Summer moisture variability in east central Sweden since the mid-eighteenth century recorded in tree rings

To make predictions of future climate it is necessary to understand the past climate-temperature as well as precipitation. While a wealth of temperature proxies exist from northern latitudes, there is still a lack of information about past precipitation variability. Here we present a 300-year-long tree-ring width chronology from xeric-site Scots pines (Pinus sylvestris L.) in Tyresta National Park, east central Sweden. Tree-ring widths were compared to the long observed temperature and precipitation records from Stockholm during 1786-2000. Analyses of the climate/growth relationship showed that, in general, May-June precipitation had a dominating influence on pine growth. However, during dry periods, negative responses to June-July temperature were stronger, especially evident in the late nineteenth century. Periods of below-average growth were associated with dry conditions in May-June, but occasionally periods of wet and cool summers also produced narrow rings. Periods of above-average growth were linked to wet, but sporadically also cool and dry, early summers. The years between 1815 and 1833 appear to be particularly dry in the 300-year context. Since growth anomalies are found in other Swedish drought-sensitive tree-ring chronologies during this period, it is likely that this dry period had a regional extent. This is the first tree-ring chronology from southern Sweden that provides multi-century information of past summer drought and moisture variability with high resolution and the study will add important information regarding past climate variability in southern Sweden.