Predicting Arctic Change through Ecosystem Molecular Proxies (PACEMAP)

The Arctic is warming faster than any other region of the planet, and the effects are already apparent. Landscapes that have been continuously ice-covered since the start of the last glacial cycle and now being revealed as cold-based ice recedes under warming summers. Climate models suggest that over the next century the Arctic will experience twice the warming seen at lower latitudes. What will that mean for the Inuit living there? Already new birds are appearing in summer; how will the vegetation change? When was the last time the Arctic experienced conditions similar to the projected climate in 2100 CE?

Those are some of the questions Giff Miller and colleagues are trying to answer with PACEMAP, an interdisciplinary project involving scientists from the University of Colorado Boulder, the University at Buffalo, University of Alaska Fairbanks, and Curtin University in Australia. PACEMAP brings together ecologists, geologists, and paleoclimatologists with organic geochemists and geneticists, using the past to predict the future. Capitalizing on lake sediment deposited in past warm times on Baffin Island, including the Early Holocene, the Last Interglacial (MIS 5e), and the penultimate interglacial (MIS 7; Figure 1), field teams will recover pristine continuous sedimentary records that span earlier warm intervals. Although lacustrine archives from these time periods have been lost from most northern lands, where repeated glaciations usually erase sediment from earlier warm intervals, Baffin Island is one of a handful of locations where pre-last glaciation sediment survived underneath non-erosive, cold-based glacial ice. The PACEMAP project seeks to analyze these unique records using new techniques to provide quantitative evidence of past ecosystems and more tightly constrain summer temperatures during past warm times to predict ecosystem status in 2100 CE.

The team is using molecular approaches to reconstruct changes in climate, hydrology, and vegetation through past warm times. Postdoc Greg deWet and PhD student Jon Raberg are working with Julio Sepúlveda at CU using bacterial membrane lipids, called branched glycerol dialkyl tetraethers (brGDGTs), to reconstruct climate back through time. The distribution of these compounds in modern environments has been empirically shown to relate to environmental temperature, and one of the goals of the project is to create a site-specific calibration for Baffin Island. Buffalo PhD students Elizabeth Thomas and Devon Gorbey are evaluating changes in precipitation source and moisture balance from the hydrogen isotopic composition of leaf waxes (d2Hwax) in terrestrial and aquatic plant sources. And CU postdoc Sarah Crump and Mike Bunce at Curtin University are using ancient sedimentary DNA extracted from interglacial sediment to provide a more authentic reconstruction of local vegetation communities, where long-distance pollen dispersal compromises pollen records. This approach, relatively untested on such long timescales, also involves modern validation work, where Martha Raynolds and Shawnee Kasanke, ecologists working with Skip Walker at UA Fairbanks, map the modern vegetation around the study sites to compare with DNA extracted from surface sediments at our coring sites.

PACEMAP is about to enter its third field season, with researchers heading to Baffin Island in May to recover sediment cores using lake ice as a coring platform, followed by a more expansive summer team that will collect modern environmental samples, recover and redeploy sediment traps and temperature loggers, and map vegetation. Data and results from the project will be made publicly available as they are published.

We thank our Inuit guides for their knowledge, support, and hard work in the field, in particular Joshua Akavak, Mina Kunilusie, and Gordie Audlakiak. We also thank the Nunavut Research Institute and Arctic College in Iqaluit for logistical support, and the Inuit of Baffin Island for permission to travel and work on their land. The PACEMAP project is funded by the Office of Polar Programs at NSF.