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.
