IN RESPONSE TO EXTERNAL FORCING, INCLUDING SEASONAL VARIATIONS AND LONG-TERM CLIMATE CHANGES. RECENT ADVANCES IN AIRBORNE RADAR SOUNDING TECHNOLOGY AND ANALYSIS APPROACHES COUPLED WITH INCREASED SURVEY COVERAGE AND DENSITY ACROSS GREENLAND PROVIDE A UNIQUE OPPORTUNITY FOR CHARACTERIZING THE BASAL WATER SYSTEM. HOWEVER, MUCH OF THE DATA REMAINS UNDERUTILIZED AND CAN BE EXPLOITED FURTHER TO OBTAIN ROBUST ESTIMATES OF HYDROLOGIC CONDITIONS. HERE, WE PROPOSE TO OBSERVATIONALLY CONSTRAIN THESE WATER SYSTEMS FOR THREE CATCHMENTS WITH RELATIVELY DENSE COVERAGE AS A PART OF NASAS OPERATION ICE BRIDGE MISSION: JAKOBSHAVN ISBRAE, PETERMANN GLACIER, AND THE NORTHEAST GREENLAND ICE STREAM (ZACHARAIE/79 NORTH GLACIERS). OUR RESEARCH PLAN INCLUDES (1) CHARACTERIZING THE DISTRIBUTION OF SUBGLACIAL WATER, INCLUDING WHERE THE BED IS FROZEN AND THAWED, (2) ESTIMATING THE ROUGHNESS AND CATCHMENT TOPOGRAPHY AT SCALES RELEVANT TO THE HYDROLOGIC SYSTEM AND (3) USING THESE TO UNDERSTAND THE SPATIAL VARIATION IN PROCESSES OCCURRING ALONG THE BED, WITH THE GOAL OF UNDERSTAND THE DIRECTIONALITY OF FLOW AND THE VARIATION RESULTING FROM THE DIFFERENCE BETWEEN THE ICE AND WATER PRESSURES. SIMILAR STUDIES HAVE PROVED SUCCESSFUL FOR THE THWAITES GLACIER CATCHMENT IN WEST ANTARCTICA, BUT THE RADAR SYSTEMS USED TO COLLECT DATA OPERATION ICE BRIDGE OVER GREENLAND ARE SIGNIFICANTLY DIFFERENT AND REQUIRE BOTH THE ADAPTATION OF TECHNIQUES AND DEVELOPMENT OF NEW CONCEPTS TO CHARACTERIZE THE GREENLAND SUBGLACIAL SYSTEMS. THESE NEW CONCEPTS INCLUDE EXPANDING EXISTING BED CHARACTERIZATION TECHNIQUES TO TAKE ADVANTAGE OF CROSS-TRACK INFORMATION AVAILABLE IN THE CRESIS MCORDS MULTI-CHANNEL RADAR SOUNDER. THIS EXPANSION WILL PROVIDE IMPROVED BED ROUGHNESS AND SMALL-SCALE TOPOGRAPHY ESTIMATES. WE WILL USE THE STATISTICS OF THE SAMPLED AREAS TO POPULATE NEARBY AREAS BETWEEN SURVEY LINES TO PROVIDE HIGHER RESOLUTION AND MORE GEOSTATISTICALLY CONSISTENT BED TOPOGRAPHIES FOR WATER ROUTING THAN OTHER INTERPOLATION APPROACHES. WE AIM TO USE THESE IN ENSEMBLE FASHION TO QUANTIFY THE OVERALL STRUCTURE OF THE SUBGLACIAL WATER SYSTEM. WHILE COMMONLY USED SUBGLACIAL ROUTING ALGORITHMS GIVE A FLAVOR FOR WHERE WATER CAN FLOW, THEY ARE ALSO SIMPLISTIC BECAUSE THEY DO NOT INCLUDE OR PREDICT DIRECTIONALITY INFORMATION. SUCH INFORMATION IS FUNDAMENTAL TO WATER FLOW AND APPEARS IN THE HYDRAULIC CONDUCTIVITY. WE PLAN TO ESTIMATE THE DIRECTIONAL INFORMATION OF THE WATER PATHWAYS FROM BED ROUGHNESS, THERMAL REGIME, EFFECTIVE PRESSURE AND WATER DEPTH. THEREFORE, WE AIM TO USE THE RADAR JOINTLY WITH IMPROVED MODELS TO PROVIDE AN ENHANCED THE UNDERSTANDING OF HYDROLOGIC CONDITIONS AT THE BED OF THE GREENLAND ICE SHEET. TOGETHER, OUR OBJECTIVES WILL PROVIDE THE FIRST COMMON TEMPLATE FOR UNDERSTANDING THE HYDROLOGY OF THREE DIFFERENT CATCHMENTS. WORK PROPOSED HERE ALSO INCLUDES MEMBERS OF THE RADAR ENGINEERING, RADIOGLACIOLOGY, AND SUBGLACIAL HYDROLOGY COMMUNITIES IN ORDER TO FACILITATE A COMMON UNDERSTANDING OF RADAR INSTRUMENT CAPABILITIES AND SIGNAL INFORMATION IN CONSTRAINING GLACIOLOGICAL OBSERVABLES. WE EXPECT THIS PLAN TO LEAD TO FURTHER DEVELOPMENTS FOR UNDERSTANDING SUBGLACIAL DRAINAGE, BOTH FROM THE PERSPECTIVE OF OPTIMIZING RADAR DATA COLLECTION AND PROCESSING AS WELL AS UNDERSTANDING THE ICE FLOW AND DISCHARGE ALONG THE BED AT LOCAL AND REGIONAL SCALES FOR THE ICE SHEET. Other Administrative Action $0 6/10/21