Periodic Reporting for period 1 - Green2Ice (When was Greenland ‘green’? – Perspectives from basal ice and sediments from ice cores.)
Période du rapport: 2023-04-01 au 2024-09-30
The purpose of the Green2Ice project is to investigate when Greenland was ‘green’ using basal ice and sediments from ice cores, that have been drilled in Greenland during the last 55 years. All the ice cores contain basal material in the deepest and oldest part of the cores, and this material that has been preserved since drilling and until now, still holds undeciphered paleoclimatic messages.
In addition to the basal material available from five previous ice core drilling projects, we will drill a replicate core at the old GRIP drill site at the top point of the Greenland ice sheet (GrIS) to ensure retrieval of sediments and rock material from beneath the summit of the ice sheet.
The breakthrough of Green2Ice is to develop and apply cutting edge dating methods on this unique sample collection and hence to reconstruct the age and the stability of the Greenland ice sheet. By investigating and dating the basal material, we can gain information on the waxing and waning of the Greenland ice sheet in the past, e.g. by establishing when each of the drilling sites was last ice free, and what the conditions were like at that time. One hypothesis we would like to test is if the present ice sheet in Greenland formed at the time of the Mid-Pleistocene Transition (MPT) 1.2-0.8 million years ago, where the glacial/interglacial cycles changed duration from appr. 40,000 years to appr. 100,000 years.
Green2Ice develops, improves and applies novel dating techniques to place constraints on past waxing and waning of the GrIS:
• Cosmogenic radioactive nuclides (26Al/10Be/36Cl, 81Kr), and radiogenic nuclides (40Ar) are used to date the basal ice and the timing of the past exposures of geological debris
• Optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL) are also used on quartz and feldspar grains, respectively, to establish when those grains were last exposed
• Modeling of gas and isotope diffusion
These methods can help us determine when different parts of Greenland were last ice free and for how long the ice-free period lasted.
State-of-the-art methodologies on fossil remains, organic matter, in situ produced and consumed greenhouse gases, and biomolecules will provide insights on the ecosystems and environmental conditions that emerged during past ice-free periods, as well as on subglacial biogeochemical processes.
All the data will be compiled to create a database on the extent of the Greenland ice sheet back in time. This information, will be used in Earth system models and ice sheet models tuned to past climate conditions to establish the climatic sensitivity of the Greenland ice sheet and determine when Greenland last was ice free.
In addition to the basal material available from five previous ice core drilling projects, we will drill a replicate core at the old GRIP drill site at the top point of the Greenland ice sheet (GrIS) to ensure retrieval of sediments and rock material from beneath the summit of the ice sheet.
The breakthrough of Green2Ice is to develop and apply cutting edge dating methods on this unique sample collection and hence to reconstruct the age and the stability of the Greenland ice sheet. By investigating and dating the basal material, we can gain information on the waxing and waning of the Greenland ice sheet in the past, e.g. by establishing when each of the drilling sites was last ice free, and what the conditions were like at that time. One hypothesis we would like to test is if the present ice sheet in Greenland formed at the time of the Mid-Pleistocene Transition (MPT) 1.2-0.8 million years ago, where the glacial/interglacial cycles changed duration from appr. 40,000 years to appr. 100,000 years.
Green2Ice develops, improves and applies novel dating techniques to place constraints on past waxing and waning of the GrIS:
• Cosmogenic radioactive nuclides (26Al/10Be/36Cl, 81Kr), and radiogenic nuclides (40Ar) are used to date the basal ice and the timing of the past exposures of geological debris
• Optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL) are also used on quartz and feldspar grains, respectively, to establish when those grains were last exposed
• Modeling of gas and isotope diffusion
These methods can help us determine when different parts of Greenland were last ice free and for how long the ice-free period lasted.
State-of-the-art methodologies on fossil remains, organic matter, in situ produced and consumed greenhouse gases, and biomolecules will provide insights on the ecosystems and environmental conditions that emerged during past ice-free periods, as well as on subglacial biogeochemical processes.
All the data will be compiled to create a database on the extent of the Greenland ice sheet back in time. This information, will be used in Earth system models and ice sheet models tuned to past climate conditions to establish the climatic sensitivity of the Greenland ice sheet and determine when Greenland last was ice free.
The early phase of the project has had four main focus areas:
1. Building up measuring facilities
• At ULB, the project developed a new state-of-the-art nitrogen isotope lab combining the most sensitive technique to measure N and O isotopes in reactive nitrogen species, and the ability to perform mass-independent oxygen isotope analysis. This system will be used to investigate the microbial turnover of nitrogen in the subglacial environment. The project also established a new gas extraction line to measure gas compositions in basal materials with low gas content.
• At UCPH, the project built up a new cutting-edge set-up for measuring Ar isotopes on gases in the basal ice. This new system enables higher precision measurements than for conventional analyses since interfering masses from molecular oxygen can be resolved. With this set-up, we will investigate the age of the basal ice and explore measurements on clumped isotopes possibly revealing the formation temperature of methane.
• At CRPG, the project significantly improved the analytical conditions of cosmogenic nuclides (10Be, 26Al) by lowering the detection limit and the accuracy of the measurements. In collaboration with the Lund University, we also performed tests on the Dye3 and GRIP cores to improve the methods used to measure these meteoric cosmogenic nuclides.
2. Assessing the material already existing from previous drilling projects and performing the first series of measurements on them
• An overview of existing samples has been created and a 2-week sampling campaign was carried out in the freezer in Copenhagen in November 2023, where samples were cut from the basal part of all the existing deep ice cores and distributed to different labs for analysis (ULB for gas and lipid biomarkers, DTU for luminescence dating, CRPG and Lund Univ. for meteoric cosmogenic nuclides).
3. Planning the field work for drilling the replicate ice core at GRIP and carrying out the first steps of this
• In May 2024, a team equipped with radar equipment and shovels went to the old GRIP drill site to try to locate the old borehole that has been buried under snow for about 10 years. During their short stay at GRIP they did not succeed in finding the borehole, but with the radar data they collected and the initial investigations they carried out, we are now in a good position to find the borehole in 2025.
• In connection to the 2024 Green2Ice annual meeting, a workshop with the NSF GreenDrill program was held and it was followed up with a workshop at University of Columbia between Green2Ice and GreenDrill on reaching the common goal to determine the evolution of the Greenland ice sheet, and discuss the best methods.
• The drilling of a replicate ice core of the bottom 200 m at GRIP requires a moving of the ice core field camp from EastGRIP in NE Greenland to GRIP at the summit of the ice cap in the summer of 2025. The planning of such an operation is a huge logistical task which is well underway.
4. Earth system models and ice sheet models including all the Northern Hemisphere ice sheets for past climate periods are being constructed. Collaboration with the Beyond EPICA program and involvement in the PAGES MPT strengthen this initiative.
1. Building up measuring facilities
• At ULB, the project developed a new state-of-the-art nitrogen isotope lab combining the most sensitive technique to measure N and O isotopes in reactive nitrogen species, and the ability to perform mass-independent oxygen isotope analysis. This system will be used to investigate the microbial turnover of nitrogen in the subglacial environment. The project also established a new gas extraction line to measure gas compositions in basal materials with low gas content.
• At UCPH, the project built up a new cutting-edge set-up for measuring Ar isotopes on gases in the basal ice. This new system enables higher precision measurements than for conventional analyses since interfering masses from molecular oxygen can be resolved. With this set-up, we will investigate the age of the basal ice and explore measurements on clumped isotopes possibly revealing the formation temperature of methane.
• At CRPG, the project significantly improved the analytical conditions of cosmogenic nuclides (10Be, 26Al) by lowering the detection limit and the accuracy of the measurements. In collaboration with the Lund University, we also performed tests on the Dye3 and GRIP cores to improve the methods used to measure these meteoric cosmogenic nuclides.
2. Assessing the material already existing from previous drilling projects and performing the first series of measurements on them
• An overview of existing samples has been created and a 2-week sampling campaign was carried out in the freezer in Copenhagen in November 2023, where samples were cut from the basal part of all the existing deep ice cores and distributed to different labs for analysis (ULB for gas and lipid biomarkers, DTU for luminescence dating, CRPG and Lund Univ. for meteoric cosmogenic nuclides).
3. Planning the field work for drilling the replicate ice core at GRIP and carrying out the first steps of this
• In May 2024, a team equipped with radar equipment and shovels went to the old GRIP drill site to try to locate the old borehole that has been buried under snow for about 10 years. During their short stay at GRIP they did not succeed in finding the borehole, but with the radar data they collected and the initial investigations they carried out, we are now in a good position to find the borehole in 2025.
• In connection to the 2024 Green2Ice annual meeting, a workshop with the NSF GreenDrill program was held and it was followed up with a workshop at University of Columbia between Green2Ice and GreenDrill on reaching the common goal to determine the evolution of the Greenland ice sheet, and discuss the best methods.
• The drilling of a replicate ice core of the bottom 200 m at GRIP requires a moving of the ice core field camp from EastGRIP in NE Greenland to GRIP at the summit of the ice cap in the summer of 2025. The planning of such an operation is a huge logistical task which is well underway.
4. Earth system models and ice sheet models including all the Northern Hemisphere ice sheets for past climate periods are being constructed. Collaboration with the Beyond EPICA program and involvement in the PAGES MPT strengthen this initiative.
The innovation of Green2Ice is to obtain and use new paleo-information on the history of the GrIS to evaluate risks of tipping points and thresholds in the future of the ice sheet. This evaluation will reduce the uncertainty on the contribution of the GrIS to future sea level rise.