Last Interglacial decadal sea surface temperature variability in the eastern Mediterranean

The Last Interglacial (-129,000-116,000 years ago) is the most recent geologic period with a warmer-than-present climate. Proxy-based temperature reconstructions from this interval can help contextualize natural climate variability in our currently warming world, especially if they can define changes on decadal timescales. Here, we established a similar to 4.800-year-long record of sea surface temperature (SST) variability from the eastern Mediterranean Sea at 1-4-year resolution by applying mass spectrometry imaging of long-chain alkenones to a finely laminated organic-matter-rich sapropel deposited during the Last Interglacial. We observe the highest amplitude of decadal variability in the early stage of sapropel deposition, plausibly due to reduced vertical mixing of the highly stratified water column. With the subsequent reorganization of oceanographic conditions in the later stage of sapropel deposition, when SST forcing resembled the modern situation, we observe that the maximum amplitude of reconstructed decadal variability did not exceed the range of the recent period of warming climate. The more gradual, centennial SST trends reveal that the maximal centennial scale SST increase in our Last Interglacial record is below the projected temperature warming in the twenty-first century.

Automated summary

This study established a 4,800-year record of sea surface temperature variability in the eastern Mediterranean Sea using mass spectrometry imaging of long-chain alkenones. The research found that the highest amplitude of decadal temperature variability occurred in the early stage of sapropel deposition during the Last Interglacial, while the subsequent reorganization of oceanographic conditions did not exceed the recent period of warming climate in terms of decadal variability.