A Postdoctoral Scientist to Synthesize Proxy Records of Arctic Holocene Climate

Northern Arizona University, Flagstaff AZ

Investigators

Abstract

This grant will support a post-doctoral investigator to develop a major new synthesis of proxy climate records of Holocene climate variability from across the Arctic, and compare the climate reconstruction with climate model simulations. The synthesis will build on proxy climate records currently being developed by teams of researchers looking at the past 8000 years of records. The data-model comparison will draw from newly available transient climate simulations by NCAR?s Community Climate System Model (CCSM3), and from the output of new model experiments planned for 2012. The Arctic climate reconstructions generated by this project will be integrated into similar syntheses from across the globe, as envisioned by two on-going international efforts led by the IGBP-Past Global Changes (PAGES) program ? the ?Two Millennia? and the ?SynTraCE? projects. Intellectual Merit. Depending on her/his background and career goals, the postdoctoral scientist will choose among the following research questions: (1) Was the climate transition from the Holocene thermal maximum (HTM) to the Neoglacial (5000 to 3000 years ago) uniform across the Arctic? Describing the spatial-temporal pattern of this major climate transition is necessary to assess the extent to which the climatic shift was the result of a dynamical redistribution of temperature by ocean-atmosphere circulation versus a shift in the mean state of climate across the Arctic. (2) Was Neoglacial cooling amplified in the Arctic compared with elsewhere around the world? Assessing the magnitude of cooling in the Arctic is necessary to understand the feedbacks associated with arctic amplification. (3) How does the latitudinal gradient of cooling from the HTM to the Neoglacial compare with the gradient of cooling driven by precessional forcing as simulated by CCSM3 in the SynTraCE experiment? Quantifying this gradient provides a straightforward target for a data-model comparison. (4) Are the magnitude and pattern of climate variability that are reconstructed from proxy records on timescales of decades to centuries from across the Arctic consistent with the variability simulated in CCSM3 SynTraCE experiment? Analyzing the principal modes of variability in both the proxy data and the model simulation is necessary to determine the extent to which climatic changes can reasonably be attributed to natural variability of known modes of atmospheric-ocean circulation. (5) In what ways can the output of available climate system simulations be used as boundary conditions in mechanistic models of environmental change that approximate the processes that drive the proxy indictors? Developing new ?inverse-proxy models? to predict how climate change drives proxy indicators such as glacier extent, oxygen-isotope values of precipitation, and primary productivity of Arctic lakes is necessary to avoid major assumptions that underlie classical regression-based approaches to climate reconstructions. Broader Impact. This project will contribute to understanding climatic variability, a key challenge facing society. The results will provide benchmarks for validating climate models and for improving their ability to accurately simulate nonlinear change. Improving models for future climate projections will contribute to the ?Climate Variability and Change? major program element of the US Climate Change Science Program. The entire funding request for this proposal is to support a postdoctoral scientist (PS). This early-career scientist will receive first- hand training as part of an international, interdisciplinary team of climate scientists. S/he will learn about a broad range of both data and model-based approaches to studying Arctic and global climate change. During the fall/winter of 2011, the PS will work at the PAGES International Project Office in Bern Switzerland, where the PI is scheduled as a Guest Scientist and where they will be well situated to engage an international group in a synthesis of proxy records. The PS will also work with climate modelers at NCAR in Boulder, Colorado where s/he will learn to analyze the output of climate model simulations. At NAU, the PS will be integrated into the full breadth of the PI?s research program, which includes an active analytical laboratory and field research program. The PS also will be encouraged to help regularly teach undergraduate and graduate courses to improve his/her teaching skills.