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Indicator: AATH-12 Survey of impacts of weather on heritage sites

Data

Available data are largely anecdotal.

Wind (and wind blown material)

‘Wind has caused structural damage, particularly affecting the buildings at Atlas Cove (Heard Island). The low walls, which are all that remains of most of the sealing huts, do not present a large profile to the wind. Wind picks up abrasive particles that cause ‘corrosion’ or erosion of surfaces’ (Hughes et. al. 2000).

‘It would appear that the majority of sudden, or catastrophic, damage to building fabric (Atlas Cove, Heard Island) has been caused by wind, either alone or in combination with sand, snow and water. Once a structure’s windward elevation has been breached by the wind, perhaps through an open door or missing roof/wall panel, wind can easily penetrate buildings during storms - the pressure differences that occur during these events can sometimes literally blow the structure apart from the inside. The Spare Diesel Hut, Arbec Huts 2, 3 and 4 and the Chippy’s Church may have been destroyed in this manner. Where a structure gradually loses components of its cladding it becomes more ‘transparent’ to the wind and as such it may have a better chance of survival. Examples of structures in this condition include the Medical Suite/Medical Annex, Arbec 1 (before repair) and the Clothing Store’ (Vincent et. al. 2002).

‘Wind-borne sand is likely to be a significant factor in the deterioration of fabric at the Old ANARE Station (Heard Island). The ferocity of the wind results in a sand-blasting effect, which strips protective surfaces, such as paint and galvanising, from metal and timber surfaces. Wind-borne sand also inundates the internal spaces of structures once they have been breached. Although the sand is generally permeable to water, within the confines of a building, the sand acts to retain moisture and as a result internal timbers and metalwork buried with sand are kept moist, speeding deterioration and corrosion. (Vincent et. al. 2002)

Corrosion

‘The maritime climate promotes corrosion, and temperatures are sufficiently high to allow bio-deterioration. Salt deposition also causes ‘defibring of timber, during which wood fibres separate from the surface of the timber, resulting in progressive reduction of structural strength ‘(Hughes et. al. 2000).

‘Hughes et. al.. (2000) carried out an extensive survey of corrosivity (standard corrosion rate, measuring in microns the thickness of metal corroded per year) measurements in Antarctic and on some sub-Antarctic islands. Data were obtained for six sites on Macquarie Island. Weighted metal plates of standardised size (‘coupons’) were sent and attached to Stevenson screens in the meteorological station at Marion Island, Signy (a British base in the South Orkney Islands) and a temporary meteorological screen at Spit Bay on Heard Island. A coupon was deployed at Atlas Cove but was lost, due to the building being torn apart by the wind.’ (Hughes et. al. 2000)

‘According to the ISO Standard 9223 classifications, the corrosivity of steel at Spit Bay is ‘very severe’. The longer period of exposure of the coupon at Macquarie Island has been taken into account, and the higher corrosivity rate is probably due to a combination of high salt deposition and the erosion of the coupon surface by windborne particles. The rate measured at Spit Bay is sufficiently high to conclude that conventional corrosion protection, such as galvanising and protective coatings, would be ineffective. Corrosivity at Atlas Cove is expected to be higher than that at Spit Bay due to its more exposed location and severe weather.’ (Hughes et. al.. 2000)

Table - Corrisivity rates at sub-Antarctic islands

Site	Days exposed	Corrosivity (m/yr)
Heard Island (Spit Bay)	341	55.3
Macquarie Island (Isthmus weather station)	721	222
Marion Island (weather station)	376	31.9
Signy (weather station)	365	36.4

‘The proximity of the Old ANARE Station (Heard Island) to the ocean results in high levels of air-borne salt. This results in increased corrosion of metal fabric throughout the station.’ (Vincent et. al.. 2002)

Rain and snow

‘Water and high humidity result in frequent wetting and drying cycles, which promote swelling and cracking of wood’ (Hughes et. al.. 2000).

‘Precipitation in the form of rain, sleet, hail or snow is an almost daily event at Heard Island. The almost continuous precipitation keeps fabric in situations sheltered from the wind moist (and in some instances water-logged) on an almost permanent basis. This has a significant impact upon timber, fibreboard and laminated timber materials such as plywood. In more exposed situations fabric is subjected to a continuous cycle of wetting and drying - this can lead to significant deterioration of this class of fabric’ (Vincent et. al.. 2002).

‘Whilst heavy snow was not observed during the field component of this assessment, meteorological records and anecdotal evidence suggest that significant quantities of snow accumulate at the Old ANARE Station site (Heard Island) during the winter months. This being the case, it would be reasonable to expect that snow loading (the build up of snow on the roof or against other components of structures) would present a potential threat to the structural integrity of some buildings at the site. (Vincent et. al.. 2002)

‘The climate (on Macquarie Island) is generally cold, wet and saline. These conditions have contributed substantially to the deterioration of historic sites. The ironwork is extremely rusty, the huts have collapsed and most of their timbers have been scattered. However, wood appears to rot fairly slowly as the coldness of the climate does not seem to promote the proliferation of mosses and fungi which would break it down rapidly. Other types of artefacts, such as ceramics, cloth, string, glass and bone appear to survive quite well in a saturated but relatively stable condition. More fragile items such as newspaper deteriorate rapidly in these saturated conditions’ (Townrow 1989).

‘The high rainfall, steep slopes and seismic activity (on Macquarie Island) result in frequent landslides where the top layer of peat slides down to the beaches. Evidence of past landslides covering sites were found at Sandy Bay and Hurd Point’ (Townrow 1989).

Source: Hughes, J and Lazer, E, 2000, Importance of Historic Sites on Heard Island for Protection of Scientific Resources and Environmental Management of a World Heritage Site.

Source: Townrow K, 1989, Survey and Excavation of Historic Sites on Macquarie Island, Department of Lands, Parks and Wildlife, Tasmania.

Source: Vincent R, Grinbergs A, 2002, Atlas Cove, Heard Island Cultural Management Plan (Isolation, Ingenuity, Innovation and Experimentation): lessons for Antarctic expeditions from a ramshackle collection of old sheds (draft), Commonwealth of Australia, Kingston, Tasmania.

What the data mean

The extreme conditions with high wind speeds, ice accumulation and snow loads contribute to the deterioration of elements of cultural heritage sites. Corrosion is also of concern. High winds, storm driven seas, rain and associated growth of vegetation pose a threat to sub-Antarctic sites. No comprehensive data by observational evidence is available from various sites. Readers should also refer to indicators relating to condition of various sites within this data reporting system for further observations on individual structures.

Data Limitations

More heritage/archaeological surveys are required for a more complete understanding of the impact of weather on heritage sites and collections.

Issues for which this is an indicator and why

Australian Antarctic Territory — Cultural heritage aspects - Pressures and risks on heritage sites and collections 

This indicator examines the impact of extreme conditions such as high wind speeds, corrosion, ice accumulation and snow loads on the condition of heritage sites.

Other indicators for this issue:

• AATH-09 Surveys of impacts of isolation on heritage sites 
• AATH-10 Surveys of impacts of tourism on heritage sites 
• AATH-11 Survey of impacts of uncontrolled visits on heritage sites 
• AATH-14 Survey of impacts of hazardous material on heritage sites 
• AATH-15 Survey of impacts of flora and fauna on heritage sites