About the project
IMMUNITY (Integrated model-data appraoach for understanding natural climate variability)
The primary object of IMMUNITY is to integrate novel, palaeoclimatic time series, at unprecedented temporal resolution and instrumental data with coupled atmosphere-ocean-sea-ice general circulation model (AOGCM) simulations in order to explore the long-term climate variations during the last 1500 years. The project is supported by internal funds from the Centre for Climate Dynamics at the Bjerknes Centre for 2012-2015, and includes partners from all Bjerknes-institutions.
Our analyses shows that paleo reconstructions of ocean state variables generated in IMMUNITY deliver a temporal resolution to the extent that they mimic the main decadal trends of instrumental data and thus can be used with confidence to develop a longer-term climate perspective. For example, the isotopic signals from surface-dwelling species of foraminifera from the Norwegian Sea have now been measured for the last 2000 years with a temporal resolution of about five years (Fig. A). Furthermore, multiproxy records from the Eirik and Gardar drifts in the sub-polar Atlantic have also been extended back in time to cover the last two millennia. This data will provide important information on surface and the deep ocean properties, as well as overflow variability during this period. In IMMUNITY we are also working on a framework for comparing the high-resolution paleo records with climate model output. In particular, we have shown that reconstructed deep ocean in the sub-polar region is well correlated to the Iceland-Scotland overflow, thus highlighting the potential for using the reconstructed velocities as a proxy for the overflow. In IMMUNITY we are also working to generate new historical climate simulations covering the last 1500 years using a computationally efficient lower-resolution version of the Norwegian Earth System Model (NorESM). A lot of effort has been made in order to set up and evaluate a new version of NorESM suitable for such large simulations, which will be employed also for decadal prediction ensemble integrations.
Figure A: Example of high-resolution paleo reconstructions generated in IMMUNITY. The plot shows d13C measurments of G.bulloides. The amplitude of the signal is large, with a maximum in d13C associated to the little ice age, and most negative values associated to medieval warm period.