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Past Climates
CCR researchers are examining the impacts of variations in the Earth’s orbit, greenhouse gases, volcanic activity, and solar fluctuations on the Earth system over periods of centuries to millennia. Areas of investigation include the response of plant species, ecotones, ice sheets, megafauna, and fire regimes to both gradual and abrupt climate change over extended time durations, along with the impact on climate and the global carbon budget of early-human agricultural practices.
Principal Investigators
Anders Carlson, Sara Hotchkiss, John Kutzbach, Zhengyu Liu, Michael Notaro, Patricia Sanford, Steve Vavrus, Jack Williams
Ongoing Projects
Project: Response of lakes to long-term drought – A paleoecological test of the landscape position hypothesis
PI: Patricia Sanford
We are providing cladoceran (Crustacea: Branchiopoda) zooplankton fossil evidence in the assessment of the frequency of droughts over the last 1000 years and then over the last 5000 years by close interval analysis of lake sediment cores from several lakes chosen from a 61 lake data base of Vilas Co. WI lakes.
Project: Reconstruction of dissolved reactive silica in northern Wisconsin lakes using sponge spicule width: Assessing limnological response to drought, fire, and/or Euro-American settlement activity
PI: Patricia Sanford
Using short lake sediment cores from 10 Vilas Co. WI lakes, undergraduate students measured smooth sponge spicule widths to obtain an estimate of dissolved reactive silica in lake waters at 6 time points covering pre- and post- Euro-American settlement times to document limnological responses to landscape and climate changes.
Project: Exploring the early anthropogenic hypothesis
PI: Steve Vavrus, John Kutzbach, Bill Ruddiman
We are investigating whether anthropogenic global climate change began thousands of years ago upon the advent of agriculture, as opposed to the traditional perspective that humans began large-scale modification of climate only with the start of industrialization.
Project: Simulating and understanding abrupt climate-ecosystem changes during Holocene with NCAR-CCSM3
PI: Zhengyu Liu
With funding from the Department of Energy, we are using NCAR CCSM3 to examine two major abrupt environmental changes: the collapse of North African monsoon-ecosystem in mid-Holocene and sudden cooling event in Pan-Atlantic ocean-atmosphere system around 8,200 years ago.
Project: Transient climate evolution of the last 21,000 years – Understanding climate sensitivity and abrupt climate change using CCSM
PI: Zhengyu Liu
With a grant from P2C2 with the National Science Foundation, we are performing the first set of synchronously coupled climate model simulations of the transient climate evolution of the last 21,000 years using NCAR CCSM3, while exploring a new paradigm of model-data comparison.
Project: PHASEMAP, a new paradigm for paleoclimate model-proxy comparisons: Stage I, Pleistocene surface climate and global monsoons
PI: Zhengyu Liu
Project: Development of an isotope-enabled CESM for testing abrupt climate changes
PI: Zhengyu Liu, Bette Otto-Bliesner
Project: A pilot study of simultaneous parameter and state estimation in coupled ocean-atmosphere general circulation models using the ensemble Kalman filter
PI: Zhengyu Liu
With funding from the National Science Foundation, we are developing a novel strategy for systematic parameter optimization in an ocean-atmosphere global climate model using an ensemble-based data assimilation strategy, with a focus on reducing tropical biases in the model.
Project: Deglacial Laurentide mass balance
PI: Anders Carlson
We are testing the response of the Laurentide Ice Sheet to climate warming during the last deglaciation.
Project: Extent of the southern Greenland Ice Sheet during past interglacial periods
PI: Anders Carlson
We are determining how much smaller than present was the Greenland Ice Sheet during earlier interglacial periods that were naturally warmer than present.
Project: Holocene sources of sea-level rise
PI: Anders Carlson
We are dating the Holocene retreat of the Laurentide and Scandinavian Ice Sheets to constrain sources of sea-level rise and how fast an ice sheet can melt in a warmer than present climate.
Project: Onset of the last deglaciation in Wisconsin
PI: Anders Carlson
We are dating when the Laurentide Ice Sheet began to retreat in Wisconsin to measure how sensitive an ice margin is to small changes in radiative forcing
Project: Deglaciation of southwest Greenland
PI: Anders Carlson
We are dating southwest Greenland Ice Sheet retreat to investigate its natural rates of retreat in a warming climate.
Project: Drought as a trigger for rapid state shifts in kettlehole ecosystems
PI: Sara Hotchkiss
This project studies the relationships among hydrological variability, floating peat mat establishment and expansion, and lake-ecosystem dynamics within kettle basins along a landscape gradient in Wisconsin to test the hypotheses that 1) floating mat development is episodic and triggered by hydroclimate variability, 2) basin morphology and landscape position determine kettle ecosystem susceptibility and response to floating peatland development, and 3) rapid development of floating peat mats triggers an abrupt ecosystem state-shift in remnant lake systems and increases in whole-system rates of carbon accumulation.
