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Future Work

1. Simulation of Quaternary climate dynamics (MegaRun)

In spite of numerous empirical and modeling studies performed during past several decades, the nature of glacial cycles remains poorly understood. The major goal of the ICE-QUEST project during 2008 and 2009 is to simulate the temporal dynamics of climate and ice sheets during the whole Quaternary with orbital forcing as the only externally prescribed forcing. Changes in the atmospheric concentration of major greenhouse gases and dust loading and deposition will be interactively simulated by the CLIMBER-2 model. Realistic simulation of the CO2 concentration represents the major challenge, since the mechanisms of the large glacial-interglacial CO2 variations are not well understood. After all components of the model required for this study will be developed and tested, we will perform initially several experiments for the most recent glacial cycles and, eventually, the MegaRun spanning the last 2 million years, the period of time which encompasses two distinct regimes of glacial variability: the dominant 40-kyrs cyclicity before to 1 Myrs BP and the dominant 100-kyrs cyclicity during the past 1 million years. Pollard’s and Clark’s “regolith” hypothesis for the Mid-Pleistocene transition will be tested by applying an appropriate parameterization for changes in terrestrial sediments distribution. The role of long-term trends in CO2 concentration will be also investigated. Apart from orbital time scales, special attention will be paid to realistic simulations of the millennial scale climate variability. After successful simulations of the past glacial cycles, the future of the ice sheets at orbital time scales will be investigated. One of the possible applications of this work would be testing of Ruddiman’s “early anthropogenic hypothesis”.

2. Mid- and long-term response of the Greenland Ice Sheet to anthropogenic global warming

Understanding the response of the Greenland Ice Sheet (GIS) to anthropogenic warming is of great importance, because of its potentially significant contribution to global sea level rise as well as its potential impact on the Atlantic thermohaline circulation. Recent studies have shown that for a sufficient high CO2 concentration, an irreversible melt back of GIS can occur on millennial time scale, which will contribute to a weakening, or even a complete shutdown, of the Atlantic thermohaline circulation. At the same time, observational data indicate a considerable acceleration of GIS melting in the recent decade, which is not properly simulated by the existing ice sheet models. One of the key aims of the future ICE-QUEST activity is to perform probabilistic assessment of the irreversible melt back of GIS for different greenhouse emission scenarios taking into account large uncertainties related to the climate sensitivity, the ice sheet surface mass balance and the role of fast glacial processes.

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