Lichenometric ages of the little ice age moraines on king george island and of the last volcanic activity on penguin island (west antarctica)

摘要

The recently observed recession of glaciers on King George Island is associated with decades of climate warming in the Antarctic Peninsula region. However, with only 60 years of glaciological observations in the study area ages of the oldest moraines are still uncertain. The goal of the study was to estimate ages of lichen colonization on the oldest moraines of the Ecology and White Eagle Glaciers on King George Island and on the Principal Cone of Penguin Island volcano. The first lichenometric studies on these islands from the late 1970s used rates that had about four to five times slower Rhizocarpon growth rates. We re-examined the sites and measured 996 thalli diameters to establish the surface ages. To estimate the age we used (1) long-term Rhizocarpon lichen group growth rates established by authors using data from a previous lichenometric study on King George Island (2) previous data of lichen growth rates from other sub-Antarctic islands. Our results suggest growth rates between 0.5 and 0.8mmyr ~(-1). According to these rates the ages of the oldest moraine ridges are of the Little Ice Age and were colonized at the beginning of the twentieth century. The mid-twentieth century age of lichen colonization on the historically active Penguin Island volcano might support the date of the last eruption reported by whalers in the end of the nineteenth and the beginning of the twentieth century.