Imprint of solar and Atlantic Multidecadal Oscillation variability in a 1000 year-long water temperature record from the varved sediments of Lake Czechowskie (northern Poland)

Temperature records with a high temporal resolution and spanning the last millennium are of primordial importance to understand climate variability beyond the instrumental period at multi-decadal to multi-centennial timescales. However, such records are rare and absolute values often suffer from large uncertainties. While tree-ring records provide excellent temperature records in the mid-latitudes at an annual timescale, they are generally not well-suited for understanding centennial to multi-millennial climate variability due to biologic age trends. Here, we provide a precisely dated, 1000 year-long temperature record with a decadal resolution from varved Lake Czechowskie located in northern Poland (Europe). The reconstruction is derived from a temperature proxy, which is based on glycerol dialkyl glycerol (GDGT) membrane lipids from bacteria thriving in the lake. The temperature record presents a trend very similar to observed June to November air temperatures for the period 1840 to 1975. However, absolute values are about 2 °C colder than observed air temperature because the estimates reflect temperature near the thermocline as suggested by lake monitoring data. The temperature reconstruction indicates that temperatures were 0.5±0.5 °C warmer and 0.8±0.5 °C colder than AD 1900–1975 during the Medieval Climate Anomaly and the Little Ice Age, respectively. A frequency analysis of Lake Czechowskie record as well as other temperature records from the Northern Hemisphere mid-latitudes reveals three main periodicity bands at 55–90, 110–190 and 210–300 years. These bands are most likely related to both solar variability (80–90-year Gleissberg and 200–210-year Suess/de Vries cycles) and to the Atlantic Multidecadal Variability/Oscillation (60–90 and 140–180-year periodicities), which is known to modulate temperature in the Baltic Sea region. Lake Czechowskie record represents a unique reconstruction of temperature decadal variability in the southern Baltic lowlands and Northern Europe during the last millennium.