Abstract:
The climatic optimum during the last interglacial was the time interval during which the
average sea level was ~5-6m higher, and more humid and warmer climate (by ~3°C
from the present value) prevailed. However, studies done so far related to this period
fail to provide any direct indicator of climate and environmental variability on annual to
decadal timescales. Hence in this study, using recent advancements in molecular Mass
Spectrometry Imaging, an ultra-high resolution reconstruction of the paleoenvironmental
conditions ~125,000 years ago was done.
Organic-rich sapropel S5 from the Eastern Mediterranean, formed during the last
interglacial, comprises informative biomarkers like glycerol dialkyl glycerol tetraethers,
alkenones and fatty acids, which were used to generate molecular stratigraphic records
of their distribution. Uk’37 and CCaT paleothermometry generated from these biomarkers
are indicative of sea surface temperature as well as oxygen limitation in response to the
stratification of water column respectively, during the sapropel deposition. The average
chain length of long-chain fatty acids records the regional vegetation changes in the
Mediterranean borderlands and plausibly indicates the response of vegetation on the
shift of Inter-Tropical Convergence Zone and variation in the North African monsoonal
intensity. Various elemental abundances document a complex interplay of
oceanographic and hydrological conditions during this period. For example, Br
abundances indicate increased productivity during sapropel deposition, while K, Ti and
Zr indicate variations in drainage and dust intensity.
The CCaT proxy derived sea surface temperature and average chain length of long-
chain fatty acids show prominent multi-decadal oscillations during this period. Similar oscillations in elemental data (for Ca, Fe, Ti and K) highlight a coupling between low
and mid-latitude hydrodynamic changes and teleconnections between various
components of the global climate system during the last interglacial.
