The Last Interglacial (LIG; ~129,000 to 116,000 years ago) is the most recent geologic period with a warmer-than-present climate. Consequently, climate reconstructions from this period provide an opportunity to relate current and projected climatic trends to natural climate variability from a warmer world. We established a ~4.800 year-long record of sea surface temperature (SST) variability from the Eastern Mediterranean Sea at 1-to-4-year resolution by applying mass spectrometry imaging of long-chain alkenones on the finely laminated saprop (...)

The Last Interglacial (LIG; ~129,000 to 116,000 years ago) is the most recent geologic period with a warmer-than-present climate. Consequently, climate reconstructions from this period provide an opportunity to relate current and projected climatic trends to natural climate variability from a warmer world. We established a ~4.800 year-long record of sea surface temperature (SST) variability from the Eastern Mediterranean Sea at 1-to-4-year resolution by applying mass spectrometry imaging of long-chain alkenones on the finely laminated sapropel deposited during the LIG. Reconstructed SSTs rapidly increased during the early part of sapropel deposition and subsequently remained at a level similar or above modern SSTs. In the early stage of sapropel deposition, the maximal amplitude of decadal variability reached higher values than recorded in the same region during the instrumental era, plausibly due to a highly stratified water column that led to reduced vertical mixing and thus different forcing of SST than today. The later stage of sapropel deposition is characterised by varve deposition, suggesting weakened stratification and its breakdown in the colder months; this implies the establishment of oceanographic conditions with SST forcing similar to modern. A comparison of the decadal SST variabilities from this varved part and the instrumental era reveals that the maximal amplitude of reconstructed decadal SST variability did not exceed the range of the recent period of warming climate. However, examining the more gradual SST trend reveals that the maximal centennial-scale SST increase from the varved sapropel section is below projected centennial-scale SST warming in the 21st century under medium-to-low-emissions scenarios, while the high-emissions scenarios suggest that future SST rise could even outpace the warming trends observed during early sapropel deposition underneath a highly stratified water column.