Alice Marzocchi and Malte Jansen will be talking about their study exploring the mechanisms leading to changes in deep ocean circulation between the present and the Last Glacial Maximum (LGM), by analyzing a suite of numerical model simulations from the Paleoclimate Modelling Intercomparison Project (PMIP). Significant discrepancies exist in the representation of LGM ocean circulation between different models, as well as between models and proxy reconstructions. These inconsistencies cast some doubts on the reliability of these models, which are also used for future climate scenarios.
This analysis attempts to explain the different model results in terms of differences in both ocean boundary conditions and physical parameterizations. A particular focus is on changes in Antarctic sea ice between the present and the LGM. Variations in the sea ice extent and formation rates, possibly correlated to shifts in the wind stress across this region, could have driven changes in the surface buoyancy fluxes and therefore played a key role in the rearrangement of deep water masses. They analyze these processes in PMIP models to evaluate their effect on the glacial deep ocean circulation and stratification. This talk will be given at the ICP12 conference in August.
PEN Data Working group leader, Caroline Lear, discussed past climate and ice sheet variability as inferred from the paleoclimate record at the ‘System Dynamics and Ocean-Ice-Continent Interactions.’ session at the 12th International Conference on Paleoceanography in September 2016. There is currently great interest in the extent to which quantitative records of past ice sheet retreat can be used to calibrate some of the processes (e.g., ice cliff collapse) incorporated in long-range ice sheet models (e.g., DeConto and Pollard, Nature, 531, pp.591, 2016). Assessing and improving the quality of climate forecasts is another key PEN aim. In this talk Caroline discussed the ‘ice sheet hysteresis problem’, which represents a fundamental mismatch between palaeoclimate records of ice sheet dynamics and ice sheet model simulations. She also highlighted the importance of understanding feedbacks in the climate system before such records can be interpreted in a quantitative framework. These feedbacks involve many different parts of the climate system, and she will present some quantitative and semi-quantitative proxies for some of them (e.g., changes in sea surface temperature and the global carbon cycle).
The Network leader Jochen Voss gave a short update of the network's activites at the 2016 CliMathNet conference. To download the slides click here.
PEN Steering Committee member, Tamsin Edwards, is giving a talk about Bayesian calibration of models at the 2016 ISBA conference in Italy.