Abrupt Climate Changes and Environmental Responses

          ACER is an IFG (International Focus Group, INQUA) that has been built on the pollen data synthesis achieved in the framework of QUEST-DESIRE project (NERC) and published in a recent issue of Quaternary Science Reviews (October 2010) “Vegetation response to millennial-scale variability during the Last Glacial”. ACER aims to understand the timing, frequency and amplitude of the rapid climate variability and the feedback mechanisms involved. This will help us in understanding the abrupt CO2 and CH4 changes recorded in ice cores.
The aims are:
• to reconstruct for several D-O cycles a suite of global maps of vegetation applying the biomisation technique. This global synthesis will enable examination of broad-scale patterns of changes in vegetation cover and composition in response to the millennial-scale variability of the last glacial and provide new insights into regional short-term variability of vegetation and climate,
• to compile marine data to create maps of sea surface temperature changes through a series of D-O cycles, for comparison with the reconstruction terrestrial data and,
• to use both compilations in conjunction with global models simulating vegetation-climate interactions and vegetation cover and composition predictions as well as biogeochemistry to investigate the mechanisms underpinning D-O variability.
The specific objectives are:
a) Achieving the pollen database and creating global vegetation maps through biomisation, comparing with maps of wetland extent and fire regimes
b) Identifying amplitude and spatial patterns of vegetation changes
c) Assessing the response time of vegetation to climate changes using ecological studies and palaeo-observations
d) Comparison of vegetation changes with marine (sea surface temperature changes, strength of oceanic circulation and iceberg discharge)
e) Evaluating climate and biogeochemical cycle simulations for rapid climate changes by comparing with our global palaeo-observations

      While the QSR special issue presents the first qualitative maps of global scale changes in biomes during D-O cycles, including Heinrich events, the ACER Biomisation workshop allowed us to achieve the related pollen database and critically assess its quality such as the chronology of the records (specific goal a). Additionally, during this meeting Colin Prentice and Patrick Bartlein developed a new biomisation technique to apply to all the reliable records included in this database for quantifying worldwide amplitude changes of biomes and pft (plant functional type).
       This work initiated by the working group “Abrupt Climate Changes” within the QUEST-DESIRE project was presented at the last PMIP 3 workshop in Kyoto (Japan, 5-10 December) and at the “Réunion des Sciences de la Terre” in Bordeaux (France, 26-30 October). Following these meetings, a number of palaeoceanographers, climate modelers and people from the ice community express their interest in joining the ACER initiative. They intend to participate in the second ACER workshop devoted to compile marine data and use both terrestrial and marine data in conjunction with model simulations to investigate the mechanisms underpinning D-O variability.