The last interglacial (MIS5e) in Jerusalem, Israel from speleothem Sr, C and O isotopes

We present a high–resolution record of unstable hydro-climate conditions in the last interglacial MIS5e (~131-116 ka) in the southern Levant by analyzing the simultaneous behavior of Sr, C, and O isotopes in a stalagmite from the Har Nof cave in Jerusalem, Israel [1]. These data are compared and integrated with data from other surrounding speleothems and the contemporaneous charcoal, fungal spores, and pollen data retrieved from the ICDP Dead Sea deep drill core.

The following environmental patterns are observed during MIS5e:

• During early MIS5e (~131-125 ka) on the rising flank of the northern hemisphere (33 N and 65 N) insolation curves, Jerusalem and the Judea Hills were experiencing a moderate Mediterranean-like climate. Desert dust accumulated in the vicinity of the cave. Salt deposition was occurring in the Dead Sea basin.
• Approaching the peak northern hemisphere insolation, and during the interval of peak insolation and Sapropel event S5 (127.5-122 ka), temperatures rose and rains arrived to the region from both Mediterranean and tropical sources. The end of this period was characterized by widespread fires, loss of C₃ vegetation, fungal proliferation, and complete soil removal from hill-slopes. Savannah-like C₄ grasses penetrated to soil-accumulation sites in the valleys. The main rainfall season appears to have shifted from winter to summer.
• At 122-120.5 ka, high ⁸⁷Sr/⁸⁶Sr ratios indicate contributions of sea salts. Extremely high δ¹³C values indicate no vegetation above the cave, suggesting an arid environment.
• At 5-118 ka, on the declining flank of the insolation curve, the area was under unstable conditions with occasional storms, and high-intensity rainfall accompanied by sea salt. Soil was formed and savannah-like C₄ vegetation developed.
• At ~118-116 ka, the sedimentation rate of Har Nof AF12 stalagmite is extremely low. The region was characterized by arid conditions and major salt deposition was occurring in the Dead Sea. Still, occasional floods reached the Dead Sea with some moisture coming mainly from southern sources.

This detailed record of environmental changes shows that the northward expansion of climatic belts over the southern Levant during MIS5e caused dramatic environmental changes, crossing a tipping point threshold, and was associated with a major ecologic disruption. Such abrupt changes are characterized by nonlinear, threshold-type responses at rates that are large relative to background variability and forcing.

The evidence from the caves and Dead Sea sediments presented here for the MIS5e period suggests that global warming can be associated with periods of increased instability in the south Levant, an area lying at the desert fringe. The tipping point threshold manifested in MIS 5e of the Levant include complete loss of vegetation and soil, devastating fires and a shift of precipitation from winter to summer. These extreme events send a warning message that elevated greenhouse gases may increase desertification and instability of Levant climate.

[1] Frumkin, A., Stein, M. and Goldstein, S.L., Palaeogeography, Palaeoclimatology, Palaeoecology 586, 110761, 2022.