Speleothem δ¹³C record suggests enhanced spring/summer drought in south-eastern Spain between 9.7 and 7.8 ka – A circum-Western Mediterranean anomaly?

Abstract

South-eastern Spain is one of the driest regions in Europe and thus, prone to drought. Terrestrial climate records covering the late Glacial and Holocene from this area are sparse. Here, we present a flowstone record from Cueva Victoria, south-eastern Spain, which covers the late Glacial (15 ka) to the mid-Holocene (7 ka) including the Younger Dryas (YD). Between the onset of the Bølling/Allerød (B/A) and the early Holocene, flowstone δ18O values progressively decrease in accordance with sea-surface temperatures in the Alboran Sea, indicating an increase in precipitation in south-eastern Spain and a supra-regional signal of North Atlantic temperature change. At the same time, decreasing δ13C values suggest progressively increasing precipitation and vegetation density. This trend is interrupted by both colder and drier conditions during the YD. Between 9.7 ± 0.3 and 7.8 ± 0.2 ka, a large positive excursion of the δ13C values indicates a strong reduction in vegetation density, probably as a consequence of very dry spring/summer conditions. In combination with the continuously low speleothem δ18O values and a nearly unchanged growth rate, this suggests increased seasonality (i.e. drier spring/summer conditions, but not a strong reduction in annual precipitation). This is consistent with several other climate records from the Western Mediterranean region, showing that the Western Mediterranean realm (Spain, Italy) experienced pronounced spring/summer drought during this time interval. Interestingly, the timing of this dry period coincided with the African Humid Period. This may be part of a teleconnection with the North African Monsoon via the Hadley cell circulation.

Western Mediterranean Climate Response to Dansgaard/Oeschger Events: New Insights From Speleothem Records

“…Naughton et al (2009) Figures 1a and 1d). This bipolar precipitation pattern has also been discussed in detail for the Holocene (Budsky et al, 2019). In contrast, the NAO particularly affects precipitation in the regions of the Iberian Peninsula that are not affected by the WeMO (Figure 1b).…”

“…Budsky et al () demonstrated a strong influence of effective precipitation on vegetation density and microbiological activity in the soil above CV during the Holocene. Higher δ 13 C values were interpreted as decreased precipitation during the season of vegetation growth (spring to summer).…”

“…The gray bars indicate the Dansgaard/Oeschger events. NGRIP = North Greenland Ice Core Project.values(Rozanski et al, 1993) even ifBudsky et al (2019) did not find a significant correlation between temperature and rainfall δ 18 O values on interannual timescales. At the same time, warmer cave air results in lower calcite δ 18 O values due to the temperature-dependent isotope fractionation between water and calcite(Hansen et al, 2019;Kim & O'Neil, 1997;Tremaine et al, 2011).…”

A 4000-year long Late Holocene climate record from Hermes Cave (Peloponnese, Greece)

“…Ages have been corrected for a residual non-carbonate (detrital) contamination of 230 Th with the 232 Th concentration using a ( 232 Th/ 238 U) activity ratio of 0.521 (i.e., a ( 230 Th/ 232 Th) activity ratio of 1.92±0.96) and assuming secular equilibrium of the detritus. The correction factor for detrital correction was determined using the procedure of Budsky et al (2019a) and is based on varying the ( 232 Th/ 238 U) activity ratio of the detritus in order to minimize the number of age inversions observed in the chronology of the corrected age data. U-series results and ages are reported relative to the year 2000 and labelled as b2k (before 2000 CE).…”

“…The lowest value and, thus, the highest degree of contamination is observed for the topmost sample. In order to constrain the ( 230 Th/ 232 Th) activity ratio of the detritus, we applied the algorithm of Budsky et al (2019a), which varies the ( 232 Th/ 238 U) activity ratio of the detritus to minimise the number and sum of age inversions observed in the corrected age data (Fig. S4).…”