Microclimate impacts of passive warming methods in Antarctica : implications for climate change studies
Faculty of Sciences. Biology
Polar biology. - New York
, p. 1421-1435
Passive chambers are used to examine the impacts of summer warming in Antarctica but, so far, impacts occurring outside the growing season, or related to extreme temperatures, have not been reported, despite their potentially large biological significance. In this review, we synthesise and discuss the microclimate impacts of passive warming chambers (closed, ventilated and Open Top ChamberOTC) commonly used in Antarctic terrestrial habitats, paying special attention to seasonal warming, during the growing season and outside, extreme temperatures and freezethaw events. Both temperature increases and decreases were recorded throughout the year. Closed chambers caused earlier spring soil thaw (828 days) while OTCs delayed soil thaw (313 days). Smaller closed chamber types recorded the largest temperature extremes (up to 20°C higher than ambient) and longest periods (up to 11 h) of above ambient extreme temperatures, and even OTCs had above ambient temperature extremes over up to 5 consecutive hours. The frequency of freezethaw events was reduced by ~25%. All chamber types experienced extreme temperature ranges that could negatively affect biological responses, while warming during winter could result in depletion of limited metabolic resources. The effects outside the growing season could be as important in driving biological responses as the mean summer warming. We make suggestions for improving season-specific warming simulations and propose that seasonal and changed temperature patterns achieved under climate manipulations should be recognised explicitly in descriptions of treatment effects.