# Theoretical and Experimental Analysis for Cleaning Ice Cores from EtisolTM 140 Drill Liquid
## 4 Conclusions and Perspectives  
The present analysis was focused on the evaluation of a suggested ventilation process at the drill site for BEOI for removing EstisolTM 140 drilling fluid from ice cores, while preserving the ice quality and avoiding ice losses. We have discussed: (1) the physical processes of ice sublimation and drilling fluid evaporation under ventilation conditions; (2) calculations of how much ice could be lost and how much drilling fluid could be removed at maximum ventilation; (3) simple tests of fluid removal, and (4) how to optimize the storage conditions of ice cores to preserve their scientific usefulness even after long time in storage. By going through a theoretical physical description of ice sublimation and fluid evaporation as well as kinetic effects and diffusion, we obtained some quantitative estimates on loss of fluid as functions of temperature, partial vapor pressure and ventilation. Our estimates indicate that, under the suggested operating conditions in the ventilated room, no significant weight loss of ice is expected, particularly if inlet air is taken from a reservoir in the firm so that the air is already saturated by water vapor. Our calculations also indicate that even if the ventilated air has lower relative humidity, the ice losses (during one week in storage) remain negligible relative to the total mass of ice core material. Our estimates on EstisolTM 140 fluid also indicate a limited effect on fluid removal in the ventilated room. Even after a full week of 40 m\({}^{3}\)/h ventilation, the maximum amount removed by evaporation is estimated to be less than 3 g (about 3 mL) for all the planned 200 ice cores stored in the room. To check that our theoretical estimates were not severely flawed, and that we did not leave out important processes, some simple experimental tests were done. Our one-week tests failed to reveal different patterns at different temperatures, so temperature appears not to be a prime factor in affecting the rates of fluid removal and the final amount of residual liquid. Our tests also failed to reveal differences between ventilated and non-ventilated cores. However, we did discover that most of the liquid is removed by gravitational run-off or dripping, and that storage in core troughs slows down the run-off process. Based on this, we recommend that cores and core troughs in the drying room at BEOI site are stored with a slight inclination along core axes. Moreover, we do not recommend ventilation as a means to speed up the drying process as ventilation both in calculations and in our tests has very little effect. Heating up the storage room to speed up the drying process is also not recommended, as the effects of temperature are small and potential consequences for ice core quality are large. Finally, for long-term storage of the BEOI ice cores, it is highly recommended to avoid exposing the cores to temperature oscillations such as in defrosting cycles of freezer units, otherwise sublimation effects will occur. Sublimation effects are particularly significant at sharp edges, in agreement with practical experience and theoretical predictions obtained by a diffusion approach. Sublimation effects can be almost completely avoided by keeping the cores inside insulated crates in the freezer. The insulation of the crate and the heat capacity of 40-60 kg ice in combination prevent the ice from experiencing short term temperature pulses such as de-frosting cycles or human activity. This approach has retained the scientific quality of ice core samples, even after 40 and 55 years in storage. Conceptualization, all; theoretical analysis, F.E. ; experimental testing, D.D.-J. and J.P.S. ; writing and revision, all. All authors have read and agreed to the published version of the manuscript. This publication was generated in the frame of Beyond EPICA. The project has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No. 815384 (Oldest Ice Core).