Characterising local climates and biologically-relevant climate changes on the Southern Ocean Islands

Samuel Graham Beale , Justine Shaw, Melodie A. McGeoch

The Southern Ocean climate has undergone significant changes over the last several decades, which has had consequences for conditions on the few small islands scattered across the region. Previous investigations of climate changes on the Southern Ocean Islands (SOIs) have examined single climate variables, such as temperature, and single islands or island groups. Furthermore, these studies have tended to focus on mean values without consideration of variability and extreme events. Consequently, we currently lack a comprehensive and up-to-date analysis of biologically-relevant climate changes that have occurred on these islands. Such insights are needed to determine the exposure of these unique and potentially fragile island ecosystems to climate change and the threats and challenges that their species will face. Here, we used weather station records to quantify the climate signature of SOIs and examine trends in a set of biologically-relevant climate parameters related to temperature, precipitation, and wind. We found that comprehensive warming has occurred across these islands but with important nuances, including differences in the rate of increase in minimum and maximum temperature contributing to an increase in diurnal temperature range. In contrast, precipitation changes have been highly localised, with severe drying on Marion and Crozet Islands in the Indian Ocean sector and wetting on Macquarie Island in the Pacific Ocean sector. Changes in wind speed have been idiosyncratic but have important consequences in combination with changes in other variables. Some of the implications of these changes for the SOIs are discussed.