Rima Rachmayani

Comparison of Climate and Carbon Cycle Dynamics During Late Quaternary Interglacials

Within the project COIN we investigated climate and carbon cycle changes during late Quaternary interglacials using ice core and terrestrial archives, as well as earth system models. The Holocene carbon cycle dynamics can be explained both in models and data by natural forcings, where the increase in CO2 is due to oceanic carbon release, while the land is a carbon sink. Climate changes during MIS 11.3 were mainly driven by insolation changes, showing substantial differences within the interglacial. Terrestrial reconstructions and model results agree, though data coverage leaves room for improvement. The carbon cycle dynamics during MIS 11.3 can generally be explained by the same forcing mechanisms as for the Holocene, while model and data disagree during MIS 5.5, showing an increasing CO2 trend in the model though reconstructions are constant.

Global Synthesis of Sea-Surface Temperature Trends During Marine Isotope Stage 11

To examine the sea-surface temperature (SST) evolution during interglacial Marine Isotope Stage (MIS) 11, we compiled a database of 78 SST records from 57 sites. We aligned these records by oxygen-isotope stratigraphy and subjected them to an Empirical Orthogonal Function (EOF) analysis. The principal SST trend (EOF1) reflects a rapid deglacial warming of the surface ocean in pace with carbon dioxide rise during Termination V, followed by a broad SST optimum centered at ~410 thousand years (ka) before present (BP). The second EOF indicates the existence of a regional SST trend, characterized by a delayed onset of the SST optimum, followed by a prolonged period of warmer temperatures. The proxy-based SST patterns were compared to CCSM3 climate model runs for three time slices representing different orbital configurations during MIS 11. Although the modeled SST anomalies are characterized by generally lower variance, correlation between modeled and reconstructed SST anomalies suggests a detectable signature of astronomical forcing in MIS 11 climate trends.