Climate variability from Hot cave (Cyprus) for the last 700 years: implications for speleothem proxies in determining long-term paleoclimate signals

The HIGH-PASM project studies the climate variability on the Island of Cyprus for the last millennium. We combine highly resolved speleothem records with archived weather data for the last 140 years in order to corroborate and understand climate signals recorded in speleothems over the last millennium. An active stalagmite of 8 cm length was collected from Hot cave in 2021 along with other secondary carbonate deposits from Lapithos Qanat, and Amiandos and Argaka Dam tunnels. U-Th dating and lamina counting were combined to produce an age model for Hot cave and Lapithos Qanat. 800 stable isotope measurements were conducted on the Hot cave stalagmite, 250 on the Lapithos sample and 45 on each of the Amiandos and Argaka deposits. Meteorological data collected since 1885 from four stations were consolidated and compared to the yearly resolved Hot cave and Lapithos records.

The Hot cave stalagmite grew continuously from 1330 to 2021 AD, the Lapithos sample covers the last 150 years and both Amiandos and Argaka deposits provide a continuous record for the last ca. 50 years. There is a general correspondence between the ẟ¹⁸O signal and precipitation peaks over the last 140 years, showing more negative ẟ¹⁸O values corresponding to times of high precipitation. The ẟ¹³C signal co-varies in general with ẟ¹⁸O, except during ~1970-1980, ~1930, ~1680, ~1650, ~1490, ~1400-1410 and ~1360-1370 AD. During these periods an anti-correlation is observed. During the 20^th century, periods of instrumental temperature rise are reflected by rising ẟ¹⁸O and ẟ¹³C values. A trend towards less negative ẟ¹⁸O values since 2000 AD is attributed to reduced rainfall amount and increased evapotranspiration as a consequence of steeply rising temperatures. During the instrumental period, the ẟ¹⁸O is a proxy of precipitation amount, and we assume that this relationship was valid for the last millennium. Strong temperature rises during certain intervals might also have affected the ẟ¹⁸O signal, reducing the sensitivity of this precipitation proxy.

Comparing the Hot cave record with global and regional records, periods with less negative ẟ¹⁸O values correspond generally to intervals of a negative NAO index and high total solar irradiance. Wet periods with more negative ẟ¹⁸O values correspond to intervals of a positive NAO index and low solar irradiation. The Hot cave record shows that the Little Ice Age (1300-1870 AD) begun with long dry intervals lasting until 1520 AD, followed by wetter intervals from 1520 to 1800 AD, and later followed by again long dry intervals until the present-day. The climate variability trend recorded in Hot cave during the last 700 years agrees generally well with the dry index reconstructed from tree-ring records in Troodos (Cyprus) and stalagmite data from Kocain cave in Southern Turkey