Deterioration processes affecting historic sites in Antarctica and the conservation implications

Abstract

Despite the widespread belief that deterioration is minimal or absent in Antarctica because of the "dry cold", field research undertaken for this thesis at twelve Antarctic sites identified diverse deterioration problems, often related to moisture and salts. Accurate diagnosis of causes of deterioration is essential to ensure appropriate conservation treatments and rate measurements can help determine treatment priorities. The main methods used in the research were field observations at 12 locations, various analyses of samples of materials and studies of temperature and relative humidity measurements and wind and other observational data from diverse sources. Temperature and humidity data measured by dataloggers inside of the AAE main hut at Cape Denison were used to assess potential changes in interior conditions following ice removal. Since exposure of sample materials to measure rates of deterioration by light and wind proved problematic, new methods based on repeated in situ observations of historic materials were developed, particularly to assess the damage to wood caused by wind. Modified ISO standard methods were used to measure salt deposition and corrosion rates and Raman microscopy and XRD were used to analyse salts. Visitor questionnaires and observations were employed to examine attitudes and awareness of conservation requirements relevant to site management. The outcomes of conservation treatments were assessed by field observations and reviews of site reports. The main conclusions of the research were that diagnosis of some conservation problems has mis-attributed or over-stated the seriousness of some problems and under-estimated others. Meltwater was found to be a greater risk than ice accumulation, except where the weight of ice is unsupported. Analysis of temperature and RH data at Cape Denison found hoarfrost formation on sensors indicate conditions are colder than in reality. Removal of ice, a key conservation strategy at most huts, has not reduced high humidity as intended and treatments aimed at removing and continued exclusion of ice may not succeed unless mass transfer changes occurring in buildings are considered. These should determine whether internal cycles involving phase change (formation of hoarfrost and melting of ice from condensation occurring inside walls and ceilings) could continue to cause cyclic melting and re-freezing on structures and artefacts inside the building even if ice ingress is excluded. Melting of ice was often associated with corrosion and biodeterioration. Corrosion rates at inland locations were the lowest measured on earth, but coastal corrosion rates exceeded predictions from ISO standard 9223 and were comparable to temperate rural Australia. Measurements found conditions for corrosion occurred above -10°C when RH exceeded 50%. Thus the ISO standard, widely used to estimate corrosion risks, underestimates these risks. Inside Ross Island huts, analyses found sulphates were more prevalent than chlorides, despite proximity to the sea. The author identified defibring at some locations at Cape Denison and more extensively at Ross Island and Cape Adare and linked this to salts rather than „freeze-thaw‟ cycles. Referring to more detailed subsequent research by others at Ross Island, the difficulties in diagnosing salt risks were identified since winds remove damaged fibres which may synergise surface loss. Observations and measurements and surface damage to timber at Cape Denison showed location of damage is consistent with the boundary layer formed by katabatic winds, thus losses at edges and corners of buildings are high, but were overstated elsewhere. Plucking of wood fibres in the lee of the wind may be as damaging as particle impacts. Photodeterioration observations showed damage events occur relatively rarely over much of the building surfaces. Observations at historic sites found significant variability in visitor impacts. Visitors‟ attitudes generally supported retention of older buildings but were generally less supportive of retaining outdoor artefacts implying a need to improve interpretation. Analysis of selected site management plans identified information gaps in diagnosing deterioration and in evaluating treatments. Scientific resources of historic sites have been frequently overlooked and removal of dateable bio-artefacts and datum points in environmental clean ups could threaten opportunities to derive further historical and environmental information. The thesis proposes a framework for identifying and conserving these resources. Significance of the findings The research helps to provide a more holistic approach to understanding deterioration of Antarctic historic sites and provides a framework for assessing conservation strategies that could be applied in other locations with severe climates.

Date of Award	2011
Original language	English
Supervisor	Dudley Creagh (Supervisor) & Lyndsie Selwyn (Supervisor)