Holocene climate variability in north-eastern Italy: potential influence of the NAO and solar activity recorded by speleothem data

Abstract

Abstract.Here we present high-resolution stable isotope and lamina thickness profiles as well as radiocarbon data for the Holocene stalagmite ER 76 from Grotta di Ernesto (northeastern Italy), which was dated by combined U-series dating and lamina counting. ER 76 grew between 8 ka (thousands of years before 2000 AD) and today, with a hiatus from 2.6 to 0.4 ka.Data from nine meteorological stations in Trentino show a significant influence of the North Atlantic Oscillation (NAO) on winter temperature and precipitation in the cave region. Spectral analysis of the stable isotope signals of ER 76 reveals significant peaks at periods of 110, 60-70, 40-50, 32-37 and around 25 a. Except for the cycle between 32 and 37 a all periodicities have corresponding peaks in power spectra of solar variability, and the 25-a cycle may correspond to NAO variability. This suggests that climate variability in northern Italy was influenced by both solar activity and the NAO during the Holocene.Six periods of warm winter climate in the cave region were identified. These are centred at 7.9, 7.4, 6.5, 5.5, 4.9 and 3.7 ka, and their duration ranges from 100 to 400 a. The two oldest warm phases coincide with the deposition of sapropel S1 in the Mediterranean Sea indicating that the climate in the cave region was influenced by this prominent pluvial phase in the Mediterranean area. For the younger warm phases it is difficult to establish a supra-regional climate pattern, and some of them may, thus, reflect regional climate variability. This highlights the complexity of regional and supra-regional scale Holocene climate patterns.

Paleoclimate variability during the Blake geomagnetic excursion (MIS 5d) deduced from a speleothem record

“…Genty et al, 2003;Scholz et al, 2012). In those records, higher d 13 C values are regularly linked to cooling events, reflecting the fact that all the feasible mechanisms influencing the d 13 C signal contribute to change it in the same direction (Johnston et al, 2013).…”

“…Even if subfreezing temperatures are not reached during a cooling event in an alpine cave, the resulting changes in the overlying soil may have a notable impact on speleothem growth and chemistry (e.g. Scholz et al, 2012). Finally, an additional advantage of using european alpine speleothems for paleoclimate reconstruction derives from the fact that their d 18 O trends are easily compared to Greenland ice d 18 O records, because both respond similarly to regional temperature changes (Meyer et al, 2008;Boch et al, 2011).…”

Constraining Holocene hydrological changes in the Carpathian–Balkan region using speleothem δ<sup>18</sup>O and pollen-based temperature reconstructions

“…9). This likely represents a shift towards the present-day rainfall domination by the winter season (Scholz et al, 2012). On the other hand, sites in Turkey (Sofular), Israel (Soreq), Lebanon (Jeita) and southern Romania (Poleva and Ascunsȃ) that are potentially influenced by the eastern Mediterranean plot well above the temperature-constrained change.…”

High‐resolution reconstruction of 8.2‐ka BP event documented in Père Noël cave, southern Belgium

“…Furthermore, a series of papers demonstrated linkages between variability in the d 18 O of precipitation and NAO (e.g. Mangini et al, 2005;Scholz et al, 2012;Smith et al, 2016). Mangini et al (2005) and Trouet et al (2009) showed that changes in the strength of the NAO might be reflected in the d 18 O values of the stalagmites.…”

“…Mangini et al (2005) and Trouet et al (2009) showed that changes in the strength of the NAO might be reflected in the d 18 O values of the stalagmites. Scholz et al (2012) demonstrated that there is a significant influence of the NAO on winter temperatures and precipitation in caves of NE Italy. This is supported by instrumental observations in central Europe between the strength of the winter NAO þ situations and the d 18 O of winter precipitation (Baldini et al, 2008).…”