Sub-project A (SPA): Ice sheet hydrology and groundwater formation
SP manager: Alun Hubbard, Aberystwyth University.
The overall focus with the SPA studies were to make indirect observations of the properties of the hydrological system at the base of the ice sheet, and to study what parts of the ice sheet contribute water for recharge into the bedrock. The latter included quantification of surface water production and information on how the water was routed from the surface to the base of the ice. This was done through studies of ice velocity variations and surface meltwater production. Main activities within SPA involved the installation and monitoring of GPS receivers and automatic weather stations on the ice sheet, ground-based radar studies, and passive and seismic studies of the subglacial environment.
SPA aimed at improving the understanding of ice sheet hydrology in order to assess how an ice sheet impacts groundwater circulation and chemistry around a deep geological repository. The data collected in SPA has been and will be utilised in numerical ice sheet flow and hydrological modelling. It is recognized that additional field observations are needed in order to verify the conceptual models and modelling assumptions that are being used by the various waste management organizations. The field investigations wwere carried out during 2009-2013.
Sub-project B (SPB): Subglacial hydrology
SP manager: Joel Harper, University of Montana.
The aims in SPB were to make direct observations and measurements of the characteristics of the hydrological system at base of the ice sheet, i.e. of the water that forms under the ice sheet. The main activity for SPB was drilling through the ice sheet at a number of locations in order to observe water pressures at the interface between the ice and bedrock. In addition to the ice drilling, remote sensing of surface conditions was be carried out. SPB provided pioneering measurements of subglacial water pressures beneath the Greenland ice sheet. This information will give important input to the conceptualization of ground water models under glacial conditions applicable in Fennoscandia and Canada. The data will be utilised in numerical ice sheet flow and hydrological modelling. Data and results from SPA served as necessary information for finding suitable locations for the ice drilling.
Sub-project C (SPC): Hydrogeochemistry and hydrogeology
SP manager: Timo Ruskeeniemi, Geological Survey of Finland.
The overall target of the SPC was to study: 1) the penetration of glacial melt water into the bedrock; 2)groundwater flow; and 3) the chemical composition of water when and if it reaches repository depth. Main activities for SPC involved deep bedrock drilling in front of the ice sheet for subsequent downhole surveys and hydrogeological/hydrogeochemical instrumentation, which facilitates multilevel sampling of recharging subglacial meltwaters and monitoring of pressure conditions at least down to a depth of 500–700 meter. The deep drilling required a detailed understanding of the geology of the area, including fracture frequencies and composition of rock types and hydrogeochemical information (i.e. chemistry of different water end-members). Data and understanding of the ice sheet hydrology from SPA and SPB provided essential information for selecting the location of the deep borehole.
Before selecting a site for the deep drilling, test drilling of two shallow holes (100–300 meters) was carried out in 2009, when two drillholes, ~200 and ~350 meters deep were drilled. These drill holes provided important information on geology and hydrology as well as information on the permafrost extent. The 2009 drilling campaigns provided an opportunity to test the drilling procedures in permafrost conditions and will be followed by an extensive research program, which aims at improving the understanding of talik and permafrost related issues. In 2011 a 650 meter deep borehole was drilled in close proximity to the Greenland ice sheet. The borehole allows water sampling and continuous monitoring of pressure, temperature and salinity of the water. The data gathered from this borehole has provided useful data needed to comprehend the fate of melt-waters when the assumed high hydraulic pressures at the ice sheet bed force water into the fracture network. Data on water formation and chemistry at the base of the ice sheet from SPB played an important part when analyzing the results of SPC.