Temperature and aridity of the African-Arabian desert belt since 1750 CE reconstructed from Red Sea coral Sr/Ca and δ18O

Abstract:

Throughout the desert regions of the globe, annually to seasonally resolved proxy records of temperature and aridity that extend the short observational record are sparse. For the African-Arabian desert belt, proxy records of temperature are virtually absent in reconstructions of continental-scale temperature variability during the past millennia. Here we present a new reconstruction of temperature from the African-Arabian desert belt back to 1750 CE, derived from bimonthly analysis of the Sr/Ca-temperature proxy in a northern Red Sea Porites coral (Ras Umm Sidd, Sinai, Egypt). The annual average coral Sr/Ca record is significantly correlated with land surface temperature throughout the eastern Sahara and the Arabian Desert during the last century. The coral Sr/Ca record is also significantly correlated with sea surface temperature (SST) in the Red Sea, Mediterranean Sea and North Atlantic Ocean, but not with Indian Ocean SST. Correlation with sea level pressure (SLP) fields identifies the advection of relatively cold continental air from southeastern Europe toward the Middle East and northeastern Africa as physical mechanism that controls temperature variability at interannual timescales. We combined the Sr/Ca record with a previously reported δ¹⁸O record from the same coral, and generated an annually resolved reconstruction of seawater δ¹⁸O. Correlation of the annual seawater δ¹⁸O reconstruction with SLP and 850 hPa geopotential height fields identifies the advection of relatively dry desert air from the eastern Sahara toward the northern Red Sea as physical mechanism that controls seawater δ¹⁸O variability at interannual timescales. This regional mechanism is associated with large-scale SLP anomalies of opposite sign throughout the Northern Hemisphere subtropics and the Arctic. The most striking feature of the seawater δ¹⁸O reconstruction is an abrupt regime shift toward fresher conditions in northern Red Sea surface waters between 1850 and 1855 CE. Because of the region’s hyperaridity, local precipitation changes can be excluded as potential cause. We use reconstructed SLP fields back to 1750 CE to study the role of changes in atmospheric circulation at the end of the Little Ice Age as potential cause for the abrupt freshening of northern Red Sea surface waters at that time.