ABSTRACT

This is an iterative data-model investigation of the relationship between paleoclimate and long-term carbon accumulation from Alaskan arctic peatland archives. The hypothesis is that climate controls carbon storage in peatlands through shifts in temperature and moisture related processes of production and decomposition. Use of an existing set of peatland cores from two arctic regions from the late-glacial to the Holocene offers a variety of climate scenarios to examine carbon sequestration. For example, the group hypothesizes that warm, dry intervals result in peatland carbon storage decline, while cool, wet climates result in increased carbon sequestration. Using new tools, including compound-specific isotope and biomarker analysis, and existing traditional paleoclimate proxies such as pollen, macrofossils, and bryophytes, the researchers will produce detailed climate and hydrological reconstructions, and high resolution AMS-14C dating, C and bulk density measurements will provide carbon accumulation rates from the late-glacial to the present and enable the team to test their carbon sequestration-climate hypotheses using a newly-developed mechanistic peatland accumulation model.

As high latitudes warm and arctic and subarctic peatlands provide positive and negative carbon feedbacks to the climate system, it is important to add the paleo-perspective to our understanding of magnitude and temporal and spatial scales. This research will couple detailed analysis of changes in paleoecology/paleoclimate (through bryophyte, compound-specific isotope analysis, pollen, and macrofossil analysis) in high latitude peatlands over the last glacial-interglacial cycle with quantification of carbon sequestration in different environments (i.e., wet vs. drier muskegs). These paleo-peatland histories will provide long-term carbon sequestration records, which can be used for comparisons with paleoclimate reconstructions from the same sediments, as well as ice cores, marine records, and lake stratigraphy. The independent paleoclimate data will be utilized by the new Holocene Peatland Model to simulate coupled carbon and water dynamics of northern peatlands at an annual time step over time scales of decades to millennia. The model-simulated carbon accumulation record can be then compared with the peatland histories, and differences evaluated in terms of plant composition, productivity, and decomposition. This iterative model-data research will provide long-term empirical information necessary to evaluate the role of the hydrological cycle in future wetland carbon cycling, and the past importance of climate and vegetation in sequestering carbon over millennia.

The selected sites for new sampling include peatlands of Alaska?s North Slope at Toolik Lake where an extensive ecological database exists as well as the arctic foothills of the western Mesa site. AMS 14C ages, as well as Pb-210 and Cs-137, will be used in conjunction with C and bulk density to determine carbon accumulation for each site. Analysis of bryophyte and isotopes/biomarkers will provide defined moisture regimes as well as possible water chemistry changes due to volcanic ash deposition in these sites. Of particular interest are climatic intervals such as the Bolling-Allerod/Younger Dryas, the early Holocene, the Preboreal and 8200-yr events, mid-Holocene, the Neoglacial, Little Ice Age, and the last 50 years.

This project will involve at least 4 undergraduate theses and one postdoc. The PI has a well-documented record of mentoring undergraduates and advising graduate students in field and lab-based programs, with many of her former advisees publishing their results in peer-reviewed journals. Students will have an opportunity to present results at the local, state, and national levels. The group will continue its long leadership in science programs training high school students and teachers at NASA/GISS summer program for minorities and Columbia University?s Department of Earth and Environmental Science graduate and undergraduate students, as well as local outreach to museums and public programs. They intend to engage a K-12 teacher in their field and lab research in the Lamont Doherty Earth Observatory VAST (Visiting Arctic/subarctic Summer Teacher) program for far-ranging impact. Additionally, their analyses can be utilized for the Columbia University courses the PI teaches on Wetlands and Climate Change, Terrestrial Paleoclimate, as well as seminars in Plant Ecology and Paleoecology, and in courses the UNH PI teaches (Biogeochemistry and Environmental Modeling). The results and conclusions of this work will have implications for arctic climate policy, ecosystem management, and education.