The investigation and experience of using ESTISOL™ 240 and COASOL™ for ice-core drilling

Abstract

Continuous good-quality deep ice cores provide excellent scientific data with which to reconstruct a past climate record for >800 ka. At depths starting from �100 m using an electromechanical drill, a drilling liquid is essential for successful recovery of the very high-quality ice cores demanded by modern scientific analysis techniques (e.g. continuous flow analysis). Finding a suitable drill fluid for use at deep ice-coring drill sites is not an easy task. Temperatures vary greatly not just from site to site, but also at a site where the average mean temperature from surface to bedrock can vary from -55°C to -2.75°C. In the past 60 years, many fluids have been used, with varying degrees of success, but for various reasons are either unavailable, are now considered unsafe and dangerous or are too environmentally damaging to be permitted. Here we report on our pre-season investigation into possible candidate drill fluids, with specific information concerning ESTISOL™ 240 and COASOL™, the rationale behind the redesign of our drill successfully used at NorthGRIP, Greenland, and EPICA DML, Antarctica, the knock-on effect of those changes, and our field experience in Greenland at Flade Isblink in 2006 and at NEEM in 2009-10.

The Relevance of Grain Dissection for Grain Size Reduction in Polar Ice: Insights from Numerical Models and Ice Core Microstructure Analysis

“…Therefore, the numerical strain rates are only qualitatively comparable with natural strain rates . The temperature in the simulations was set to −30 • C, which is comparable to Holocene ice conditions in NEEM ice core (Sheldon et al, 2014). The initial grain sizes were set by varying the initial number of grains in a foam texture ( Table 1).…”

Prospects for reconstructing paleoenvironmental conditions from organic compounds in polar snow and ice

“…The most obvious of these impurities is the drilling fluid which keeps the borehole open during deeper ice core drilling projects, and which typically consists of a poorly characterised and variable hydrocarbon mixture but some compounds present in drilling fluid might also be of interest for paleo-environmental markers. The main examples used in recent years are dearomatised kerosenes (D30, D40, D60, with or without added densifier) (Talalay and Gundestrup, 2002), butyl acetate, and the aliphatic ester Estisol series, with or without Coasol (Sheldon et al, 2014). Any such fluid freely coats the outside of all deep cores and remains on the surface throughout transport and storage.…”

Deep ice-core drilling performance and experience at NEEM, Greenland

“…The hardware of the prototype drill itself is still in use and was deployed for the shallowest and deepest parts of the NEEM drilling in the main borehole, including warm-ice and silty-ice retrieval. It was also used to drill a separate intermediate-depth (411 m) ice core at NEEM in 2011, as well as the 423.3 m ice core from Flade Isblink ice cap, northeast Greenland, in 2006 where the new Estisol-240/Coasol drill fluid was field-tested prior to its use at NEEM (Sheldon and others, 2014a). The prototype hardware was most recently mounted on a new tilting-tower-and-winch configuration and was successfully deployed to drill the main core for the Aurora Basin North project in cooperation with the Australian Antarctic Division (Sheldon and others, 2014b).…”

“…The difficulties drilling warm ice that characterized the deepest parts of the NGRIP (Gundestrup and others, 2002; Johnsen and others, 2007) and EPICA (Augustin and others, 2007) drillings were largely not present at NEEM, in part due to the Estisol-240/Coasol drill fluid mixture (Sheldon and others, 2014a). The oily and viscous nature of the liquid seemed to prevent chips and refrozen water from packing and building up on the surfaces of the cutters and shoes, processes which caused the penetration problems and stuck drills in the former drillings.…”

“…As much as possible, hardware from the NorthGRIP (NGRIP) drilling was reused, and design modifications specifically for the lower sections of the NEEM drill arose mainly to account for the new, highly viscous drill fluid used at NEEM. The Estisol-240/Coasol drill fluid mixture introduced at NEEM has a kinematic viscosity 9–15 times higher than the drilling fluids used in previous deep drillings in Greenland and Antarctica (Talalay and Gundestrup, 1999; Sheldon and others, 2014a), which made design changes favorable for achieving fast travel speed of the drill in the liquid-filled hole and for maintaining the efficient collection of ice cuttings (chips) in an enlarged chip chamber. While the scope of this paper cannot describe all of the detailed experiences of the NEEM drilling, it should provide a source of information and experience useful to groups using similar drill systems, for both deep and intermediate-depth ice-core drilling projects.…”