Abstract
Annual resolution reconstructions of alpine temperatures are rare, particularly for the Southern Hemisphere, while no snow cover reconstructions exist. These records are essential to place in context the impact of anthropogenic global warming against historical major natural climate events such as the Roman Warm Period (RWP), Medieval Climate Anomaly (MCA) and Little Ice Age (LIA). Here we show for a marginal alpine region of Australia using a carbon isotope speleothem reconstruction, warming over the past five decades has experienced equivalent magnitude of temperature change and snow cover decline to the RWP and MCA. The current rate of warming is unmatched for the past 2000 years and seasonal snow cover is at a minimum. On scales of several decades, mean maximum temperatures have undergone considerable change ≈ ± 0.8 °C highlighting local scale susceptibility to rapid temperature change, evidence of which is often masked in regional to hemisphere scale temperature reconstructions.
Highlights
Historical documents, written and oral histories give insight to impacts that shifts in global climate had on empires, economies and the environment over the past two thousand years
The marginal alpine snowpack of the Australian Alps is critical to water resources of south-eastern Australia due to the concentration of population; agricultural production, hydroelectric power generation and seasonal snow sport industry, worth an estimated AUD $1.5 billion annually[17]
We present a 2000 year reconstruction of temperature and snow cover for the Australian Alps based on a near annual resolution δ13C speleothem record
Summary
The Yarrangobilly Caves karst complex (950 to 1,050 m above Australian Height Datum) located in the northern section of Kosciusko National Park offers a unique potential for preservation of long and detailed records of alpine hydroclimate (Fig. 1). The warmth in the Australian alpine area corresponding to the MCA was followed by a cooling trend coeval with the LIA widely reported in temperature reconstructions for the Northern Hemisphere[40,41,57] and seen in New Zealand palaeoclimate archives before onset of very cold conditions through 1600 to 1700 CE58 This period has been linked to increased southerly airflow[50,56], solar variability and volcanic forcing of climate[57,59]. Recent rapid decrease in our reconstructed snow cover record (Fig. 3e) over the past 5 decades is at least an order of magnitude greater than for similar periods over the past 2000 yrs and is driven by corresponding global warming This effect is being compounded by change in atmospheric circulation that has seen a reduction in winter snowfall associated with the passage of cold fronts, and an increase in rainfall events with moisture sourced from the tropical seas northwest of Australia[22]. Such research will give insight to variability of alpine hydrometeorology essential to plan for future sustainable alpine water resources in a changing and warming climate
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